Розробка багатостадійної технології промислового синтезу АФІ левосимендану та енантіомерного розділення проміжних продуктів
A method for obtaining Levosimendan suitable for industrial application has been developed. Two literature routes for the synthesis have been evaluated. It has been found that the use of enantiopure (R)-2-chloropropionyl chloride in the initial step is ineffective due to racemization at the stage of...
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| Date: | 2025 |
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| Pages: | 35-47 |
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| author | Sokolenko, Liubov V. Sokolenko, Taras M. Filatov, Andrey A. Shchehlov, Oleksandr D. Rudiuk, Vitalii V. Yagupolskii, Yurii L. |
| author_facet | Sokolenko, Liubov V. Sokolenko, Taras M. Filatov, Andrey A. Shchehlov, Oleksandr D. Rudiuk, Vitalii V. Yagupolskii, Yurii L. |
| author_institution_txt_mv | [
{
"author": "Liubov V. Sokolenko",
"institution": "Institute of Organic Chemistry of the National Academy of Sciences of Ukraine",
"orcid": ""
},
{
"author": "Taras M. Sokolenko",
"institution": " Institute of Organic Chemistry of the National Academy of Sciences of Ukraine",
"orcid": ""
},
{
"author": "Andrey A. Filatov",
"institution": " Institute of Organic Chemistry of the National Academy of Sciences of Ukraine",
"orcid": ""
},
{
"author": "Oleksandr D. Shchehlov",
"institution": "JSC \"Farmak\", Chuiko Institute of Surface Chemistry of the National Academy of Sciences of Ukraine",
"orcid": ""
},
{
"author": "Vitalii V. Rudiuk",
"institution": "JSC \"Farmak\"",
"orcid": "0000-0003-3440-1139"
},
{
"author": "Yurii L. Yagupolskii",
"institution": " Institute of Organic Chemistry of the National Academy of Sciences of Ukraine",
"orcid": ""
}
] |
| author_orcid_str_mv | 0000-0003-3440-1139 |
| author_sort | Sokolenko, Liubov V. |
| baseUrl_str | https://ophcj.nuph.edu.ua/oai |
| collection | OJS |
| container_end_page | 47 |
| container_issue | 2 |
| container_start_page | 35 |
| container_title | Журнал органічної та фармацевтичної хімії |
| container_volume | 23 |
| datestamp_date | 2026-08-22T19:54:27Z |
| description | A method for obtaining Levosimendan suitable for industrial application has been developed. Two literature routes for the synthesis have been evaluated. It has been found that the use of enantiopure (R)-2-chloropropionyl chloride in the initial step is ineffective due to racemization at the stage of the synthesis based on the malonic ester. Instead, a reported method based on the synthesis of the Levosimendan precursor, 6-(4-aminophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one (1), from racemic 2-bromopropionyl bromide has been modified to allow for scale-up and adaptation to industrial processes. A practical resolution method has been developed to isolate the (R)-enantiomer of amine 1 from the racemic mixture with a high enantiomeric purity (the content of (R)-enantiomer is up to 99%). It has been shown that (R)-1 can be converted to Levosimendan in a high yield without the stereochemical purity loss at the chiral center. |
| doi_str_mv | 10.24959/ophcj.25.322447 |
| first_indexed | 2025-07-23T04:43:38Z |
| format | Article |
| fulltext |
ISSN 2308-8303 (Print) / 2518-1548 (Online) 35
Original Research
http://ophcj.nuph.edu.ua
UDC 547.1+661.1:615.4
L. V. Sokolenko1, T. M. Sokolenko1, A. A. Filatov1, O. D. Shchehlov2,3,
V. V. Rudiuk2, Yu. L. Yagupolskii1
1 Institute of Organic Chemistry of the National Academy of Sciences of Ukraine,
5 Akademik Kuhar str, 02094 Kyiv, Ukraine
2 JSC “Farmak”, 63 Kyrylivska Str., 04080 Kyiv, Ukraine
3 Chuiko Institute of Surface Chemistry of the National Academy of Sciences of Ukraine,
17 General Naumov Str., 03164 Kyiv, Ukraine
Development of a Multistage Technology for the Industrial
Synthesis of the Levosimendan API and Enantiomeric
Separation of Intermediates
Abstract
A method for obtaining Levosimendan suitable for industrial application has been developed. Two literature routes for the
synthesis have been evaluated. It has been found that the use of enantiopure (R)-2-chloropropionyl chloride in the initial
step is ineffective due to racemization at the stage of the synthesis based on the malonic ester. Instead, a reported method
based on the synthesis of the Levosimendan precursor, 6-(4-aminophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one (1),
from racemic 2-bromopropionyl bromide has been modified to allow for scale-up and adaptation to industrial processes.
A practical resolution method has been developed to isolate the (R)-enantiomer of amine 1 from the racemic mixture with
a high enantiomeric purity (the content of (R)-enantiomer is up to 99 %). It has been shown that (R)-1 can be converted to
Levosimendan in a high yield without the stereochemical purity loss at the chiral center.
Keywords: Levosimendan; 4,5-dihydropyridazine-3(2H)-one; enantiomers separation; diastereomeric salts; S,S-2,3-bis-(4-
methoxybenzoiloxy)butanedioic acid
Л. В. Соколенко1, Т. М. Соколенко1, А. А. Філатов1, О. Д. Щеглов2,3, В. В. Рудюк2, Ю. Л. Ягупольський1
1 Інститут органічної хімії Національної академії наук України,
вул. Академіка Кухаря, 5, м. Київ, 02094, Україна
2 АТ «Фармак», вул. Кирилівська, 63, м. Київ, 04080, Україна
3 Інститут хімії поверхні ім. О. О. Чуйка Національної академії наук України,
вул. Генерала Наумова, 17, м. Київ, 03164, Україна
Розробка багатостадійної технології промислового синтезу АФІ левосимендану
та енантіомерного розділення проміжних продуктів
Анотація
Розроблено метод одержання левосимендану, придатний для промислового використання. Перевірено два літератур-
них методи синтезу левосимендану та з’ясовано, що використання (R)‑2-хлоропропіонілхлориду на першій стадії не
ефективне через рацемізацію на стадії синтезу на основі малонового естеру. Літературний метод синтезу попередни-
ка левосимендану, 6-(4-амінофеніл)-5-метил-4,5-дигідропіридазин-3(2Н)-ону (1), було модифіковано з використан-
ням рацемічного 2‑бромопропіонілброміду з метою зробити його придатним для масштабування та перетворення на
промислову технологію. Розроблено метод виділення (R)‑енантіомеру аміну 1 з рацемату з високою енантіомерною
чистотою (вміст (R)‑енантіомеру до 99 %). Показано, що амін (R)-1 може бути перетворено на левосимендан зі збере-
женням конфігурації хірального центру та високим виходом.
Ключові слова: левосимендан; 4,5-дигідропіридазин-3(2Н)-он; розділення енантіомерів; діастереомерні солі; S,S-2,3-біс-
(4-метоксибензоїлокси)бутандіова кислота
ISSN 2308-8303 (Print) / 2518-1548 (Online) 36
Журнал органічної та фармацевтичної хімії 2025, 23 (2)
Citation: Sokolenko, L. V.; Sokolenko, T. M.; Filatov, A. A.; Shchehlov, O. D.; Rudiuk, V. V.; Yagupolskii, Yu. L. A Development of a Multistage
Technology for the Industrial Synthesis of the Levosimendan API and Enantiomeric Separation of Intermediates. Journal of Organic and
Pharmaceutical Chemistry 2025, 23 (2), 35 – 47.
https://doi.org/10.24959/ophcj.25.322447
Received: 19 February 2025; Revised: 3 April 2025; Accepted: 12 April 2025
Copyright© 2025, L. V. Sokolenko, T. M. Sokolenko, A. A. Filatov, O. D. Shchehlov, V. V. Rudiuk, Yu. L. Yagupolskii. This is an open access
article under the CC BY license (http://creativecommons.org/licenses/by/4.0).
Funding: The author received no specific funding for this work.
Conflict of interests: The authors have no conflict of interests to declare.
■ Introduction
Levosimendan (Figure 1) represents a new
class of cardiotonic agents reported as Ca2+ sen-
sitizers without cardiovascular side effects. It in-
creases the sensitivity of contractile proteins to
calcium by binding to cardiotroponin C. Levosi-
mendan increases the strength of contractions
but does not depend on the ventricular relaxation.
In addition, Levosimendan opens ATP-sensitive
potassium channels in the vascular smooth muscle,
stimulating the vasodilation of systemic arteries,
coronary arteries, and systemic veins. It is a se-
lective phosphodiesterase III inhibitor in vitro.
In patients with heart failure, the positive ino-
tropic and vasodilator effects of Levosimendan
lead to an increase in the contractile force of the
myocardium and a decrease in the preload and
postload without the adverse impact on the diasto-
lic function. Levosimendan activates the “ische-
mic” myocardium in patients after coronary an-
gioplasty or thrombolysis [1 – 3]. Levosimendan
is used for the short-term treatment of acute,
severe decompensated chronic heart failure [2].
This drug is registered in Ukraine, and at least
one domestic manufacturer, JSC Farmak, is pre-
sent in the pharmaceutical market of Ukraine.
Due to the complicated logistics, the develop-
ment of a domestic industrial method for the syn-
thesis of Levosimendan is an urgent task. The com-
mercial production of Levosimendan requires
a cheap, convenient, and efficient synthetic ap-
proach, which can be converted into technology.
In all methods of the synthesis of Levosimen-
dan described, the last stage is common, namely
the conversion of the R-enantiomer of amine 1
((R)-1) into a diazo compound, followed by the in-
teraction with malononitrile, as it has been pre-
sented in the patent [4] (Scheme 1). This makes
amine 1 the key compound in the synthesis of
Levosimendan.
The scientific literature describes the four main
approaches to 6-(4-aminophenyl)-5-methyl-4,5-
dihydropyridazin-3(2H)-one 1 [5 – 9] (Routes 1 – 4,
Schemes 2 – 5).
Scheme 2 (Route 1) shows the method based
on utilizing the chiral starting materials from
the first stage [5]. The authors reported that
this route led to a crude amine (R)-1 with 84 % ee
in the total yield of 30 %, and further recrystal-
lization of the crude product from ethyl acetate
increased ee up to 98 %.
Similar methods of the preparation of ami-
ne 1 starting from racemic 2‑bromopropionyl
bromide [6] or propionyl chloride [7] were de-
scribed with the total yields of racemic com-
pound 1 of 58 % and 22 %, respectively (Route 2,
Scheme 3). In the work by Wang et al. [7], the
separation of pyridazine-3(2H)-one 1 enantio-
mers via the crystallization of diastereomeric
salts with L-(+)-tartaric acid was reported with
the yield of 8 %.
If a racemic 2-chloropropionyl chloride was
used in such a route, racemic amine 1 was ob-
tained with the total yield of 23 % [8].
The preparation of the enantiomerically pure
amine (R)-1 starting from acetanilide 2 and cit-
raconic anhydride (Route 3, Scheme 4) was de-
scribed in [9]. This method includes a double bond
reduction stage by hydrogen in the presence of
a chiral Ru-catalyst (S)-BINAP-Ru. The total
yield of the product (R)-1 was ~14 %.
( )R
HN N
O NH
Me
N
CN
CN
Figure 1. The structure of Levosimendan
( )-R 1
1. NaNO2, HCl
Levosimendan, 80 %
HN N
O NH2
Me
( )R
HN N
O NH
Me
N
CN
CN
2. CH2(CN)2
Scheme 1. The last stage of the Levosimendan synthesis [4]
ISSN 2308-8303 (Print) / 2518-1548 (Online) 37
Journal of Organic and Pharmaceutical Chemistry 2025, 23 (2)
NHAc NHAc
O
Me
Cl
AlCl3 H2SO4
N2H4•H2
1,2,4-trichlorobenzene
( )R
BnO2C CO2Me
1. H2 (1 bar), Pd/C, EtOAc
NH2
O
Me
CO2Me
NH2
Me
NH
N
O
2 3 4 5
6 ( )-R 1
MeOH
NaH, DMF
91 % yield
84 % ee
NH2
Me
NH
N
O
( )-R 1
50 % recovery
98 % ee
crystallization
from ethyl acetate
79 % yield
90 % ee
89 % yield
84 % ee
84 % yield
55 % yield
86 % ee
Cl
O
Me
Cl
NH2
O
Me
Cl
H2N
O
Me
CO2Me
CO2Bn
Scheme 2. The synthesis of 6-(4-Aminophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one starting from (R)-2-chloropropionyl chloride [5]
CH2(CO2Et)2, base
NHAc
AlCl3, CS2
NHAc
O
Me
Br
NHAc
O
Me
CO2EtEtO2C
NHR1
O
Me
COOR2
3, CS2
2. Br2
[6]
[7]
9: R1 = H, R2 = Et [6]
10: R1 2 = H [7]
racemic 1
N2H4•H2
N2H4•H2O, EtOH
separation of
enantiomers [7]
1. hydrolysis
2 7 8
( )-R 1
HN
N
O
NH2
Me
HN
N
O
NH2
Me
Br
O
Me
Br
or
2. decarboxylation
[6]
Scheme 3. The preparation of 6-(4-Aminophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one starting from racemic 2‑bromopropionyl
bromide or propionyl chloride [6, 7]
NHAc
AcHN
O
Me
COOH
H2, ( )-BINAP-RuS
65 % yield
79 % ee
AcHN
O
Me
COOH
93 % yield
99 % ee
2. column
chromatography
3, DMF
100 bar
2 11 ( )-R 10
( )-R 12
66 % yield
99 % ee
( )-R 1
HN
N
O
NH2
Me
HN
N
O
NHAc
Me
N2H4N2H4
O
MeO
O
Scheme 4. The preparation of the enantiomerically pure (R)-6-(4-aminophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one starting
from citraconic anhydride via the double bond reduction stage [9]
ISSN 2308-8303 (Print) / 2518-1548 (Online) 38
Журнал органічної та фармацевтичної хімії 2025, 23 (2)
Another method for the preparation of race-
mic amine 1 using keto-acid 13 with the to-
tal yield of 28 % was reported in [8] (Route 4,
Scheme 5). This method, like the previous one,
includes a double bond reduction with hydrogen
on a Raney Ni catalyst.
As can be seen from the literature data, the
enantiomerically pure amine (R)-1 was obtained
either by using chiral substances from the first
stage [5], or by creating the desired configuration
of the chiral center during the synthesis process
[9], or by separating the racemate of amine 1 [4, 7].
The comparison of the aforementioned synthetic
pathways is shown in Table 1.
The aim of this study was to evaluate the
known methods of synthesis of Levosimendan
and develop an optimal synthetic route suitable
for converting into the technology and produc-
tion of Levosimendan on the industrial scale.
■ Results and discussion
The synthesis pathways to 6-(4-aminophenyl)-
5-methyl-4,5-dihydropyridazin-3(2H)-one (1), in-
cluding the stage of reduction with gaseous hy-
drogen (Routes 3, 4; Schemes 4, 5), are unsuit-
able for industrial use at JSC “Farmak” due to
the lack of specific conditions for working with
gaseous hydrogen under high pressure.
Therefore, for our research, we chose two me-
thods shown in Scheme 2 [5] and Scheme 3 [6]
(Routes 1, 2), starting from (R)‑2-chloropropio-
nyl chloride or 2-bromopropionyl bromide, re-
spectively.
AcHN
O
COOH
AcHN
O
CO2H
N
piperidine, CH2O MeOH, H2SO4
H2N
O
CO2Me
N
Ac2O, pyridine
AcHN
O
CO2Me
H2, Raney Ni
NHAc
Me
HN
N
O
NH2
Me
HN
N
O
aq. HCl
13 14 15
16 17 12
N2H4•H2O
AcHN
O
CO2Me
Me
1
Scheme 5. The preparation of racemic 6-(4-aminophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one using 4-(4-acetamidophenyl)-
4-oxobutanoic acid [8]
Table 1. The comparison of the literature synthetic pathways of 6-(4-aminophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one
Route 1 (Scheme 2 [5]) Route 2 (Scheme 3 [6, 7]) Route 3 (Scheme 4 [9]) Route 4 (Scheme 5 [8])
• total yield – 30 %
• ee – 84 %
• total yield – 22-58 %a
• racemate
• total yield – 14 %
• ee – 99 %
• total yield – 28 %
• racemate
+ high eeb
+ without the enantiomer
separation
+ cheap and available starting
materials
+ creation of a chiral
center with high ee in the
synthesis process
+ without the enantiomer
separation
+ cheap and available starting
materials
– the use of a non-
commercial unsymmetrical
malonic esterc
– the additional stage of the
benzyl methyl malonate
synthesis
– the low total yield starting
from 2‑propionyl chloride
[7]
– the low yield (8 %) at the
enantiomer separation
stage [7]
– the mixture of products at
the first stage requires the
column chromatography for
separation
– the low yield (34 %) of
desired product at the first
stage
– the use of gaseous
hydrogen
– expensive Ru-catalysts
– the low total yield
– the use of gaseous
hydrogen
– expensive catalysts
Notes: a 22 % yield starting from propionyl chloride [7]; 58 % yield starting from 2-bromopropionyl bromide [6]; b “+” indicates advantages of the method;
c “–” indicates disadvantages of the method
ISSN 2308-8303 (Print) / 2518-1548 (Online) 39
Journal of Organic and Pharmaceutical Chemistry 2025, 23 (2)
The authors in [5] (Scheme 2) noted that the
use of unsymmetrical benzyl methyl malonate
allowed obtaining compound 6 under mild con-
ditions while preserving the configuration of the
chiral center. In addition, it was stated that the
use of aniline 4 (rather than acyl-protected ani-
line 3) in the reaction with malonic ester allowed
them to analyze the enantiomeric purity of the
product by the HPLC method using chromato-
graphic columns with a chiral stationary phase.
While reproducing this scheme (Scheme 2),
we faced some difficulties. Compound 4 was ob-
tained as described in [5] with the same yield
and ee. However, the following stages gave un-
expected and disappointing results. The interac-
tion of chloride 4 with unsymmetrical malonic
ester using the conditions described proceeded
very slowly. To achieve a conversion of 90 %, it
was necessary to carry out the reaction for 6 days,
contrary to 24 h in [5]. Moreover, the analysis
of the enantiomeric purity of product 5 showed
that during the interaction of compound 4 with
benzyl methyl malonate, the racemization of the
initial chiral center occurred. In addition, unreact-
ed amine 4 with the initial ee of 92 % was reco-
vered from the reaction mixture as a racemate.
This indicates that the racemization occurred in
starting amine 4 due to the enolization of the keto
function under the action of the base. Attempts
to use a symmetrical dimethyl malonate in the
reaction with either amine 4 or acylated amine 3
resulted in the racemization of the initial chiral
center as well.
This failure showed that the utilization of
a chiral starting material, namely (R)‑2-chloro-
propionyl chloride, was ineffective. Therefore,
we evaluated the second selected route starting
from 2-bromopropionyl bromide [6] (Scheme 3)
with the following separation of the enantiomers
of amine 1 via the crystallization of diastereome-
ric salts.
The first stage of the synthesis, namely the
Friedel-Crafts reaction, was described in [6] us-
ing carbon disulfide as a solvent. This compound
is very toxic and flammable; therefore, it is un-
suitable for application in modern pharmaceuti-
cal manufacturing. We tested other organic sol-
vents in this reaction to find the optimal condi-
tions that would give high yields of product 7
(Scheme 6). Thus, heating the reaction mixture
in dichloroethane at 80°С for 1.5 h led to the sig-
nificant tar formation, and as a result, the product
isolation failed. If the reaction mixture was re-
fluxed in dichloromethane for 4 or 6 h, the con-
version of acetanilide 2 was about 90 %. An iso-
lated yield of product 7 was 80 % after column
chromatography. The best results were achieved
in 1,2,4-trichlorobenzene at 80°С after heating
for 3 h, as described for (R)-2‑chloropropionyl chlo-
ride in [5]. Product 7 was isolated in the yield
of 99 %.
The malonic synthesis was described using
diethyl malonate, sodium hydride as a base and
THF as a solvent [6]. We used dimethylmalonate
instead of diethylmalonate in our research
(Scheme 7). This choice is made as at the next
step of hydrolysis/decarboxylation, an alcoholic
solution of HCl is used, and the solution of HCl
in methanol is a commercial reagent. In addi-
tion, it is difficult to obtain such a solution from
ethanol in the laboratory or industry since abso-
lute alcohol is required to prepare the solution.
Sodium hydride or potassium tert-butoxide was
used as a base, and DMF or THF as a solvent.
Table 2 summarizes the results of the experi-
ments.
NHAc
AcHN
O
Me
Br
AlCl3
solvent
2 7
O
Br
Me
Br
Scheme 6. The Friedel-Crafts reaction of acetanilide and 2‑bromopropionyl bromide
AcHN
O
Me
Br
AcHN
O
Me
CO2Me
CO2MeMeO2C CO2Me
18
base, solvent
7
Scheme 7. The synthesis of dimethyl 2-(1-(4-acetamidophenyl)-1-oxopropan-2-yl)malonate via the malonic ester synthesis
ISSN 2308-8303 (Print) / 2518-1548 (Online) 40
Журнал органічної та фармацевтичної хімії 2025, 23 (2)
It is evident from Table 2 that tBuOK gave bet-
ter results if compared with sodium hydride, and
THF was a better solvent than DMF for this reac-
tion. It should be noted that when using 1.0 equiv.
tBuOK and dimethyl malonate in THF the star-
ting bromide in the amount of up to 1 % was
identified in the 1H NMR spectrum. The use of
1.25 equiv. tBuOK and dimethyl malonate in THF
was shown to be optimal (see entry 5).
It is noteworthy to mention that attempts to
purify product 18 by the recrystallization were
unsuccessful. However, it was found that all the
impurities present in the product after the ma-
lonic synthesis disappeared after the next stage
of the hydrolysis/decarboxylation sequence.
Therefore, we believe that it is impractical to pu-
rify compound 18 before the next step.
The stages of hydrolysis and decarboxylation
(Scheme 8) were carried out similarly to the trans-
formations described in [6]. As we used dimethyl
ester instead of diethyl, we also used the methanol
solution rather than the ethanol solution of HCl.
The cyclization reaction (Scheme 9) was per-
formed according to [6]. We only slightly modi-
fied amine 1 isolation since the procedure de-
scribed was not reproducible. If the precipitate
product was isolated by filtration from the etha-
nolic reaction mixture as described in [6], the
yield of amine 1 was up to 50 %. Therefore, we
first removed the solvent (EtOH) from the re-
action mixture to dryness and then treated the
residue with water. The precipitate formed was
filtered and purified as described in the article
[6], yielding pure amine 1 with a high yield.
Thus, the overall optimized scheme for the syn-
thesis of racemic amine 1 is as follows (Scheme 10)
with the total isolated yield of 67 %. All stages can
be easily scaled up in the laboratory and amount
of each substance obtained per loading is shown
in Scheme 10.
The separation of racemic amine 1 was de-
scribed in [7] and included the following stages:
(1) the synthesis of the salt with L-(+)-tartaric
acid; (2) the crystallization of the resulting mix-
ture of diastereomeric salts using 2-propanol;
(3) the conversion of the salt to amine 1. It was
mentioned in the article that one crystallization
was required for the complete separation of en-
antiomers.
We have found that amine 1 with (R)-enan-
tiomer content >98 % can be reached by 20 – 32
crystallizations of diastereomeric salts, depend-
ing on the amount of the starting mixture of di-
astereomeric salts. If 4.5 g of the mixture was
used for the separation, the (R)-enantiomer con-
tent of 98.4 % was reached after 20 crystalliza-
tions. At the same time, 45 g of the mixture of
diastereomeric salts needed 32 crystallizations
Table 2. The malonic ester synthesis – optimization of reaction conditions
Entry Base Equiv. of the base and
dimethyl malonate Solvent Isolated yield of 18, % LC-MS purity of 18, %
1 NaH 2 DMF 30 78
2 tBuOK 2 DMF 67 83
3 tBuOK 2 THF 97 100
4 tBuOK 1 THF 94 93
5 tBuOK 1.25 THF 96 93
AcHN
O
Me
CO2Me
CO2Me 1. HCl/MeOH
H2N
O
Me
CO2H
18, 78 %
2. HCl/H2O
HCl*
19
Scheme 8. The preparation of 4-(4-Aminophenyl)-3-methyl-4-oxobutanoic acid hydrochloride via the hydrolysis and decarboxylation
of dimethyl 2-(1-(4-acetamidophenyl)-1-oxopropan-2-yl)malonate
NH2
Me
HN
N
O
1, 90 %19
EtOH
N2H4•H2O
H2N
O
Me
CO2H
HCl*
Scheme 9. The cyclization reaction of 4-(4-aminophenyl)-3-methyl-4-oxobutanoic acid hydrochloride with hydrazine hydrate
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Journal of Organic and Pharmaceutical Chemistry 2025, 23 (2)
for the isolation of the R-enantiomer with its con-
tent of 98.6 %.
The application of tartaric acid derivatives 20,21
for the separation of enantiomers of 6-(4-amino-
phenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-
one (1) for the further use of the desired R-enan-
tiomer in the synthesis of Levosimendan was de-
scribed in the patent [4]. The patent stated that
any derivative 20,21 with any configuration of
chiral centers can be used for the separation
(Figure 2). The separation of enantiomers using
acids 20,21 included the following stages as in the
case of L-(+)-tartaric acid: (1) the synthesis of the
salt with tartaric acid derivative 20,21; (2) the cry-
stallization of the resulting mixture of diastere-
omeric salts using the ethanol/H2O 1:1 mixture;
(3) the conversion of the salt to amine 1. Authors
of [4] stated that one crystallization was suffi-
cient to separate diastereomeric salts. Depend-
ing on the configuration of acids 20,21 used, the
desired (R)-1 either precipitated or remained in
the solution.
When we used acid 20 for the enantiomer se-
paration as it was described in patent [4], after
two crystallizations of diastereomeric salts we ob-
tained racemic amine 1 without any enrichment
with a desired (R)-enantiomer. We showed that
the best results were achieved when using a small
excess of S,S-2,3-bis-(4-methoxybenzoyloxy)bu-
tanedioic acid (21). One crystallization of the mix-
ture of diastereomeric salts of racemic amine 1,
as it was described in [4], did not lead to the full
enantiomer separation. The R-enantiomer of ami-
ne 1 with the (R)-enantiomer content of up to
99 % was isolated after five crystallizations of the
mixture of diastereomeric salts.
Table 3 summarizes our results of both me-
thods selected for obtaining (R)-6-(4-aminophenyl)-
5-methyl-4,5-dihydropyridazin-3(2H)-one (1).
(R)-1 was easily converted into Levosimen-
dan as it was described in [4] with preserving
the configuration of the chiral center and the
yield of 96 % (Scheme 11).
CH2(CO2Me)2
NHAc
AlCl3, CS2 AcHN
O
Me
CO2Me
CO2Me
2
Br
O
Me
Br
1,2,4-trichlorobenzene
NHAc
O
Me
Br 7, 99 %
tBuOK, THF
18, 96 %
1. HCl, MeOH
2. HCl, H2O
NH2
Me
HN
N
O
H2N
O
Me
CO2H
1, 90 %19, 78 %
EtOH
N2H4•H2O
HCl*
up to 170 g up to 70 g
up to 50 g up to 40 g
Scheme 10. The optimized scheme for the synthesis of racemic 6-(4-aminophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one
HOOC
COOH
O
O
20: Ar = Ph
21: Ar = 4-MeO-C6H4
Ar
O
O
Ar
Figure 2. Tartaric acid derivatives used for the separation
of enantiomers of amines [4]
( )-R 1
1. NaNO2, HCl
Levosimendan, 96 %
HN N
O NH2
Me ( )R
HN N
O NH
Me
N
CN
CN
( )-enantiomer content >98 % ( )-enantiomer content >98 %R R
2. CH2(CN)2
Scheme 11. The last step for the preparation of Levosimendan
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Журнал органічної та фармацевтичної хімії 2025, 23 (2)
The (R)-Enantiomer content was the main
quality indicator that was focused on in the pro-
cess of the synthetic route optimization.
Since Levosimendan is the active pharmaceu-
tical ingredient (API), it is important to check
certain quality parameters specific to such sub-
stances. The quality tests were performed ac-
cording to the following general chapters of the
European Pharmacopoeia (EP): identification by
NMR (2.2.33), loss on drying (2.2.32), sulfated
ash (2.4.14), and HPLC assay, related substan-
ces, and (R)-enantiomer content tests (2.2.29,
2.2.46) [12]. The results of the final sample quali-
ty of the Levosimendan obtained are shown in
Table 4.
■ Conclusions
We have evaluated two literature methods
for obtaining 6-(4-aminophenyl)-5-methyl-4,5-
dihydropyridazin-3(2H)-one (1). It has been
found that the use of (R)-2-chloropropionyl
chloride in the initial step is ineffective due
to racemization at the stage of the synthesis
based on the malonic ester. The method of the
synthesis of 6-(4-aminophenyl)-5-methyl-4,5-
dihydropyridazin-3(2H)-one (1) starting from
racemic 2-bromopropionyl bromide has been
modified to be suitable for scaling up and used
for converting it into the industrial technology.
The separation of racemic 6-(4-aminophenyl)-
5-methyl-4,5-dihydropyridazin-3(2H)-one yield-
ing R-enantiomer with the high enantiomeric
purity ((R)-enantiomer content of up to 99 %) has
been developed. It has been shown that amine
(R)-1 can be converted into Levosimendan with
the configuration retention of the chiral center
and a high yield.
Table 3. A brief summary of our results for obtaining (R)-6-(4-aminophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one (1)
NHAc
( )R
2
Cl
O
Me
Cl
( )-R 1
HN
N
O
NH2
Me
Br
O
Me
Br
Route 1
Route 2
Route 1 Route 2
– the expensive chiral starting compounda
– racemization on the malonic synthesis stage
+ high yields at all stagesb
+ 67 % total yield of the racemate
+ 24 % yield at the enantiomer separation stage
+ the separation of enantiomers up to 99 % of the
(R)‑enantiomer content
+ scalable
Notes: a “–” indicates disadvantages of the method; b“+” indicates advantages of the method
Table 4. The results of quality testing of the final sample
of Levosimendan
Parameter
Eur. Ph.
General
Chapter
Results
Appearance A dark-yellow crystalline
powder
Solubility Very slightly soluble
in ethanol (96 %)
Identification 2.2.33 Conform to the
structure
pH 2.2.3 6.00
Loss on drying 2.2.32 1.26 %
Sulfated ash 2.4.14 3.13 %
Impurities:
• individual impurity
• total impurities 2.2.29,
2.2.46
0.30 %
1.21 %
(R)-Enantiomer content up to 99 %
Assay 93.1 %
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Journal of Organic and Pharmaceutical Chemistry 2025, 23 (2)
■ Experimental part
1H NMR spectra were recorded using a Va-
rian VXR-300 instrument at 300 MHz, or a Va-
rian UNITY-Plus 400 instrument at 400 MHz.
13C NMR spectra (proton decoupled) were re-
corded on a Bruker AVANCE DRX 500 instru-
ment at 125 MHz. The chemical shifts are given
in ppm relative to TMS as an internal or exter-
nal standard.
Thin-layer chromatography (TLC) was carried
out on aluminium-backed plates coated with sili-
ca gel (Merck Kieselgel 60 F254). LC-MS spec-
tra were registered on an “Agilent 1100 Series”
instrument with a diode-matrix and an “Agi-
lent 1100 LS/MSD SL” mass-selective detector
(the ionization method – chemical ionization at
atmospheric pressure; the ionization chamber
operation conditions – simultaneous scanning
of positive and negative ions in the range of
80 – 1000 m/z).
Melting points were determined in open capil-
laries using a SMP3 instrument (Stuart Scien-
tific Bibby Sterlin Ltd, Stone, Staffordshire, UK).
Unless otherwise stated, commercially avail-
able reagents were used without purification af-
ter being purchased. The solvents were purified
according to standard procedures.
N-(4-(2-Bromopropanoyl)phenyl)acetami-
de (7)
Acetanilide 2 (30 g, 0.222 mol) in 1,2,4-trichlo-
robenzene (500 mL) was placed into a three-necked
flask equipped with a thermometer, a mechani-
cal stirrer, and an addition funnel. Anhydrous
aluminum chloride (90 g, 0.667 mol) was added
to the solution. The reaction mixture was heat-
ed to 70°С, and 2-bromopropionyl bromide (60 g,
0.25 mol) was added dropwise for ~30 min at such
a rate that the temperature did not rise higher
than 80°С. After the addition was completed,
the reaction mixture was heated at 80°С for 3 h.
The heating source was removed, and dichloro-
methane (500 mL) was added to the reaction mix-
ture at 80°С. The temperature of the reaction mix-
ture decreased to (50±5)°С. The warm reaction
mixture was slowly poured into the ice/water mix-
ture (1 L). The organic layer was separated, and
the product was extracted from water with dichlo-
romethane (5×100 mL). Dichloromethane solutions
were combined, washed with water (5×70 mL),
and dried over MgSO4. The solvent was evapora-
ted in vacuum. The residue containing product 7
and 1,2,4-trichlorobenzene was washed with hexa-
ne (5×200 mL) to remove 1,2,4-trichlorobenzene.
After removing 1,2,4-trichlorobenzene, the resi-
due was placed into the flask and dried in vacuum
(0.5 – 1 mm Hg) at 50°С for 4 – 5 h.
A yellow solid. Yield – 59 g (99 %). M. p. 118 – 120°C
(Lit. 128 – 131°C [6]). 1H NMR (300 MHz, CDCl3),
δ, ppm: 1.88 (3H, d, 3JHH = 6.6 Hz, CH3), 2.21
(3H, s, COCH3), 5.26 (1H, q, 3JHH = 6.6 Hz, CH),
7.65 (2H, d, 3JHH = 8.7 Hz, ArH), 7.98 (2H, d, 3JHH
= 8.7 Hz, ArH). (Lit. [10])
Dimethyl 2-(1-(4-acetamidophenyl)-1-oxo-
propan-2-yl)malonate (18)
Dimethyl malonate (37 g, 0.28 mol) was added
dropwise to the solution of tBuOK (31 g, 0.28 mol)
in THF (350 mL). The reaction mixture was stir-
red at room temperature (15 – 20°С) for 1 h, and
bromide 7 (60 g, 0.22 mol) in THF (300 mL) was
slowly added at the same temperature. The re-
action mixture was stirred at room temperature
(15 – 20°С) for 48 h (until the disappearance of
the starting bromide 7 by TLC, eluent hexane/
MTBE 1:5, Rf (7) = 0.3, Rf (18) = 0.2), and then
poured into water (700 mL). The pH of the solu-
tion was adjusted to 5.5 – 6 using 10 % HCl so-
lution. The product was extracted with MTBE
(4×300 mL), and the organic layer was washed
with water (3×250 mL) and dried over MgSO4.
The solvent was distilled off in vacuum (10 mm Hg),
then the residual solvent and the excess of dime-
thyl malonate were removed in vacuum (1 mm Hg,
60°С, 6 h), yielding 18 as a yellow solid (68 g, 96 %).
1H NMR (300 MHz, CDCl3), δ, ppm: 1.18 (3H,
d, 3JHH = 7.2 Hz, CH3), 2.20 (3H, s, COCH3), 3.66
(3H, s, COOCH3), 3.80 (3H, s, COOCH3), 4.00 (1H,
d, 3JHH = 10.9 Hz, CH), 4.12 – 4.14 (1H, m, CH),
7.60 (2H, d, 3JHH = 8.1 Hz, ArH), 7.95 (2H, d, 3JHH
= 8.1 Hz, ArH). LC-MS, m/z: 320 [M–H]- (nega-
tive ionization); 322 [M+H]+ (positive ionization).
4-(4-Aminophenyl)-3-methyl-4-oxobuta-
noic acid hydrochloride (19)
To compound 18 (74 g, 0.23 mol), the solu-
tion of HCl in methanol (1.4 L, c = 3 mol L–1) was
added, and the reaction mixture was refluxed
for 8 h. The solvent was removed to dryness in
vacuum, and an aqueous solution of HCl (1.4 L,
c = 6 mol L–1) was added to the residue. The re-
sulting solution was refluxed for 5 h. The sol-
vent was evaporated to dryness in vacuum, and
50 mL of conc. HCl was added to the residue.
The precipitate was filtered off and washed with
conc. HCl (10 mL) and 2-propanol (40 mL), and
dried in vacuum (1 mm Hg, 60°С, 4 h).
A brownish solid. Yield – 43.5 g (78 %). M. p.
186 – 188°C (dec.) (Lit. 187 – 188°C (dec.) [6]). 1H NMR
(300 MHz, D2O), δ, ppm: 1.16 (3H, d, 3JHH = 7.2 Hz,
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Журнал органічної та фармацевтичної хімії 2025, 23 (2)
CH3), 2.62 (1H, dd, 2JHH = 17.2 Hz, 3JHH = 4.8 Hz,
CH2), 2.85 (1H, dd, 2JHH = 17.2 Hz, 3JHH = 9.3 Hz,
CH2), 3.91-3.99 (1H, m, CH), 7.44 (2H, d, 3JHH =
8.7 Hz, ArH), 8.07 (2H, d, 3JHH = 8.7 Hz, ArH).
6-(4-Aminophenyl)-5-methyl-4,5-dihydro-
pyridazin-3(2H)-one (1)
The hydrazine hydrate solution (90 mL, 90 %
aqueous solution) was added to the solution of
compound 19 (44 g, 0.18 mol) in ethanol (500 mL).
The reaction mixture was refluxed for 5 h and
then cooled to room temperature. The solvent was
removed in vacuum to dryness. Water (50 mL)
was added to the residue. The precipitate was
filtered off, washed with water and 2-propanol,
and dried in vacuum (1 mm Hg, 50 °С, 4 h).
A brownish solid. Yield – 33 g (90 %). M. p.
193 – 195°C (Lit. 211 – 212°C [9], 195 – 197°C [6]).
1H NMR (300 MHz, DMSO-d6), δ, ppm: 1.03 (3H,
d, 3JHH = 7.2 Hz, CH3), 2.17 (1H, d, 2JHH = 16.7 Hz,
CH2), 2.59 (1H, dd, 2JHH = 16.7 Hz, 3JHH = 6.6 Hz,
CH2), 3.23 – 3.29 (1H, m, CH), 5.49 (2H, s, NH2),
6.57 (2H, d, 3JHH = 8.4 Hz, ArH), 7.48 (2H, d, 3JHH
= 8.4 Hz, ArH), 10.67 (1H, s, NH). (Lit. [5])
(R)-6-(4-Aminophenyl)-5-methyl-4,5-dihyd-
ropyridazin-3(2H)-one ((R)-1). The enantio-
mer separation using L-(+)-tartaric acid
The racemate of amine 1 (23 g, 0.11 mol),
L-(+)-tartaric acid (34 g, 0.23 mol), and 2-propa-
nol (450 mL) were placed into a flask and heated
under reflux for 30 min. The reaction mixture was
allowed to cool to room temperature overnight.
The precipitate was filtered off and dried in vac-
uum (1 mm Hg, 40°С, 5 h), yielding 45 g (100 %)
of a mixture of diastereomeric salts as a solvate
with one molecule of 2-propanol.
The mixture of diastereomeric salts was
crystallized from 2-propanol 32 times (until the
(R)-enantiomer content in the sample reached
98.6 %). The first crystallization was carried out
using activated carbon. As the amount of the pre-
cipitate used for the crystallization decreased, the
amount of the solvent decreased proportionally
(for example, 450 mL of the solvent was used for
45 g of the precipitate, and 300 mL of the sol-
vent was used for 30 g of the precipitate).
When required the (R)-enantiomer content in
the sample was reached, (R)-6-(4-aminophenyl)-
5-methyl-4,5-dihydropyridazin-3(2H)-one L-(+)-
tartrate was converted to (R)-6-(4-Aminophenyl)-
5-methyl-4,5-dihydropyridazin-3(2H)-one ((R)-1)
as follows.
An aqueous solution of potassium carbonate
was added to the suspension of (R)-6-(4-amino-
phenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one
L-(+)-tartrate (7 g, 21 mmol) in water (50 mL)
to pH 8. The precipitate was filtered off, washed
with the aqueous solution of potassium carbo-
nate (15 mL) and water (2×35 mL), and dried in
vacuum (1 mm Hg, 40°С, 5 hours), yielding 3 g
(86 %) of amine (R)-1 with the (R)-enantiomer con-
tent of 98.6 %.
(R)-6-(4-Aminophenyl)-5-methyl-4,5-dihyd-
ropyridazin-3(2H)-one ((R)-1). Enantiomers
separation using S,S-2,3-bis-(4-methoxyben-
zoyloxy)butanedioic acid (21)
The racemate of amine 1 (23 g, 0.11 mol) was
placed into a 1-L flask, ethanol (200 mL) was
added, and the suspension formed was heated
at 65°С for 30 min, followed by the addition of
S,S-2,3-bis-(4-methoxybenzoyloxy)butanedioic
acid (21) (57 g, 0.136 mol) and water (200 mL)
at the same temperature. The resulting solution
was heated at 65°С for 1 h, and then refluxed
for 5 min. The reaction mixture was allowed to
cool to room temperature. In 24 h, the precipi-
tate was filtered off and used for further crystal-
lization.
After obtaining the salt or after the prelimi-
nary crystallization, the crude precipitate was
placed into a flask, the solvent (ethanol/water 1:1)
was added, and the resulting solution was reflu-
xed for 5 – 10 min and allowed to slowly cool to
room temperature. In 24 h, the precipitate was
filtered and used for the subsequent crystalliza-
tion. For the first crystallization, approximately
the same amount of the solvent was used as for
the preparation of the salt. During the subsequent
crystallizations, the amount of the solvent was
gradually reduced (1/3 of the previous volume of
the solvent was added, the suspension was heated
to boiling, and more solvent was added in por-
tions until a clear solution was formed). The first
crystallization was carried out using activated
carbon. After the fifth crystallization, the preci-
pitate was dried in vacuum (1 mm Hg, 65°С, 1 h)
from alcohol residues and used for conversion to
the amine.
A 25 % aqueous solution of ammonia was add-
ed to the suspension of the salt of amine ((R)-1)
with acid (21) in water (~4 mL of water per 1 g
of the salt) to pH 8. The suspension was stirred
for 15 – 20 min, and the pH was again controlled.
If the medium became neutral, the solution of
ammonia was added to pH 8. The addition of the
ammonia solution was repeated until the pH of
the medium (pH 8) did not change while stirring
for 30 – 40 min. The precipitate was filtered off,
washed with water, and dried in vacuum (1 mm Hg,
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Journal of Organic and Pharmaceutical Chemistry 2025, 23 (2)
60°С, 2 h), yielding 2.8 g (12 % based on the race-
mate, 24 % based on the content of the R-enanti-
omer in the racemate) of amine ((R)-1) with the
(R)-enantiomer content of up to 99 %.
(R)-N-(4-(4-Methyl-6-oxo-1,4,5,6-tetrahydro-
pyridazin-3-yl)phenyl)-carbono-hydrazo-
noyl dicyanide (Levosimendan)
The solution of sodium nitrite (1.16 g, 17 mmol)
in water (20 mL) was added dropwise to the solu-
tion of amine (R)-1 (3.4 g, 17 mmol, the (R)-enan-
tiomer content >98 %) in a diluted HCl (prepared
from 10 mL of conc. HCl and 135 mL of water)
at 10 – 12°C. The reaction mixture was stirred at
this temperature for 10 min, and the solution of
malononitrile (1.11 g, 17 mmol) in water (20 mL)
was added dropwise at the same temperature.
The reaction mixture was stirred at room tem-
perature (20°C) for 1 h and then neutralized with
an aqueous solution of sodium acetate to pH 7.
The suspension formed was stirred for 30 min at
room temperature. The precipitate was filtered
off, washed with water (4×50 mL), and dried in
vacuum (1 mm Hg, 65°С, 4 h).
A yellow solid. Yield – 4.5 g (96 %). M. p. >210°C
(dec) (Lit. 210 – 214°C [13]). (R)-enantiomer con-
tent >98 %. 1H NMR (400 MHz, DMSO-d6), δ, ppm:
1.07 (3H, d, 3JHH = 6.4 Hz, CH3), 2.24 (1H, d, 2JHH
= 16.4 Hz, CH2), 2.65 (1H, dd, 2JHH = 16.4 Hz, 3JHH
= 6.0 Hz, CH2), 3.33 – 3.37 (1H, m, CH), 7.48 (2H,
d, 3JHH = 8.0 Hz, ArH), 7.81 (2H, d, 3JHH = 8.0 Hz,
ArH), 10.96 (1H, s, NH), 12.77 – 13.32 (1H, br.s,
NH). 13C NMR (125.6 MHz, DMSO-d6), δ, ppm:
16.8, 28.0, 34.4, 86.2, 110.7, 115.1, 117.4, 127.9,
133.0, 142.8, 152.7, 167.3. (Lit. [11]).
The (R)-enantiomer content analysis
The (R)-enantiomer content was determined
by the HPLC method on an Agilent 1260 Infini-
ty II instrument. The separation was performed
on a Lux Cellulose-3 column (250 mm × 4.6 mm
and 5 μm particle size) at a flow rate of 1.0 mL
min–1 and the UV detection at 311 nm. The column
temperature was set at 25°C. The isocratic elu-
tion was carried out using a mobile phase com-
posed of water, acetonitrile, and acetic acid
(60:40:0.1 v/v/v, respectively).
In a typical analysis system, the suitability
solution containing Levosimendan and Dextro-
simendan (0.25 mg mL–1, Clearsynth) was used.
It was previously dissolved in DMSO and then
diluted with the mobile phase. The test solution
was prepared in the same way at a concentra-
tion of about 1 mg mL–1. The volume of the in-
jected solutions was 10 μL.
Typical chromatograms of blank, system suit-
ability, and test solutions are shown in Figure 3.
The chromatographic system was considered suit-
able if the resolution between Levosimendan and
Dextrosimendan peaks calculated from the sys-
tem suitability solution chromatogram was not
less than 2.0.
The Levosimendan assay in the final sample
was carried out by the HPLC method on an Agi-
lent 1260 Infinity II instrument. A Hypersil BDS
C18 column (250 mm × 4.6 mm and 5 μm parti-
cle size) was used as the stationary phase. The
column temperature was set at 40°C. A mobile
phase mixture of acetonitrile, water, and 0.1 % tri-
fluoroacetic acid solution adjusted to pH 3.0 with
triethylamine (40:10:50 v/v/v, respectively) was
used. The isocratic elution was performed at a flow
rate of 1.0 mL min–1 with the UV detection at
375 nm.
As a reference solution, 0.1 mg mL–1 Levosi-
mendan solution, previously dissolved in DMSO
and then diluted with mobile phase, was used.
The test solution was prepared in the same way
in the same concentration. The volume of the in-
jected solutions was 10 μL.
Typical chromatograms of blank, reference,
and test solutions are shown in Figure 4. The chro-
matographic system was considered suitable if
the relative standard deviation calculated for
Figure 3. The (R)-enantiomer content test of the Levosimendan final sample, typical chromatograms: a – blank solution, b – system
suitability solution, c – test solution
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Журнал органічної та фармацевтичної хімії 2025, 23 (2)
6 injections of the reference solution chromato-
grams was not more than 2.0 %, and the peak
symmetry was not more than 2.0.
The test of related substances in the final
sample was performed by the HPLC method on
an Agilent Infinity II instrument and a Hypersil
BDS C18 column (150 mm × 4.6 mm and 5 μm
particle size) with the UV detection at 285 nm.
The column temperature was set at 30°C. Mobile
phase A was 0.2 % triethylamine solution with
pH 4.0 adjusted with trifluoroacetic acid, and
mobile phase B was methanol. The gradient elu-
tion was carried out with a gradient program
(0 – 10 min: 70 % A – 30 % B; 10 – 30 min: 40 % A –
60 % B, 30–65 min: 40 % A – 60 % B, 65–66 min:
70 % A – 30 % B, 66 – 75 min: 70 % A – 30 % B) and
the flow rate at 1.0 mL min–1.
The Levosimendan solution (0.003 mg mL–1)
was used as a reference solution. It was previ-
ously dissolved in DMSO, and then diluted with
the solvent (0.05 % trifluoroacetic acid solution
in 50 % methanol water solution). The solution
of the final sample (2 mg mL–1) was prepared for
the test in the same way as the reference solu-
tion. All solutions were prepared in amber volu-
metric flasks, and the volumes of the injected
solutions were 10 μL.
Typical chromatograms of blank, reference, and
test solutions are shown in Figure 5. The chro-
matographic system was considered suitable if
the relative standard deviation calculated for
6 injections of the reference solution chromato-
grams was not more than 5 %, and the retention
time was approximately 23 min.
■ References
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Figure 4. The assay test of the Levosimendan final sample typical chromatograms: a – reference solution, b – test solution, c – blank
solution
Figure 5. The assay test of the Levosimendan final sample typical chromatograms: a – reference solution, b – test solution, c – blank
solution
ISSN 2308-8303 (Print) / 2518-1548 (Online) 47
Journal of Organic and Pharmaceutical Chemistry 2025, 23 (2)
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Information about the authors:
Liubov V. Sokolenko (corresponding author), Ph.D. in Chemistry, Senior Researcher, Organofluorine Compounds Chemistry
Department, Institute of Organic Chemistry of the National Academy of Sciences of Ukraine; https://orcid.org/0000-0002-4757-0305;
e-mail for correspondence: sokolenko.liubov@gmail.com.
Taras M. Sokolenko, Ph.D. in Chemistry, Senior Researcher, Organofluorine Compounds Chemistry Department, Institute of Organic
Chemistry of the National Academy of Sciences of Ukraine; https://orcid.org/0000-0002-3944-5571.
Andrey A. Filatov, Ph.D. in Chemistry, Senior Researcher, Organofluorine Compounds Chemistry Department, Institute of Organic
Chemistry of the National Academy of Sciences of Ukraine; https://orcid.org/0000-0001-7050-8131.
Oleksandr D. Shchehlov, Ph.D. student of the Chuiko Institute of Surface Chemistry of the National Academy of Sciences of Ukraine;
Engineer of the API Synthesis Laboratory, JSC “Farmak”; https://orcid.org/0009-0009-7772-3083.
Vitalii V. Rudiuk, Ph.D. in Chemical Technology and Engineering, Head of the API Synthesis Laboratory, JSC “Farmak”;
https://orcid.org/0000-0003-3440-1139.
Yurii L. Yagupolskii, Dr.Sci. in Chemistry, Professor, Head of the Organofluorine Compounds Chemistry Department, Institute of Organic
Chemistry of the National Academy of Sciences of Ukraine; Scientific advisor, Enamine Ltd.; https://orcid.org/0000-0002-5179-4096.
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| id | oai:ojs.journals.uran.ua:article-322447 |
| institution | Journal of Organic and Pharmaceutical Chemistry |
| issn | 2518-1548 |
| keywords_txt_mv | |
| language | English |
| last_indexed | 2026-08-23T01:00:33Z |
| publishDate | 2025 |
| publisher | National University of Pharmacy |
| record_format | ojs |
| resource_txt_mv | ophcjnupheduua/86/645cffd94b0dc4cd8be59c9dbd0ae986.pdf |
| spelling | oai:ojs.journals.uran.ua:article-3224472026-08-22T19:54:27Z Development of a Multistage Technology for the Industrial Synthesis of the Levosimendan API and Enantiomeric Separation of Intermediates Розробка багатостадійної технології промислового синтезу АФІ левосимендану та енантіомерного розділення проміжних продуктів Sokolenko, Liubov V. Sokolenko, Taras M. Filatov, Andrey A. Shchehlov, Oleksandr D. Rudiuk, Vitalii V. Yagupolskii, Yurii L. левосимендан 4,5-дигідропіридазин-3(2Н)-он розділення енантіомерів діастереомерні солі S,S-2,3-біс-(4-метоксибензоїлокси)бутандіова кислота Levosimendan 4,5-dihydropyridazine-3(2H)-one enantiomers separation diastereomeric salts S,S-2,3-bis-(4-methoxybenzoiloxy)butanedioic acid A method for obtaining Levosimendan suitable for industrial application has been developed. Two literature routes for the synthesis have been evaluated. It has been found that the use of enantiopure (R)-2-chloropropionyl chloride in the initial step is ineffective due to racemization at the stage of the synthesis based on the malonic ester. Instead, a reported method based on the synthesis of the Levosimendan precursor, 6-(4-aminophenyl)-5-methyl-4,5-dihydropyridazin-3(2H)-one (1), from racemic 2-bromopropionyl bromide has been modified to allow for scale-up and adaptation to industrial processes. A practical resolution method has been developed to isolate the (R)-enantiomer of amine 1 from the racemic mixture with a high enantiomeric purity (the content of (R)-enantiomer is up to 99%). It has been shown that (R)-1 can be converted to Levosimendan in a high yield without the stereochemical purity loss at the chiral center. Розроблено метод одержання левосимендану, придатний для промислового використання. Перевірено два літературних методи синтезу левосимендану та з’ясовано, що використання (R)‑2-хлоропропіонілхлориду на першій стадії не ефективне через рацемізацію на стадії синтезу на основі малонового естеру. Літературний метод синтезу попередника левосимендану, 6-(4-амінофеніл)-5-метил-4,5-дигідропіридазин-3(2Н)-ону (1), було модифіковано з використанням рацемічного 2‑бромопропіонілброміду з метою зробити його придатним для масштабування та перетворення на промислову технологію. Розроблено метод виділення (R)‑енантіомеру аміну 1 з рацемату з високою енантіомерною чистотою (вміст (R)‑енантіомеру до 99%). Показано, що амін (R)-1 може бути перетворено на левосимендан зі збереженням конфігурації хірального центру та високим виходом. National University of Pharmacy 2025-06-24 Article Article application/pdf https://ophcj.nuph.edu.ua/article/view/322447 10.24959/ophcj.25.322447 Journal of Organic and Pharmaceutical Chemistry; Vol. 23 No. 2 (2025); 35-47 Журнал органической и фармацевтической химии; Том 23 № 2 (2025); 35-47 Журнал органічної та фармацевтичної хімії; Том 23 № 2 (2025); 35-47 2518-1548 2308-8303 en https://ophcj.nuph.edu.ua/article/view/322447/322352 Copyright (c) 2025 Liubov V. Sokolenko, Taras M. Sokolenko, Andrey A. Filatov, Oleksandr D. Shchehlov, Vitalii V. Rudiuk, Yurii L. Yagupolskii http://creativecommons.org/licenses/by/4.0 |
| spellingShingle | левосимендан 4,5-дигідропіридазин-3(2Н)-он розділення енантіомерів діастереомерні солі S,S-2,3-біс-(4-метоксибензоїлокси)бутандіова кислота Sokolenko, Liubov V. Sokolenko, Taras M. Filatov, Andrey A. Shchehlov, Oleksandr D. Rudiuk, Vitalii V. Yagupolskii, Yurii L. Розробка багатостадійної технології промислового синтезу АФІ левосимендану та енантіомерного розділення проміжних продуктів |
| title | Розробка багатостадійної технології промислового синтезу АФІ левосимендану та енантіомерного розділення проміжних продуктів |
| title_alt | Development of a Multistage Technology for the Industrial Synthesis of the Levosimendan API and Enantiomeric Separation of Intermediates |
| title_full | Розробка багатостадійної технології промислового синтезу АФІ левосимендану та енантіомерного розділення проміжних продуктів |
| title_fullStr | Розробка багатостадійної технології промислового синтезу АФІ левосимендану та енантіомерного розділення проміжних продуктів |
| title_full_unstemmed | Розробка багатостадійної технології промислового синтезу АФІ левосимендану та енантіомерного розділення проміжних продуктів |
| title_short | Розробка багатостадійної технології промислового синтезу АФІ левосимендану та енантіомерного розділення проміжних продуктів |
| title_sort | розробка багатостадійної технології промислового синтезу афі левосимендану та енантіомерного розділення проміжних продуктів |
| topic | левосимендан 4,5-дигідропіридазин-3(2Н)-он розділення енантіомерів діастереомерні солі S,S-2,3-біс-(4-метоксибензоїлокси)бутандіова кислота |
| topic_facet | левосимендан 4,5-дигідропіридазин-3(2Н)-он розділення енантіомерів діастереомерні солі S,S-2,3-біс-(4-метоксибензоїлокси)бутандіова кислота Levosimendan 4,5-dihydropyridazine-3(2H)-one enantiomers separation diastereomeric salts S,S-2,3-bis-(4-methoxybenzoiloxy)butanedioic acid |
| url | https://ophcj.nuph.edu.ua/article/view/322447 |
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