Покращений синтез, спектральні характеристики та просторова будова етилового естеру 2-гідрокси-8-метил-4-оксо-4Н-піридо[1,2-а]піримідин-3-карбонової кислоти

• Date: 2014
• Main Authors: Ukrainets, I. V., Bereznyakova, N. L., Taran, K. A., Davidenko, O. O.
• Format: Article
• Language: Russian
• Published: National University of Pharmacy 2014
• Subjects: гетероциклічні похідні трикарбонілметану; 2-амінопіридини; естери; 2-гідрокси-4-оксо- 4Н-піридо[1; 2-а]піримідин-3-карбонові кислоти; УДК 54.057; 542.951.1; 547.831.9; 615.28; 616.441
• Online Access: https://ophcj.nuph.edu.ua/article/view/ophcj.14.800
• Journal Title: Journal of Organic and Pharmaceutical Chemistry

The improved method for obtaining ethyl 2-hydroxy-8-methyl-4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carboxylate being of interest as a base for synthesis of antiviral medicines has been suggested. The method involves a gradual addition of the solution of 2-amino-4-methylpyridine in triethylmethanetricarboxylate used as an acylating and condensing agent, as well as a high boiling heating agent simultaneously in the excess of triethylmethanetricarboxylate preheated to 150°C. This modification allows not only to reduce considerably regeneration of triethylmethanetricarboxylate taken in excess, but practically to avoid completely the undesirable formation of by-product – 2-hydroxy-8-methyl-N-(4-methypyridin-2-yl)-4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carboxamide. It has been found by X-ray diffraction analysis that in the crystal the ethyl 2-hydroxy-8-methyl-4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carboxylate synthesized exists in the zwitterionic form with localization of the positive charge at the protonated nitrogen atom and the negative charge at the carbon atom in position 3 of the pyridopyrimidine ring. Based on the study of NMR 1H and 13C spectra the assumption that the test compound exits as an equilibrium mixture of two tautomeric forms in solution has been expressed.