FIELD: medicine.
SUBSTANCE: invention relates to medicine, pharmacology and chemical-pharmaceutical industry, specifically to a novel improved method of producing sodium (4R,12aS)-N-(2,4-difluorobenzyl)-7-hydroxy-4-methyl-6,8-dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1',2':4,5]pyrazino[2,1-b][1,3]oxazine-9-carboxamide (compound of formula (II)). Method involves reaction of (4R,12aS)-N-(2,4-difluorobenzyl)-7-hydroxy-4-methyl-6,8-dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1',2':4,5]pyrazino[2,1-b][1,3]oxazine-9-carboxamide with sodium hydroxide in a mixture of solvents consisting of methylene chloride, alcohol and tert-butyl methyl ether in volume ratios of 2.00:1.00:1.00-10.00:10.00:1.00, respectively.
EFFECT: disclosed method enables to achieve high output and/or purity of the end product.
6 cl, 5 tbl, 1 ex
