FIELD: organic chemistry, chemical technology.
SUBSTANCE: invention relates to a method for synthesis of an intermediate compound used in preparing quinolone antibiotic. Invention describes a method for synthesis of intermediate compound for quinolone antibiotic corresponding to the formula: 
wherein R represents (C1-C2)-alkyl, (C1-C2)-fluoroalkyl, (C2-C4)-alkenyl, methoxy-group, chlorine or bromine atom; R1 represents a substitute chosen from the group comprising (C1-C2)-alkyl, (C2-C3)-alkenyl, (C3-C5)-cycloalkyl and phenyl wherein each of them can be substituted with one or some fluorine atoms. Indicated method involves the cyclization step of mixture of quinolone precursors of the formula: 
and 
comprising 2-ethoxy-substituted intermediate substance corresponding to the formula:
in the presence of a silylating agent. Proposed method is based on unexpected result wherein by-side substances, 3-(2-alkoxyphenyl)-2-enamino-3-oxopropionic acid esters can be converted further and represent suitable intermediate compounds for synthesis of final quinolone preparations.
EFFECT: improved method of synthesis.
25 cl, 1 ex
