| abstract |
FIELD: organic chemistry, antibiotics, chemical technology. n SUBSTANCE: invention relates to a novel method for preparing 3-substituted cephalosporins of the formula (I): n n n n wherein R 1 represents para-nitrobenzyl or allyl; X represents halogen atom. Method involves the following stages: (a) cyclization reaction of trimethylphosphine compound of the formula (IIIa): n n n n wherein R 1 represents para-nitrobenzyl or allyl; R 2 is taken among the group including (C 1 -C 6 )-alkyl, (C 6 -C 10 )-aryl, (C 6 -C 10 )-aryl-(C 1 -C 6 )-alkyl and dithianyl in solvent to form compound of the formula (II): n n n n wherein R 1 represents para-nitrobenzyl or allyl; R 2 is taken among the group including (C 1 -C 6 )-alkyl, (C 6 -C 10 )-aryl, (C 6 -C 10 )-aryl-(C 1 -C 6 )-alkyl and dithianyl, and (b) interaction of indicated compound of the formula (II) with acid. Invention relates also to compounds of the formula (I), the formula (II), the formula (III), the formula (V), and the formula (VI) given in the description that are used in the described method. Prepared compounds elicit such favorable properties as crystalline form and high excess of enantiomers. n EFFECT: improved preparing method, valuable properties of compounds. n 17 cl, 1 tbl, 15 ex |