The present invention provides novel
thioester derivatives of thiazolyl
acetic acid of the general formula (I),wherein, R1 represents H, trityl, CH3, or CRaRbCOOR3, in which Ra and Rb, independently of one another, represents
hydrogen or methyl and R3 represents H or C1-C7
alkyl; and R2 represents C1-C4
alkyl or phenyl. The invention also provides a method for preparation of the
thioester derivatives and reaction of the
thioester derivatives with
cephem carboxylic acids to produce
cephalosporin antibiotic compounds having general formula (II),wherein, R1 represents H, trityl, CH3, or CRaRbCOOR3, in which Ra and Rb, independently of one another, represents
hydrogen or methyl and R3 represents H or C1-C7
alkyl; R4 is CH3, -CH=CH2, CH2OCH3, CH2OCOCH3,and R5 is H or a salt or a carboxylic
protecting group, comprising,acylating a compound of formula (III),wherein, R4 and R5 are defined as above, and R6 is H or
trimethylsilyl;with a compound of formula (I).