Process for the selective preparation of Z-isomers of 3-(2-substituted vinyl)cephalosporins

摘要

Z-Isomers of compounds of general formula (IV): [wherein R1 is 2-(2-N-protected aminothiazol-4-yl)-2-alkoxyiminoacetyl or the like, R2 is hydrogen or the like; R3 is hydrogen, a carboxyl-protecting group or the like; and R8 is alkyl or the like] can be prepared at high selectivities and in high yields by reacting a compound of general formula (I): [wherein R1, R2 and R3 are each as defined above; and R4 is aryl or the like] with a 4-substituted or -unsubstituted thiazole-5-carbaldehyde in a mixed solvent comprising a chlorinated hydrocarbon and a lower alkanol at a temperature of as low as +5 °C or below.