Compounds of formula (I)
wherein
R1 represents a hydrogen atom or a C1-4 alkyl group optionally substituted by one to three halogen atoms;
R2 and R3, which may be the same or different, each represents a hydrogen atom or a carboxyl blocking group;
R4 represents a hydrogen atom or an amino protecting group;
R5 and R6 each represents a hydroxy or substituted hydroxy group or R5 and R6 together represent a cyclic protected diol group;
Z is -S-or -SO-(α-or β-) and the dotted line bridging the 2-, 3-, and 4-positions indicate that the compound is a ceph-2-em or ceph-3-em compound; and salts and solvates thereof.
                            式(I)化合物 其中 R1 代表氢原子或任选被一至三个卤素原子取代的 C1-4 烷基;R2 和 R3 可以相同或不同,各自代表氢原子或羧基封端基;R4 代表氢原子或
氨基保护基;R5 和 R6 各自代表羟基或取代羟基,或 R5 和 R6 共同代表环状保护二元醇基;Z 为 -S-or -SO-(α-or β-),连接 2、3、4 位的虚线表示该化合物是头孢-2-em 或头孢-3-em 化合物;以及它们的盐和溶剂。