New cephalosporin derivatives of the formula: ##STR1## in which R' represents a protected carboxyl radical, Hal represents a halogen atom, X.sub.1 represents a sulphur or oxygen atom or a sulphinyl radical and R represents an acyl radical or an amine-protecting radical, are useful as intermediates for the preparation of cephalosporins having antibacterial activity.
新的
头孢菌素衍
生物的
化学式:##STR1## 其中R'代表一个受保护的羧基,Hal代表一个卤素原子,X.sub.1代表一个
硫或氧原子或一个亚砜基,R代表一个酰基或一个
氨基保护基,可用作制备具有抗菌活性的
头孢菌素的中间体。