ACIDES 7-(AMINO SUBSTITUE OU NON)-3-METHYL SUBSTITUE-3-CEPHEME-4-CARBOXYLIQUES

Cephalosporin derivs. of formula (I) and their salts are new. In (I) R1 is H or protecting gp. R2 is opt. substd. aryl, acylamino, aromatic heterocycle (C-bonded), triazolyl or tetrazolyl (both N-bonded). R3 is H or halo. R4 is H or amino (opt. protected or substd.) A is methyl or of formula (X) (syn or anti, or a mixt.) R5 is H or alkyl. B is H or lower alkoxy. (B) also new are cpds. of formulae (II) and (IV), and cpds. similar to (I) in which A is replaced by carbonyl (cpds. (III)), where R16 is halo. R26 is opt. substd., N-bonded, 1,2,4- triazolyl or tetrazol-2-yl.R10 is amino, R11R12.C=C(R13)NH or R14R5C=N. R11, R12, R13, R14 and R15 are H or inert organic gps. (I) are antibiotics effective against Gram negative and positive species and stable towards beta-lactamase. All cpds. tested had intravenous LD50 in mice over 3g per kg. (I) can be administered orally or parenterally in human or veterinary medicine. Cpds. (II), (III) and (IV) are intermediates for (I). 14 Cpds. (I) (and their salts and in vivo convertible esters are claimed, e.g. 7-(2-(2-aminothiazol-4-yl- 2-(Syn)-methoxyiminoacetamido)- 3-Q-ceph-3-em-4-carboxylic acid where Q is 3-acetamido-1,2,4- triazolylmethyl; furan-2-yl carboxamidomethyl; acetamidomethyl; 4-hydroxybenzyl or tetrazol- 1-ylmethyl.