Novel antibiotic analogues of cephalosporins

A process for preparing a compound of the formula:

• ##STR177## wherein R is a carboxylic acyl radical;
• B is H, CH.sub.3, OCH.sub.3 or SR wherein R is lower alkyl of 1-6 carbon atoms or phenyl;
• R.sup.1 is hydrogen or a protecting group;
• A is azido, halo, cyano, quaternary ammonium, hydroxy, carbamoyloxy, N-loweralkyl carbamoyloxy, N,N-di-lower alkyl carbamoyloxy, amino, mercapto, lower alkylthio, lower alkanoyloxy, aroyloxy or a 5-membered heterocyclic thio radical selected from the group consisting of 1-methyltetrazolylthio and 2-methyl-1,3,4-thiadiazolylthio;
• and
• X is --O--
• which comprises treating a compound of the formula:
• ##STR178## wherein X and A are as defined above;
• R.sup.1' is a blocking group;
• R.sup.4 is hydrogen or both R.sup.4 are joined to form a benzylidene with an acylating agent;
• and removal of said blocking group to form the free acid.

A compound of the formula:

• ##STR179## wherein B is H, CH.sub.3, OCH.sub.3 or SR wherein R is lower alkyl of 1-6 carbon atoms or phenyl;
• A.sup.1 is azido, halo, cyano, quaternary ammonium, hydroxy, carbamoyloxy, N-loweralkyl carbamoyloxy, N,N-di-lower aljyl carbamoyloxy, amino, mercapto, lower alkylthio, lower alkyanoyloxy, aroyloxy or a 5-membered heterocyclic thio radical selected from the group consisting of 1-methyltetrazolylthio andd 2-methyl-1,3,4-thiadiazolylthio;
• R.sup.1' is H or a protecting group;
• X is --O--,;
• and
• R.sup.6 is azido, amino, or a benzaldimino.