Process for the manufacture of 1-sulpho-2-oxoazetidine derivatives

Abstract

The manufacture of 1-sulpho-2-oxazetidine derivatives of the formula ##STR1## in which Het is an optionally amino-substituted, 5- or 6-membered, aromatic heterocycle containing 1 or 2 nitrogen atoms and optionally also an oxygen or sulphur atom, R.sup.1 is hydrogen, lower alkyl, phenyl-lower alkyl, lower alkanoyl, lower alkoxycarbonyl, lower alkenyl-lower alkyl, lower alkoxycarbonyl-lower alkyl, phenyl-lower-alkoxycarbonyl-lower alkyl, nitrophenyl-lower-alkoxycarbonyl-lower alkyl or carboxy-lower alkyl and R.sup.2 is hydrogen, lower alkyl, lower alkenyl, lower alkynyl, lower alkoxycarbonyl, lower alkanoyloxy-lower alkyl, lower alkoxycarbonyl-lower alkenyl, hydroxyiminomethyl, lower alkoxyiminomethyl, carbamoyl, carbamoyl-lower alkenyl or carbamoyloxy-lower alkyl, the group .dbd.NOR.sup.1 being present at least partially in the syn-form, in racemic form or in the form of the 3S-enantiomer, and of readily hydrolyzable esters and pharmaceutically compatible salts of these compounds, by acylating a compound of the formula ##STR2## in which R.sup.20 equals R.sup.2 or can also represent a 2,2-dimethyl-1,3-dioxolan-4-yl group and R.sup.3 is hydrogen or sulpho, or a salt thereof with a thioester of the formula ##STR3## in which Het is as above and R.sup.10 has any of the values of R.sup.1 except carboxy-lower alkyl, and can also represent a tri-lower alkyl-silyl-lower-alkoxycarbonyl-lower alkyl group or a carboxy-lower alkyl group converted into a readily hydrolyzable ester group, and the group .dbd.NOR.sup.10 is present at least partially in the syn-form, and carrying out subsequent steps (N-sulphonation, conversion of R.sup.20 into R.sup.2, R.sup.10 into R.sup.1), some of which are optional. The invention also provides certain novel products of formula I and benzthiazolyl thioesters of formula III per se and the preparation of the benzthiazolyl thioesters by esterifying corresponding carboxylic acids. Finally, the invention provides a process for the preparation of carboxylic acids in which R.sup.1 is t-alkoxycarbonylmethyl. The compounds of formula I have antimicrobial activity.