GB2300856A — Beta-lactam preparation

USPTO Abstract

A compound of formula (I) or a salt thereof: wherein R is a substituent group, R 1 is hydrogen, methoxy or formamido; R 2 is an acyl group; CO 2 R 3 is a carboxy group or a carboxylate anion, or R 3 is a readily removable carboxy protecting group (such as a pharmaceutically acceptable in vivo hydrolysable ester group); and X is S,SO,SO 2 ,O or CH 2 , is prepared by base induced cyclisation of a compound of formula (II): ```where R' is alkyl or aryl, and R, R 1 , R 2 , R 3 , R 4 , X, and m are as defined in formula (I). A compound of formula (II) is prepared by reacting the corresponding novel compound in which the P(=O)(OR') 2 group is replaced by halogen with a phosphite of formula P(OR') 3 .