| abstract |
Intermediates in the production of cephalosporins of formula <CHEM> wherein either alpha ) R<a> denote hydrogen or a silyl group; R<b> denotes a group of formula -OR<e>, wherein R<e> denotes hydrogen or alkyl; and R<c> and R<d> together denote a bond; or beta ) R<d> and R<a> denote hydrogen or a silyl group; and R<b> and R<c> together denote an imino group of formula = N - Y, wherein Y denotes alkyl, aryl or heterocyclyl; or gamma ) R<d> denotes hydrogen or a silyl group; R<a> denotes hydrogen, if R<d> denotes hydrogen; or, R<a> denotes hydrogen or a silyl group, if R<d> denotes a silyl group; and R<b> and R<c> together denote the oxo group; in free form or in salt form.l |