| 摘要 |
<p>1503581 Preparation of ceph-2- or -3-em derivatives CIBA-GEIGY AG 24 Feb 1975 [26 Feb 1974 5 June 1974 12 Aug 1974] 7625/75 Heading C2C Compounds IA and IB (R 1 <SP>a</SP> is H or a protecting group; R 1 b is H or acyl; or R 1 <SP>a</SP> and R 1 <SP>b</SP> together form a divalent protecting group; R 2 is OH or a group which with the adjacent -CO- group forms protected carboxyl; and R 3 is H, 1-7C alkyl or a protecting group) and the 1-oxides of the ceph- 3-em compounds are prepared by cyclization of a compound II followed, where necessary, by deprotection and/or other conventional modifications.</p> |
