| 摘要 |
<p>An improved process for preparing cephalosporins having a 7-position substituent of the formula:- <CHEM> wherein R<a> and R<b> represent hydrogen or alkyl or are joined to form a C3-5 cycloalkyl group, which comprises reacting a 7-amino cephalosporin with a compound of the formula:- <CHEM> wherein R<4> is hydrogen or an amino protecting group, R<1>, R<2> and R<3> are alkyl, aryl or arylalkyl and R<5> is the residue of a displaceable thioester group (R<5>SCO-) and subsequently removing the silyl group and, if necessary, the amino protecting group.</p> |
