| 摘要 |
<p>An improved process for the preparation of compounds of the formula …<IMAGE>… or salts thereof, starting from compounds of the formulae …<IMAGE>… via compounds of the formulae …<IMAGE>… in which compounds R1 represent hydrogen or lower alkyl, R2 represents an organic radical which may carry a functional group which is unprotected or protected by a customary protecting group R, R3 represents hydrogen or a customary carboxyl protecting group R, W represents a group exchangeable for a thiocarboxyl radical of the formula III and Z represents oxygen or sulphur.</p> |
