| 摘要 |
<p>(4R)-3,4-trans-disubstituted azetidinones of the formula <IMAGE> in which R1 denotes hydrogen or lower alkyl, R2 denotes hydrogen or a hydroxyl-protecting group R, R3 denotes phenyl, substituted phenyl or lower alkyl and R4 denotes hydrogen or an amino-protecting group R, are valuable intermediates for the preparation of optically active penem or carbapenem compounds which act as antibiotics. The processes comprise the ring closure between carbon atoms 3 and 4 of the azetidinone ring.</p> |
