An efficient asymmetric synthesis of 3S, 4S-3-acylamino-4-hydroxymethylazetidin-2-ones
作者:Richard C. Thomas
DOI:10.1016/s0040-4039(01)93751-7
日期:1989.1
An efficient method for the synthesis of azetidinones 1 and 2 from readily available precursors is presented. [2 + 2]-Cycloaddition gives enantiomerically pure azetidinone 5 in 46% isolated yield after a single crystallization. Olefin cleavage and N-1-deprotection afford the desired products in high yield via crystalline intermediates.
Diastereospecific synthesis of novel tetracyclic β-lactams via 6-exo-trig radical cyclization
作者:Sudhir N. Joshi、V.G. Puranik、A.R.A.S. Deshmukh、B.M. Bhawal
DOI:10.1016/s0957-4166(01)00550-x
日期:2001.12
An efficient and diastereospecific synthesis of a tetracyclic, 3.6.6.4 ring system fused to a β-lactam has been achieved in high yield via 6-exo-trig radicalcyclization.
The thermally induced [3,3] sigmatropic (Cope) rearrangement of cis-β-lactams 1 having alkenyl groups at both the C3 and C4 positions to yield new functionalized eight-membered lactams (tetrahydroazocinones) 2, in racemic as well as optically pure forms, is reported. This process involves a novel, concerted C3C4 bond breakage of the β-lactam nucleus helped by ring strain.