This invention provides a process for preparing azetidinones useful as intermediates in the synthesis of penems and as hypocholesterolemic agents, particularly for azetidinones substituted in the C 3 and C 4 positions and optionally substituted at the ring nitrogen, comprising reacting a β amide, a β acid ester, or {HEAD ~ a β thiolcarbonic acid ester} with a silylating agent and {TAIL ~ a cyclizing agent} 
with
This invention provides a process for preparing azetidinones useful as intermediates in the synthesis of penems and as hypocholesterolemic agents , particularly for azetidinones substituted in the C 3 and C 4 positions and optionally substituted at the ring nitrogen , comprising reacting a β amide , a β acid ester , or { HEAD ~ a β thiolcarbonic acid ester } with a silylating agent and { TAIL ~ a cyclizing agent }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL