cis-1-p-Methoxyphenyl-3-vinyl-4-ethoxycarbonylazetidinone

ethyl 3-ethylidene-1-(4-methoxyphenyl)-4-oxoazetidine-2-carboxylate

4-acetoxy-1-(tert-butyldimethylsilyl)-3-ethyl-2-azetidinone

cis-1-p-anisyl-3-ethyl-4-carbethoxy-2-azetidinone