The synthesis of novel tricyclic β-lactams, 1, 9b-dihydro-2H, 4H-2-oxoazeto [1, 2-c] [1, 3]-benzoxazine-4-carboxylic acid (3), were examined by two approaches involving imineacid chloride cycloaddition reaction as a key step. The cyclization was found to proceed stereoselectively to form 4-(4-chlorophenyl)-1, 9b-dihydro-9b-methylthio-1-phenoxy-2H, 4H-2-oxo-azeto [1, 2-c] [1, 3] benzoxazine (8), cis-1-benzyl-4-(2-benzyloxyphenyl)-3-phenoxy- and cis-1-benzyl-4-(2-benzyloxyphenyl)-2-oxo-3-phthalimidoazetidine (16 and 17).
