Formation and reactions of ethyl 2,2-dimethyl-7-oxo-4-oxa-1-azabicyclo[3.2.0]heptane-6-carboxylate, a penam analogue

Abstract

U.v. irradiation of ethyl 2-diazo-3-(4,4-dimethyloxazolidin-3-yl)-3-oxopropionate (3) gives a product whose spectroscopic properties and reactions are consistent with its formulation as ethyl 2,2-dimethyl-7-oxo-4-oxa-1-azabicyclo[3.2.0]heptane-6-carboxylate (1d). Nucleophilic reagents rapidly cleave the β-lactam ring of compound (1d)[e.g. treatment with benzylamine yields the benzylamide (4a)]. In solution in carbon tetrachloride (1d) is converted into the 14-membered ring dilactone (7). The structures of compounds (4a) and (7) are supported by independent syntheses.