Synthesis of optically active spiro-β-lactams by cycloadditions to α- alkylidene-β-lactams

Article abstract of DOI:10.1016/S0040-4020(98)00296-8

New optically active α-methylene-β-lactam 18 and the α-ethylidene- β-lactams 11-E and 11-Z were synthesized and submitted to 1,3-dipolar cycloadditions with diazomethane, 4-methoxybonzonitrile oxide, and diphenylnitrone as well as to epoxidation by dimethyldioxirane. All cycloadditions proceed with complete regioselectivity giving products 20 - 25 in an anti-fashion with respect to the substituent at the C-4-position of the starting β-lactam in diastereomeric ratios of about 80:20. Pure optically active compounds could be obtained in almost all cases after chromatography. Unambiguous structure elucidation could be achieved by X-ray crystal analysis and NOE investigations.