Synthesis of Phamacologically Active Compounds using Asymmetric Radical Cyclization

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Asymmetric induction in radical cyclization of N-vinylic alpha-halo amides was investigated.1, Radical cyclization of 2-bromo-N- [2- (m-methoxyphenyl) -2- phenylthio-1-ethenyl] butanamide dearing (S) -1-phenylethyl group on the nitrogen atom as a chiral auxiliary group gave the (3R,4R) -2-azetidinone as the major product, which was transformed into the intermediate for the synthesis of (+) -PS-5.2, Radical cyclization of (2R,3S) -3-acetoxy-2-bromo-N- [2- (m-methoxyphenyl) -2-phenylthio-1-ethenyl] butanamide gave the (3S,4R) -2-azetidinone as the major product, which was transformed into the intermediate for the synthesis of (+) -thienamycin.3, Radical cyclization of (2R,3S) -3-acetoxy-2-bromo-N- [2- (m-methoxyphenyl) -1-propenyl] butanamide gave the (3S,4R) -2-azetidinone as the major product, which was transformed into the intermediate for the synthesis of (-) -1beta-methylcarbapenem.4, Radical cyclization of N- (cyclohexen-1-yl) -N-methyl-alpha-haloacetamide bearting (S) -1- (1-naphethyl) ethyl group on the nitrogen atom gave the (3aR,7aR) -octahydroindol-2-one as the major product.