Total synthesis of (+[over]-)-methyl 3-(3-isocyano-6-oxabicyclo [3.1.0] hex-2-en-5-yl)-2-propenoate
Yung, Yat Ming
Master of Arts
(i)-Methyl 3-(3-isocyano-6-oxabicyclo OJhex-2-en-5-yl)-2-propenoate was prepared from 3tosyl-2-azabicyclo [2.2.l] hepta-2, 5-diene 14 was treated with methyl acetate carbanion in THF to afford the L-amino-oL-unsaturated ester ,15 which was converted into endo-product 1_6 by reduction with NaBHCN and CFCOOH in methanol. Compound was converted to formamide by treatment with AcO, HCOOH in pyridine. Epoxidation of was effected by treatment with m-chloroperoxybenzoic acid giving solely the exo-epoxide which was treated with t-BuOK/t-BuOH in THF to afford the desired diene ester. Epoxidation of JL9 with m-CPBA giving regio-stereospecifically the hydroxy epoxide, which was directly converted into the isocyanide by treatment with methanesulfonyl chloride and EtN in CHCl followed by the addition of phosgene. Elimination of the mesylate was effected by treatment with t-BuOK in THF-toluene (1:6) to yield the unstable Ot L-unsaturated isonitrile. The details of the experimental procedures are described.