ASYMMETRIC SYNTHESES OF 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID-DERIVATIVES

Optically active D-erythro-4-(tert-butoxycarbonyl)-3-(dimethoxyphosphoryl)-5,6-diphenyl-2,3,5,6-tetrahydro-4H-1,4-oxazin-2-one (13) can be efficiently condensed with various aldehydes via the Emmons-Horner-Wadsworth procedure to provide alpha-beta-dehydrolactone adducts (14). It was found that the adducts (14) were smoothly cyclopropanated with the ylide of racemic [[(diethylamino)methyl]phenyl]oxosulfonium tetrafluoroborate to furnish in high chemical and optical yields the desired cyclopropanes (15). Final deblocking to the requisite amino acids was accomplished with dissolving-metal reduction. The syntheses of [H-2(2)]ACC, MeACC (norcoronamic acid), EtACC (coronamic acid), and BuACC are described.