The cationic carbocyclisation of the allyl silane substituted beta-hyd
roxycobaloxime (+)-4 was effected by treatment with catalytic amounts
of pTSA to form the cyclopentane derivative (+)-5 which was elaborated
to the aldehyde (-)-7 via the alcohol (-)-6. Both the optical rotatio
n of (-)-7 and the ee of (-)-6 determined by Mosher esterification rev
ealed that (+)-5 had been formed in an enantiospecific fashion with re
tention of configuration at the inducing stereogenic centre. (C) 1998
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