HYDROXYLATED ALPHA-VINYLPYRROLIDINES FROM SUGAR-DERIVED 2,5-DIHYDROFURANS - SYNTHESIS OF (1S,2S,8AR)1,2-DIHYDROXYINDOLIZIDINE BY RING CLOSING OLEFIN METHATHESIS

Sugar-derived dihydrofurans carrying an amino function at the terminus of a two-carbon branch undergo Hg(II)-promoted cyclization to give me rcury substituted oxa-aza bicyclic compounds. Thiol promoted deoxymerc uration results in cleavage of the tetrahydrofuran ring and formation of hydroxylated 2-vinylpyrrolidines. These appear to be convenient pre cursors for the synthesis of indolizidines via ring-closing olefin met athesis. As an example the synthesis of a new lentiginosine epimer is reported.