The stereospecific synthesis of cis and trans 1-oxabicyclo[4,4,0]decanes and 9-methoxycarbonyl-1-oxabicyclo[4,3,0]nonanes

The allylic sulphoxides 1b and 1e reacted with 1-pyrrolidinylcyclohexene an d 2-ethoxycarbonyl cyclopentanone to yield the 2-substituted keto-sulphoxid es 10 and 14 respectively, which on reduction followed by oxidation yielded in each case a mixture of cis and trans sulphones that were separated by c olumn chromatography. Base induced cyclisation followed by reductive desulp hurisation of the cyclised sulphones yielded the corresponding bicyclic com pounds 6, 7, 8 and 9 in good yields. (C) 1999 Elsevier Science Ltd. All rig hts reserved.