Six-membered cyclic sulfites derived from glucofuranose and 1,2,4-butanetriol

Six-membered cyclic sulfites derived from glucofuranose derivatives 5, 6 an d from 1-O-tert-butyldimethylsilil-1,2,4-butanetriol 12 were synthesized an d separated into pure diastereomers which were in turn subjected to the seq uence of reactions leading to the introduction of the terminal vinyl ether fragment. Reactivity and applicability of cyclic sulfites as intermediates in [2+2]cycloaddition of chlorosulfonyl isocyanate (CSI) to vinyl ethers we re studied. The cycloaddition to vinyl ethers 19 and 20 proceeded in low yi eld and low asymmetric induction, in the case of the former, and moderate y ield and pronounced asymmetric induction, in the case of the latter. The H- 1-NMR spectra of sulfites 13-16 reveal a preference of the sulfite oxygen a tom for the axial position. Thus, well-defined conformation in solution for compounds 13 and 15 and a mixture of the two possible chair forms for sulf ites 14 and 16 could be assigned. The stretching frequency of the S -->O bo nd in stable conformation with an axial sulfite oxygen occurs in the range 1,160-1,210 cm(-1), whereas conformationally mobile sulfites exhibit corres ponding absorption above 1,220 cm(-1). The absolute configuration assignmen ts of sulfites 7, 8, 15, 16 and 25-28 were done empirically based on the co mbined analysis of the NMR, IR, X-ray, and dichroic data. It was demonstrat ed that the sign of the Cotton effect around 194 nm correlated with the abs olute stereochemistry at the sulfur atom in a sulfite chromophore. Chiralit y 13:533-540, 2001. (C) 2001 Wiley-Liss, Inc.