The reactions of (E,E)-1-benzyloxy-2-methylpenta-1,3-diene (9) with 3,3-dimethyl-2-(trimethylsilyloxy)butene and (Z)-3-(trimethylsilyloxy)pent-2-ene in SO2 and a Lewis acid give silyl sulfinates that are quenched with Met to generate the corresponding (Z)-4-benzyloxy-1,3-dimethylalk-2-enyl methyl sulfones with unlike relative configuration at C-l and C-4 (by X-ray diffraction studies), in support of processes involving the intermediacy of a sultine arising from the suprafacial hetero-Diels-Alder addition of SO2 to diene 9. (C) 2001 Elsevier Science Led. All rights reserved.