10, X= Br, C1 butene (4) 5 by its oxidation with osmium (VII1) oxideso-dium metaperiodate. Treatment of 3 with acetic anhy-dride-triethylamine in the presence of 44dimethyl-amino) pyridine6 afforded 1 (93: 7 mixture of 2 isomer la and E isomer lb)'in 30% overall yield from 4s (Scheme