Structure of a cycloheptenone derivative

Racemic (1R,7S,9R)-2-methyl-6-oxobicyclo- (5.3.0)dec-2-en-9-yl methanesulfonate, C12HlsO4 S, Mr=258.3, orthorhombic, Pbca, a=8.745(2), b =33.451(5), c=8.845(2) A, V=2588A 3, Z=8, D x = 1.326 Mg m -3, 2(Mo Ka) = 0.71069 A, /z = 0.24 mm -1, F(000) = 1104, T = 298 K, R = 0.049 for 1387 unique observed reflections. The seven-membered ring adopts a boat and the five-membered ring a half-chair conformation; the ring junction is cis and the mesyloxy group axial. It had not proved possible to