Caryophyllene rearrangement products. Part II. Crystal structure and absolute stereochemistry of the mono-p-bromobenzenesulphonyl ester of pseudoclovene-A-diol

Abstract

The determination of the crystal structure and absolute stereochemistry of a mono-p-bromobenzenesulphonyl ester of pseudoclovene-A-diol has established the structure and absolute stereochemistry of pseudoclovene-A. The crystals of the derivative, a substituted tricyclo[6,3,1,0^1,5] dodecane, are monoclinic, space-group P2₁, with four molecules of C₂₁H₂₉O₄SBr in a unit cell of dimensions a= 9·97, b= 21·41, c= 9·97 Å, and β= 90°. The structure was solved by the phase-determining heavy-atom method and has been refined by least-squares methods to a final residual R of 0·087 over 3072 independent reflexions estimated from photographic data. The two molecules in the asymmetric unit are closely related by a pseudo-four-fold screw axis, and have within experimental error similar conformations. In each molecule the cyclopentane ring is in an envelope conformation and the two cyclohexane rings adopt slightly distorted chair and classical boat conformations.