Structure and absolute configuration of enhydrin bromohydrin

Abstract

X-ray study of enhydrin bromohydrin, C₂₃H₂₉BrO₁₀, reveals that the crystal has space group P2₁2₁2₁ with cell parameters a =10.08, b = 26.97, and c = 8.94 Å. There are four molecules in the unit cell. The structure was solved by direct methods, with three-dimensional CuKα diffractometer data to θ= 75°, and refined by block-diagonal least squares to anR index of 11.4% for 2254 reflections. The molecule is a germacronolide sesquiterpene having acis sterochemistry at the C(1), C(10) double bond and atrans configuration at the epoxide ring, C(4)-O-C(5). The absolute configuration established on the basis of the anomalous scattering of CuKα. radiation by the bromine atom shows that the asymmetric atoms have the 4R, 5R, 6S, 7S, 8S, 9S, 20S, and 22S configurations.