Absolute configuration of (+)-trans-chrysanthemic acid. Crystal structure analysis of a p-bromoanilide derivative

The absolute configuration of (+)-trans-chrysanthemic acid, deduced previously from chemical considerations as 1R,2R has been confirmed by a three-dimensional X-ray analysis of a p-bromoanilide derivative using Bijvoet's anomalous dispersion method. Crystals are orthorhombic, space group P212121, with Z= 4 in a unit cell of dimensions a= 9.58(2), b= 6.06(2), c= 27.53(5)Å. The structure was solved from photographic data by the heavy-atom method, and refined by least-squares calculations to R 0.109 for 400 reflexions.