Crystal and molecular structure of adiantol B bromoacetate

Abstract

The crystal structure of adiantol B bromoacetate, C₃₁H₅₁O₂Br, has been determined by a three-dimensional X-ray analysis. The crystals are monoclinic, a= 19·138, b= 7·437, c= 9·849 Å, β= 94° 04′, Z= 2, space group P2₁. The intensities were measured with a Hilger and Watts automatic four-circle diffractometer using Mo-K_α radiation. The structure was solved by the programme SEARCH, for the automatic heavy-atom analysis, and refined by full-matrix least-squares calculations to a final R of 0·076 for 1570 independent observed reflexions. The absolute configuration was determined by the anomalous dispersion method. The rings A, B, C, and D of the triterpenoid skeleton have a chair form, and ring E is represented by the α-envelope conformation. The configuration at C(21) was S-form.