Conformational studies. Part 7. Crystal and molecular structure of 17β-bromoacetoxy-19-nor-5α-androstan-3-one and 17β-bromoacetoxy-5α-androstan-3-one

Abstract

The crystal and molecular structures of the title compounds have been determined by X-ray crystallography. Whereas the 19-nor-derivative (1) C20H29BrO3, crystallises in the orthorhombic system, space group P212121 with Z= 4 in a unit cell of dimensions a= 6.134(1), b= 12.580(2), and c= 25.297(3)A, the other (2) C21H31BrO3, crystallises in the monoclinic space group P21 with Z= 2 in a unit cell a= 12.972(2), b= 7.321(1), c= 10.580(2)A, β= 99.71(1)°. Both structures were solved by the heavy-atom method and refined by full-matrix least-squares calculations from three-dimensional diffractometer data, to R 0.961 for 1 057 reflections (1), and R 0.042 for 1 075 reflections (2). The conformation of ring A in both molecules is affected by intramolecular packing effects. Ring A in (1) is abnormally flattened whereas in (2) it is more puckered than expected. Bond lengths and angles are normal.