The Crystal Structure of Cholesteryl δ-Monohydrofluoropentanoate

Abstract

Crystals of cholesteryl δ-monohydrofluoropentanoate (CδHFP), C₃₂H₄₆O₂F₈, are orthorhombic, space group P2₁2₁2₁ with cell dimensions a= 11.278(1), b = 46.511(4), c = 6.207(2)A, and Z = 4. The C(17) cholesterol side chains have in almost fully extended conformation, but the δ-monohydrofluoropentanoate chain bends out of the lath-like cholesterol skeleton by a gauche conformation about C(31)-C(34) bond. Molecular packing in the crystal structure is a unique bilayer structure which may be caused by the bend. The non-existence of a mesophase in CδHFP is explained by the bend of the δ-monohydrofluoropentanoate chain out of the cholesterol skeleton.