Enantioresolution and Chameleonic Mimicry of 2-Butanol with an Adamantylacetyl Derivative of Cholic Acid

Abstract

[3β,5β,7α,12α]-3[(Adamantyl-1-acetyl)-amino]-7-12-dihydroxycholan-24-oic acid (AdCH2CA) was synthesized by the reaction between 1-adamantyl acetyl chloride and the methyl ester of 3β-amino-cholic acid and hydrolysis of the ester. The acid was recrystallized from racemic 2-butanol (0.1% water). Crystals are orthorhombic (P212121) and form inclusion complexes with water and 2-butanol with a 1:1:1 stoichiometry. Only the S-enantiomer is included into the structure of the crystal, exhibiting a chameleonic mimicry with the steroid bilayers. The isolation of crystals allows the enantioresolution of the racemate with a high purity (≈99%) of S-2-butanol. The steroid molecules are disposed in an antiparallel orientation in the hydrophobic layer and a parallel orientation in the hydrophilic one.