Synthesis of betulin derivatives and the determination of their relative using reversed-phase thin-layer chromatography

A series of superlipophilic or highly lipophilic semisynthetic betulin derivatives was prepared and their relative lipophilicity was measured by reversed-phase thin-layer chromatography (RP-TLC) at different pH values using 1,4-dioxane-acetate buffer mixtures as mobile phases. Cholesterol, 17 beta-estradiol and pure betulin were used as the reference compounds. Linear relationships were found between R-M values and 1,4-dioxane concentrations in the mobile phases. LogP values were also calculated with computer programs ACD/LogP (ChemSketch 11.0, Advanced Chemistry Development Inc.) and ClogP (Daylight Chemical Information Systems Inc.). The empirical and theoretical data were compared, and the R-Mo values correlated ell with logP. Two of the synthesized betulin derivatives are reported for the first time. Copyright (C) 2009 John Wiley & Sons, Ltd.