Abstract
1,12-Dimethylbenz[a]anthracene (1,12-DMBA) cis-5,6-dihydrodiol was synthesized by oxidation of 1,12-DMBA with osmium tetroxide in pyridine in low yield (less than or equal to 3%) and was purified by sequential use of reversed-phase and normal-phase HPLC. Two pairs of 1,12-DMBA cis-5,6-dihydrodiol enantiomers, derived from P (right-handed helix) and M (left-handed helix) conformers, were eluted as a single chromatographic peak on both reversed-phase and normal-phase HPLC. However, these four enantiomers were resolved by sequential use of two chiral stationary phase (CSP) HPLC columns. CSP (Pirkle type I) columns were packed with either (R)-N-(3,5-dinitrobenzoyl)phenylglycine or (S)-N-(3,5-dinitrobenzoyl)leucine, which is ionically bonded to gamma-aminopropylsilanized silica. Absolute configurations of enantiomers were determined by comparing their circular dichroism spectra with those of conformationally similar cis-5,6-dihydrodiol enantiomers of 4-methylbenz[a]anthracene and 7,12-dimethylbenz[a]anthracene with known absolute stereochemistry.
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