Chiral-phase high-performance liquid chromatography of rotenoid racemates.
The high-performance liquid chromatographic (HPLC) behavior of parent rotenoids (type I) and the hydroxy-analogues (type II) on three different chiral stationary phases (CSPs) was studied. Separations of optical isomers were achieved in various degrees depending largely upon the rotenoidal structures and the CSP types employed. Enantiomers of all but elliptone compounds were separable on beta-cyclodextrin-bonded silica (CDS). Without exception, the 12a-hydroxyrotenoid antipodes were resolved on Pirkle's phenylglycine-bonded silica (PGS) despite unsuccessful attempts to resolve the type I rotenoidal racemates. Conversely, optical resolution of the latter rotenoids was accomplished by using a helical polytriphenylmethylacrylate-coated silica (TPS) column and the observed separation factors (alpha values) ranged from 1.14 to 1.90. The results from HPLC of type II rotenoids on TPS (alpha = 1.00-1.63) suggested that variations in E-ring structures had profound influence on the resolution outcome. Conjugated double bonds on the E-ring and the desisopropylation of the five-membered E-ring of type II rotenoids appeared to be important structural features for chiral recognition involving the TPS substrate. In both reversed-phase (CDS) and normal-phase (PGS and TPS) HPLC modes, the less polar enantiomers were the 6a beta,12a beta-rotenoids as observed in most cases, though this relationship was reversed in the cases of deguelin and hydroxyelliptone probably due to conformational effects of rotenoidal ring systems.
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U.S. Fish and Wildlife Service, National Fishery Research Center, La Crosse, WI 54602-0818.
D002851:Chromatography, High Pressure Liquid; D007202:Indicators and Reagents; D012402:Rotenone / Q000031:analogs & derivatives* / Q000032:analysis; D013237:Stereoisomerism
D007202:Indicators and Reagents; D012402:Rotenone