Asymmetric syntheses and lanthanide-induced CD studies of (24R and 24S) 5β-cholestane-3α,7α,12α,24,25-pentols
cholest-24-ene-3a,7a, 12a-trio1 was efficiently converted to the corresponding (24R and 24s) isomers of 5~-cholestane-3a,7a, 12a,24,25-pentols with the 0s-catalyzed Sharpless asymmetric dihydroxylation process. Utilizing a new phthalazine class of cinchona alkaloid based ligands, namely (DHQDhPHAL and (DHQhPHAL and the use of methylsulfonamide for the acceleration of the reaction rate, the enantiomeric excess achieved ranged from 9598%. The absolute configurations and enantiomeric excess of the (24R,24S)-5~-cholestane-3a,7a, 12a,24,25-pentols achieved were confirmed by the lanthanide-induced CD Cotton effect Measurements.