Asymmetric isopropylation of steroidal 24-aldehydes for the synthesis of 24(R)-hydroxycholesterol
作者:Makoto Okamoto、Masayasu Tabe、Takao Fujii、Toshio Tanaka
DOI:10.1016/0957-4166(95)00073-x
日期:1995.3
The chiral beta-amino alcohols-catalyzed addition of diisopropylzinc to steroidal 24-aldehydes successfully provided 24(R)-hydroxycholesterols in good yields with high diastereoselectivities, which are synthetic intermediates of 1 alpha,24(R)-dihydroxyvitamin D-3 (1). alpha,beta-Unsaturated steroidal aldehydes were found to give the corresponding isopropylated adducts in much higher yields (up to 91%) than those of saturated steroidal aldehydes.