Allylpotassium derivatives were prepared from a variety of olefins by using Schlosser's base (BuLi/KOt-Bu). Reaction with (20S)-20-(iodomethyl) pregnane i-methyl ether (1) followed by deprotection gave in high yields a wide variety of and A24 (2a) sterols, including the naturally occurring desmosterol (37), fucosterol (33),