Positional orientation effects in quinone dehydrogenation of 5β,14α-bufa-20(22)-enolide
Abstract
The DDQ dehydrogenation of (IV) can be directed towards formation of either a 1 : 1-mixture of (VII) and (VIII), in the presence of anhydrous hydrogen chloride, or exclusively to an α-pyran system (VI) under the influence of toluene-p-sulphonic acid.