ABSTRACT
Oxysterols having the second oxygen function in the side-chain region of the sterol structure are termed side-chain oxysterols. Sterols bearing a second oxygen function in addition to that at carbon-3 are termed oxysterols and have been demonstrated to possess diverse biological activities. A significant property of many oxysterols is their ability to repress HMG-CoA reductase activity in cultured mammalian cells. Oxysterols having the second oxygen function in the side-chain region of the sterol structure are termed side-chain oxysterols. In studies, 25-fluorocholesterol was prepared by treatment of 25-hydroxycholesterol with hydrogen fluoride-pyridine and its inhibition of HMG-CoA reductase in CHO-K1 cell studied. Moreover, the actions of oxysterols which depress the rate of cholesterol biosynthesis from lanosterol and possibly inhibit the 14-demethylation of lanosterol are also postulated to exert their actions by an oxysterol binding protein. As a class of compounds, side-chain oxysterols are known to be potent inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, a key regulatory enzyme in the biosynthesis of sterols.
