Synthesis and in vitro biological activity of 4 alpha-(2-propenyl)-5 alpha-cholest-24-en-3 alpha,12 alpha-diol, a 12 alpha-hydroxyl analog of 4 alpha-(2-propenyl)-5 alpha-cholest-24-en-3 alpha-ol: The latter is a potent activator of the low-density lipoprotein receptor promoter

4 alpha-(2-Propenyl)-5 alpha-cholest-24-en-3 alpha-ol (3) was shown recentl y in a Chinese hamster ovary (CHO) cell-based low-density lipoprotein recep tor/luciferase (LDLR/Luc) assay to be a potent transcriptional activator of the LDL receptor promoter in the presence of 25-hydroxycholesterol. Becaus e of the involvement of 12 alpha-hydroxylation in the metabolism of cholest erol, we are interested in investigating the effect of introducing a 12 alp ha-hydroxyl group to 3 on the transcriptional activity of the LDL receptor promoter. Thus 4 alpha-(2-propenyl)-5 alpha-cholest-24-en-3 alpha,12 alpha- diol (14), a 12 alpha-hydroxyl analog of 3, was synthesized from deoxycholi c acid via the formation of 12 alpha-[[(tert-butyl)dimethylsilyl]oxy]-4 alp ha-(2-propenyl (11). Test results show that 14 is inactive at concentration s of up to 20 mu g/ml, compared to 3 with an EC30 value of 2.6 mu M, in the CHO cell-based LDLR/Lac assay. Apparently introduction of a 12 alpha-hydro xyl group abolishes the capability of 3 alpha-sterol 14 to activate the tra nscription of the LDL receptor promoter. However, in the [1-(14)Cacetate]ch olesterol biosynthesis inhibition assay in CHO cells, 14 at 10 mu g/ml (23 mu M) is shown to inhibit the cholesterol biosynthesis by 51% relative to t he control cells. Our previous studies indicated that 3 showed a 38% inhibi tion, but 4 alpha-(2-propenyl)-5 alpha-cholestan-3 alpha-ol (1) exhibited n o inhibition in the same assay at 10 mu g/ml. In summary the results indica te that, in addition to the 24,25-unsaturation, the 12 alpha-hydroxyl group in 14 has also conferred an inhibitory effect on cholesterol biosynthesis in CHO cells; however, the inhibition of cholesterol biosynthesis by 14 doe s not lead to the transcriptional activation of the LDL receptor promoter. (C) 1999 Published by Elsevier Science Inc. All rights reserved.