10538-65-5

1448-36-8

15073-97-9

Using (R)-methyl 4-((3R,5S,7R,8R,9S,10S,12S,13R,14S,17R)-3,7,12-trihydroxy-10,13-dimethylhexadecahydro-1H-cyclopenta[a]phenanthracenecarbonyl17-yl)valerate as a starting material, the methyl ester (2) was first obtained by protection of the hydroxyl group of the cholate. Subsequently, the methyl ester (2) was oxidized to the corresponding ketone (3) using N-bromosuccinimide (NBS). Next, the ketone (3) was protected as diacetate (4) and converted to the key intermediate bromide (5) by reaction with molecular bromine. Afterwards, the bromide (5) was hydrolyzed to produce the hydroxyketone (6). Finally, the target product (R)-4-((3R,5S,8R,9S,10S,12S,13R,14S,17R)-3,12-dihydroxy-10,13-dimethyl-7-oxohexadecahydro-1H-cyclopenta[a]phenanthren-17-yl)pentanoic acid methyl ester (7) was obtained by reduction of acetate and methyl ester portions and full deprotection.