合成路线1

The oxidation of chenodeoxycholanic acid methyl ester (I) by known methods gives the 3-oxo derivative (II), which is treated with CH2(OMe)2 and P2O5 in chloroform to yield the 7-O-Mom protected compound (III). The reaction of (III) with ethyleneglycol and TsOH in refluxing benzene affords the ethyleneketal (IV), whose ester group is reduced with LiAlH4 in THF to provide the pentanol derivative (V). The oxidation of (V) with oxalyl chloride and DMSO in dichloromethane gives the aldehyde (VI), which is condensed with the phosphonium iodide (VII) by means of BuLi in THF to yield steroid (VIII) with an unsaturated side chain. The dihydroxylation of (VIII) by means of (DHQD)2PHAL, K2OsO2(OH)4 and K3Fe(CN)6 affords the 24(R),25-dihydroxysteroid (IX), which is monoacylated with Ac2O and pyridine to provide the monoacetate (X). The dehydration of (X) by means of MsCl and TEA gives the unsaturated acetoxy compound (XI), which is reduced and hydrolyzed by means of hydroxylamine and KOH to yield the 24(R)-hydroxysteroid (XII). Elimination of the ethylene ketal and Mom protecting groups of (XII) by means of TsOH in t-butanol affords the ketosteroid (XIII).