A new highly stereoselective synthesis of cerebrosterol, an agonist of the nuclear receptor LXRs

Synthesis of 24(S)-hydroxycholesterol esters responsible for the induction of neuronal cell death

We synthesized several candidates of 24(S)-hydroxycholesterol (24S-OHC) esters, which are involved in neuronal cell death, through catalysis with acyl-CoA:cholesterol acyltransferase-1 (ACAT-1). We studied the regioselectivity of the acylation of the secondary alcohol at the 3- or 24-position of 24S-OHC. The appropriate saturated and unsaturated long-chain fatty acids were esterified with the protected 24S-OHC and then de-protected to afford the desired esters at a satisfactory yield. We then confirmed by HPLC monitoring that the retention times of four esters of 24S-OHC, namely 3-oleate, 3-linoleate, 3-arachidonoate and 3-docosahexaenoate, were consistent with those of 24S-OHC esters observed in 24S-OHC-treated SH-SY5Y cells.

A highly stereoselective synthesis of C-24 and C-25 oxysterols from desmosterol

A new highly stereoselective construction of the side chain of the C-24 and C-25 oxysterols has been achieved by using desmosterol acetate as the starting material and an improved Sharpless catalytic asymmetric dihydroxylation with 100% d.e. (diastereomeric excess) as the key step. The result is much better than the usual asymmetric dihydroxylation procedure. t-Butyl nitrite/2,2,6,6-tetramethylpiperidine N-oxyl radical/FeCl3 catalyst system was developed to activate molecular oxygen for the aerobic oxidation of 24-hydroxycholesterol and the 24-ketocholesterol was obtained in 86.2% yield. The oxidation system has never been reported before. The mechanism for the catalytic aerobic oxidation was also proposed.

A new synthesis of cerebrosterol and its 24-epimer from lithocholic acid

A new method for the synthesis of both isomers of 24-hydroxycholesterol starting from lithocholic acid is proposed.

[Synthesis of (24S)-hydroxy- and (24S)-24,25-epoxycholesterol analogues, potential agonists of nuclear LXR receptors]

A new approach to the synthesis of a series of isomeric 24-hydroxy- and 24,25-epoxysteroids starting from lithocholic acid was proposed. Sharpless asymmetric hydroxylation of intermediate delta24-olefines was used as a reaction determining the stereochemistry of target compounds. The resulting derivatives are potential agonists of nuclear receptors LXRalpha and LXRbeta and are potentially useful in the structure-function studies.