Chemical Synthesis of 7-Oxygenated 12α-Hydroxy Steroid Derivatives to Enable the Biochemical Characterization of Cytochrome P450 8B1, the Oxysterol 12α-Hydroxylase Enzyme Implicated in Cardiovascular Health and Obesity

Publication date: Available online 3 November 2018Source: SteroidsAuthor(s): Samuel D. Offei, Hadi D. Arman, Mirza Oais Baig, Lazaro S. Chavez, Carlos A. Paladini, Francis K. YoshimotoAbstractCholic acid is the endogenous 12α-hydroxylated bile acid, which possesses enhanced cholesterol absorption properties compared to its 12-desoxy counterpart, chenodeoxycholic acid. The oxysterol 12α-hydroxylase enzyme is cytochrome P450 8B1 (P450 8B1), which regioselectively and stereoselectively incorporates the 12α-hydroxy group in 7α-hydroxycholest-4-en-3-one, the biosynthetic precursor of cholic acid. Despite the vital role of P450 8B1 activity in cardiovascular health, research studies of other 12α-hydroxy steroid derivatives are rare. A synthetic route to incorporate a C12α-hydroxy group into the C12-methylene (-CH2-) in dehydroepiandrosterone derivatives is disclosed. The incorporation of the C12-oxygen was accomplished through a copper mediated Schönecker oxidation of an imino-pyridine intermediate, introducing the 12β-hydroxy group. The resulting 12β-hydroxy steroid derivative was oxidized to the C12-ketone, which was stereoselectively reduced with lithium tri-sec-butylborohydride to afford the 12α-hydroxy stereochemistry. The C7-position was oxidized to yield the various 7-keto, 7β-hydroxy, and 7α-hydroxy derivatives. Furthermore, 7-ketodehydroepiandrosterone and 12 α -hydroxy-7-ketodehydroepiandrosterone both displayed NMDA receptor antagonistic activities at 10 μM...
Source: Steroids - Category: Drugs & Pharmacology Source Type: research