Synthesis of steroids fused with a pyridine at C11-C12 to accommodate the active site ceiling of cytochrome P450 8B1.

The inhibition of cytochrome P450 8B1 (CYP8B1), the oxysterol 12α-hydroxylase enzyme, is a therapeutic strategy to treat obesity, non-alcoholic fatty liver disease, and diabetes. While nitrogenous heterocycles coordinating the heme are common P450 inhibitors, previous work revealed that a compound incorporating a pyridine ring at the steroidal C12-position could not access the CYP8B1 active site due to a low ceiling 8.6 Å above the heme. Therefore, in this current study, a pyridine ring was fused at the C11-C12 position of the steroid through the condensation of a C12-ketosteroid intermediate with propargylamine and a copper catalyst in the presence of air. The oxidation states at C3 and C17 were varied as the ketone or the alcohol. These new pyridine steroid analogs bearing a 17-hydroxy group, with the 6.6 Å length from the pyridine to the C6-position, bind in the CYP8B1 active site but do not coordinate the heme iron as anticipated.