Synthesis and biological activity of 21,22-cyclosteroids and their derivatives.

Synthesis of 21,22-cyclosteroids has been achieved starting from pregnenolone acetate. The key transformation was the Kulinkovich reaction of 17-vinyl steroids with esters. The resulting cyclopropanols were further subjected to three-membered ring-opening under various conditions including to base-, palladium or visible light-promoted isomerization and cross-coupling reaction. A number of steroidal Δ2-6-ketones and 3β-hydroxy-Δ5-enes with functional groups at C-21 - C-23 have been synthesized via the 21,22-cyclosteroids. The antiproliferative and antihormonal activity of the obtained compounds on the cell lines of prostate (22Rv1) and breast (MCF-7) cancer was studied. The androgen receptor activity was assessed by reporter assay when the expression of signalling proteins was evaluated by immunoblotting. (20S,22R)-22-Acetoxy-21,22-cyclo-5α-cholest-5-ene with the moderate antiandrogenic potency revealed IC50 values of 18.4 ± 1.2 and 14.6 ± 1.4 µM against MCF-7 and 22Rv1 cells, respectively, and its effects on the expression of AR-V7, cyclin D1 and BCL2 were explored.