Steroidal 21-imidazolium salt derivatives: Synthesis and anticancer activity.

Nitrogen-containing steroids are known as prostate cancer therapeutics. In this work, a series of pregnane derivatives bearing an imidazolium moiety were synthesized using Δ16-20-ketones as starting material. An improved approach for the construction of the 20-keto-21-heterocycle-substituted fragment involved the rearrangement of 16,17-epoxides with HCl, followed by reaction of the formed α-chloroketone with 1-substituted imidazoles. Binding affinity analysis of the imidazolium steroids and their synthetic intermediates to human CYP17A1 showed only type I (substrate-like) interactions. The strongest affinity was observed for 16α,17α-epoxy-5α-pregnan-20-on-3ß-ol (Kd = 0.66 ± 0.05 µM). The steroid derivatives have been evaluated for antitumor activity against a range of prostate cancer cells as well as against various other solid tumor and hematologic cancer cell lines. All 21-imidazolium salts were active against the hormone-dependent prostate cancer line LNCaP. The most pronounced cytotoxicity in solid tumor and hematologic cancer cell lines was observed for intermediate product, 21-chloro-5α-pregn-16-en-20-on-3ß-ol. Among the imidazolium salts, the derivatives with a single bond were more cytotoxic than their unsaturated congeners.

Highly enantio- and diastereoselective generation of two quaternary centers in spirocyclopropanation of oxindole derivatives.

Spirocyclopropanes: Only one out of eight possible stereoisomers was obtained in the asymmetric cascade cyclopropanation of alkylidene oxindoles with ethyl 2-chloroacetoacetate. Improved catalyst design ensured that spirocyclopropyl oxindoles featuring two quaternary centers were synthesized in high yield and high enantio- and diastereoselectivity (see scheme).