2β-(N-Substituted piperazino)-5α-androstane-3α,17β-diols:: Parallel solid-phase synthesis and antiproliferative activity on human leukemia HL-60 cells

Leukemia is the most common cancer affecting children. A steroid possessing a methylpiperazine nucleus was recently reported to inhibit the proliferation of HL-60 leukemia cells. To speed up the development of this promising potential new drug, we generated libraries of analogues using parallel solid-phase organic synthesis (SPOS). A 6-step sequence of reactions, starting from dihydrotestosterone, afforded a steroidal 2,3 alpha-epoxide, which was selectively opened to give, after N-Fmoc protection, a diol with suitable stereochemistry. The difference of reactivity between 3 alpha-OH and 17 beta-OH was then used to allow the regioselective coupling of 17 beta-OH to chloro-activated butyldiethylsilane polystyrene. We next generated three libraries of 2 beta-piperazinyl-5 alpha-androstane-3 alpha,17 beta-diol N-derivatives with 1, 2, or 3 levels of molecular diversity in acceptable yields and purities for our biological screening assay. Several members of these libraries were more potent than the lead compound, especially five members with a proline as the first level of diversity and a cyclohexylcarbonyl, methylbutyryl, cyclohexylacetyl, cyclopentylpropionyl, or hexanoyl as the second level of diversity. They efficiently inhibited HL-60 cell proliferation with IC50 values of 0.58, 0.66, 1.78, 1.98, and 2.57 mu M, respectively. The present work demonstrates the potential of our SPOS approach for the optimization of a new class of cytotoxic agents.