Transformations of A-seco-18αH-oleanane hydroxynitriles

Abstract

2,3-Secooleanane hydroxynitriles undergo dehydration and anionotropic 1,2-migration of the methyl group C(24)H₃ under the action of the SOCl_2-CH₂Cl₂ system to form a mixture of isomeric Δ⁴-alkenes. A similar E1-elimination process in the presence of the H₂SO₄—AcOH system is accompanied by hydrolysis of the CN group giving A-ring unsaturated C(2)-ketones and diastereomeric ε-lactones. Epimeric 4,23-epoxides and isopropyl ketone were synthesized by oxidative transformations of 4,23-alkene, which was selectively formed from 2,3-secooleanane hydroxynitrile under the action of the POCl_3-Py system. The in vitro cytotoxic evaluation by the MTT assay showed that the synthesized compounds are not toxic (IC₅₀ > 100 μmol L⁻¹) against the human cancer cell lines HEp-2, HCT116, MS, RD TE32, MCF-7, A549, and PC-3.