Structures of three oxygenated 24-methyl-steroids (Nic-3, -7, and -11) from the insect repellant plant Nicandra physaloides(solanaceae): X-ray analysis of Nic-3 acetate and Nic-11 ethyl ether

Abstract

Seventeen compounds (Nic 1–17) have been isolated from aqueous extracts of the leaves of Nicandra physaloides which inhibit the feeding of certain insect larvae. X-Ray analysis of its acetate (direct methods) showed Nic-3 to be (20S,22R,24S,25S,26R)-6α,7α:22,26:24,25-triepoxy-5,26-dihydroxy-5α-ergost-2-en-1-one (3). Similar examination of Nic-11 as its ethyl ether showed it to be the 6α,7α:17,24:22,26-triepoxy-5,25,26-trihydroxy-5α-17α-ergost-2-en-1-one (6). Spectroscopic correlation of Nic-7 with Nic-3 shows the former to be the corresponding 1,12-dione (4). Snatzke's chiroptical correlation for cyclohexenones supports the assigned absolute configuration.

Biogenetic relationships between these compounds, withanolides, physalins, and the aromatic ring D steroids of the following paper are outlined.