10 一點〓の新ステロール,ネルビステロール,サイクロネルビラステロール,及びジヒドロサイクロネルビラステロールの構造

抄録

Sterol components of Nervilia purpurea SCHLECHTER (I-tiam-hong), an Orchidaceous plant, were examined. Repeated silica gel chromatography of the neutral fraction of the etherial extracts gave two sterol fractions. The more polar fraction was further purified by column chramatography on 20% AgNO_3-SiO_2 and preparative TLC using AgNO_3-SiO_2 plates to give a new sterol, nervisterol (7a), and seven known sterols: 24-epi-brassica-sterol (1a), campesterol (6a), ergosterol (8), stigmasterol (2a), 22-dehydro-24-isopropylcholesterol (3a), 24-isopropylcholesterol (4a), and 24-isopropenylcholesterol (5a). Of these, 3a, 4a, and 5a, having unusual hydrocarbon side chains, have recently isolated from marine invertebrates. Our present result provided the first example of isolation of these non-conventional sterols from terrestrial sources. Another sterol fraction (substance MB) was also separated by preparative TLC on 20% AgNO_3-SiO_2 to give two new sterols: cyclo-nervilasterol (9a) and dihydrocyclonervilasterol (12a). Structures of these novel sterols were deduced on the basis of chemical and spectroscopic evidence.