Isolation, Partial Synthesis and Stereochemical Study of 10-Hydroxystrictosamide, a Constituent of Nauclea orientalis in Thailand

From the Rubiaceous plant, Nuuclea orientalis, in Thailand, seven nonalkaloidal and two glycosidic indole compounds were isolated.10-Hydroxystrictosamide (5) and its pentaacetyl derivative (11) were prepared to determine the C3 stereochemistry.Presently, more than forty monoterpenoid indole alkaloids have been found from the Nauclea plants.In our previous papers, we described the synthesis of Nuuclea indole alkaloids, nauclefidinel and naucleidinal.2the former of which was isolated from Nuuclea officinalis3 and the latter was found in N. lm(olia/l and N. officinalis.3In turn, by recent chemical and biological studies on the components of Nuuclea orient& native to Papua New Guinea, several monoterpenoid indole alkaloids were i ~o l a t e d , ~ some of which have an angustine skeleton exhibiting antiprolirerative activity.6Since the Nuuclea plants are potentially valuable as candidates of new medicinal resources, we have been interested in the chemical components of Nauclea orientalis growing in Thailand.In this paper, we describe the constilueuts in the leaves of N. orienralis as well as the partial synthesis and stereochemical study of 10-hydroxystrictosamide, one of the alkaloidal constituents in this plant.The plant material was collected at Chiang Rai Province of Thailand in December in 1994.The dried powdered leaves (2.9 kg) of the plant were extracted with MeOH (5x3 liters) at room temperature and then filtered.The filtrate was evaporated to give a syrupy mass (517 g), a portion (241 g) of which was partitimed with CHC13-H20.By evaporation of the CHC13 layer, the crude CHC13 extract (4.9 g) was obtained.The aqueous layer was extracted with n-BuOH to yield the extract (28.9 g) after evaporation.The CHC13 and n-BuOH extracts were respectively purified by a combination of Si02 column chromatography,