A general, efficient, and conceptually new approach to the total syntheses of marine-derived indole alkaloids, including (+/-)-flustramines A (1) and B (2), (+/-)-flustramides A (3) and B (4), and (+/-)-debromoflustramine B (5), is outlined. The key step in the syntheses involves the conjugated addition of an organomagnesium species derived from prenyl bromide to 2-hydroxyindolenines. Compounds 1, 2, and 5 have been synthesized in five steps with 23%, 17%, and 16% overall yield, respectively, whereas flustramides 3 and 4 have been synthesized in only four steps with 24% and 18% overall yield, respectively, on the basis of 2-hydroxyindolenines.

No abstract

Two new diteipene glycosides, 8-0^-D-xylopyranosyl-«sf-8P-hydroxylabdan-15-oic acid II] and 8-0-ß-D-glucopyranosyl-«z/-8ß-hydroxylabdan-15-oic acid 12], were isolated from Heterotbalamus alienus. Their structures were elucidated by nmr spectroscopy, and their absolute configurations were determined by tranformation of both natural products into methyl -8ß-1^ ^ 8 -15-oate. The sugar residues were identified after acid hydrolyses of the two natural products.The small genus Heterothalamus is composed of ca. seven species which are primitives from South America (1,2), and to our knowledge there are only limited studies of this genus (3,4). This paper describes the chemical study of Heterothalamus alienus (Spreng.) O.Kuntze (Compositae), a very ramified shrub which grows in the mountains near San Luis and Comechingones, Argentina and is often used as an ornamental (1,2). RESULTS AND DISCUSSIONThe MeOH extracts of H. alienus afforded two new diterpene glycosides: 8-0-ß-xylopy anosyl-e«É-8ß-hydroxylabdan-15-oic acid [1] and 8-0^-D-glucopyranosyl-e«iß-^ ^ -15 -oic acid [2],

No abstract