Takahiko Tsuyuki

Astrogorgiadiol and astrogorgin, inhibitors of cell division in fertilized starfish eggs, from a gorgonian astrogorgia sp.

A novel secosterol, astrogorgiadiol(1), a known diterpene ophirin(2) and a closely related diterpene, astrogorgin(3), have been isolated from a gorgonian Astrogorgia sp. as inhibitors of cell division in fertilized starfish eggs.

Bitter principles of Picrasma ailanthoides planchon. Nigakilactones A, B, C, D, E and F

Abstract Five new crystalline bitter principles were isolated from the stem-chips of Picrasma ailanthoides Planchon (Simaroubaceae). Structures of nigakilactones A, B, C, E and F were shown to be II, III, IV, V and VI, respectively. A sixth constituent, nigakilactone D, was proved to be identical with quassin (I).

Bitter principles of Picrasma ailanthoides Planchon : Nigakihemiacetals A, B and C, and nigakilactones G, H and I

Abstract Three new crystalline bitter principles, nigakihemiacetal A (I), nigakihemiacetal C (IIIa) and nigakilactone H (V), have been isolated from the stem-chips of Picrasma ailanthoides Planchon (Simaroubaceae), and their structures determined. The other three bitter constituents, nigakihemiacetal B, nigakilactone G and nigakilactone I proved to be identical with neoquassin (II), picrasin A (IVa) and picrasin B (VI), respectively.

Two new quassinoid glycosides, yadanziosides N and O isolated from seeds of Brucea javanica (L.) merr

Two new quassinoid glycosides, yadanziosides N and O (1 and 2), were isolated from “Ya-dan-zi”, seeds of Brucea javanica (L.) MERR and the aglycone (4) of 2 was found to exhibit an antitumor activity against the murine P388 lymphocytic leukemia.

Mechanism of formation of unusual photodegradation products from friedelin

Abstract From the photolysate of friedelin1, 3,4-seco-3-nor-friedelan-2-al2 and 3,4-seco-3-nor-friedelan-2-oic acid3 were obtained in addition to the expected photoproducts. Evidence is provided that2 and3 are autoxidation products of the ketene13 produced by α-cleavage of1 followed by hydrogen transfer.

Conversion of ailanthone into shinjulactone C through an ionic [4+2] cycloaddition reaction

Abstract Ailanthone was converted into shinjulactone C with a 1α,12α: 5α,13α-dicyclo-9β H -picrasane skeleton. The key reaction consists of an intra-molecular ionic [4+2] cycloaddition between a pentadienyl cation and an olefin.

The occurrence of 19,28-bisnorlanostane derivatives in a plant fossil: A novel geochemical degradation process of triterpenoids

Abstract Four novel triterpene ketones bearing 24-methyl-28-nor- and 24-methyl-19,28-bisnor-5α-lanostane skeletons were identified in a fossil of a stem of a plant belonging to the Lauraceae family. The structures of these compounds have been determined by comparison of their spectral data with those of authentic specimens derived from lanosterol and 24-methylenecycloartanol. This is the first finding of compounds bearing a 19,28-bisnorlanostane skeleton, which implies a novel possible microbiological pathway of degradation of lanostanes in the sedimentary environment.

Revised structures of cymbopogone and cymbopogonol

Abstract The structures of cymbopogone and cymbopogonol were revised to D:A-friedo-18β,19αH-lupan-3-one and D:A-friedo-18β,19αH-lup-4(23)-en-3β-ol, respectively.