Tatsushi Murae

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.

Synthesis of bruceantin skeleton

Abstract A stereoselective synthesis of a compound (3), which satisfies all requirements for bruceantin skeleton and has preferable functional groups at suitable positions for the total synthesis of bruceantin, is described.

Shinjulactone C, a new quassinoid ith a 1α, 12α:5α, 13α-dicyclo-9β-picrasane skeleton from SWINGLE

Abstract A new non-bitter quassinoid, named shinjulactone C ( 1 ), was isolated from the root bark of Ailanthus altissima SWINGLE and shown to be 1α, 12α:5α, 13α-dicyclo-1β, 12β, 20-trihydroxy-9β H -picras-3-ene-2, 11, 16-trione by X-ray diffraction method.

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.

A formal synthesis of bruceantin

Abstract A 15-deoxybruceolide derivative (3) whose total synthesis had been achieved previously was converted into bruceantin (1).

Synthesis of bruceantin precursor: 15-deoxybruceolide

Abstract A 15-deoxybruceolide, 11,12-di-O-acetyl-3-O-t-butyldimethylsilyl ether ( 3 ), was synthesized stereoselectively starting from the previously reported ABCE tetracyclic alcohol ( 5 ). The authentic sample of 3 was derived from naturally occurring brusatol ( 2 ).