A partial synthesis of (-)-shinjulactone H from (+)-quassin
摘要:
A partial synthesis of (-)-shinjulactone H (3) from (+)-quassin (1) required the selective manipulation of two similar O-methyldiosphenol groups. Protection of the delta-lactone in 1 as an ortho ester, selective reduction of the C-1 carbonyl group, hydrolysis of the resulting enol ether in the A ring, and catalytic hydrogenation of the O-methyldiosphenol in the C ring delivered an intermediate possessing an alpha-ketol group in the A ring and an alpha-methoxy ketone group in the C ring. Demethylation and concomitant alpha-ketol tautomerization in the A ring delivered (-)-shinjulactone H (3).
New Quassinoid Glucosides, Picrasinoside-A, -B, -C, -D, -E, -F, and -G and New Hemiacetals, Picrasinol-A and -B, from the Stem Bark of<i>Picrasma ailanthoides</i>PLANCHON
New quassinoid glucosides, picrasinoside-A, -B, -C, -D, -E, -F, and -G and new quassinoid hemiacetals, picrasinol-A and -B, were isolated from the stem bark of Picrasma ailanthoides PLANCHON, and their structures were established by spectral analyses and chemical transformations.
A novel quassinoid glucoside picrasinoside-A was isolated from Pierasma ailanthoides PLANCHON and the structure was established from spectral data, chemical transformations into picrasin B and quassin, and enzyme hydrolysis. The aglycon picrasin B showed a significant clastogenic activity in cell cultures of Don lung cells of Chinese hamster.