On the reduction of quassin

✍ Scribed by Paolo Ceccherelli; Massimo Curini; Marco Diamantini; Maria Carla Marcotullio; Giuliano Grandolini

• Book ID: 104205047
• Publisher: Elsevier Science
• Year: 1987
• Tongue: French
• Weight: 333 KB
• Volume: 43
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)89950-6

✦ Synopsis

The reduction of quassin (3) with sodium borohydride in the presence Of alkali was investigated. The process appeared to be regio-and stereo-selective leading to &, which was utilized for the preparation of Z-epi-castelanolide-methylcthcr (G). The structure of quassfn, _?_a, the most famous member of the quassinoid family, was elucidated by ValeI-&, culminating a study started by Clark2 on the isolated of Quassia wood. Despite the large amount of information accumulated defining most of the chemical properties of quassin, little is known on the reduction of this compound, except for its transformation into neoquassin, z, by interaction with sodium borohydride or diisobuthyl-aluminium hydride. 3,4

RESULTS and DISCUSSION

This report details attempts to achieve positional selectivity in the sodium borohydride reduction 5 of the car-bony1 groups of quassin, for the preparation of more complex quassinoids.

The carbonyl functions at C-l and C-11 of s proved to be unexpectedly inert toward sodium borohydride. When the reaction was carried out in the presence of aqueous base at 60°C and quenched with acetone