Approaches to the total synthesis of triterpenes. VIII. The ABC + D/E approach. Synthesis and X-ray structure determination of 1β,4a β-dimethyl-7-methoxy-1α- (7′,7′-ethyleneketal-6′,6′-dimethyl-3′-ketooctyl)-3,4,4a,9,10,10aα-hexahydro- 2(l-H)phenanthrone

• Published in: Canadian journal of chemistry 1982-02, Vol.60 (4), p.509-513
• Main Authors: ApSimon, John W, Sequin, Rick P, Huber, Carol P
• Format: Article
• Language: English
• ISSN: 0008-4042; 1480-3291
• DOI: 10.1139/v82-074

The title compound was made following a projected synthetic route to pentacyclic triterpenes. The key step in the route is the alkylative trapping of the enolate derived from the enol trimethylsilyl ether 8 . The stereochemical consequence of this reaction is confirmed by a single crystal X-ray structure determination on 4 , which although of no further utility in the projected synthesis, nevertheless served as a useful template for this determination. In this way, ongoing work in a parallel series of compounds rests on a firm stereochemical footing.