Experiments Directed toward the Total Synthesis of Terpenes. XVII. Development of Methods for the Synthesis of Pentacyclic Triterpenes Based on a Mechanistic Interpretation of the Stereochemical Outcome of the Friedel–Crafts Cyclialkylation Reaction
Journal Article
The α-methylene ketone 11 was prepared and found to undergo conjugate addition with m-methoxybenzylmagnesium chloride with great facility. The initial adduct was trapped with acetic anhydride, and the resulting enol acetate 12 was used either in methylation experiments to prepare vicinal-dimethylated ketone 13 or to generate the ketone 16 by saponification. Cyclization of the former ketone 13 with polyphosphoric acid served to delineate a route to β-amyrin-type triterpenes, while polyphosphoric acid cyclization of the product from methyllithium and the latter ketone 16 provided a means for the construction of friedelin-type triterpenes. The stereochemical outcome of the latter cyclialkylation reaction is interpreted in the light of recent mechanistic concepts. © 1972, American Chemical Society. All rights reserved.
Full Text
Duke Authors
Cited Authors
- Ireland, RE; Baldwin, SW; Welch, SC
Published Date
- March 1, 1972
Published In
Volume / Issue
- 94 / 6
Start / End Page
- 2056 - 2066
Electronic International Standard Serial Number (EISSN)
- 1520-5126
International Standard Serial Number (ISSN)
- 0002-7863
Digital Object Identifier (DOI)
- 10.1021/ja00761a044
Citation Source
- Scopus