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 (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