Publications [#231785] of Steven W. Baldwin

Journal Articles

1. Ireland, RE; Baldwin, SW; Welch, SC, 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 of the American Chemical Society, vol. 94 no. 6 (March, 1972), pp. 2056-2066, American Chemical Society (ACS), ISSN 0002-7863 [doi]
   (last updated on 2026/01/21)

   Abstract:
   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.