1996 Merck Frosst Award Lecture Synthetic adventures along a Rocky Mountain road

Abstract

This paper describes the chemistry presented during the Merck Frosst Centre for Therapeutic Research Lecture Award given at the 79th Chemistry in Canada Conference held in St. John's, Newfoundland in June 1996. The first section describes the synthesis of (+)-xestoquinone using an asymmetric palladium-catalyzed polyene cyclization as the key step that creates the C and D rings and the stereogenic centre (68% ee) in one step. Extensions of the work involving an in situ Suzuki reaction are presented. The synthesis of C2-symmetric biaryls and the synthesis of a recently isolated binaphthyl natural product is described using this new method. A new one-pot desilylation–oxidation procedure of silyl ethers is described in detail for the preparation of aldehydes and ketones directly without the need for the isolation of the alcohol intermediate. Finally, a highly diastereoselective (>97%) Diels–Alder reaction is presented using (+)-cis,cis-spiro[4.4]nonane-1,6-diol as a new chiral auxiliary. One of the alcohols is attached to a pivalate, the other to an acrylate, and the Diels–Alder reaction with cyclopentadiene provides only one adduct (by 1H NMR and HPLC) with the endo stereochemistry. Keywords: (+)-xestoquinone, asymmetric palladium-catalyzed polyene cyclization, in situ Suzuki reaction, desilylation–oxidation reaction, spirodiols, chiral auxiliaries.