Asymmetric Conjugate Addition of Crotylstannane: Synthesis of (-)-Lasiol

Abstract

Lasiol, the major component of the mandibular gland secretion, serves as the primary sex attractant of the male ant, Lasius meridionalis. Our interest in lasiol stems from the stereochemistry of the chiral methyl substituents and the synthetic challenges posed by this common structural motif. As such, an asymmetric 1,4-conjugate addition of an allylic stannane to produce the 1,2-anti-dimethyl arrangement with high stereocontrol has resulted in the synthesis of (-)-lasiol.

Asymmetric Total Synthesis of Fawcettimine-Type Lycopodium Alkaloid, Lycopoclavamine-A

“…For the conjugate addition, we commenced with the preparation of bicyclic enedione compound 12 from commercially available crotonamide 15 (Scheme ). Weinreb amide 14 , which was prepared via the diastereoselective Hosomi–Sakurai allylation , of 15 , was coupled with an alkynyl anion prepared from trimethylsilyl (TMS) acetylene to give alkynyl ketone 17 . A three-step operation that included the stereoselective reduction of the carbonyl group in 17 with ( S )-Corey–Bakshi–Shibata (CBS) reagent, ,, methoxymethyl acetal (MOM) protection of the resulting secondary hydroxyl group, and the removal of the TMS group affording enyne compound 18 .…”