title: Aziridine-Allylsilane-Mediated Total Synthesis of (-)-Yohimbane.
abstract: A total asymmetric synthesis of (-)-yohimbane and ent-alloyohimbane is reported. The synthesis utilizes a novel aziridine-allylsilane cyclization reaction as a key step in the synthesis. Treatment of optically pure aziridine-allylsilane 16 with BF(3).OEt(2) provided a mixture of aminomethyl substituted carbocycles trans-20a and cis-20b in excellent yield and modest diastereoselectivity (trans/cis 3:1). Alkylation of the tosylamide followed by oxidation of the olefin in 20 provided the lactam 38, which was converted to (-)-yohimbane and ent-alloyohimbane by a Bischler-Napieralski reaction. The synthesis provided (-)-yohimbane in eight steps and 24% overall yield (from 16).
authors.affiliation: Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy and the Comprehensive Cancer Center, The Ohio State University, 500 West 12th Avenue, Columbus, Ohio 43210-1291.
authors.forename: Stephen C.
authors.initials: SC
authors.lastname: Bergmeier
authors.forename: Punit P.
authors.initials: PP
authors.lastname: Seth