title: Cyclopentanone ring expansion leading to functionalized delta-lactams: short synthesis of simple sedum alkaloids.
abstract: Monosubstituted epoxides react with (cyclopentenyloxy)trimethylsilane to afford, after subsequent oxidative fragmentation, a pair of diastereomeric 8-membered iodolactones. When these lactones are separately treated with sodium azide, followed by reduction over Lindlar's catalyst, lactone ring contraction yields 6-membered monosubstituted lactams. When (R)-1,2-epoxypentane is used in this 5 + 3 - 2 overall ring expansion sequence, one final step involving delta-lactam to piperidine reduction yields natural (-)-halosaline and (-)-epihalosaline in five steps and 12% and 23% overall yields, respectively.
authors.affiliation: Department of Chemistry, School of Arts and Sciences, The Johns Hopkins University, Baltimore, MD 21218, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Maio
authors.forename: Sandra
authors.initials: S
authors.lastname: Sinishtaj
authors.forename: Gary H
authors.initials: GH
authors.lastname: Posner