RESUMO
The permanganate-mediated oxidative cyclization of a series of 2-methylenehept-5-eneoates bearing different chiral auxiliaries was investigated, leading to the discovery of trans-2-tritylcyclohexanol (TTC) as a highly effective chiral controller for the formation of the 2,5-substituted THF diol product with high diastereoselectivity (dr â¼97:3). Chiral resolution of (±)-TTC, prepared in one step from cyclohexene oxide, afforded (-)-(1S,2R)-TTC (er >99:1), which was applied to the synthesis of (+)-trans-(2S,5S)-linalool oxide.
Assuntos
Cicloexanóis/química , Compostos de Manganês/química , Monoterpenos/síntese química , Óxidos/síntese química , Compostos de Tritil/química , Monoterpenos Acíclicos , Ciclização , Estrutura Molecular , Monoterpenos/química , Oxirredução , Óxidos/química , EstereoisomerismoRESUMO
A formal synthesis of eurylene is described, where both cis- and trans-THF-containing fragments were prepared using diastereo- and chemoselective permanganate-mediated oxidative monocyclizations of trienes.
Assuntos
Furanos/síntese química , Catálise , Ciclização , Furanos/química , Estrutura Molecular , Oxirredução , EstereoisomerismoRESUMO
Permanganate oxidation of farnesoate esters 12a-d afforded perhydro-2,2'-bifuranyl compounds 16a-d, with control of relative stereochemistry at four new stereocenters. Subsequent oxidative cleavage of 16a-d then provided tetrahydrofuran-containing fragments 17a-d, one of them 17b possessing the same relative stereochemistry present in the C13-C21 portion of the polyether antibiotic semduramycin (1). Control of the absolute stereochemistry was achieved through the use of the Oppolzer sultam chiral auxiliary. The requisite starting trienes were prepared stereoselectively in just three steps from geranyl chloride or neryl chloride, providing a short and versatile route to polyether fragments.