RESUMEN
An efficient method for the synthesis of (+)-buergerinin F is established via the enantioselective aldol reaction of a tetra-substituted ketene silyl acetal with crotonaldehyde, followed by intramolecular Wacker-type ketalization.
Asunto(s)
Aldehídos/química , Carbono/química , Compuestos Heterocíclicos con 3 Anillos/síntesis química , Acetales/química , Etilenos/química , Compuestos Heterocíclicos con 3 Anillos/química , Cetonas/química , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Estructura Molecular , Silanos/química , EstereoisomerismoRESUMEN
Octalactin A, an antitumor agent containing an eight-membered lactone moiety, has been stereoselectively prepared by means of enantioselective aldol reactions of selected silyl enolates with achiral aldehydes, promoted by a chiral Sn(II) complex. The medium-sized lactone part was effectively constructed by way of a new and rapid mixed-anhydride lactonization using 2-methyl-6-nitrobenzoic anhydride (MNBA) with a catalytic amount of 4-(dimethylamino)pyridine (DMAP) or 4-(dimethylamino)pyridine 1-oxide (DMAPO). The use of only 5 mol % of DMAP or 2 mol % of DMAPO rapidly promoted formation of the medium-sized ring of the octalactin, demonstrating the remarkable efficiency of the new lactonization protocol.