RESUMEN
Naturally occurring hyacinthacines B1 and B2 have been prepared from a common, easily available, advanced intermediate. The approach features several highly stereoselective transformations: inter alia, a dichloroketene-enol ether [2 + 2] cycloaddition, a Bruylants alkylation, and an amino-nitrile alkylation-reduction.
Asunto(s)
Productos Biológicos/síntesis química , Alcaloides de Pirrolicidina/síntesis química , Productos Biológicos/química , Modelos Moleculares , Conformación Molecular , Alcaloides de Pirrolicidina/química , EstereoisomerismoRESUMEN
The first non-chiral pool total synthesis of (+)-hyacinthacine A(1) is described. This synthesis is based on an effective [2 + 2] cycloaddition of dichloroketene to a Stericol-based enol ether, a diastereoselective dihydroxylation, and an efficient Tamao-Fleming oxidation.
Asunto(s)
Alcaloides de Pirrolicidina/síntesis química , Ciclización , Dicloroetilenos/química , Estructura Molecular , Alcaloides de Pirrolicidina/química , EstereoisomerismoRESUMEN
Three natural pyrrolizidines, (+)-amphorogynines A and D and (+)-retronecine, have been prepared from a common lactam intermediate. This central compound, in turn, was synthesized in diastereomerically enriched form through a highly selective [2 + 2]-cycloaddition of dichloroketene with a chiral enol ether, followed by Beckmann ring expansion and reduction. Subsequent stereocenters were then cleanly introduced through internal induction.