RESUMEN
Organocatalysis: A concise synthesis of L-pyrrolysine has been accomplished in six steps from simple starting materials. The facile synthetic strategy relies on an organocatalytic Michael addition, an efficient amide coupling, and a challenging method for the imine-bond construction.
Asunto(s)
Lisina/análogos & derivados , Amidas/química , Iminas/química , Lisina/síntesis química , Estructura Molecular , EstereoisomerismoRESUMEN
[Reaction: see text] The first chemical synthesis of dl-chamaejasmine (1), a structurally unique 3,3'-biflavanone natural product, was achieved as shown above, by a two-step sequence starting from trimethyl ether derivatives of 3-iodonaringenin (cis + trans) involving (i) metallic lanthanum-mediated reductive dimerization in refluxing THF and (ii) global demethylation with BBr3 in CH2Cl2. This synthesis represents a generally applicable biomimetic (reductive) radical dimerization approach to the 3,3'-biflavonoids.
Asunto(s)
Biflavonoides/síntesis química , Flavanonas/síntesis química , Biflavonoides/química , Biomimética/métodos , Cristalografía por Rayos X , Flavanonas/química , Lantano/química , Estructura Molecular , Oxidación-ReducciónRESUMEN
A formal total synthesis of cephalotaxine (CET), the parent structure of antileukemia Cephalotaxus alkaloids, was achieved through a novel synthesis of the pentacyclic amino enone 4 by a rapid annulation of readily available beta-(3,4-methylenedioxy)phenethylamine (2), delta-valerolactone, and bromoacetone.
Asunto(s)
Acetona/análogos & derivados , Antineoplásicos Fitogénicos/síntesis química , Harringtoninas/síntesis química , Acetona/química , Alcaloides/síntesis química , Homoharringtonina , Estructura Molecular , Pironas/químicaRESUMEN
A novel alternative synthesis of the Dolby-Weinreb enamine (2) was achieved from readily available amino dione 6 by a mild transannular Clemmensen-Clemo-Prelog-Leonard reductive rearrangement, which thus constitutes a formal total synthesis of cephalotaxine.