Synthesis of functionalized furopyrazines as restricted dipeptidomimetics
摘要:
Herein, an efficient synthetic approach to a furopyrazine scaffold with four points of diversity, starting from 2(1H)-pyrazinones, with dipeptomimetic properties, is presented. R-groups corresponding to amino acid side chains were introduced during the 2(1H)-pyrazinone and subsequent furopyrazine formation. The furopyrazine scaffold was further functionalized with an amino- and a carboxy-terminus resulting in a conformationally restricted dipeptidomimetic scaffold. The carboxy-terminus was introduced via a chemoselective vinylation of the 7-position followed by oxidative cleavage, while the amino-terminus was obtained via Buchwald-Hartwig amidation of the 2-position of the scaffold. The versatility of the synthetic method was demonstrated by the synthesis of a small library of diversely substituted furopyrazines having various amino acid side chains on the four points of diversity. Evaluation with an X-ray structure of the scaffold and computational analysis supports the exploitation of the furopyrazine scaffold as a restricted dipeptide mimic, which can mimic the two central residues of a beta-turn. (C) 2012 Elsevier Ltd. All rights reserved.
Ag<sup>+</sup>-Mediated Synthesis of Substituted Furo[2,3-<i>b</i>]pyrazines
作者:Erik Van der Eycken、Denis Ermolat’ev、Vaibhav Mehta
DOI:10.1055/s-2007-992358
日期:——
A highly efficient method for the preparation of trisubstituted furo[2,3-b]pyrazines has been developed. Sonogashira coupling reaction with the readily available 1-(4-methoxybenzyl)-3,5-dichloropyrazin-2(1H)-ones was followed by silver-catalyzed heteroannulation to provide the corresponding 2-chlorofuro[2,3-b]pyrazines in excellent yields. The latter were subjected to Suzuki or Buchwald-Hartwig coupling reaction for further decoration.
The First Palladium-Catalyzed Desulfitative Sonogashira-Type Cross-Coupling of (Hetero)aryl Thioethers with Terminal Alkynes
作者:Vaibhav Pravinchandra Mehta、Anuj Sharma、Erik Van der Eycken
DOI:10.1021/ol800054b
日期:2008.3.1
An unprecedented desulfitative Sonogashira-type cross-coupling protocol is exemplified by the synthesis of substituted 5-chloro-3-alkynylpyrazinones from the corresponding 5-chloro-3-(phenylsulfanyl) pyrazin-2(1H)-ones. The applicability of the method is extended to solid-phase linked pyrazin-2(1H)-ones as well as to some oxazinones, pyrazines, and phenyl thioesters.