3,642 research outputs found
ChemInform Abstract: Parallel Synthesis of Dihydropyrimidinones Using Yb(III)‐Resin and Polymer‐Supported Scavengers under Solvent‐Free Conditions. A Green Chemistry Approach to the Biginelli Reaction.
No full textAn efficient synthesis of an array of 3,4-dihydropyrimidin-2-(1H)-ones using solid-supported ytterbium(III) reagent from aldehydes, 1,3-dicarbonyl compounds and urea (Biginelli reaction) under solvent-free conditions is described. Purification of each member of the library was carried out using a cocktail of acid and basic polymer-supported scavengers © 2001 Elsevier Science Ltd. All rights reserved
Asymmetric organocatalysis: From infancy to adolescence
No full textAfter an initial period of validating asymmetric organocatalysis by using a wide range of important model reactions that constitute the essential tools of organic synthesis, the time has now been reached when organocatalysis can be used to address specific issues and solve pending problems of stereochemical relevance. This Review deals with selected studies reported in 2006 and the first half of 2007, and is intended to highlight four main aspects that may be taken as testimony of the present status and prospective of organocatalysis: a) chemical efficiency; b) discovery of new substrate combinations to give new asymmetric syntheses; c) development of new catalysts for specific purposes by using mechanistic findings; and d) applications of organocatalytic reactions in the asymmetric total synthesis of target natural products and known compounds of biological and pharmaceutical relevance. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA
Design and Synthesis of New Classes of Heterocycle Glycoconjugates and Amino Acid by Asymmetric Multicomponent Reactions (AMCRs)
No full textMulticomponent Syntheses of glycoside-decorated N-heterocyclic pharmacophores
No full textWe report in this communication on the synthesis of carbohydrate decorated N-heterocycles, namely dihydropyrimidin-2-ones, dihydropyridines, and azetidin-2-ones, via multicomponent Biginelli, Hantzsch, and Staudinger reactions respectively
Unconventional organocatalytic strategies by N-heterocyclic carbene (NHC) catalysis: umpolung reactivity and beyond
No full textThe word umpolung was first introduced to Chemistry by Wittig in 1951,1 and later popularized by Seebach as “any process by which donor and acceptor reactivity of an atom are interchanged”.2 Indeed, the lone pairs present on a heteroatom X (N, O) are responsible for an alternating donor(d)/acceptor(a) reactivity in the carbon skeleton of the molecule (Figure 1); the inversion of this normal reactivity by a chemical modification (polarity reversal) is commonly defined as umpolung process
Design and Synthesis of New Classes of Heterocycle C-Glycoconjugates, and Carbon-Linked Sugar and Heterocycle Amino Acids by Asymmetric Multicomponent Reactions (AMCRs)
No full textWhile chemical efficiency relies on several factors, the multi-component reaction (MCR) approach was considered as a powerful synthetic tool for preparing target molecules of biological relevance in an efficient manner. Four classes of new bioactive molecules were designed and synthesized by asymmetric MCRs, in some cases with the cooperation of polymer-assisted solution-phase (PASP) technique. These include (a) C-glycosyl dihydropyrimidines and dihydropyridines via Biginelli and Hantzsch cyclocondensations, (b) C-glycosyl β-amino acids via Mannich- and Reformatsky-type reactions, (c) C-glycosyl β-lactams via Staudinger reaction, and (d) heterocyclic α-amino acids (glycine and alanine) via the Biginelli and Hantzsch reactions. © 2006 American Chemical Society
Critical surveys covering the year 2006: introduction and transformation of functional groups
No full textintroduction and transformation of functional groups are describe
Synthesis of Heterocycle-Linked C-Glycosyl alpha-Amino Acids and C-Glycopeptides
No full textNon-natural C-glycosyl alpha-amino acids are building-blocks for the co-translational modification of natural glycopeptides. These are key components of the complex machinery that operates in vital processes of all living organisms, ranging from eubacteria to eukaryotes. While a wide range of C-glycosyl amino acids have been synthesized, we have designed and prepared a small collection of a new class of these amino acids whose structure features a heterocycle ring holding the carbohydrate and the amino acid fragments. Isoxazole, triazole, tetrazole, and pyridine moieties were used as suitable linkers in this project owing to their easy construction via Huisgen cycloaddition and Hantzsch multicomponent reaction. Details on the synthesis of each family of these glycolconjugates are given below, some emphasis being given to the efficiency and generality of each method employed. The potential of these glycosyl amino acids in non-natural glycopeptide synthesis is exemplified by the coupling of a pyridine-linked derivative with two natural amino acids to give a non-natural glycotripeptide
Polymer supported reagents in synthesis: Preparation of bicyclo[2.2.2]octane derivatives via tandem Michael addition reactions and subsequent combinatorial decoration
No full textPreparation of bicyclo[2.2.2]octane derivatives via tandem Michael addition reactions is reporte
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