Synthesis of alkyl 4,6-di-o-acetyl-2,3-dideoxy-α-d-threo-hex-2- enopyranosides from 3,4,6-tri-o-acetyl-1,5-anhydro-2-deoxy- d-lyxo-hex-1-enitol (3,4,6-tri-o-acetyl-d-galactal)
TL;DR: In this article, Stannic chloride-catalysis was used for rearrangement of 3,4,6-tri-O -acetyl-1,5-anhydro-2-deoxy-d -hex-l-enitol.
About: This article is published in Carbohydrate Research.The article was published on 1979-01-01. It has received 77 citations till now. The article focuses on the topics: Glucal & Allylic rearrangement.
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TL;DR: Glycals (or usually their O-substituted derivatives) are readily converted into 2,3-unsaturated glycosyl compounds with O-, C-, N-, S- or otherwise linked substituents at the anomeric position as discussed by the authors.
Abstract: Glycals (or usually their O-substituted derivatives) are readily converted into 2,3-unsaturated glycosyl compounds with O-, C-, N-, S- or otherwise linked substituents at the anomeric position. These products have been found to be useful for a range of synthetic purposes. In particular, the C-glycosidic compounds have served as readily available starting materials for the preparation of useful non-carbohydrate compounds. While these allylic rearrangement processes are usually conducted under the influence of Lewis acid catalysts, adaptations that involve activation of the allylic substituents of the starting glycals as leaving groups under neutral conditions have been developed. General features of the reactions are described as well as applications in synthesis and extensions of the basic processes.
146 citations
TL;DR: The combination of the glycosylation and subsequent functionalization provides a novel entry to saccharides which are otherwise difficult to prepare and should make this method a useful tool in synthetic carbohydrate chemistry.
Abstract: A highly stereoselective palladium-catalyzed O-glycosylation reaction is described. The reaction of a glycal 3-acetate or carbonate with the zinc(II) alkoxide of acceptors establishes the glycosidic linkage under palladium catalysis to give rise to disaccharides as the product in good yields and with high stereoselectivity. In contrast to the Lewis acid mediated Ferrier procedure, the anomeric stereochemistry of this reaction is controlled by the employed ligand. Whereas the use of a complex of palladium acetate and 2-di(tert-butyl)phosphinobiphenyl as the catalyst results in the exclusive beta-glycoside formation, the same reaction using trimethyl phosphite ligand furnishes an alpha-anomer as the major product. The utility of the 2,3-unsaturation present in the resulting glycoside is demonstrated by the further transformations such as dihydroxylation, hydration, and hydrogenation reactions. Thus, the combination of the glycosylation and subsequent functionalization provides a novel entry to saccharides which are otherwise difficult to prepare. The broad scope of the process, mildness of the reaction conditions, and experimental simplicity should make this method a useful tool in synthetic carbohydrate chemistry.
137 citations
TL;DR: A review of recent developments in the use of promoters for the Ferrier rearrangement of O-, N-, C- and S-nucleophiles with glycals can be found in this paper.
121 citations
TL;DR: Perchloric acid supported on silica gel acts as an excellent reagent system in converting glucals into 2,3-unsaturated-O-glucosides in good to excellent yields in short reaction time with good alpha selectivity.
Abstract: Perchloric acid supported on silica gel acts as an excellent reagent system in converting glucals into 2,3-unsaturated-O-glucosides in good to excellent yields in short reaction time with good a selectivity. Primary, secondary, and allylic alcohols, phenols, and thiols react with 3,4,6-tri-O-acetyl glucal with equal ease. In addition to this, a chiral furan diol is obtained from unprotected D-glucal or D-galactal in good yields.
113 citations
TL;DR: Indium and its salts have emerged as promising catalysts for effecting various functional group transformations in last two decades as discussed by the authors, and there are a great number of reported reactions involving indium reagents; the versatility and applicability of these reactions makes it a hot field to explore, and it attracts much interest from organic chemists.
93 citations
References
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50 citations
TL;DR: In this article, the methoxymercuration of the acetates of d -glucal, d -galactal, l -arabinal and d -xylal was studied by n.m. spectroscopy.
41 citations
TL;DR: In this article, the reaction of 3,4,6-tri-O-acetyl-1,2-dideoxy-hex-1-enopyranoses (acetylglycals) in acetonitril with the sodium salt of methyl dicyanoacetate was discussed.
Abstract: 3,4,6-Tri-O-acetyl-1,2-didesoxy-hex-1-enopyranosen (Acetylglycale) reagieren in Acetonitril mit dem Natriumsalz von Dicyanessigsaure-methylester (2) unter Bortrifluorid-Atherat-Katalyse zu den kettenverzweigten 3-Desoxy-3-C-(dicyanmethyl)-hex-1-enopyranosen. Entsprechend verlaufen die Reaktionen von Methyl-4,6-di-O-acetyl-2,3-didesoxy-hex-2-enopyranosid mit 2. Bei den Reaktionen von Glycalen mit Alkoholen unter BF3-Atherat-Katalyse entstehen Alkyl-α,β-hex-2-enopyranoside, die auch durch Substitution von Methyl-4,6-di-O-acetyl-α-D-hex-2-enopyranosid gebildet werden. Unter diesem Aspekt wird der Reaktionsmechanismus diskutiert. An dem von R. J. Ferrier postulierten Allylcarboxonium-Ion (5-Acetoxy-6-acetoxymethyl-D-erythro-5,6-dihydropyrylium-Ion), das als reaktive Zwischenstufe bei der Umsetzung von Tri-O-acetylglucal sowie auch von Di-O-acetylpseudoglucal unter Bortrifluorid-Atherat-Katalyse angesehen werden mus, ist neben der 1-Substitution zum Glycosid auch eine 3-Substitution zum 3-Desoxy-3-C-glycal zu diskutieren. Ferner wurden die molaren Drehwerte fur cyclische Olefine berechnet, wobei fur den Ringbeitrag von 2,3-Dihydro-4H-pyran der empirische Wert ±240° und fur allylische Hydroxygruppen ±95° (quasi-axial) bzw. ±130° (quasi-aquatorial) verwendet wurde.
Reaction of Acetylglycals and Acetylpseudoglycals with Sodium Salt catalysed by Boron Trifluoride
The reaction of 3,4,6-tri-O-acetyl-1,2-dideoxy-hex-1-enopyranoses (acetylglycals) in acetonitril with the sodium salt of methyl dicyanoacetate (2) catalysed by boron trifluoride affords branched chain 3-deoxy-3-C-(dicyanomethyl)-hex-1-enopyranoses. - A corresponding reaction proceeds between methyl 4,6-di-O-acetyl-2,3-dideoxy-hex-2-enopyranosid and 2. By reactions of glycals with alcohols catalysed by boron trifluoride the same alkyl α-β-hex-2-enopyranosides are obtained, which are formed via substitution of methyl 4,6-di-O-acetyl-α-D-hex-2-enopyranosides. The reaction mechanism is discussed under these aspects. The allyloxocarbenium ion (5-acetoxy-6-acetoxymethyl-D-erythro-5,6-dihydropyrylium ion) postulated by R. J. Ferrier as reactive intermediate in reactions of tri-O-acetylglucal as well as di-O-acetylpseudoglucal with alcohols catalysed by boron trifluoride can undergo a 1-substitution to yield the glycoside and also a 3-substitution by which a 3-deoxy-3-C-glycal is obtained. The molecular rotation for cyclic olefines has been calculated in which were taken as the empirical value ±240° for the ring contribution of 2,3-dihydro-4H-pyran and for the allylic hydroxy group ±95° (semiaxial) and ±130° (semiequatorial).
18 citations
TL;DR: In this article, the replacement of the tosyloxy group by the diethylamine was introduced, which led to products resulting from the substitution of the TOS group with the LD group.
Abstract: Attempts to dehydrobrominate tri-O-acetyl-3-O-tosyl-α-D-glucopyranosyl bromide with diethylamine led directly to products resulting from the replacement of the tosyloxy group by the diethylamine. I...
18 citations