A mild one-step selective conversion of primary hydroxyl groups into azides in mono- and oligo-saccharides (original) (raw)
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ChemInform, 2000
In a convenient one-pot acetalation procedure using chloral/DCC, methyl (-)-quinate and methyl (-)-shikimate were converted into their 4-epi-derivatives containing a carbamoyl function in 3-position and the trichloroethylidene acetal group in 4,5-position. Additionally, an spiro-byproduct, 1R, 3R, 4R, 5R)-3 H -N-cyclohexyl-3-O-(cyclohexylcarbomyl)-4,5-O-(2,2,2-trichloroethylidene) spiro[[cyclohexane-3,4,5-triol-1,5 H -[1,3]oxazolidine]]-2 H ,4 H -dione, was formed from methyl (-)-quinate in 10% yield. Decarbamoylation of the compounds is possible by heating in methanolic sodium methoxide. #
Azide–Alkyne 1,3Dipolar Cycloadditions: a Valuable Tool in Carbohydrate Chemistry
Recent applications of the 1,3-dipolar cycloaddition reaction of azides and alkynes in carbohydrate chemistry are summarized in the present review. The efficient catalyzed version of this reaction, also referred to as one of the so-called click chemistry reactions, has joined in a short period of time a select group of the most efficient and useful organic reactions. In particular, its application in the carbohydrate field has shown its value as a synthetic tool allowing the preparation of a wide range of carbohydrate-containing molecular constructs such as glycopeptides, glycoaminoacids, glycoclusters, glycodendrimers, glycopolymers, glycosylated biomolecules, and immobilization of carbohydrates onto solid surfaces (glycoarrays) as the most representative examples. In the majority of cases, the formed 1,2,3-triazole heterocycle plays the role of a linking tether between the coupling partners.
Carbohydrate Research, 2000
A series of glucals, protected by cyclic acetal protecting groups to conformationally constrain the C-4 and C-6 hydroxyl groups, were subjected to the azidonitration reaction to furnish the corresponding C-2 azidodeoxy-D-glucoses. 4,6-O-Isopropylidene-3-O-triisopropylsilyl-D-arabino-hex-1-enitol afforded 2-azido-2-deoxy-4,6-O-isopropylidene-3-O-triisopropylsilyl-D-glucopyranosyl nitrate and its D-manno isomer in a 20:1 ratio. These findings allow the azidonitration reaction to be now used for the preparation of a variety of glucosamine building blocks from differentially protected glucal precursors.
A New Approach for Preparing Methyl 6-azido-2,3,4-tri-O- benzyl-6-deoxy-alpha-D-glucopyranoside
Azide sugars are key intermediates in the synthesis of aminglycosides, which themselves are useful for the synthesis of glycopeptides. A new method has been achieved by using DPPA and DBU in dry DMF with high temperature for replacement of the azide group from alcohol (glucoside) on the position 6. The results of this method are very important for preparing 6-azido sugar without needing to prepare and separate glucosyl halide completely. The proposed method was successfully applied with direct, simple, and time saving. In addition, excellent yield of 95% was obtained from azide, which could be used to obtain pharmaceutical active compounds.
Efficient access to azadisaccharide analogues
Tetrahedron Letters, 2001
The synthesis of various aminocyclitols as pseudo-azadisaccharide candidates for glycosidase inhibition is described. The strategy involves the reductive amination with several amines of polyhydroxycycloheptanones resulting from a tandem alkylation-cyclisation of C 2 -symmetrical bis-epoxides derived from D-mannitol.
Efficient Synthesis of Azido Sugars using Fluorosulfuryl Azide Diazotransfer Reagent
Azide-containing sugars are important tools for the synthesis of biologically relevant 1,2-cis-glycosides and for bioconjugation chemistry. Previous strategies for the installation of a non-participating C2-azido functionality use harsh conditions and long reaction times. Herein, we report the synthesis of azido sugars using fluorosulfuryl azide (FSO2N3; 1) with a Cu(II) catalyst as a safe and efficient diazotransfer reagent. Common hexosamine substrates were converted to 2-azido-2-deoxy sugars in less than 5 minutes in quantitative yield. Glycosyl donors with orthogonal protecting groups were readily prepared from these azido sugars with good overall yield and a single column purification. The diazotransfer protocol was also efficiently used on other amino sugar derivatives, including aminoglycosides and substrates with amine-containing linkers. This optimized method will expand access to important non-participating C2-azido protecting groups and other azido sugar derivatives.
THE SYNTHESIS OF MEDICINALLY IMPORTANT PHARMA MOLECULES FROM CARBOHYDRATES BUILDING BLOCKS
Mukesh Chander, 2023
The carbohydrate molecules forms a variety of natural products named "glycoconjugateskey components of different biological processes". The challenge lies in preparation of bulk quantities of these organics for industrial application and processes. The monosaccharide as raw material to synthesize glycoconjugates are available in large quantities so as to oligomerise these monosaccharides.The chiral nature of monosaccharide has made them suitable to use as starting material also for the synthesis of compounds other than glycoconjugates. Glycal a cyclic enol ether derivatives of sugars can be formed as pyranose (six-membered) or furanose (five-membered) rings, depending on the monosaccharide used as a starting material to synthesize the glycal which can be transformed to an exo-glycal. More recently, glycals have also been shown to be excellent starting substrates for library development and preparation of exo-glycals. The Fischer-Zach method has been one of the most popular methods for synthesizing glycals. It has been suggested that heterolytic cleavage of the carbon-halogen bond occurs under these acidic conditions ,initially to give an anomeric carbocation that, after taking two electrons from the zinc atom, generates a transient carbanion that evolves through the splitting off of an acetate anion. In present study we have investigated the role of other reducing agents in this transformation with glycosyl halides include sodium and potassium metal, sodium naphthalide, zinc/silver graphite, aluminum amalgam, SmI2, potassium graphite ,lithium/ammonia, chromium(II), zinc/base, cobalt(II), and titanium(III). A glucal derivative has also been prepared by introduction of a halogen atom at C-2, followed by a reductive elimination reaction in the opposite sense.
Tetrahedron Letters, 1998
Fully O-benzylated mono-, di-and trisaccharide glycosyl azides representing the reducing terminal of the core structure of N-glycans were synthesized. Totally and partially benzylated thioalkyl glucosamine glycosides were converted into the corresponding glycosyl azides with trimethylsilyl azide in the presence of methyl triflate. The 13-mannosidic linkage was created by C-2 epimerization of the initially introduced f3-D-glucounit via oxidation followed by stereoselective reduction with tetrabutylammonium borohydride.
The Journal of Organic Chemistry, 1999
Nitrogen-in-the-ring "aza-sugars" have been synthesized in enantiomerically pure form from the amino acid L-alanine in excellent overall yield. The O'Donnell's Schiff base of L-alanine methyl ester 9a was converted to aza-sugar L-fuco-1-deoxy-nojirimycin, 18, and to the epimer L-gulo-1deoxy-nojirimycin, 20, in eight steps. The overall yields were 20 and 29%, respectively. The methodology for the efficient generation of silyl-and benzyl-protected (E)-3-lithio-2-propen-1-ols, and the use of these alkenyllithiums with iBu 5 Al 2 H as nucleophiles in the threo-selective tandem reduction-alkenylation of the Schiff base esters is described. Osmium-catalyzed cis-oxygenation of the resulting olefin products was selective for the galacto (fuco) amino polyols in all cases for the acyclic olefins, and was gulo-selective for the cyclic D-4,5-dihydropyridine pivalate, 17c. TEMPO-NaOCl was selective for oxidation of the primary position of the acyclic Schiff bases, and allowed for minimal protection/deprotection of the intermediates. The resulting N-benzhydryl heterocycles were easily deprotected with H 2-Pd at atmospheric pressure.