The Glycosyl Halides and Their Derivatives

Haynes, L. J.; Newth, F. H.

doi:10.1016/s0096-5332(08)60393-8

Cited by 73 publications

(21 citation statements)

References 249 publications

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“…Depending upon the influence of the annulation and of the configuration (cf. [ 161 [ 181 [30][31][32][33]), 9 may be more or less stable than 8. We were also interested in the nature of the products of thermolysis in an aprotic environment, as they are invariably formed when 1-azisugars are exposed to a relatively unreactive partner [8] [34][35][36], and of which only a relatively minor component, the alkoxyglycal 59 [37] (ca.…”

mentioning

confidence: 99%

Glycosylidene Carbenes. Part 13. Synthesis and thermolysis of representative 1‐azi‐glycoses

Vasella

Witzig

Waldraff

et al. 1993

Helvetica Chimica Acta

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Dedicated to Duilio Arigoni on the occasion of his 65th birthday (1.X.93)In the context of the hypothesis postulating a heterolytic cleavage of a C-N bond during thermolysis of alkoxydiazirines (Scheme I ) , we report the preparation of the diazirines4,5,7, and 8, the kinetic parameters for the thermolysis in MeOH of the diazirines 1 and 4-9, and the products of their thermolysis in an aprotic environment. The diazirines 4,5,7, and 8 (Schemes 2-5) were prepared from the known hemiacetals 10,19,34 (prepared from 31 in an improved way), and 42 according to an established method. The oximes 11,20,35, and 43 were obtained from the corresponding hemiacetals as (E/Z)-mixtures; 43 was formed together wlth the cyclic hydroxylamine 44. Oxidation of 11,35, and 43 (N-chlorosuccinimide/l,8-diazabicyclo[5.4.0]undec-7-ene (NCS/DBU) or NaIO,) gave good yields of the (Z)-hydroximolactones 12, 36, and 45, while the oxime 20 led to a mixture of the (E)-and (2)-hydroximolactones 21 and 22, which adopt different conformations. Their configuration was assigned, inter alia, by a comparison with the enol ethers 28 and 29, which were obtained, together with 30, from the reaction of the diazirine 5 with benzaldehyde and PBu,. Treatment of the hydroximolactone 0-sulfonates 13,23,37, and 46 with NH,/MeOH afforded the diaziridines 15,25,38, and 47 in good yields, while the (E)-sulfonate 24 decomposed readily. Oxidation of the diaziridines gave 4, 5, 7, and 8, respectively. Thermolysis of the diazirines 1 and 4-9 in MeOH yielded the anomeric methyl glycosides 50/51,16/17,26/27,52/53,39/40,48/49, and 54/55, respectively. A comparison of the kinetic data of the thermolysis at four different temperatures shows the importance of conformational and electronic factors and is compatible with the hypothesis of a heterolytic cleavage of a C-N bond. An early transition state is evidenced by the absence of torsional strain by an annulated 1,3-dioxane ring. Thermolysis of 1 in MeCN at 23" led mostly to the diastereoisoineric (Z,Z)-, (E,E)-, and (E,Z)-lactone azines 56, 57, and 58 (Scheme 6), which convert to 56 under mild conditions, and to 59 (3%). The benzyloxyglucal59 was obtained in higher yields (IS%), together with 44% of 5658, by thermolysis of solid 1. Similarly, thermolysis at higher temperatures of4 in toluene, THF, or dioxane and of 9 in CH2C12 or THF yielded the (Z,Z)-lactone azines 60 and 61, respectively, the latter being accompanied by the dihydro-oxazole 62.Introduction. -Diazirines [I] are important precursors of carbenes, and the mechanism of their thermolysis attracted considerable attention, which focused on the concertedness of the cleavage of the two C-N bonds and the homo-or heterolytic nature of the bond breaking [2-71. The mechanism and the kinetics of the thermolysis of (a1koxy)alkyldiazirines (see [8] and earlier papers of the series [9-131) have not been studied, but we hypothesized that thermolysis of 1-azisugars, such as 1, i.e. cyclic (alkoxy)alkyldiazirines, is initiated by heterolysis of one of the C( 1)-N bonds, accord-

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confidence: 99%

Glycosylidene Carbenes. Part 13. Synthesis and thermolysis of representative 1‐azi‐glycoses

Vasella

Witzig

Waldraff

et al. 1993

Helvetica Chimica Acta

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“…(The information about acylhalogenosugars of the 2-amino-2-deoxysugar series accumulated at the present time is summarised in Table 1.) As early as 1911, it was shown 32 that the hydrobromide of 2-amino-3,4,6-tri-O-acetyl-2-deoxy-ar-D-glucopyranosyl bromide (I) is converted into the glycoside hydrobromide (Π) on reaction with methanol: However, the bromides of fully acetylated 2-amino-2deoxysugars differ significantly from the bromides of the corresponding neutral analogues 31 , and for this reason the structures and properties of the acylated bromides and chlorides of 2-amino-2-deoxysugars must be specially considered.…”

Section: Acylhalogeno-derivatives Of Aminosugars In the Koenigs-knorrmentioning

confidence: 99%

Advances in the Synthetic Chemistry of Aminoglycosides

Zurabyan¹,

Khorlin²

1974

Russ. Chem. Rev.

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Data on the methods for the formation of the aminoglycosidic linkage in the synthesis of alkyl and aryl aminoglycosides and oligosaccharides containing 2-amino-2-deoxyglycosyl residues are reviewed systematically. The bibliography includes 229 references. CONTENTS I. Introduction II. The synthesis of alkyl and aryl aminoglycosides III. The Koenigs-Knorr reaction and its modifications in the synthesis of aminoglycosides IV. 2-Substitutedglyco-[2', 1':4,5]-2-oxazolines V. Oxazoline synthesis of 1,2-taww-2-acetamido-2-deoxyglycosides VI. Stereospecific synthesis of 1,2-c/s-2-amino-2-deoxyglycosides VII. Enzymatic synthesis of aminosugar oligosaccharides VI11. Synthesis of S-and iV-aminoglycosides 887

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“…This reagent (henceforward called HBA) is a well known reagent in carbohydrate chemistry, used since the turn of the century for the preparation of glycosyl bromides (Ref. 4). In this procedure an acylated (usually acetylated) sugar is treated with HBA at room temperature and the glycosyl bromide is usually formed in high yield as the only product.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of bromodeoxy sugars from hexoses, alditols, and aldonic acids

Pedersen¹,

Bock²,

Lundt³

1978

Pure and Applied Chemistry

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-Reaction of hexoses, anhydroalditols, and aldonic acids with hydrogen bromide in acetic acid leads to the formation of acetylated bromodeoxy compounds. The reaction proceeds by partial acetylation and formation of acetoxonium ions followed by substitution with bromide. Hexases react only in the furanose form to give 6-bromo compounds. Most 1,4-and 1,5-anhydrides of hexitols give mono-or dibromides. Aldonic acids, or their lactones, yield mono-or dibromolactones with bromine at C-2 and at the primary carbon atom. Same aspects of the chemistry of the bromolactones are discussed.

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The Glycosyl Halides and Their Derivatives

Cited by 73 publications

References 249 publications

Glycosylidene Carbenes. Part 13. Synthesis and thermolysis of representative 1‐azi‐glycoses

Glycosylidene Carbenes. Part 13. Synthesis and thermolysis of representative 1‐azi‐glycoses

Advances in the Synthetic Chemistry of Aminoglycosides

Synthesis of bromodeoxy sugars from hexoses, alditols, and aldonic acids

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