Methyl O-pivaloyl-α-d-glucopyranosides

Tomić-Kulenović, Srdanka; Keglević, Dina

doi:10.1016/s0008-6215(00)84679-0

Cited by 25 publications

(12 citation statements)

References 7 publications

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“…Preparation of 3 was described in the literature by reaction of 5 with pivaloyl chloride in pyridine at 0°C in 83% yield. 27 We have reinvestigated the reaction conditions reported by Klausener et al 25 and obtained 3 in 89% yield, together with methyl 3,6-di-O-pivaloyl-a-D Dglucopyranoside (6), 28 methyl 2,3,6-tri-O-pivaloyl-a-D Dglucopyranoside (7) 29 and methyl 2,4,6-tri-O-pivaloyla-D D -glucopyranoside (8) 29 in 0.6%, 3.3% and 2.8% yield, respectively. Reaction of 5 with N-pivaloyl imidazole in DMF 30 at rt for 8 h and for 5 days afforded compounds 3, 6, 7 (Table 1).…”

Section: Resultsmentioning

confidence: 88%

Sugar bislactones by one-step oxidative dimerisation with pyridinium chlorochromate versus regioselective oxidation of vicinal diols

Rauter

Piedade

Almeida

et al. 2004

Carbohydrate Research

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Section: Resultsmentioning

confidence: 88%

Sugar bislactones by one-step oxidative dimerisation with pyridinium chlorochromate versus regioselective oxidation of vicinal diols

Rauter

Piedade

Almeida

et al. 2004

Carbohydrate Research

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“…76 (1993) Scheme 3 , OR N -18 R = Ally1 1 9 R = H 20 21 R = H 2 3 R = M s Bnb \ / NH 25 28 MeOC.H, = CMethoxyphenylwhich was stored in the freezer for several days without noticeable decomposition (TLC). Methanolysis yielded the methyl glucosides 16 [66] and 17 in 69% and in a ratio of 85:15. Aziglucase 5.…”

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confidence: 99%

“…[65], 16/17 [66], 26/27 [41], 52/53 [65] [67], 39/40 [68] [69], 48/49 [70], and 54/55 (Schemes 2-5) and was faster than bimolecular reactions of carbenes and diazirines (see below). First-order rate constants were thus obtained for the decrease [64] of diazirine concentration.…”

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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“…Most of these rules build on the knowledge gained from the glycosylation chemistry of partially protected acceptors and regioselective protective group manipulations. [4] Some of the conclusions on hydroxy group reactivity, obtained from studies on the acylation of methyl glycosides, are misleading because they do not take into account the effect of monoacylation of the remaining hydroxy groups [5] and the effect of different solvents [6] and reagent systems. In an early NMR study by Horton and Lauterback, the relative distribution of acetyl groups in the partial acetylation of methyl a-d-glucopyranoside using acetic anhydride-[D 5 ]pyridine was found to be 0.4 (O-6) to 0.2 (for each of the secondary hydroxy groups), that is, the secondary hydroxy groups have a similar reactivity.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the Electronic Effects of Carbohydrate Hydroxy Groups by Using Aminosugar Models

Pedersen¹,

Olsen²,

Brka³

et al. 2011

Chemistry A European J

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Methyl amino-deoxy-glycosides with α- and β-gluco, α-galacto, or α-manno stereochemistry with the amino functionality in each of the four possible non-anomeric positions have been synthesized and their pK(a) values determined by titration. These model compounds were chosen because they are the amino derivatives of the most common glycosyl acceptors. From this study it was possible to evaluate the electron density at each of the given positions in the carbohydrate and compare them. Some general trends were observed: The basicity of the amino groups decreases in the order 6-NH(2)>3-NH(2)>2-NH(2)>4-NH(2) (referring to the position). The basicity of a of an amino-deoxy-sugar generally increases when one or more substituents on the sugar ring are axial. The basicity decreases when the amine is antiperiplanar to an oxygen atom. These findings are in agreement with the observations obtained from glycosylation chemistry and the regioselective protection of sugars.

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Methyl O-pivaloyl-α-d-glucopyranosides

Cited by 25 publications

References 7 publications

Sugar bislactones by one-step oxidative dimerisation with pyridinium chlorochromate versus regioselective oxidation of vicinal diols

Sugar bislactones by one-step oxidative dimerisation with pyridinium chlorochromate versus regioselective oxidation of vicinal diols

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

Quantifying the Electronic Effects of Carbohydrate Hydroxy Groups by Using Aminosugar Models

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