摘要:

Four routes from “triacetyl glucal” to methyl 2,3-dideoxy-a-D-erythro-hex-2-enopyranoside have been examined. The timing and procedure for the 6-deoxygenation step, which can be carried out before or after a Ferrier rearrangement, is of crucial importance to the yield and “ease” of the process. The preferred procedure with respect to yield (62% overall), ease, and efficiency involves (i) a Ferrier rearrangement, (ii) deacetylation, (iii) selective sulfonylation, and (iv) lithium aluminum hydride reduction.

ISSN:0732-8303    

DOI:10.1080/07328308308057860

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The title compound (C15H21NO10)' Mr=375.34, crystallized in the orthorhombic space group P2121,21with a=8.989(1), b=9.350(2), c=22.839(2)Å, V=1919.4(7)Å3, Z=4 and Dc=1.299 Mgm−3. The structure was solved by direct methods and refined to an R-index of 0.043. The compound is in the α-D-configuration and displays the5C2conformation. The carbamoyl group is axially oriented and the remaining substituants are 3a, 4e, 5e and 6e. The absence of the anomeric effect in this C-glycoside results in equal and normal endocyclic C-O bond distances (1.425(3)Å). The carbamoyl nitrogen is involved in a bifurcated hydrogen bond, intramolecularly with the pyranosyl ring oxygen atom 0-6, and intermolecularly with the carbonyl oxygen atom 0-9.

ISSN:0732-8303    

DOI:10.1080/07328308308057861

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

When treated with a large excess of 2,2-dimethoxypropane in the presence ofp-toluenesulfonic acid in 1,4-dioxane, 2-acetamido-2-deoxy-D-galactose gave methyl 2-acetamido-2-deoxy-5,6-0-iso-propylidene-α- and -β-D-galactofuranosides, which were converted,viabenzoylation andO-deisopropylidenation, into methyl 2-acetami-do-3-O-benzoyl-2-deoxy-α- and -β-D-galactofuranosides (3,4). Selective benzoylation of 4, followed by mesylation, gave methyl 2-acetamido-3,6-di-O-benzoyl-2-deoxy-5-O-mesyl-β-D-galactofurano-side (6), which was treated with sodium methoxide to give the 5,6-anhydro derivative (7). Treatment of7with thiourea, followed by cleavage of the epithio ring in8, afforded the 5-thio compound9. Alkaline treatment of10, derived from9by hydrolysis, yielded the title compound.

ISSN:0732-8303    

DOI:10.1080/07328308308057862

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

S-Methylation of α-ketothioethers of sugars gave in good yields the corresponding sulfonium derivatives whose alkaline treatement led to the expected, stable, carbohydrate sulfylides3and .8. When asymmetric, the sulfur atom is configurationally stable as shown by dynamic NMR. These sugar sulfylides are prone toStevensrearrangement, react withMichaelacceptors to give cyclopropane derivatives and most unexpectedly lead to “exotic” oxathiolenedioxide C-glycosides when reacted with sulfenes.

ISSN:0732-8303    

DOI:10.1080/07328308308057863

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

(3-Oxo) butyl-l-arabinopyranosides undergo Norrish II type photocyclization giving hydroxyspiroketals with a low stereo-selectivity but with a greater reactivity for α -l-anomers according to stereoelectronic effects for the photolysis of axial anomeric hydrogens.

ISSN:0732-8303    

DOI:10.1080/07328308308057864

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Partial benzoylation ofl-rhamnono-l,4-lactone (1) gave 2,5-di-O-benzoyl-l-rhamnono-1,4-lactone (2) as the main product. In similar conditions,d-mannono-l,4-lactone (3) gave preferentially 2,5,6-tri-O-benzoyl-d-mannono-l,4-lactone (4). 2,3,5,6-Tetra-O-benzoyl- (5) and 3,6-di-O-benzoyl-d-mannono-1,4-lactone (6) were isolated in low yield from the reaction mixture. The structures of the partially benzoylated compounds2,4and6were assigned on the basis of spectroscopic data.

ISSN:0732-8303    

DOI:10.1080/07328308308057865

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The rate constants for the hydrolysis of some al-kyl α- and β-d-fructofuranosides in aqueous perchloric acid have been determined at various temperatures. The effects of varying the aglycon structure on the hydrolysis rate suggest, together with the markedly positive entropies of activation, that the substrate, protonated on the glycosidic oxygen atom, undergoes a rate-limiting unimolecular heterolysis to form a glycosyl oxocar-benium ion. The rate variations in mixtures of aqueous perchloric acid and dimethyl sulfoxide are interpreted as lending further support for the proposed mechanism.

ISSN:0732-8303    

DOI:10.1080/07328308308057866

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The title compound3, which is the first member of a new class of anhydroglycosides, was initially isolated from the methanolysis mixture of the pyranoid isomer1in about 1% yield. Improved yields of greater than 30 % of3are obtained by treating the main product of the aforementioned methanolysis, the dimethylacetal2, with a catalytic amount of p-toluenesulfonic acid in boiling xylene.3(C7H12O5) crystallizes from diisopropyl ether in the monoclinic space group P21 (Z=2) with a = 552.4(1), b = 685.2(1), c = 1052.9(3) pm, α = 90.0, β = 98.95(6) and Y = 90.0°. The structure was solved by X-ray crystal structure analysis using direct methods to R indices of 0.036 and 0.045, respectively, for 1180 independent reflections. The furanoid ring in3adopts a conformation intermediate between2T3(D) and E3(D) (puckering parameters: Q = 48.9 pm; Φ = 102.4°). The oxane ring adopts ana2Ca5(D) conformation, which is heavily distorted by flattening at C-6 (puckering parameters: Q = 64.2 pm; Φ = 58.1° and 0 = 159.5°). Orientation of the glycosidic methyl group is in accord with theexo-anomeric effect. The molecules of3are interchained in three dimensions by a system of hydrogen bonds.

ISSN:0732-8303    

DOI:10.1080/07328308308057867

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The stereoselective base catalyzed conversion of tri-0-acetyl-l,7-dichloro-l,7-dideoxy-xylo-2,6-heptodiulose todl-(2,3,4,6/5)-4,5,6-tri-0-acetyl-2-chloro-3-C-(chloromethyl)-3,4,5,6-tetrahydroxy-cyclohexanone has been described,1and it has also been shown that branched cyclose formation from the corresponding 1,7-dibromo and 1,7-diazido-2,6-heptodiuloses also occurs in the same stereoselective manner.1Reduction of the cyclose ketone function followed by appropriate deprotective leads to branchedepi-inositols.1,2The general structure of the starting 2,6-heptodiulose, and the product cyclose and cyclitol are given as I, II and III respectively.

ISSN:0732-8303    

DOI:10.1080/07328308308057868

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0732-8303    

DOI:10.1080/07328308308057859

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor