摘要:

(+)-Pseudoconhydrine, one of hemlock alkaloids, has been synthesized from methyl 2-acetamido-2,3,4-trideoxy-α-D-erythro-hexopyranoside by an eleven step reaction sequence. An intramolecular nucleophilic attack of the nitrogen atom on 2-acetamido-5-0-benzyl-2,3,4-trideoxy-6-0-tosyl-D-reythro-hexose diethyl di-thioacetal to the terminal tosyloxymethylene group proceeded smoothly and gave the desired disubstituted piperidine compound. A conversion of the thioacetal group into an aldehyde, a two-carbon elongation by Wittig olefination, and a successive hydro-genation completed the chiral synthesis of the title alkaloid.

ISSN:0732-8303    

DOI:10.1080/07328308508058828

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Model reactions of 0-(α-D-glucopyranosyl)trichloroacetimidate 2α with methanol and choTesterol under various conditions demon-strated that stereocontrolled glucosyl transfer with inversion of configuration at the anomeric center is best carried out in di-chloromethane at low temperatures with boron trifluoride-ether as a catalyst. Under these conditions β-glucoside 4β and β-disaccha-rides 5β- 9β were obtained in good to excellent yields.

ISSN:0732-8303    

DOI:10.1080/07328308508058829

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The1H and13C NMR spectra of ethylidene derivatives of simple diols and of carbohydrates were measured to determine whether NMR parameters could be found which could be related to structure. Four NMR parameters were considered; the chemical shifts of the acetal proton and carbon, the2JC,Hvalue between the acetal proton and methyl carbon and the1JC,Hvalue of the acetal carbon. The values,.of these parameters were all somewhat related to ring-size; the2JC,Hvalue was most closely related. The sign of2JC,Hwas shown to be positive for 2-methy l-l,3-dioxolane and Z-methy l-l,3-dioxane by means of selective population transfer experiments. Comparison of the13C NMR chemical shifts of the acetal with the parent diol was found to give information about acetal location.

ISSN:0732-8303    

DOI:10.1080/07328308508058830

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Replacement of the alkyl group of l-aryl-3-alkyltriazenes with a sugar moiety did not significantly modify their tautomeric behaviour. The same replacement done on 1-aryl-3-alkyl-3-methyl-triazenes did not affect to any large extent their rotameric properties. In contrast, the most prominent biological properties, anticancer activity and toxicity, of 1-aryl-3-methyltria-zenes disappeared on replacement of the methyl group with a sugar moiety. Unexpectedly, the N-acetyltriazene 15 was highly cyto-toxic.

ISSN:0732-8303    

DOI:10.1080/07328308508058831

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Reduction of methyl 6-deoxy-2,3-0-isopropylidene-3-C-methyl-α-L-lyxo-hexopyranosid-4-ulose (2) with sodium tetrahydroborate or L-selectride produces exclusively the L-talo-configurated 4-hydroxy compound (3), which is transformed to methyl 6-deoxy-3,4-O-isopropylidene-3-C-methyl-α-L-talopyranoside (4). Methylation of the 2-hydroxy group and hydrolysis yields L-vinelose (6) .

ISSN:0732-8303    

DOI:10.1080/07328308508058832

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

β-D-Galactopyranosides which suffered galactosidic bond cleavage upon treatment with bases that are normally used for deesteri-fication, were successfully deesterified with KCN in 95% ethanol. Also α-D-galactopyranosides bearing acid- or base-sensitive sub-stituents were deesterified using the same reagent without damage to those substituents.

ISSN:0732-8303    

DOI:10.1080/07328308508058833

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Methyl α-D-mannopyranoside (4) was converted into methyl 2,6-dideoxy-3-C-methyl-ct-D-ribo-hexopyranoside (20) (methyl α-D-mycaroside) by an efficient sequence of reactions (Schemes 1 and 3). A similar set of reactions also was used to convert L-rhamnose (2) into methyl α-L-mycaroside (21). Attempted synthesis of methyl 2,6-diseoxy-3-C-methyl-a-D-arabino-hexopyranoside (22) (methyl α-D-olivomycosidej from methyl 6-deoxy-3-C-methyl-4-O-(2,2-dimethylpropanoyl)∼2-O-trif lyl-α-D-arabino-hexopyranoside (18), a compound generated during∼synthesis of 20, was thwarted by a methyl migration which produced methyl 2,6-dideoxy-2-C-methyl-α-D-ribo-hexopyranoside (23).

ISSN:0732-8303    

DOI:10.1080/07328308508058834

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

When methyl 2,4,6-tri-0-benzoyl-3-0-benzyl-β-D-galacto-pyranoside (JO is treated in purified chloroform at 55-60′ with excess of dichloromethyl methyl ether in the presence of a catalytic amount of freshly fused zinc chloride for 1 h the corresponding α-glycosyl chloride 2 can be isolated by column chromatography in 75-80% yield. Compound 2 is an important intermediate in the synthesis of oligosaccharides containing a glycosyl-3-0-galactosyl sequence. Under the described reaction conditions the conversion 1 - 2 is accompanied by a slow anomerisation of 1 to give methyl 2,4,6-tri-0-benzoyl-3-0-benzyl-α-D-galactopyranoside. Prolonged treatment of 2 with the used excess of the reagent results in complete debenzylation of the substrate and the conversion of the putative 2,4,6-tri-O-benzoyl-α-D-galactopyranosyl chloride into the corresponding 3-0-formyl and 3-0-dichloromethyl derivatives.

ISSN:0732-8303    

DOI:10.1080/07328308508058835

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Sodium bis(3-O-hydroxy-2-furyl methyl ketone) (3) and sodium 3-O-hydroxy-2-methyl-4-pyrone hydrate (4) were isolated and characterized from the interaction of isomaltol and maltol with sodium methoxide in boiling benzene (toluene or acetone). Elemental analyses of3furnished the formula C12H11NaO6, and this composition was confirmed by conversion to isomaltolO-benzoyl ester.

ISSN:0732-8303    

DOI:10.1080/07328308508058836

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Interest in fluorinated sugars labelled with {18F} positron-emitting radionuclides as tracers for the measurement of glucose utilization in man by positron emission tomography1(PET) and in animals by autoradiography2has resulted in the development of numerous syntheses3-11of 2-deoxy-2-fluoro-D-glucose (3a). Some of these syntheses are not practical because the carbohydrate substrates for the fluorination reactions are not readily available.

ISSN:0732-8303    

DOI:10.1080/07328308508058837

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor