摘要:

In recent years attention has been directed toward the synthesis of modified sugars wherein the oxygen atom in the sugar ring is replaced by sulfur, selenium or phosphorus. Synthesis of sugar analogs with phosphorus as the ring heteroatom is interesting from the point of view of their possible biological activity.

ISSN:0732-8303    

DOI:10.1080/07328308308057883

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Reductive cleavage of the glycosidic carbon-oxygen bonds of methyl 2,3,4,6-tetra-O-methyl-β-d-glucopyranoside (1), methyl 2,3,4,6-tetra-O-methyl-α-d-glucopyranoside (2), permethylated cellulose (6) and permethylated cyclohexaamylose (7) was carried out in the presence of deuteriotriethylsilane, and the configuration of deuterium in the l-deuterio-1,5-anhydro-d-glucitol derivatives (4, 5and9, 10) that were produced was established by1H- and2H-NMR spectroscopy. All reductions were carried out with boron trifluoride etherate as the catalyst as originally reported [D. Rolf and G. R. Gray,J. Am. Chem. Soc., 104, 3539 (1982)], as well as with trimethylsilyl trifluoromethanesulfon-ate which we now report efficiently catalyzes the regiospecific reductive cleavage of glycosides. Spectroscopic studies revealed that the configuration of deuterium in the products was independent of the configuration of the starting glycoside. The predominant (∼95%) axial configuration observed leads us to propose that free oxonium ions (3and8) are formed as intermediates in these reductions.

ISSN:0732-8303    

DOI:10.1080/07328308308057884

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

1,5-Anhydro-2,3,6-tri-O-methyl-d-glucitol (1) is formed as the major product in the reductive cleavage of permethylated 4-linked glucopyranosyl residues, but a small amount of 1,4-anhydro-2,3,6-tri-O-methyl-d-glucitol (2) is formed as an artifact when water is present. The formation of 2 can be minimized by carrying out the reductive cleavage under anhydrous conditions. The independent synthesis of2and its 5-O-acetyl derivative (4) is described.

ISSN:0732-8303    

DOI:10.1080/07328308308057885

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Pyridiniump-toluenesulfonate (PPTS) is a reagent of choice for the selective removal of anO-isopropylidene group in a 1,6-anhydro-β-d-aldohexopyranose, where the remaining OH-group is protected.

ISSN:0732-8303    

DOI:10.1080/07328308308057886

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Kinetic data for the deuteration ofN-acetyl-d-neuraminic acid at C-3 in basic solution at different pD values are given and discussed. With the same method Tritium has been introduced. A mechanism is proposed for the exchange reaction.

ISSN:0732-8303    

DOI:10.1080/07328308308057887

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The enzymatic cleavage ofN-acetyl-2-azido-2-deoxy-α-d-neuraminic acid in the probe of the NMR spectrometer allows the accumulation of1H NMR spectra of the released a anomer of the N-acetyl-d-neuraminic acid before it mutarotates to the β anomer. The analysis and computer simulation of the spectra yield the1H NMR data set of chemical shifts and coupling constants ofN-acetyl-α-d-neuraminic acid. Using this data set, configuration and conformation in solution are discussed by comparing it with the1H NMR data set of the β anomer, the structure of which is known from an X-ray study.

ISSN:0732-8303    

DOI:10.1080/07328308308057888

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Acid hydrolysis of 6-deoxy-1,2-O-isop ropylidene-α-d-xylo-hexo-furanos-5-ulose (4) yielded gummy 6-deoxy-d-xylo-hexos-5-ulose (1) as an isomeric mixture of two furanose forms, 6-deoxy-α-d-xylo-hexo-furanos-5-ulose and 6-deoxy-β-d-xylo-hexofuranos-5-ulose, and a pyranose structure1R, 5R-6-deoxy-d-xylo-hexopyranos-5-ulose. The combined percentage (64%) of the furanoses represents an unusually large amount of free carbonyl form for a sugar when compared to simple hexoses and 2-hexuloses. Isomeric structures were determined in deuterium oxide solution by1H and13C NMR.

ISSN:0732-8303    

DOI:10.1080/07328308308057889

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Reaction of equiraolecular amounts of xylose and urea in D2O at 68 °C, monitored by13C NMR, gave a six carbon xylofuranosyl derivative as the major product. No intermediate in the formation of this monomeric compound was detected. The xylofuranosyl derivative was subsequently isolated and purified from a six week 0.1 molar reaction of xylose and urea in H2O. Its structure, α-d-xylo-furano[1,2-d]oxazolidin-2-one1, was confirmed by elemental analysis,1H coupled and decoupled13C NMR,1H NMR, IR and DCI-MS. The1H NMR and GC-MS (El, DCI) of theN-acetyl-di-O-acetyl derivative2were in agreement with structure1.

ISSN:0732-8303    

DOI:10.1080/07328308308057890

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

2-Deoxy-d-arabino-hexose (1), 2-acetamido-2-deoxy-d-glucose (2), and 2-deoxy-2-trifluoroacetamido-d-glucose (3) were each treated with 1,1-dimethoxycyclohexane or 1,1-dibenzyloxycyclohexane in 1,4-dioxane in the presence ofp-toluenesulfonic acid. The major products were the 1,1-dimethyl or 1,1-dibenzyl acetals (4-9) of 3,4:5,6-di-O-cyclohexylidene-2-deoxy-aldehydo-d-arabino-hexose, and of 2- (acylamino)-3,4:5,6-di-O-cyclohexylidene-2-deoxy-aldehydo-D-glucose. The dibenzyl acetal derivatives were converted, by hydro-genolysis, into the corresponding, acyclic aldehydes (10-12) in good yields.

ISSN:0732-8303    

DOI:10.1080/07328308308057891

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

C-verzweigte Kohlenhydrate sind typische Bausteine der Makrolid-Antibiotica und Aureolsäuren, von denen einige in der Humanmedizin große Bedeutung haben.1In der Regel handelt es sich um C-3 verzweigte Vertreter vom Typ, häufig ist zusätzlich - meist benachbart - eine Desoxy- oder Aminogruppe oder eine anomal konfigurierte Hydroxylgruppe vorhanden.1

ISSN:0732-8303    

DOI:10.1080/07328308308057892

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor