摘要:

This review examines recent syntheses of carbohydrates in which the target compounds are viewed as acyclic carbon frameworks. The synthetic approaches are divided into two categories in which critical asymmetry is placed either by (a) stereo-selective carbon-carbon bond formation, or (b) stereoselective carbon-heteroatom bond formation. This account focuses its attention on the methodology utilized to place acyclic stereo-centers as the key feature of the synthetic strategy.

ISSN:0732-8303    

DOI:10.1080/07328308408058813

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The triphenylphosphine-iodine-imidazole, and the triphenylphosphine-triiodoimidazole systems have been used to effect 3,4-unsaturation in 2-amino-2-deoxy-D-giucopyranosides. The yields were optimized by variation of solvent, amino protection group and proportions of reagents.

ISSN:0732-8303    

DOI:10.1080/07328308408058814

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

NMR spectra of crystalline α-D-glucose DH2O (1), α-D-glucose (2), and β-D-glucose (3) were examined by 13C cross polarization magic angle spinning (CPMAS) methods. Each of the three forms of glucose exhibited a distinctly different spectrum. Chemical interconversion of2and3as well as thein situdehydration of1during the course of the CPMAS NMR experiment was monitored in the13C spectra. Samples of1, 2, and3specifically enriched at C-1 and C-6 with13C yielded13C spectra in which the resonances corresponding to the adjacent C-2 and C-5 carbons were not visible due to strong homonuclear13C dipolar interactions with the high abundance label. Spectra of these analogues as well as the C-2 and C-3 labeled materials provided the complete13C chemical shift assignments of crystalline12, and3. A comparison of the solid state and solution13C spectra revealed substantial resonance shifts for each of the three structures examined.

ISSN:0732-8303    

DOI:10.1080/07328308408058815

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The title compound was synthesized in four steps from D-glucono-1,5-lactone. Reduction of 2,4,6-tri-O-benzoyl-3-deoxy-D-arabino-hexono-1,5-lactone (1) with disiamylborane afforded 2,5,6-tri-O-benzoyl-3-deoxy-D-arabino-hexopyranoae (2) which, on debenzoylation, gave 3-deoxy-D-arabino-hexoae (3). Tautomeric equilibrium of3was studied by1H and13C NMR spectroscopy.

ISSN:0732-8303    

DOI:10.1080/07328308408058816

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

To confirm the potential usefulness of amino acid residues as protecting groups for sugar hydroxyls, methyl 2,3-di-O-glycyl-α-D-glucopyranoside (5) and methyl 4,6-di-O-glycyl-2,3-di-O-methyl-α-D-gluco-pyranoside (7) were synthesized as reference compounds. Conditions were then established for the removal of these aminoacyl groups from the sugar molecules. The reference compounds were easily prepared by condensation of methyl α-D-glucopyranoside derivatives withN-protected glycine in the presence of dicyclohexyl-carbodiimide (DCC). The aminoacyl groups were removed by alkaline treatment, as were conventional acyl groups and also with ease by enzymatic hydrolysis using Pronase E. Conventional ester and ether protecting groups are not removed by such enzymatic treatment. Removal of aminoacyl group from sugar moieties on a practical scale is also described.

ISSN:0732-8303    

DOI:10.1080/07328308408058817

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

No convenient pathway is known to synthesize methyl-2-amino-2-deoxy-D-arabinopyranosides. Methyl-4-O-allyl-2,3-anhydro-β-D-ribopyranoside is easily obtained starting from D-arabinose but the opening of this epoxide with diallylamine is not regioselective, giving bothxyloandarabinocompounds. We found that participation of the diallylamino group, after mesylation of the mixture, leads to alyxoaziridinium ion which is regioselectively opened. Trideallylation with palladium on charcoal gives methyl-2-amino-2-deoxy-β-D-arabinopyranosides in good yield.

ISSN:0732-8303    

DOI:10.1080/07328308408058818

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A13C NMR fingerprint method previously developed for galactosides and glucosides is extended to arabinosides and ribosides. This approach demonstrates the capability of13C NMR to determine ring size and anomeric configuration in four isomeric arabinosides and ribosides.

ISSN:0732-8303    

DOI:10.1080/07328308408058819

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Starting from the kanamycin A 4″,6″-ditriflate6und -6″-brosy-late-4″-triflate8, respectively, the following derivatives were prepared: 4″,6″-dideoxy-4″,6″-difluoro-4″-epi- (20), 4″,6″-dideoxy-4″-fluoro-4″-epi- (22), 6″-deoxy-6″-fluoro-4″-epi- (19), and 6″-deoxy-4″-epi-kanamycin A (21). C NMR and antibacterial data are given.

ISSN:0732-8303    

DOI:10.1080/07328308408058820

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

α-Cyclodextrin mainly underwent monoiodo substitution on treatment withN-iodosuccinimide and triphenylphosphine in DMF, giving 6-monodeoxy-6-monoiodo-α-cyclodextrin. A small amount of 6,6′-dideoxy-6,6′-diiodo-α-cyclodextrin was also obtained as a by-product. The structures of these compounds were elucidated from their elemental analyses and13C NMR spectra.

ISSN:0732-8303    

DOI:10.1080/07328308408058821

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The hexuronic acid methyl ester glycals with L-ribo (7), D-lyxo(9), and D-xyloconfiguration (11a) were synthesized and their conformations and that of the D-arabinoderivative2awere studied. Using theN-iodosuccinimide alycosylation procedure these glycals were transformed into cyclohexyl 2-deoxy-2-iodoglycosides13-28and their α/β-anomer ratios determined by1H NMR spectrocopy. The mechanism of theN-iodosuccinimide glycosylation and the correlation between glycal conformation and glycoside configuration are discussed.

ISSN:0732-8303    

DOI:10.1080/07328308408058822

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor