摘要:

The dimeric nitrosyl chloride adducts of tri-O-acetyl-1,5-anhydro-2-deoxy-D-arabino-hex-1- andD-lyxo-hex-1- enitols (glycals) dissociate in dimethylformamide to the monomeric forms which rapidly isomerize to the corresponding tri-O-acetyl-2-oximino-α-D-hexopyranosyl chlorides. Evidence is provided for the dehydrochlorination of these latter compounds to highly reactive tri-O-acetyl-1,5-anhydro-2-deoxy-2-nitroso-D-hex-1-enitols.

ISSN:0008-4042    

DOI:10.1139/v73-001

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The kinetics of the reactions of dimeric tri-O-acetyl-2-deoxy-2-nitroso-α-D-glucopyranosyl chloride (1) with simple aliphatic alcohols (4 mol equiv) in dimethylformamide to form alkyl tri-O-acetyl-2-oximino-α-D-arabino-hexopyranosides (5) were investigated by n.m.r. and optical rotation. It is concluded that the conversion of1to5proceeds basically by way of three successively formed intermediates, namely, the monomeric form (2) of1, the tri-O-acetyl-2-oximino-α-D-arabino-hexopyranosyl chloride (3), and the tri-O-acetyl-1,5-anhydro-2-deoxy-2-nitroso-D-arabino-hex-1-enitol (4). Direct evidence was obtained only for the intermediacy of3and the transient existence at low concentration of an uncharacterized intermediate which may be the β-anomer of5. The intermediate4could form directly from2and thereby provide a mechanism for the formation of5which by-passes3. However, the kinetic investigations showed this route to be of very minor, if any, importance. In all cases, the rate of the disappearance of1was virtually the same and within experimental error the same as for the isomerization of1to3in the absence of the alcohol for which the rate-controlling stage is dissociation of1to2. Methanol reacts with4only about 5 times faster than doest-butanol.The utility of the reaction for the preparation of oximinoglycosidic structures related to disaccharides is illustrated by glycosidations of 1,2;3,4-di-O-isopropylidene-α-D-galactopyranose, 1,2;5,6-di-O-isopropylidene-α-D-glucofuranose both by1and by the dimeric tri-O-acetyl-2-deoxy-2-nitroso-α-D-galactopyranosyl chloride (6) and of 2,3;5,6-di-O-isopropylidene-α-D-mannofuranose by1. The reaction of6with 1,2,3,4-di-O-isopropylidene-α-D-galactopyranose provided an 8.7% yield of the β-oximinoglycoside along with an 80% yield of the α-anomer.

ISSN:0008-4042    

DOI:10.1139/v73-002

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A variety of methods are described for the deoximation of isopropyl tri-O-acetyl-2-oximino-α-D-arabino-hexopyranoside (1) to isopropyl tri-O-acetyl-α-D-arabino-hexopyranosuloside (3). Using acetaldehyde in acetonitrile and hydrochloric acid, both3and itslyxo-isomer (4), from the corresponding oxime (2), were obtained in crystalline form. Comparisons of the chemical shifts of the anomeric hydrogens of the ulosides with those of the corresponding oximes require the oximes to possess the C-1/OHsyn- orZ-configuration.

ISSN:0008-4042    

DOI:10.1139/v73-003

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Reduction of isopropyl tri-O-acetyl-α-D-arabino-hexopyranosuloside with sodium borohydride or diborane leads almost exclusively to thegluco-configuration. Catalytic reductions, on the other hand, provide an epimeric mixture with themanno-configuration predominating in ratios of about 2:1. The reduction of isopropyl tri-O-acetyl-α-D-lyxo-hexopyranosuloside with either sodium borohydride or diborane is less stereoselective than in the case of thearabino-isomer and leads to compounds of thegalacto-andtalo-configurations in the ratio of 3:2. The latter is formed highly stereoselectively when the lyxosuloside derivative is hydrogenated catalytically.2-O-(α-D-Mannopyranosyl)-glycerol and thegluco-isomer are synthesized.

ISSN:0008-4042    

DOI:10.1139/v73-004

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Hydrogénation of 2-oximino-α-D-arabino-hexopyranosides in the presence of palladium and hydrazine provided high stereoselectivity for the formation of 2-amino-2-deoxy-α-D-glucopyranosides including disaccharide structures. Similar yields ofgluco-isomer were normally obtained on reduction by borane of 2-acetoximino-tri-O-acetyl-α-D-arabino-hexopyranosides in tetrahydrofuran. However, reduction of 2-O-(2-acetoximino-tri-O-acetyl-α-D-arabino-hexopyranosyl)-1,3-dibenzoylglycerol provided a ratio of about 3:2 of thegluco-tomanno-isomers. Reductions with lithium aluminum hydride were not appreciably stereoselective. Treatment of isopropyl 2-oximino-α-D-arabino-hexopyranoside with hydrazine in the presence of palladium catalyst gave isopropyl 2-deoxy-α-D-arabino-hexopyranoside in a novel room-temperature Wolff–Kishner type reaction.Reduction of isopropyl tri-O-acetyl 2-oximino-α-D-lyxo-hexopyranoside both with borane and lithium aluminum hydride proceeded with slight stereoselectivity for thegalacto-isomer.

ISSN:0008-4042    

DOI:10.1139/v73-005

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Chemical syntheses of six α-linked disaccharides are described, namely, 6-O-(α-D-glucopyranosyl)-D-galactose (1), 6-O-(α-D-galactopyranosyl)-D-galactose (2), 6-O-(α-D-talopyranosyl)-D-galactose (3), 3-O-(α-D-glucopyranosyl)-D-glucose (nigerose) (4), 3-O-(α-D-galactopyranosyl)-D-glucose (5), and 3-O-(α-D-talopyranosyl)-D-glucose (6).

ISSN:0008-4042    

DOI:10.1139/v73-006

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The reduction by borane in tetrahydrofuran of the 2-acetoximino-tri-O-acetyl-α-D-arabino-hexo-pyranosyl derivatives of 1,2;3,4-di-O-isopropylidene-α-D-galactopyranose and 1,2;5,6-di-O-isopropylidene-α-D-glucofuranose (1and4, respectively) proceeds with a high degree of stereoselectivity for the α-D-gluco-configuration and affords a convenient route to 2-amino-2-deoxy-α-D-glucopyranosides. The reduction of the corresponding 2-acetoximino-tri-O-acetyl-α-D-lyxo-hexopyranosyl derivatives (7and12) proceeds with slight stereoselectivity favoring the α-D-talo-configuration. Chromatographic separation was required to provide theN-acetyl derivatives of 2-amino-2-deoxy-α-D-galactopyranosides and 2-amino-2-deoxy-α-D-talopyranosides.

ISSN:0008-4042    

DOI:10.1139/v73-007

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The procedure developed in this laboratory for the synthesis of α-D-glucopyranosides based on the reaction of dimeric tri-O-acetyl-2-deoxy-2-nitroso-α-D-glucopyranosyl chloride with alcohols was employed to synthesize the three α-D-glucopyranosyl deoxystreptamines and 4,6-di-O-α-D-glucopyranosyl deoxystreptamine. Effects of pHchange on the n.m.r. spectra of kanamycins A and B and of the above synthetic compounds are interpreted in terms of a conformational change.

ISSN:0008-4042    

DOI:10.1139/v73-008

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The kinetics of complex formation Ni(DMSO)62+with dithiocarbamate ligands at 25 °C in DMSO is reported. The reactions display the apparent "anomaly" in the direction of slow reaction reported earlier for some other complex formation reactions of Ni(DMSO)62+in DMSO.

ISSN:0008-4042    

DOI:10.1139/v73-009

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The structure of synthetic chervetite has been refined by full matrix least-squares to a ωR = 0.029 using 1105 reflections. Unit cell dimensions area = 13.3689(7),b = 7.1607(4),c = 7.1027(4) Å, β = 105935(5)°, and the space group isP21/a. The structure, originally solved by Kawahara, is a dichromate-type structure with a V2O74−group eclipsed to within 11 ± 5°. The Pb2+ions are irregularly coordinated to 8 or 9 oxygens with distances from 2.40 to 3.20 Å. The distortion of the Pb–O distances is considerably greater than the corresponding distortions of the Sr–O distances in the similar β-Sr2V2O7structure and is related to the tendency of Pb2+to form directional covalent bonds. The V–O distances range from 1,665 to 1.720 Å for terminal oxygens and are 1.812 and 1.821 Å for the bridging oxygens. The V–O distances are consistent with the strengths of the Pb—O bonds.

ISSN:0008-4042    

DOI:10.1139/v73-010

出版商:NRC Research Press    

年代:1973

数据来源: NRC