摘要:

The structure of anO-(2-acetamido-2-deoxy-α-D-galactopyranosyl)-myo-inositol isolated from human pregnancy urine has previously been identified as that of 1-O-(2-acetamido-2-deoxy-α-D-galactopyranosyl)-myo-inositol. In order to ascertain the absolute configuration in the inositol part of the compound, the 1D- and 1L- isomers were synthesised. Since none of these two stereoisomers corresponded to the natural product, the corresponding 2-O-, the mixture of the two 1DL-4-O-, and 5-O- isomers were also synthesised. None of these gave1H NMR spectra corresponding to the natural product, the structure of which therefore remains unresolved.

ISSN:0732-8303    

DOI:10.1080/07328309108543963

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Synthesis of the terminal trisaccharide sequence of the ganglioside GD3, α-D-Neup5Ac-(2→8)-α-D-Neup5Ac-(2→3)-β-D-Galp-(1→4)-β-D-Glcp-(1→1)-Cer (2) was achieved by employing an α-(2→8) disialyl glycosyl donor (1). Condensation of1with the glycosyl acceptor6, propyl 4,6-O-benzylidene-β-D-galactopyranoside, gave the desired protected trisaccharide10(14%) as well as the elimination and hydrolysis products of6, compounds8and9respectively.O-Deacetylation and debenzylation of10gave the final trisaccharide11, as its propyl glycoside.

ISSN:0732-8303    

DOI:10.1080/07328309108543964

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Photolysis of peracetylated D-glucopyranosylidene diazide in the presence of acrylonitrile in excess leads to new isomeric spiro C-1 cyclopropanic sugars (65% combined yield). Such structures, thus readily accessible by a new route which probably involves the addition of carbenic intermediates to an electrophilic alkene, have been identified by NMR investigations. In particular, the1H NMR spectra show that the location and the orientation of the cyano substituent on the cyclopropyl ring can be easily established by way of the deshielding effect (0.2 - 0.3 ppm) which is induced on a sugar ring proton attached at C-2, C-3 or C-5. In order to unambiguously identify the obtained spirosugars, the crystal structure of one of them was determined by X-ray analysis. C17H21NO9, orthorhombic P212121, a=9.093(1), b=9.933(1), c=21.588(3) Å, Z=4, R=0.041 for 1645 unique observed reflexions.

ISSN:0732-8303    

DOI:10.1080/07328309108543965

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Preparation of the α-glucosides11, 12, 13and14were accomplished through glycosylation of racemictrans-1-hydroxy-2-(hydroxymethyl)cyclohexane using 2-thiopyridyl tetra-O-benzyl-glucoside as the glycosyl donor in acceptable overall yield for α-selectivity, but with poor regioselectivity. Glycosylation under thermodynamic control using tetrabenzyl glucopyranose acetate and trimethylsilyl triflate as the promotor gave similar results. The unprotected glucosides12and13were separated and characterized by NMR spectroscopy. Similarly methyl 4-deoxy-α-isomaltoside (5a) was prepared through halide catalyzed glycosylation of methyl 2,3-di-O-benzoyl-4-deoxy-α-D-glucopyranoside (15) in acceptable yield and the unprotected compound characterized by NMR spectroscopy. Compounds5a, 12a, 13aand the mixture11aand14awere all tested as substrates for the enzyme glucoamylase fromAspergillus nigerand proved to be very poor substrates for the enzymic hydrolysis.

ISSN:0732-8303    

DOI:10.1080/07328309108543966

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

For five carbohydrate substrates [methyl 4,6-O-(phenylmethylene)-1-thio-α-D-glucopyranoside1a, 1-cyano-1-deoxy-4,6-O-(phenylmethylene)-α-D-galactopyranose2a, methyl α-D-xylopyranoside3a, methyl β-D-arabinopyranoside4a, and methyl5-O-(tert-butyldiphenylsilyl)-α-D-ribofuranoside5a], selective mono-triflation was achieved where the reacting hydroxyl iscisand vicinal to a heteroatom.

ISSN:0732-8303    

DOI:10.1080/07328309108543967

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Diastereoselective hydroxymethylation of a suitably protected α-D-manno-hexodialdo-1,5-pyranoside with the Grignard reagent derived from (phenyldimethylsilyl)methyl chloride gives, after additional protecting group manipulations, an easy access to one donor and two acceptors of LD-Hepp. The latter derivatives could be applied successfully for the preparation of the disaccharides α-D-GlcpN-(1-7)-L-α-D-Hepp-OMe and L-α-D-Hepp-(1-6)-L-α-D-Hepp-OMe.

ISSN:0732-8303    

DOI:10.1080/07328309108543968

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Coupling of the sodium salt ofS-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-galacto-2-nonulopyranosylonate)-(2→'6)-2,3,4-tri-O-acetyl-1,6-dithio-β-D-glucopyranose (5), -β-D-galactopyranose (8), orS-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→'6)-O-(2,3,4-tri-O-acetyl-6-thio-β-D-galactopyranosyl)-(1→'4)-2,3,6-tri-O-acetyl-1-thio-β-D-glucopyranose (12), which were prepared from the corresponding 1-hydroxy compounds,1, 2, and9,via1-chlorination, displacement with thioacetyl group, andS-deacetylation, with (2S,3R,4E)-2-azido-3-O-benzoyl-1-O-(p-toluenesulfonyl)-4-octadecene-1,3-diol (13), gave the corresponding β-thioglycosides14, 18and22, respectively in good yields. The β-thioglycosides obtained were converted,viaselective reduction of the azide group, condensation with octadecanoic acid, and removal of the protecting groups, into the title compounds.

ISSN:0732-8303    

DOI:10.1080/07328309108543969

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Di- and trifucosylated derivatives (21 and 22) of para-lacto-N-hexaose were synthesized. Both structures have been shown to be present in small quantities in human milk, and have also been indicated as tumor-associated antigens. Thioglycoside mono- and disaccharide blocks were used to assemble a properly protected linear hexaose. Di- and trifucosylation at appropriate positions followed by deprotection then gave the desired oligosaccharides.

ISSN:0732-8303    

DOI:10.1080/07328309108543970

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

TheN,N'-dibenzoyl derivative of (2R,5R)-hept-6-yne-2,5-diamine, a very powerful inhibitor of the enzyme ornithine decarboxylase, was prepared from D-glucosamine in fourteen steps.

ISSN:0732-8303    

DOI:10.1080/07328309108543971

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Syntheses are described of a new ring system, namely derivatives ofN-acetyl [2-deoxy-β-D-mannopyranosid]urono-6,2-lactam. These were formed by participation of a 2-acetamido-2-deoxy group in the oxidation using pyridinium dichromate of a 6-hydroxyl group in a mannopyranosidic system The structures of the new compounds were determined mainly by NMR experimentsinter aliaby HMBC techniques.

ISSN:0732-8303    

DOI:10.1080/07328309108543972

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor