摘要:

Maytansine (1) is a macrocyclic natural product with significant anti-cancer activity. A derivative (4) of D-glucal is converted to a model compound (10) for the lower periphery of the maytansinoid ring via alkylation at C-6 using an allylic sulfide anion, followed by oxidation to the sulfoxide and [2,3]-sigmatropic rearrangement to the sulfenate ester. In addition, a method is disclosed for conversion of D-arabinose to a chiron (18) for a portion of the upper periphery of the maytansinoids.

ISSN:0732-8303    

DOI:10.1080/07328309808002895

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The following analogs of the title determinant, methyl 4,6-dideoxy-4-(3-deoxy-L-glycero-tetronamido)-2-O-methyl-α-D-mannopyranoside, have been prepared: methyl 3,4,6-trideoxy-4-(3-deoxy-L-glycero-tetronamido)-2-O-methyl-α-D-mannopyranoside, methyl 4,6-dideoxy-4-(4-hy droxybutyramido)-2-O-methyl-α-D-mannopyranoside, methyl 4,6-dideoxy-4-(3,4-dideoxy-L-glycero-tetronamido)-2-O-methyl-1-a-D-mannopyranoside, methyl 4,6-dideoxy-4-(3-deoxy-D-glycero-tetronamido)-2-O-methyl-α-D- mannopyranoside, methyl 4,6-dideoxy-4-(2-deoxy-L-glycero-tetronamido)-2-O-methyl-α-D- mannopyranoside, methyl 4-acetamido-4,6-dideoxy-2-O-methyl-α-D-mannopyranoside, methyl 4,6-dideoxy-4-(3-deoxy-L-glycero-tetronamido)-2-O-ethyl-α-D-mannopyranoside, and methyl 4,6-dideoxy-4-(3-deoxy-L-glycero-tetronamido)-2-O-propyl-α-D- mannopyranoside.

ISSN:0732-8303    

DOI:10.1080/07328309808002896

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The product distribution of the iodine-catalyzed methyl glycosidation of four pentoses (D-ribose, D-arabinose, D-xylose, and D-lyxose) and two 6-deoxyhexoses (L-rhamnose, and D-fucose) was studied by HPLC using an APS column (dihydrogen sulphate form) with different acetonitrile-water mobile phases. In agreement with earlier results, a temperature dependent on-column isomerization was observed for all the investigated aldoses, except for ribose. The first-eluted furanosides were followed by pyranosides, and the free sugars were eluted last with the highest retention volumes.

ISSN:0732-8303    

DOI:10.1080/07328309808002897

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

All possible nine regioisomers ofmyo-inositol bisphosphate were synthesized using various isopropylidene and benzoyl inositol derivatives as intermediates. These intermediates were successfully phosphorylated with diethyl chlorophosphite followed by oxidation. Selective diphosphorylations on several IBz3intermediates were also examined as possible routes to IP2S. All of the protecting groups were easily removed in a one-pot procedure to give the sodium salts of the title compounds, IP2regioisomers.

ISSN:0732-8303    

DOI:10.1080/07328309808002898

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A D-myo-inositol derivative (3), obtained from methyl α-D-glucopyranoside by Ferrier rearrangement, was efficiently transformed to D-myo-inositol 1,2,6-trisphosphate (1, α-trinositol) and D-myo-inositol 2,6-bisphosphate (2).

ISSN:0732-8303    

DOI:10.1080/07328309808002899

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Imidazylates1-3were irradiated in methanol in the presence and in the absence of the electron donortriethylamine. In each case photochemical deprotection occurred in excellent yield to form the partially protected sugar from which the imidazylate was synthesized. Reactions in the presence of triethylamine required much shorter irradiation times.

ISSN:0732-8303    

DOI:10.1080/07328309808002900

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Esterification of L-ascorbic acid in concentrated sulfuric acid with 0.33 moles of gallic acid gave a 90% yield of a 2:5 mixture of L-ascorbyl 5- and 6-gallate esters. The 6-gallate ester (1) was purified from the 5-gallate ester (2) by fractional crystallization in 40% yield. Three other aromatic derivatives of L-ascorbic acid also were prepared. The order of antioxidant activities of the L-ascorbyl derivatives determined by thiobarbituric acid number in methyl linolenate at 37 °C was as follows: 6-gallate (1) > 6-(3′,4′ -dihydroxy)benzoate (3) = 6-(4′ -hydroxy)phenyl ether (4) >6-(4′ methoxy)phenyl ether (5).

ISSN:0732-8303    

DOI:10.1080/07328309808002901

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A new family of bolaamphiphiles in which two glucosylamine or galactosylamine moieties are linked via a β-N-glycosidic bond to an α,ω-dicarboxylic acid has been described. The 1-D-glucosamide and 1-D-galactosamide bolaamphiphiles were obtained in good yield by the condensation of the dicarboxylic acid dichloride with the corresponding 1-aldopyranosylamine.

ISSN:0732-8303    

DOI:10.1080/07328309808002902

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

For the construction of N-glycoprotein glycan chains, valuable potential glycosyl donors,O-α-D-mannopyranosyl-(1→2)-α-D-mannopyranose octaacetate (19) andO-α-D-mannopyranosyl-(1→2)-O-α-D-mannopyranosyl-(1→2)-α-D-mannopyranose undeca-acetate (20) were obtained in gram-scale by the acetylation and subsequent partial acetolysis of baker's yeast, without the isolation of mannan. The acetolytic products were investigated by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Octaacetates of mannobiose (1→3) (11) and (1→6) (17) were chemically synthesized.

ISSN:0732-8303    

DOI:10.1080/07328309808002903

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

4,6-O-[(R)-1-carboxylethylidene]Galβ1 →4GlcNAcβ1 →3Fucβ1 →OMe, a pyruvated trisaccharide unit involved in the aggregation factor of the marine spongeMicrociona prolifera, was synthesized stereospecifically and unambiguously employing thioglycosides as glycosyl donors to construct glycosidic bonds.

ISSN:0732-8303    

DOI:10.1080/07328309808002904

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor