1-O-2′-hydroxyalkyl and 1-O-2′-ketoalkyl glycerols

1-O-2′-Hydroxyalkyl glycerols were synthesized from 1,2-alkanediols and, alternatively, from 1,2-epoxyalkanes. Their 2,3-isopropylidene derivatives, 2′-acetoxy-2,3-isopropylidene derivatives and 2′,2,3-triacetoxy derivatives were prepared. 1-O-2′-Ketoalkyl-2,3-isopropylidene glycerols were prepared from the corresponding 2′-hydroxy derivatives; they were hydrolyzed to 1-O-2′-ketoalkyl glycerols. The compounds were characterized by thin-layer and gas-liquid chromatography, by infrared spectroscopy and mass spectrometry.     

Toward the synthesis of fine chemicals from lactose: preparation of d-xylo and l-lyxo-aldohexos-5-ulose derivatives

The transformation of (5R)-2,6-di-O-benzyl-5-C-methoxy-β-d-galactopyranosyl-(1→4)-2,3:5,6-di-O-isopropylidene-aldehydo-d-glucose dimethyl acetal (8) into partially protected derivatives of d-xylo- and l-lyxo-aldohexos-5-ulose has been reported, applying appropriate epimerisation methods to its 3′-O- and 4′-O-protected alcoholic derivatives.     

The action of thiols on derivatives of D-xylose

The action of thiols on 1,2,3,4-tetra-O-acetyl-β-D-xylopyranose gave 2- and 5-alkylthiopentose dithioacetals and alkyl 1-thio-D-xylopyranosides. On treatment with thiols and trifluoroacetic acid- 3-O-acetyl-1,2-O-isopropylidene-α-D-xylofuranose derivatives rapidly formed 4-O-acetyl-2,3-dialkylthio-D-ribose dithioacetal derivatives, which were in turn converted into 4-O-acetel-3-S-benzyl-2,5-epithio-3-thio-D-ribose (or D-arabinose) dithioacetal.     

Photo-oxygenation of glycosylfurans. Rearrangement of C-glycosyl into O-glycosyl derivatives

Photo-oxygenation of 3-ethoxycarbonyl-5-(2,3-O-isopropylidene-β-d-erythrofuranosyl)-2-methylfuran and 3-hydroxymethyl-5-(2,3-O-isopropylidene-β-d-erythrofuranosyl)-2-methylfuran yields the corresponding endo-peroxides which rearrange at room temperature into the O-glycosyl derivatives ethyl 2,3-O-isopropylidene-β-d-erythrofuranosyl 2-acetylfumarate and 2,3-O-isopropylidene-β-d-erythrofuranosyl 3-acetyl-3-hydroxymethylacrylate, respectively. The endo-peroxides can be reduced without rearrangement, yielding C-glycosyl derivatives. Alcoholysis of the O-glycosyl derivatives yields 2,3-O-isopropylidene-d-erythrose, dialkyl 2-acetyl-3-alkoxysuccinates, 4-ethoxycarbonyl-5-methoxy-5-methyl-2-oxo-2,5-dihydrofuran and 4-hydroxymethyl-5-methoxy-5-methyl-2-oxo-2,5-dihydrofuran.     

Separation and identification of O-acetyl-O-methyl-galactononitriles by gas-liquid chromatography and mass spectrometry

The gas-liquid-chromatographic retention-times and the mass-spectral features of partially methylated d-galactononitrile acetates are reported. Distinctive fragmentation of each of the mono-O-methyl derivatives allows their identification, and the results are applicable to the same substituted derivatives of the other aldohexoses. A new fragmentation-pathway, typical of the acetylated and the O-acetyl-O-methylaldononitriles, is proposed in order to justify previously unexplained fragments. This fragmentation competes with the known ones in derivatives that do not carry vicinal methoxyl groups.     

Proton spin-lattice relaxation-rates and nuclear Overhauser enhancement,in relation to the stereochemistry of β-d-mannopyranose 1,2-orthoacetates

Data are reported on spin-lattice relaxation-rates and nuclear Overhauser enhancement of protons of exo and endo diastereoisomers of 1,2-O-(1-methoxyethylidene) and 1,2-O-(1-benzyloxyethylidene) derivatives of 3,4,6-tri-O-acetyl-β-d-mannopyranose, and of some specifically deuterated analogs of these derivatives. The results verified assignments of the orientation at the quaternary carbon atom of the acetal ring, and yielded information about the orientations favored by the exocyclic C-methyl and benzyloxy substituents.     

Nucleophilic displacement reactions of some N-acetyl-N-aryl-β-d-xylopyranosylamines

The 4-O-methanesulphonyl (and toluene-p-sulphonyl), 3,4-di-O-methanesulphonyl (and toluene-p-sulphonyl), and 3,4-di-O-benzoyl-2-O-methanesulphonyl derivatives of N-acetyl-N-p-methoxyphenyl- and N-acetyl-N-p-chlorophenyl-β-d-xylopyranosylamine have been synthesised together with the N-acetyl-N-p-methoxyphenyl and N-acetyl-N-p-chlorophenyl derivatives of 3,4-di-O-benzoyl-2-O-methanesulphonyl-β-d-lyxopyranosylamine. The relative reactivity of the hydroxyl groups of the N-acetyl-N-aryl-β-d-xylopyranosylamines towards sulphonylation has been established. On heating the 2- and 4-mesylates of N-acetyl-N-aryl-β-d-xylopyranosylamines and the 2-mesylate of N-acetyl-N-aryl-β-d-lyxopyranosylamines with sodium azide in N,N-dimethylformamide or acetonitrile, either nucleophilic replacement of the mesyl groups of their solvolysis with participation of the N-acetyl group occurred. In this way, β-d-xylo compounds were converted into α-l-arabino and β-d-lyxo derivatives.     

Facile synthesis of 1,2-trans-O-acetyl glycosyl chloride derivatives of cellobiose,lactose, and D-glucose

Solutions of O-acetyl-α-glycosyl bromide derivatives of d-glucose, cellobiose, and lactose in hexamethylphosphoramide were converted into corresponding β-chlorides at room temperature by the action of lithium chloride. At 3:1 mM ratios of chloride ion to glycose, 5–10% w/v solutions of glycosyl bromide formed α- and β-chlorides in ratios of (or greater than) 1:19 within 2–13 min and produced crystalline β-chlorides in 70–80% yields. Anomeric compositions were determined by n.m.r. spectroscopy in hexamethylphosphoramide. Older methods of preparing 1,2-trans-O-acetylgIycosyl chlorides, with aluminum chloride or titanium tetrachloride, gave the α- and β-cellobiosyl and -Iactosyl chlorides in ratios that varied from 2:3 to 1:4 and reached 85–95% levels of β-chloride only with β-d-glucose pentaacetate. When hydrolyzed under conditions that controlled solution acidity, the β-cellobiosyl and -Iactosyl chlorides each gave 2-hydroxy derivatives in yields that could be varied from 16 to 60%. Hepta-O-acetyl-2-O-methyl-α-cellobiose was prepared to demonstrate how these hydrolysis mixtures can be used to synthesize a 2-O-substituted derivative.     

Thermodynamic stabilities and conformational analyses of 4,6-O-acetalized 1,5-anhydro-5-thio-dl-threo-2-enitols

4,6-O-Methylidene and 4,6-O-neopentylidene derivatives of 1,5-anhydro-2,3-dideoxy-5-thio-dl-thero-hex-2-enitol having the C-inside form were found to be thermodynamically more stable than the corresponding O-inside conformers. Thermodynamic stabilities, as well as the conformation of sulfoxide and sulfone derivatives of the 4,6-O-neopentylidene compound were examined by experiment and ab initio MO and DFT calculations. These thermodynamic stabilities, and the most stable conformations determined by NMR data, were corroborated by calculations.     

4-O[(S)-1-carboxyethyl]-D-glucuronic acid: a component of the Klebsiella type 37 capsular polysaccharide

The acidic sugar component in the Klebsiella type 37 capsular polysaccharide (K 37) has been identified as 4-O-[(S)-1-carboxyethyl]-D-glucuronic acid. The identification is based upon chemical and spectroscopic studies, and the identity of the carboxyl-reduced sugar, 4-O-[(S)-2-(1-hydroxy)propyl]-D-glucose and derivatives, with the corresponding substances synthesized by an unambiguous route.     

Chemistry of 1,1-bis(acylamido)-1-deoxyalditols. Base-catalyzed,intramolecular O,N-transacylation of per-O-acyl-1,1-bis(benzamido)-1-deoxy-d-glucitols in aprotic solvents

Penta-O-acetyl and penta-O-propanoyl derivatives of 1,1-bis(benzamido)-1-deoxy-d-glucitol are transformed into 1-acetamido-1-benzamido-1-deoxy-d-glucitol and 1-benzamido-1-deoxy-1-propanamido-d-glucitol, respectively, by heating with a suspension of potassium cyanide in acetonitrile, and subsequently O-deacylating with sodium methoxide in methanol. The reaction was also studied in the presence of a crown ether. When other nucleophiles (HO^? and CH³O^?) or other aprotic solvents (propanonitrile, benzene) were employed, the yields of transacylation products diminished noticeably; likewise, the use of sodium as the counter-ion significantly affected this reaction. These results are qualitatively discussed in terms of the solvent effects on the reactivity of the nucleophiles employed.     

1,4-anhydride formation of solvolysis of 1,6-disubstituted derivatives of 2,3,4,5-tetra-O-acetylallitol

The 6-O-mesyl, 6-O-tosyl, 6-bromo-6-deoxy, and 6-deoxy-6-iodo derivatives of 1,4-anhydro-DL-allitol were obtained by treatment of the corresponding 1,6-di-substituted derivatives (2, 3, 6, 4) of 2,3,4,5-tetra-O-acetylallitol with hot, methanolic hydrogen chloride. Compounds 2 and 3 were prepared by the acetolysis of the 1,6-di-O-mesyl and 1,6-di-O-tosyl derivatives (8 and 11) of di-O-benzylideneallitol. Iodide displacement on 2 gave 4, and detritylation-bromination of 2,3,4,5-tetra-O-acetyl-1,6-di-O-tritylallitol (5) gave 6. The acetal residues of di-O-benzylideneallitol have been shown to span the secondary carbon atoms.     

Methanolysis as a model reaction for oligosaccharide synthesis of some 6-substituted 2,3,4-tri-O-benzyl-D-galactopyranosyl derivatives

In the methanolysis of some 2,3,4-tri-O-benzyl-D-galactopyranosyl derivatives, the nature of the C-6 substituent appears to have minor influence on the steric outcome of the reaction compared with the effects of solvent and the nature of the leaving group at C-1. Different combinations of experimental parameters have given methyl glycosides mixtures, the compositions of which vary between 0–70% of α-anomer. Attempts to prepare oligosaccharides from 6-O-substituted 2,3,4-tri-O-benzyl-D-galactopyranosyl derivatives have shown methanolysis to be a less satisfactory model reaction than is the case for the D-glucose series, even when the alcohol and glycosyl derivative are in near equivalent quantities.     

Chemical synthesis of 1-O-alkyl and 1-O-acyl dihydroxyacetone-3-phosphate

A method for the chemical synthesis of 1-O-hexadecyl dihydroxyacetone-3-phosphate is described. The synthesis was started with the preparation of O-hexadecyl glycolic acid by condensing 1-iodohexadecane with ethyl glycolate in the presence of silver oxide, followed by saponification and free acid liberation with HC1. O-Hexadecyl glycolic acid was converted to the acid chloride (with oxalyl chloride) which was condensed with diazomethane in diethyl ether to form hexadecyloxy diazoacetone. The diazoketone was decomposed by H₃PO₄ in dioxane to give the desired product, 1-O-hexadecyl dihydroxyacetone-3-phosphate. The product was purified by chromatography on silicic acid column followed by an acid wash. The final yield was 50% starting from O-hexadecyl glycolic acid. Analytical, spectral (IR, NMR) and chromatographic properties of 1-O-hexadecyl dihydroxyacetone-3-phosphate are described. The method described here may be used to prepare different acyl and alkyl derivatives of dihydroxyacetone phosphate in good yield as illustrated by describing the procedure for the synthesis of 1-O-palmitoyl dihydroxyacetone-3-phosphate, 1-O-hexadecyl dihydroxyacetone-3-[³²P] phosphate and the dimethyl ketal of 1-O-palmitoyl [2-¹⁴C]dihydroxyacetone phosphate.     

Hydrogenolysis of the isomeric 1,2:4,6-di-O-benzylidene-α-d-glucopyranose derivatives with the LiAlH4AlCl3 reagent

Both isomers of 1,2:4,6-di-O-benzylidene-α-d-glucopyranose (and their 3-O-acetyl and 3-O-benzyl derivatives) have been prepared and their ¹H- and ¹³C-n.m.r. spectra assigned. The mode of hydrogenolysis of the dioxolane ring in these isomers by the LiAlH₄AlCl₃ reagent is determined by the configuration at the acetal carbon and is independent of the electronic character of the two oxygen atoms.     

Arbutin derivatives from the buds of Vaccinium dunalianum and their MS/MS spectrometric fragmentations

Four arbutin derivatives were isolated from the buds of Vaccinium dunalianum in which 4-hydroxyphenyl-6′-(3''-O-β-D-glucopyranosyl-4''-hydroxycinnamoyl)-O-β-D-glucopyranoside (1) was a new compound. The structure of the new compound was determined on the basis of NMR and HR-ESI-MS data. All the arbutin derivatives were subjected to the MS/MS analyses from which the MS/MS spectrometric fragmentations were summarized.     

Derivatives of S-α- and -β-d-hexopyranosyl thiophosphates

Di-tert-butyl esters of the tetra-O-acetyl and tetra-O-benzyl derivatives or S-α- and -β-D-glucopyranosyl thiophosphates were prepared by reaction of di-tert-butyl triethylammonium phosphorothioate with tetra-O-acetyl- or tetra-O-benzyl-hexopyranosyl halides.     

A convenient synthesis of p-nitrophenyl 2-deoxy-2-(thio-acetamido)-β-d-glucopyranoside, -galactopyranoside,and their 1-thio analogs as inhibitors of 2-acetamido-2-deoxy-β-d-glucosidase

The acetamido group of p-nitrophenyl 2-acetamido-2-deoxy-β-d-glucopyranoside, -β-d-galactopyranoside, and their 1-thio analogs was modified by replacement of the amide-carbonyl oxygen atom with sulfur by treatment of their fully acetylated derivatives with phosphorus pentasulfide in pyridine. The resulting p-nitrophenyl 2-deoxy-2-thioacetamido-β-d-hexopyranoside triacetates were O-deacetylated with catalytic amounts of sodium methoxide in methanol to obtain p-nitrophenyl 2-deoxy-2-thioacetamido-β-d-glucopyranoside, -β-d-galactopyranoside, and their 1-thio analogs. These derivatives inhibited 2-acetamido-2-deoxy-β-d-glucosidase from Turbatrix aceti to various extents. Also obtained in significant yields in the aforementioned reaction with phosphorus pentasulfide in pyridine were the two hitherto unreported thiazolines, namely, 2-methyl(2-acetamido-3,4,6-tri-O-acetyl-α-d-glucopyrano)[2′,1′:4,5]-2-thiazoline and 2-methyl(2-acetamido-3,4,6-tri-O-acetyl-α-d-galactopyrano)[2′,1′:4,5]-2-thiazoline.     

Dérivés Monotritylés du D-xylose

Monotritylation of O-acetyl derivatives of D-xylopyranose and D-xylofuranose with trityl chloride in acetonitrile-pyridine gave the tri-O-acetyl derivatives of 1-,2-, 3-, and 5-O-trityl-D-xylofuranose and of 1-, 2-, 3-, and 4-O-trityl-D-xylopyranose which were required for the identification of the various monotrityl derivatives obtained in the tritylation at 50° of D-xylose with trityl chloride in pyridine or hexamethylphosphoric triamide-silver acetate.     

Synthesis of glycopeptide derivatives containing the 2-acetamido-N-(L-aspart-4-oyl)-2-deoxy-β-D-glucopyranosylamine linkage and having the amino acid sequences 32–34, 33–35,33–37, and 33–38 of bovine ribonuclease

The synthesis is described of the glycotripeptide derivatives 2-acetamido-3,4,6-tri-O-acetyl-N-[N-(benzyloxycarbonyl)-L--seryl-L-nitroarginyl-L-aspart-4-oyl]-2-deoxy-β-D-glucopyranosylamine, 2-acetamido-3,4,6-tri-O-acetyl-N-[N-(benzyloxycarbonyl)-L-seryl-L-nitroarginyl-L-aspart-1-oyl-(1-p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine, and 2-acetamido-3,4,6-tri-O-acetyl-N-[N-(benzyloxycarbonyl)-L-nitroarginyl-L-aspart-1-oyl-(L-leucine methyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine, and of the glycopentapeptide and glycohexapeptide derivatives 2-acetamido-3,4,6-tri-O-acetyl-N-[N-(benzyloxycarbonyl)-L-nitroarginyl-L-aspart-1-oyl-(L-leucyl-L-threonyl-threonyl-N^ε-tosyl-L-lysine-(p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-D-glycopyranosylamine and 2-acetamido-3,4,6-tri-O-acetyl-N-[N-(benzyloxycarbonyl)-L-nitroarginyl-L-aspart-1-oyl-(L-leucyl-L-threonyl-N^ε-tosyl-L-lysyl-L-aspartic 1,4-di-p-nitrobenzyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine.