A convenient synthesis of l-ribose from d-fructose

An efficient method for the stereoselective synthesis of l-ribose was accomplished starting from commercially inexpensive d-fructose. The intermediates in the process can serve as versatile precursors for the preparation of l-nucleoside analogues.     

Boiling point of aqueous d-glucose and d-fructose solutions: Experimental determination and modeling with group-contribution method

Boiling points of aqueous solutions affect the design and operation of evaporators. Hence, boiling points of aqueous solutions of d-glucose and d-fructose were experimentally determined at soluble solute concentration from 10 to 60% sugar by mass and pressure from 20 to 93.6 kPa. The experimental data were correlated with data predicted by the calculation of the activity coefficients with the UNIFAC-Lyngby model using different approaches for decomposition of the molecular structure: the aliphatic groups and the cyclic groups. Moreover, the rise in experimental boiling point of the aqueous sugar solutions was evaluated by the Dühring's rule. It was observed that the cyclic approach resulted in better accuracy for liquid–vapor equilibrium prediction and the non-ideality of these solutions are relevant in the boiling point rise, confirming that the rise in boiling point of aqueous d-glucose and d-fructose concentrated solutions is significant to the design of heat and mass transport operations.     

Stereoselective synthesis of nonsymmetrical difructose dianhydrides from xylylene-tethered d-fructose precursors

Nonsymmetrical furanose-pyranose difructose dianhydrides (DFAs), a class of cyclic disaccharides present in foodstuffs, have been prepared in high yield by connecting the reacting monosaccharide moieties through a xylylene bridge prior to triflic acid-promoted bis-spiroketalization. The reaction can then proceed either intra- or intermolecularly, both the regio- and the stereoselectivity being strongly dependent on the spacer length. Noteworthy, the longer m- and p-xylylene positional isomers led to the thermodynamic α-d-fructofuranose β-d-fructopyranose 1,2′:2,1′-dyanhydride 1, the major DFA in commercial caramel, in a stereoselective manner. The shorter o-xylylene tether afforded preferentially the elusive contra-thermodynamic β-d-fructofuranose α-d-fructopyranose diastereomer 2, a trace constituent of caramel. The results have been rationalized in terms of stereoelectronic and conformational properties and offer new perspectives for the preparation of pure DFA standards for analytical and nutritional studies.     

Synthesis of l-α-phosphatidyl-d-myo-inositol 3,5-bisphosphate from d-glucose

Efficient synthesis of l-α-phosphatidyl-d-myo-inositol 3,5-bisphosphate was achieved from 1,2,5,6-diisopropylidene-d-glucose by utilizing ring-closing metathesis and catalytic OsO₄ dihydroxylation.     

Asymmetric synthesis of homo-apioneplanocin A from d-ribose

Homo-apioneplanocin A was efficiently synthesized via stereoselective hydroxymethylation, regio- and chemoselective hydroboration, and chemoselective oxidation as key steps from d-ribose.     

A highly efficient synthesis of unnatural l-sugars from d-ribose

A preparative and short synthesis of l-ribose and l-apiose was accomplished starting from d-ribose via stereoselective cis-dihydroxylation and C2-hydroxymethylation, respectively. These l-sugars can serve as versatile intermediates for the synthesis of l-nucleosides.     

Building carbohydrates on the dioxanone scaffold: stereoselective synthesis of d-glycero-d-manno-2-octulose

The title compound has been synthesized via two proline-catalyzed aldol addition reactions of 2,2-dialkyl-1,3-dioxan-5-ones: the first addition to 1,3-dithiane-2-carboxaldehyde, followed by reduction to the corresponding diol, protection of the OH groups and dithiane hydrolysis afforded a protected d-ribose that was used in the second aldol addition reaction.     

Benzamidinium d-glucuronate: Spectroscopic and structural elucidation

Benzamidinium d-glucuronate (1) crystallizes in the orthorhombic space group P2₁2₁2₁ and exhibits a 3 D network with molecules linked by moderate intermolecular hydrogen bonds (HNH…O_(solvent) 2.993 Å, HNH…OCO 2.894 Å, HNH…O_(cycle) 2.844 Å, OH…NH₂ 2.931 Å, OH…O_(solvent) 2.894, 2.924 and 2.715 Å (stronger)) with participation of cations, anions and solvent molecules. The IR-band assignment of carbohydrate moieties is elucidated by a comparison between the types and bond lengths of intermolecular interactions with participation of OH groups in d-glucuronate and linear polarized IR-(IR-LD) spectroscopic data. Experimental results are supported by theoretical ab initio calculations of benzamidinium cation and d-glucuronate anion.     

Syntheses and structural comparisons of two copper(II) complexes with the same formula having d-(+)- and d,l-1,2,2-trimethylcyclopentane-1,3-diamine ligands

Two five-coordinate copper(II) complexes, formulated as [Cu(L_a)₂Cl]BF₄ (1) and [Cu(L_b)₂Cl]BF₄ (2) having d-(+)-1,2,2-trimethylcyclopentane-1,3-diamine (L_a) and d,l-1,2,2-trimethylcyclopentane-1,3-diamine (L_b) ligands, have been synthesized and characterized. X-ray diffraction studies of 1 and 2 demonstrate that they crystallize in the different space groups (P2₁2₁2₁ for 1 and Pnma for 2), although they have identical unit cell volumes, due to the use of enantiomeric and racemic diamine ligands. One dimensional (1D) hydrogen-bond-sustained dimeric zigzag chains are formed by means of eight-membered N₂H₂CuBF₂ as well as 10-membered N₂H₄ClBF₂ hydrogen-bonded cycles. Thermal analyses for 1 and 2 are also described herein.     

One-pot inversion of d-mannono-1,4-lactone for the practical synthesis of l-ribose

l-Ribose was synthesized in a concise manner from d-mannono-1,4-lactone using one-pot inversion conditions. Treatment of d-mannono-1,4-lactone with piperidine, followed by mesylation-induced S_N2-type O-alkylation, afforded the desired one-pot inversion in an optimum yield, and the following straightforward transformations provided l-ribose in good yields.     

An efficient synthesis of d-ribo-C18-phytosphingosine and l-arabino-C18-phytosphingosine from d-fructose

d-ribo-C₁₈-phytosphingosine and l-arabino-C₁₈-phytosphingosine were synthesised starting from commercially inexpensive d-fructose. Metal-mediated fragmentation and stereoselective reduction were used as key steps to provide the hydrophilic portion of d-ribo and l-arabino phytosphingosines. Grubbs’ cross-metathesis and hydrogenation allowed the incorporation of hydrophobic tail.     

A convenient approach to total synthesis of synargentolide-B from l-ascorbic acid and d-ribose

A convenient and practical approach for the total synthesis of naturally occurring lactone synargentolide-B has been accomplished in 14 steps from the commercially available l-ascorbic acid and d-ribose involving Bestmann–Ohira reaction, zinc mediated allylation, ring closing-metathesis, and cross-metathesis reactions. The highlight of our strategy describes a one-pot reaction involving stereoselective addition of allylzinc reagent and selective reduction of terminal alkyne to obtain the key advanced intermediates.     

Stereoselective total synthesis of (−)-synrotolide diacetate from d-ribose

Stereoselective total synthesis of synrotolide as its diacetate from d-ribose utilizing a diastereoselective Grignard reaction, preferential (Z)-Wittig olefination, asymmetric allylation, and ring closing metathesis as key steps is reported.     

Quantitative thin-layer chromatography of carbohydrates using pentavalent vanadium in sulphuric acid : Determination of mixtures of d-Fructose, d-Glucose and sucrose

Pentavalent vanadium in sulphuric acid can be used for the quantitative analysis of sugars. The yellow pentavalent vanadium is reduced by carbohydrates to the blue tetravalent form, and either the consumption of vanadium(V) or the amount of vanadium(IV) formed can be measured. For model studies, different d-fructose-d-glucose-sucrose mixtures were used. The monosaccharides were separated from the disaccharide by thin-layer chromatography. Owing to the great difference in reactivity between aldohexoses and ketohexoses, d-fructose and d-glucose can be determined separately without prior separation. The method enables 10 μg of each sugar to be determined.     

New entry to pyrrolidine homoazasugars: conversion of d-arabinose into 2,5-anhydro-2,5-imino-d-glucitol via aminohomologation

The title homoazasugar, also referred as (2R,5S)-bis(hydroxymethyl)-(3R,4R)-dihydroxypyrrolidine, has been synthesized by addition of 2-lithiothiazole to the 2,3,5-tri-O-benzyl-d-arabinofuranose-derived nitrone---hydroxylamine mixture followed by reductive N-dehydroxylation and conversion of the thiazole ring into the hydroxymethyl group.     

Interactions of aluminum(III) with the biologically relevant ligand d-ribose

Aluminum(III) can be absorbed when it is appropriately complexed. There are several plasma components which can bind weakly Al(III). Many proteins bind Al(III) in solution quite strongly. Carbohydrates bearing an abundance of electronegative functional groups can interact with metal cations. In solution, d-ribose exists as a mixture at equilibrium of many isomers and only a few of them bear a ‘complexing’ sequence of the hydroxyl groups. The presence of d-ribose in an Al(III) solution experiences a decrease of its Brönsted-acid sites. The lowering of the Brönsted acidity of an Al(III)-d-ribose mixture suggests the existence of attractive interactions (‘association’) between Al(III) ion and the complexing sequence of the hydroxyls of d-ribose. There is enhancement in the stability of the interaction complexes between Al(III) and d-ribose through strong intramolecular hydrogen bonding, which offers the possibility to investigate the kinetics of the subsequent proton release reactions. On the basis of the kinetic results, it may be concluded that proton release reactions, which are associated with the complexation reactions, are associatively activated. The complexes (Al(H₂O)_6−n(d-ribose_−nH)⁽³⁻ⁿ⁾⁺) resulting from the various ‘complexing’ forms of d-ribose are formed at mainly acidic pH. As the pH increases, the values of the activation enthalpy, ΔH^≠, are changing, because of the formation of mixed hydroxo-complexes (Al(H₂O)_6−n−m(OH)_m(d-ribose_−nH)^(3−n−m)+); finally, OH⁻ displaces d-ribose from the coordination sphere of Al(III) in a rather slow process, i.e. with high values of ΔH^≠; the activation enthalpy values, ΔH^≠, decrease with the progression of the displacement, becoming finally very small due to the formation of a precipitate. Chelate coordination of d-ribose with some divalent and trivalent metal ions has been also reported.     

Asymmetric syntheses of the methyl glycosides of 2-deoxy-2-aminohexoses: d-allosamine, d-mannosamine, d-idosamine and d-talosamine

A range of the methyl glycosides of 2-deoxy-2-aminohexoses, comprising d-allosamine, d-mannosamine, d-idosamine and d-talosamine, were prepared from the corresponding d-aldopentoses via a seven step synthetic sequence. The doubly diastereoselective conjugate addition of the requisite antipode of lithium N-benzyl-N-(α-methylbenzyl)amide and in situ enolate oxidation with the requisite antipode of camphorsulfonyloxaziridine (CSO) was used as the key, stereodefining step. Sequential reduction of the resultant α-hydroxy-β-amino esters and oxidative cleavage of the C(1)–C(2) diol unit furnished the corresponding α-amino aldehydes. Subsequent N- and O-deprotection gave the target compounds (as mixtures of anomers) in good yield and high diastereoisomeric purity.     

Polyhydroxylated pyrrolidines. Part 4: Synthesis from d-fructose of protected 2,5-dideoxy-2,5-imino-d-galactitol derivatives

The readily available 3-O-benzoyl-4-O-benzyl-1,2-O-isopropylidene-5-O-methanesulfonyl-β-d-fructopyranose (5) was straightforwardly transformed into its d-psico epimer (8), after O-debenzoylation followed by oxidation and reduction, which caused the inversion of the configuration at C(3). Compound 8 was treated with lithium azide yielding 5-azido-4-O-benzyl-5-deoxy-1,2-O-isopropylidene-α-l-tagatopyranose (9) that was transformed into the related 3,4-di-O-benzyl derivative 10. Cleavage of the acetonide in 10 to give 11, followed by regioselective 1-O-pivaloylation to 12 and subsequent catalytic hydrogenation gave (2R,3S,4R,5S)-3,4-dibenzyloxy-2,5-bis(hydroxymethyl)-2′-O-pivaloylpyrrolidine (13). Stereochemistry of 13 could be determined after O-deacylation to the symmetric pyrrolidine 14. Total deprotection of 14 gave 2,5-imino-2,5-dideoxy-d-galactitol (15, DGADP).     

Practical synthesis of 1-deoxy-d-xylulose and 1-deoxy-d-xylulose 5-phosphate allowing deuterium labelling

An optimised gram scale synthesis allows the production of 1-deoxy-d-xylulose and 1-deoxy-d-xylulose 5-phosphate with possible deuterium labelling at C-5. Such substrates are required for investigations on the mevalonate-independent 2-C-methyl-d-erythritol 4-phosphate pathway for isoprenoid biosynthesis in bacteria and chloroplasts of phototrophic eukaryotes and for the biosynthesis of vitamins B₁ (thiamine diphosphate) and B₆ (pyridoxol phosphate) in bacteria.