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.     

Fragmentation of deprotonated d-ribose and d-fructose in MALDI—Comparison with dissociative electron attachment

We present a detailed, collaborative study on the fragmentation of deprotonated native d-ribose and d-fructose and the isotopically labelled 1-¹³C-d-ribose, 5-¹³C-d-ribose and C-1-d-d-ribose. The fragmentation is studied in a matrix assisted laser desorption/ionization time of flight mass spectrometer (MALDI ToF MS), both in in-source decay (ISD) and post-source decay (PSD) mode and compared with fragmentation through dissociative electron attachment (DEA). Fragmentation of deprotonated monosaccharides formed in the MALDI process, as well as their transient molecular anions formed upon electron attachment are characterized by loss of different numbers of H₂O and CH₂O units. Two different fragmentation pathways leading to cross-ring cleavage are identified. Metastable decay of deprotonated d-ribose proceeds either via an X-type cleavage yielding fragment anions at m/z = 119, 100 and 89, or via an A-type cleavage resulting in m/z = 89, 77 and 71. A fast and early metastable cross-ring cleavage of deprotonated d-ribose observed in in-source decay is dominated by X-type cleavage leading mainly to m/z = 100 and 71. For dissociative electron attachment to d-ribose a sequential dissociation was identified that includes metastable decay of the dehydrogenated molecular anion leading to m/z = 89. All other fragmentation reactions in DEA to d-ribose are likely to proceed directly and on a faster timescale (below 400 ns).     

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.     

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.     

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.     

Stereoselective total synthesis of ophiocerin D from d-xylose

A stereoselective total synthesis of ophiocerin D is reported by a combination of a ‘chiron’ approach and an asymmetric synthesis, from d-xylose. Of the four stereogenic centers, the vic diols C3/C4 and C5/C6 were obtained by Sharpless asymmetric dihydroxylation and from d-xylose, respectively.     

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.     

From d-xylose to a d-glycero-l-altrose derivative

A key intermediate corresponding to a rare sugar framework has been synthesized, starting from d-xylose, an inexpensive carbohydrate. This approach gave access to new elaborated sugar moieties for structure–activity relationships in the KRN research.     

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.     

An efficient synthesis of d-ribo- and l-lyxo-phytosphingosine from d-tartaric acid

The preparations of d-ribo- and l-lyxo-phytosphingosines (1, 2) are described. Chelation-controlled addition of tetradecylmagnesium bromide to pentylidene-protected d-threitol aldehyde 6 afforded the key intermediate tetrol 7, providing the desired l-lyxo stereochemistry of phytosphingosine. Inversion at C4 of intermediate 7 provided the d-ribo stereochemistry.     

New phosphine-imine and phosphine-amine ligands derived from d-gluco-, d-galacto- and d-allosamine in Pd-catalysed asymmetric allylic alkylation

New phosphine-imine and phosphine-amine chiral ligands which were easily prepared from d-gluco-, d-galacto- and d-allosamine furnished a high level of enantiomeric excess (up to 99%) in the Pd(0)-catalysed asymmetric allylic alkylation of racemic 1,3-diphenyl-2-propenyl acetate with malonates.     

Highly efficient stereoselective synthesis of d-erythro-sphingosine and d-lyxo-phytosphingosine

Starting from a single suitable functionalised epoxide, a highly efficient stereoselective synthesis of d-erythro-sphingosine and d-lyxo-phytosphingosine is described. The approach allows the formal preparation of all stereoisomers of these sphingoid structures.     

Stereo-controlled approach to pyrrolidine iminosugar C-glycosides and 1,4-dideoxy-1,4-imino-l-allitol using a d-mannose-derived cyclic nitrone

Intramolecular N-alkylation of 2,3-O-isopropylidene-5-O-methanesulfonyl-6-O-t-butyldimethylsilyl-d-mannofuranose-oxime 7 afforded a five-membered cyclic nitrone 9, which on N–O bond reductive cleavage followed by deprotection of –OTBS and acetonide functionalities gave 1,4-dideoxy-1,4-imino-l-allitol (DIA) 3. Addition of allylmagnesium chloride to nitrone 9 afforded α-allylated product 10a in high diastereoselectivity providing an easy entry to N-hydroxy-C1-α-allyl-substituted pyrrolidine iminosugar 4a after removal of protecting group, while N–O bond reductive cleavage in 10a afforded C1-α-allyl-pyrrolidine iminosugar 4b.     

Stereoselective synthesis of 3-glycosyl-5-methoxycarbonyl-isoxazolidines from d-galactose and d-glucose

Regio- and stereoselective cycloaddition of methyl acrylate to C-glycosyl nitrones derived from d-galactose and d-glucose, giving 5-methoxycarbonyl-3-(pentoglycos-5-yl or pentitol-1-yl)isoxazolidines, is reported. Transformation of one of them into a 4-hydroxy-2-(pentoglycos-5-yl)pyrrolidine derivative, potentially useful in a route to polyhydroxy-perhydroazaazulenes, was achieved.     

Transport characterisation of a PIM system used for the extraction of Pb(II) using d2ehpa as carrier

The facilitated transport of lead(II) through polymeric inclusion membranes consisting of cellulose triacetate as polymeric support, bis-(2-ethylhexyl)-phosphoric acid (d2ehpa) as carrier, and tris-(2-butoxyethyl)phosphate as plasticiser (tbep), is investigated. The influence of some of the aqueous and membrane components on the permeability of Pb(II) was studied. The maximum flux obtained with these membranes is 3.5×10⁻⁶ mol m⁻² s⁻¹, which is of the same order of magnitude of those reported for supported liquid membranes and is in the upper range of those reported for polymeric inclusion membranes. Aqueous and membranes resistances were determined from a model that describes the transport mechanism across the membranes using the stoichiometric relationship and the extraction equilibrium constant value of 6.2×10⁻⁴ determined independently by solid–liquid extraction. An activation energy of 11 kJ mol⁻¹ was also determined for Pb(II) migration, which suggest that the transport of Pb(II) is controlled by a membrane diffusion mechanism. Membrane characterisation was performed using several techniques including atomic force microscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and thermal analysis.     

Synthesis of ent-gabosine E from d-mannose by intramolecular nitrone–olefin cycloaddition

Intramolecular nitrone–olefin cycloaddition in a mannose template followed by N–O cleavage, quaternization of the resulting amine, and finally oxidative elimination of the amino group affords, after deprotection, ent-gabosine E in enantiomerically pure form.     

EPR and optical absorption studies of Cr ions in d-gluconic acid monohydrate

EPR studies are carried out on Cr³⁺ ions doped in d-gluconic acid monohydrate (C₆H₁₂O₇·H₂O) single crystals at 77 K. From the observed EPR spectra, the spin Hamiltonian parameters g, |D| and |E| are measured to be 1.9919, 349 (×10⁻⁴) cm⁻¹ and 113 (×10⁻⁴) cm⁻¹, respectively. The optical absorption of the crystal is also studied at room temperature. From the observed band positions, the cubic crystal field splitting parameter Dq (2052 cm⁻¹) and the Racah interelectronic repulsion parameter B (653 cm⁻¹) are evaluated. From the correlation of EPR and optical data the nature of bonding of Cr³⁺ ion with its ligands is discussed.