The first ring inversion of pyranoses induced by bulky silyl protections at the 2- and 3-positions

The pyranose rings of the 2,3-bis-O-tert-butyldiphenylsilyl-α- and β-d-glucopyranoses, and of the 2,3-bis-O-tert-butyldimethylsilyl-β-d-glucopyranose were in the ¹C₄ form. These findings indicate that the introduction of bulky silyl protecting groups at the 2- and 3-positions can flip a pyranose ring into the axial-rich chair form. Previous such ring inversions have been carried out by the silyl protections at the 3- and 4-positions.     

Total synthesis of (+)-lentiginosine from d-glucose

A total synthesis of (+)-lentiginosine, a potent and selective amyloglucosidase inhibitor, is reported from a d-glucose-derived epoxide in 38% overall yield. In this synthesis, ambient conditions and readily available starting materials and reagents are used.     

Amperometric simultaneous sensing system for d-glucose and l-lactate based on enzyme-modified bilayer electrodes

An amperometric biosensor system which uses screen-printed electrodes to simultaneously detect d-glucose and l-lactate has been developed and applied for simple and rapid determination of d-glucose and l-lactate levels in lactic fermenting beverages. The system was constructed from three-dimensionally layered electrodes. Taking into consideration the effects of easily oxidized substances contained in the samples, ferricyanide ions, which are electrochemically oxidized at a lower voltage, were chosen as a mediator. A linear relationship between steady-state current and concentration was found over a range of 1-100 mM (d-glucose) and 1-50 mM (l-lactate); the variation coefficients were 1.43% (n = 10) and 3.50% (n = 10) for the d-glucose and l-lactate sensors, respectively. When applied to lactic fermenting beverages, there was good agreement between the results obtained by the proposed sensing system and those obtained by the HPLC method. Using the proposed method, assays were completed within 5 min.     

Novel formal synthesis of stereospecifically C-6 deuterated d-glucose employing configurationally stable alkoxymethyllithiums

The synthesis and testing of configurational stability of chirally monodeuterated PMB- and THP-substituted oxymethyllithiums are described. Macroscopically they are configurationally stable up to −35 °C, the limit of their chemical stability, and microscopically even up to 0 °C. Furthermore, THP-protected oxy-[D₁]methyllithium has been applied in the formal synthesis of (6R)-[6-D₁]-d-glucose (four steps, 40% yield), an example of its use as a homochiral hydroxymethyl synthon.     

Selection of synthetic receptors capable of sensing the difference in binding of d-Ala-d-Ala or d-Ala-d-Lac ligands by screening of a combinatorial CTV-based library

Screening of a combinatorial CTV-based artificial, synthetic receptor library 1 {1-13, 1-13, 1-13} for binding of a variety d-Ala-d-Ala and d-Ala-d-Lac containing ligands (6-11) was carried out in phosphate buffer (0.1 N, pH=7.0). After screening and Edman sequencing, synthetic receptors were found containing amino acid sequences, which are either characteristic for binding dye labeled d-Ala-d-Ala or d-Ala-d-Lac containing ligands. For example, receptors capable of binding d-Ala-d-Ala containing ligands 6, 7, 9 and 11 contained—almost in all cases—at least one basic amino acid residue—predominantly Lys—in their arms. This was really a striking difference with the arms of the receptors capable of binding d-Ala-d-Lac containing ligands 8 and 10, which usually contained a significant number of polar amino acids (Gln and Ser), especially in ligand 8, but hardly any basic amino acids. Use of different (fluorescent) dye labels showed that the label has a profound, albeit not decisive, influence on the binding by the receptor. A hit from the screening of the CTV-library with FITC-peptidoglycan (6) was selected for resynthesis and validation.     

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.     

Improved synthesis of 6-amino-6-deoxy-d-galactono-1,6-lactam and d-mannono-1,6-lactam from corresponding unprotected d-hexono-1,4-lactones

Regioselective bromination of unprotected d-galactono-1,4-lactone and d-mannono-1,4-lactone with PPh₃/CBr₄ led to 6-bromo-6-deoxy derivatives. These intermediates were treated with LiN₃ and hydrogenated to give 6-amino-6-deoxy-d-galactono-1,6-lactam (8) and 6-amino-6-deoxy-d-mannono-1,6-lactam (13) in 74 and 67% overall yield, respectively.     

Novel synthesis of 5-thio-hexopyranoside: preparation of 5-thio-d- and l-glucose and 1,6-anhydro-5-thio-l- and d-altrose

Asymmetric synthesis of both d- and l-isomers of 5-thioglucose and 1,6-anhydro-5-thioaltrose are described. The key intermediates, l- and d-threose diethylacetal derivatives, were derived by chemical transformation from d-xylose or d-arabinose and by Sharpless asymmetric dihydroxylation from γ-hydroxycrotylaldehyde diethylacetal. They transformed to γ-thiiranyl diethylacetal via trans-2,3-epoxy alcohol in seven steps. Acetic acid-promoted cyclization of γ-thiiranyl diethylacetal gave 5-thiopyranoside. Removal of the protected groups under the acidic conditions afforded 5-thio-d- and l-glucose and 1,6-anhydro-5-thio-l- and d-altrose, respectively.     

An efficient synthesis of selectively functionalized d-rhamnose derivatives

d-Rhamnose is an important component of bacterial lipopolysaccharides. This paper describes a short and highly efficient synthesis of d-rhamnose from d-mannose. The synthesis of selectively C-4 modified d-rhamnosides and 6-deoxy-d-talosides as potential building blocks for complex oligosaccharide synthesis is also discussed.     

Novel practical synthesis of d-cycloserine

The synthesis of d-cycloserine has been successfully accomplished from the readily available d-serine through three simple and efficient routes. In each synthetic strategy, cyclization reactions are involved as the key step, and one-pot processes are employed. The simple treatment and mild reaction conditions are attractive features in this methodology.     

New building blocks for peptide and depsipeptide synthesis: hexafluoroacetone protected l-homoisoserine and d,l-homoisocysteine derivatives

Efficient syntheses of l-homoisoserine and d,l-homoisocysteine derivatives starting from l-malic and d,l-thiomalic acid using hexafluoroacetone as protecting and activating agent are described. The new compounds are interesting building blocks for the preparation of non-natural peptides and depsipeptides as well as for the construction of new GABA derivatives.     

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.     

Synthesis of homochiral 2-C-perfluoroalkyl substituted d- and l-riboses

Homochiral 2-C-perfluoroalkyl substituted d- and l-riboses were synthesized via Barbier, Grignard and Ruppert type reactions. The influence of the size of the perfluoroalkyl groups, attached to C-2, on the furanose/pyranose as well as on the α-furanose/β-furanose and α-pyranose/β-pyranose ratio in solution was studied.     

A general strategy for the stereoselective synthesis of l-1-deoxyallonojirimycin and d-1-deoxygulonojirimycin

A general strategy for the synthesis of deoxyazasugars from d-glucose is described. Ring-closing metathesis and stereoselective dihydroxylation reactions were used as key steps.     

In situ 1,3-dipolar azide cycloaddition reaction: synthesis of functionalized d-glucose based chiral piperidine and oxazepine analogues

Functionalized furanose-fused piperidines 4-6 and oxazepines 15-17, useful precursors for structurally unique bioactive nucleosides as well as for potential glycosidase inhibitors, have been synthesized by the application of 1,3-dipolar azide cycloaddition (DAC) reaction on d-glucose based substrates. The strategy works well even with the nucleoside analogue 8, affording the bicyclic nucleoside analogues 11 and 12.     

Efficient synthesis of new N-alkyl-d-ribono-1,5-lactams from d-ribono-1,4-lactone

d-Ribono-1,4-lactone was treated with ethylamine in DMF to afford N-ethyl-d-ribonamide 9a in quantitative yield. Bromination of amide 9a by the system SOBr₂ in DMF or PPh₃/CBr₄ in pyridine led, after acetylation, to epoxide 7. However, treatment of amide 9a with acetyl bromide in dioxane followed by acetylation gave 2,3,4-tri-O-acetyl-5-bromo-5-deoxyl-N-ethyl-d-ribonamide 10a. Methanolysis of 10a, with sodium methoxide, afforded the N-ethyl-d-ribonolactam 11a in 51% overall yields. Using this method, N-butyl, N-hexyl, N-dodecyl, and N-benzyl-d-ribonolactams 11b-e were obtained in good yields (48-53%).     

Carbanucleosides: synthesis of both enantiomers of 2-(6-chloro-purin-9-yl)-3,5-bishydroxymethyl cyclopentanol from d-glucose

The key intermediate 1,2:5,6-di-O-isopropylidene-3-deoxy-3β-allyl-α-d-glucofuranose (8) could be conveniently prepared through radical induced allyl substitution at C-3 of appropriate 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose derivatives (7a,b) and used to synthesize enantiomeric bishydroxymethyl aminocyclopentanols 13 and 19 by the application of a 1,3-dipolar nitrone cycloaddition reaction involving the C-5 or C-1 aldehyde functionality. The products were subsequently transformed into carbanucleoside enantiomers 15 and 21. The diastereomeric isoxazolidinocyclopentane derivative 20 was similarly converted to carbanucleoside 22.     

Total synthesis of (+)-epiquinamide from d-mannitol

The total synthesis of (+)-epiquinamide, a novel quinolizidine alkaloid isolated from the Ecuadoran poison frog, Epipedobates tricolor is described. The key step includes a ring-closing metathesis reaction to construct both the six member rings. d-Mannitol was used as a chiral pool material.     

Stereoselective synthesis of muco-quercitol, (+)-gala-quercitol and 5-amino-5-deoxy-d-vibo-quercitol from d-mannitol

Synthesis of muco-quercitol, (+)-gala-quercitol, and 5-amino-5-deoxy-d-vibo-quercitol is described from d-mannitol using ring closing metathesis and diastereoselective dihydroxylations as key steps.     

Characterization and release of triptolide-loaded poly (d,l-lactic acid) nanoparticles

Triptolide (TP), which has immunosuppressive effect, anti-neoplastic activity, anti-fertility function and severe toxicities on digestive, urogenital, blood circulatory system, was used as a model drug in this study. TP-loaded poly (d,l-lactic acid) (PLA) nanoparticles were prepared by the modified spontaneous emulsification solvent diffusion method (modified-SESD method). Dynamic light scattering system (DLS), transmission electron microscope (TEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), X-ray powder diffractometry and Fourier transform infra-red spectroscopy (FT-IR) were employed to characterize the nanoparticles fabricated for size and size distribution, surface morphology, the physical state of drug in nanoparticles, and the interaction between the drug and polymer. Encapsulation efficiency (EE) and the in vitro release of TP in nanoparticles were measured by the reverse phase high-performance liquid chromatography (RP-HPLC). The produced nanoparticles exhibited a narrow size distribution with a mean size of approximately 150 nm and polydispersity index of 0.088. The morphology of the nanoparticles exhibited a fine spherical shape with smooth surfaces without aggregation or adhesion. TP-entrapped in nanoparticles was found in the form of amorphous or semicrystalline. It was found that a weak interaction existed between the drug and polymer. In all experiments, more than 65% of EE were obtained. The in vitro release profile of TP from nanoparticles exhibited a typical biphasic release phenomenon, namely initial burst release and consequently sustained release. In this case, the particle size played an important role for the drug release. The modified-SESD method was a potential and advantage method to produce an ideal polymer nanoparticles for drug delivery system (DDS).