Concise Stereoselective Synthesis of β-Hydroxy-γ-lactones: (4R,5R)-4-Hydroxy-γ-decalactone from the Japanese Orange Fly and Enantiomers of Arachnid Harvestmen Isolates

The naturally occurring (4R,5R)-4-hydroxy-γ-decalactone from the Japanese orange fly and the antipode of (4S,5R)-4-hydroxy-γ-dodecalactone from the harvestmen arachnid and their stereoisomers are synthesized from the chiral pool material d-glucono-δ-lactone in a few steps. The one-pot conversion of the latter to γ-vinyl-β-hydroxy-γ-lactone, cross-metathesis with requisite olefin, and hydrogenation enabled the synthesis of syn-lactones in just a two-pot operation. An additional efficient Pd-catalyzed allylic isomerization of γ-vinyl-β-hydroxy-γ-lactone led to the anti-lactones in high yields.

Impact of ultrasound on galactooligosaccharides and gluconic acid production throughout a multienzymatic system

Galactooligosaccharides (GOS), recognised prebiotic, can be industrially produced from lactose and commercial β-galactosidase (β-gal) from Kluyveromyces lactis. Residual lactose and glucose limit GOS applications. To handle this problem, a multienzymatic system, with β-gal and glucose oxidase (Gox), was proposed to reduce glucose content in reaction media through its oxidation to gluconic acid (GA). Besides, ultrasound (US) probe effect over the multienzymatic system to produce GOS and GA has been evaluated. A production around 40% of GOS was found in all treatments after the first hour of reaction. However, glucose consumption and GA production was significantly higher (P < 0.05) for sequential reaction assisted by US, obtaining the best production of GOS (49%) and GA (28%) after 2 h of reaction. The conformational and residual activity changes of enzymes under US conditions were also evaluated, Gox being positively affected whereas in β-gal hardly any change was found.

Efficient Aerobic Oxidation of Glucose to Gluconic Acid over Activated Carbon-Supported Gold Clusters

The catalytic performance of the atomically precise gold cluster-Au₃₈ (PET)₂₄ (PET=2-phenylethanethiolate), immobilized on activated carbon (AC), was investigated for the aerobic oxidation of glucose to gluconic acid. The Au₃₈ (PET)₂₄ /AC-120 catalysts, annealed at 120 °C in air, exhibited high catalytic activity and significantly better performance than the corresponding catalysts Au₃₈ /AC-150 and Au₃₈ /AC-300 (treated at 150 and 300 °C to remove the protecting thiolate ligands). The high activity of the robust Au cluster was a result of the partial ligand removal, providing catalytically active sites, which were evidenced by TEM, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier-transform IR spectroscopy. Au₃₈ (PET)₂₄ /AC-120 also showed excellent recyclability (up to seven cycles). The turnover frequency for the Au₃₈ (PET)₂₄ /AC-120 catalyst was 5440 h^-1 , which is higher than for the Pd/AC, Pd-Bi/AC, and Au/AC under identical reaction conditions. This new ultra-small gold nanomaterial is expected to find wide application in other catalytic oxidations.

Novel organic salts based on fluoroquinolone drugs: synthesis, bioavailability and toxicological profiles

In order to overcome the problems associated with low water solubility, and consequently low bioavailability of active pharmaceutical ingredients (APIs), novel organic salts containing fluoroquinolones (e.g. ciprofloxacin and norfloxacin) were prepared, using an optimized synthetic procedure based on direct protonation, with different biocompatible counter ions such as mesylate, gluconate and glycolate. All the prepared organic salts were characterized by spectroscopic techniques, mass spectrometry and thermal analysis. Solubility studies in water and simulated biological fluids at 25°C and 37°C were also performed. Additionally, octanol-water and phospholipid-water partition coefficients were measured at 25°C. The cytotoxicity and anti-inflammatory efficacy using an human cell model of intestinal epithelia (Caco-2 cells) were also evaluated and compared to those of the parent APIs. The adequate selection of the biocompatible anions allows the tuning of important physical, thermal and toxicological properties.

De novo asymmetric syntheses of C-4-substituted sugars via an iterative dihydroxylation strategy

A short and highly efficient route to various C-4 substituted sugar lactones has been developed. The key to the overall transformation is the sequential osmium-catalyzed dihydroxylation reaction of substituted 2,4-dienoates and an allylic substitution at the C-4 position. When the Sharpless AD-mix procedure is used in a matched sense for the second dihydroxylation reaction, it results in an exceedingly diastereo- and enantioselective synthesis of several C-4-substituted sugars.

The 2-aminogluconate isomer of rhizobium sin-1 lipid A can antagonize TNF-alpha production induced by enteric LPS

The naturally occurring lipopolysaccharide (LPS) from Rhizobium sin-1, a nitrogen-fixing bacterial species, can prevent the induction of the tumor necrosis factor TNF-alpha induced by enteric LPS. The proximal saccharide moiety of R. sin-1 lipid A can exist in two forms, namely as a 2-aminogluconolactone or 2-aminogluconate. As it is unknown which of these forms is responsible for the antagonistic properties of R. sin-1 lipid A, compound 4 was prepared, and its inflammatory properties were studied. This compound contains a methyl ether at the C-5 hydroxyl, which prevents lactonization and therefore is ideally suited to determine whether the 2-aminogluconate possesses antagonistic properties. Compound 4 was synthesized by a highly convergent approach with a key disaccharide building block functionalized with a set of orthogonal protecting groups. The novel synthetic compound lacks proinflammatory properties, as indicated by an absence of TNF-alpha protein production. This compound was, however, able to antagonize the production of TNF-alpha induced by enteric LPS; this indicates that the 2-aminogluconate form of R. sin-1 lipid A is responsible for its biological properties.

White biotechnology for green chemistry: fermentative 2-oxocarboxylic acids as novel building blocks for subsequent chemical syntheses

Functionalized compounds, which are difficult to produce by classical chemical synthesis, are of special interest as biotechnologically available targets. They represent useful building blocks for subsequent organic syntheses, wherein they can undergo stereoselective or regioselective reactions. "White Biotechnology" (as defined by the European Chemical Industry [ http://www.europabio.org/white_biotech.htm ], as part of a sustainable "Green Chemistry,") supports new applications of chemicals produced via biotechnology. Environmental aspects of this interdisciplinary combination include: Use of renewable feedstock Optimization of biotechnological processes by means of: New "high performance" microorganisms On-line measurement of substrates and products in bioreactors Alternative product isolation, resulting in higher yields, and lower energy demand In this overview we describe biotechnologically produced pyruvic, 2-oxopentaric and 2-oxohexaric acids as promising new building blocks for synthetic chemistry. In the first part, the microbial formation of 2-oxocarboxylic acids (2-OCAs) in general, and optimization of the fermentation steps required to form pyruvic acid, 2-oxoglutaric acid, and 2-oxo-D-gluconic acid are described, highlighting the fundamental advantages in comparison to chemical syntheses. In the second part, a set of chemical formula schemes demonstrate that 2-OCAs are applicable as building blocks in the chemical synthesis of, e.g., hydrophilic triazines, spiro-connected heterocycles, benzotriazines, and pyranoic amino acids. Finally, some perspectives are discussed.

Oxidation of Glucose to Gluconic Acid by Glucose Oxidase in a Membrane Bioreactor

Glucose oxidase (GO) (EC 1.1.3.4) was used as catalyst for oxidizing glucose into gluconic acid utilizing a 10-mL Bioengineering Enzyme Membrane Reactor or a 400-mL Millipore Stirred Ultrafiltration Cell (MSUC) coupled with a Millipore UF membrane (cutoff of 100 kDa) and operated for 12 h under an agitation of 100 rpm, pH 5.5, and 30 degrees C. The effect of feeding rate (0.10, 0.15, or 0.20 min-1), glucose (2.5 or 5.0 mM), and GO (1.0 or 2.0 mg/mL) concentrations on the catalysis were studied. A yield of about 75% was attained when the MSUC filled with 1.0 mg/mL of GO was fed with 2.5 mM glucose solution at a rate of 0.15 min-1.

[Synthesis and the drug release properties of poly(acrylamide-co-glycosylallylamide) hydrogels]

Sugar-containing monomer glycosylallylamide (AAG) was synthesized by allyl amine and delta-gluconolactone in dimethylformamide (DMF) solution. The sugar-based hydrogels were prepared by free radical crosslinking copolymerization of AAG and acrylamide (AM). The release properties of Aspirin from xerogels matrices were studied and the release mechanism of Aspirin was further identified by evaluating the n value in Peppas equation. The results indicate that the drug release decreases with the increase of the sugar content of hydrogel.

Synthesis and biological evaluation of substrate-based inhibitors of 6-phosphogluconate dehydrogenase as potential drugs against African trypanosomiasis

The synthesis and biological evaluation of three series of 6-phosphogluconate (6PG) analogues is described. (2R)-2-Methyl-4,5-dideoxy, (2R)-2-methyl-4-deoxy and 2,4-dideoxy analogues of 6PG were tested as inhibitors of 6-phosphogluconate dehydrogenase (6PGDH) from sheep liver and also Trypanosoma brucei where the enzyme is a validated drug target. Among the three series of analogues, seven compounds were found to competitively inhibit 6PGDH from T. brucei and sheep liver enzymes at micromolar concentrations. Six inhibitors belong to the (2R)-2-methyl-4-deoxy series (6, 8, 10, 12, 21, 24) and one is a (2R)-2-methyl-4,5-dideoxy analogue (29b). The 2,4-dideoxy analogues of 6PG did not inhibit both enzymes. The trypanocidal effect of the compounds was also evaluated in vitro against T. brucei rhodesiense as well as other related trypanosomatid parasites (i.e., Trypanosoma cruzi and Leishmania donovani).

Synthesis of 2,3,4,5-tetra-O-methyl-D-glucono-1,6-lactone as a monomer for the preparation of copolyesters

2,3,4,5-tetra-O-methyl-D-glucono-1,6-lactone has been prepared as a crystalline compound in acceptable yield by two different routes. An initial assay of copolymerization with L-lactide by ring-opening polymerization was carried out. The incorporation of the carbohydrate monomer into the polymer chain was about 2%.

Synthesis of (R)-2-methyl-4-deoxy and (R)-2-methyl-4,5-dideoxy analogues of 6-phosphogluconate as potential inhibitors of 6-phosphogluconate dehydrogenase

The synthesis of (2R)-2-methyl-4,5-dideoxy and (2R)-2-methyl-4-deoxy analogues of 6-phosphogluconate is described. The synthetic strategy relies on the Evans aldol reaction for the installation of the chiral centres in the 2- and 3-positions. The selective phosphorylation at the primary alcohol function of (2R,3S)-3,6-dihydroxy-2-methylhexanoic acid benzyl ester (5) and (2R,3S,5S)-3,5,6-trihydroxy-2-methylhexanoic acid benzyl ester (20) was achieved with dibenzyl phosphochloridate and dibenzyl phosphoiodinate respectively, working at low temperature. (2R,3S)-3-Hydroxy-2-methyl-6-phosphonoxyhexanoic acid (9) was obtained in 25% overall yield from 4-benzyloxybutanol and (2R,3S,5S)-3,5-dihydroxy-2-methyl-6-phosphonoxyhexanoic acid (28) in 10% overall yield from L-malic acid.

Synthesis and NMR spectroscopy of nine stereoisomeric 5,7-diacetamido-3,5,7,9-tetradeoxynon-2-ulosonic acids

Derivatives of 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids are essential constituents of some bacterial polysaccharides and glycoproteins. In order to establish reliably the configuration of the natural sugars, nine stereoisomeric 5,7-diacetamido-3,5,7,9-tetradeoxynon-2-ulosonic acids were synthesized, including di-N-acetyl-legionaminic and -pseudaminic acids (the D-glycero-D-galacto and L-glycero-L-manno isomers, respectively) and their isomers at C-4, C-5, C-7, and C-8 having the L-glycero-D-galacto, D-glycero-D-talo, L-glycero-D-talo, D-glycero-L-altro, L-glycero-L-altro, D-glycero-L-manno, and L-glycero-L-gluco configurations. Synthesis was performed by condensation of 2,4-diacetamido-2,4,6-trideoxy-L-gulose, -D-mannose, -D-talose, and -L-allose with oxalacetic acid under basic conditions, the reaction of the last two precursors being accompanied by epimerisation at C-2. The 1H and 13C NMR data of the synthetic compounds are discussed. Acetylated methyl esters of the C-7 and C-8 isomeric nonulosonic acids were prepared and used for analysis of the side-chain conformation by NMR spectroscopy.

The reduction of CrVI to CrIII by the alpha and beta anomers of D-glucose in dimethyl sulfoxide. A comparative kinetic and mechanistic study

The reduction of CrVI by alpha-D-glucose and beta-D-glucose was studied in dimethyl sulfoxide in the presence of pyridinium p-toluensulfonate, a medium where mutarotation is slower than the redox reaction. The two anomers reduce CrVI by formation of an intermediate CrVI ester precursor of the slow redox step. The equilibrium constant for the formation of the intermediate chromic ester and the rate of the redox steps are different for each anomer. alpha-D-Glucose forms the CrVI-Glc ester with a higher equilibrium constant than beta-D-glucose, but the electron transfer within this complex is slower than for the beta anomer. The difference is attributed to the better chelating ability of the 1,2-cis-diolate moiety of the alpha anomer. The CrV species, generated in the reaction mixture, reacts with the two anomers at a rate comparable with that of CrVI. The EPR spectra show that the alpha anomer forms several linkage isomers of the five-coordinate CrV bis-chelate, while beta-D-glucose affords a mixture of six-coordinate CrV monochelate and five-coordinate CrV bis-chelate. The conversion of the CrV mono- to bis-chelate is discussed in terms of the ability of the 1,2-cis- versus 1,2-trans-diolate moieties of the glucose anomers to bind CrV.

An alpha hydroxy acid derivative suitable for sensitive skin

BACKGROUND

Individuals with sensitive skin may not tolerate some products formulated with alpha hydroxy acids (AHAs) due to unacceptable levels of stinging and irritation.

OBJECTIVE

To develop a neutral molecule that is well tolerated by individuals with sensitive skin without stinging or irritation, yet retains the beneficial effects of AHAs.

METHODS

A neutral amide derivative, methoxypropylgluconamide (MPG), was invented. Formulations containing MPG (15%) were tested by cummulative irritation, repeat insult patch testing, and lactic acid stinging assay. Bilateral comparison clinical and histological studies of xerosis and photoaging assessments were performed.

RESULTS

MPG was nonirritating and nonsensitizing. Clinically significant improvements in xerosis and photoaging including uneven pigmentation were seen. Improvement in the morphology of the stratum corneum epidermis and in the amount of glycosaminoglycans in the epidermis and dermis were seen histologically.

CONCLUSIONS

A molecule was invented (MPG) that could be formulated in a neutral vehicle to avoid skin irritation and produced improvements in xerosis and photoaging.

Phosphoenolpyruvate as a dual purpose reagent for integrated nucleotide/nicotinamide cofactor recycling

An efficient technique is presented which integrates cofactor dependent enzymic phosphorylation and dehydrogenation into a single, closed-loop system by employing phosphoenolpyruvate as the sacrificial reagent for sequential ATP and NAD+ recycling steps. Exemplary applications are developed for the synthesis of 6-phosphogluconate from glucose, and that of dihydroxyacetone phosphate from glycerol. The latter system is combined with exergonic diastereoselective aldol additions for the one-flask synthesis of a ketosugar (D-sorbose), thiosugar (L-threo-5-thiopentulose), or a sugar acid (L-threo-pent-4-ulosonic acid) starting from a mixture of glycerol and simple aldehydes.

Microbial synthesis of 3-deoxy-D-erythro-hex-2-ulosonic acid 6-phosphate

A microbial route was explored for the synthesis of 3-deoxy-D-erythro-hex-2-ulosonic acid 6-phosphate (2-keto-3-deoxy-6-phosphogluconate, KDPG). Two strains of bacteria, Alcaligenes eutrophus H16 F34 (DSM 529) and Escherichia coli DF 71 (CGSC 4880), lacking in KDPG-aldolase activity were tested for excretion of KDPG. Using pyruvate and gluconate as carbon sources, Alcaligenes eutrophus H16 F34 accumulated and excreted 3-deoxy-D-erythro-hexulosonic acid 6-phosphate into the culture broth, while the E. coli strain, using pyruvate and glucuronate, failed. KDPG was isolated from the culture supernatant of Alcaligenes eutrophus H16 F34 in 78% yield and 5 g scale with respect to the consumed gluconate.

Blood cell phosphogluconolactonase: assay and properties

6-Phosphogluconolactonase (6-PGL) catalyses the second reaction of the hexosemonophosphate pathway. Although the delta-lactone of 6-phosphogluconic acid is the natural substrate for this enzyme, the more stable gamma-lactone may also be used. We prepared the gamma-lactone of 6-phosphogluconic acid from 6-phosphogluconate. When stored in dimethylsulfoxide, this material was found to be stable in liquid nitrogen for several months. A method for measuring 6-phosphogluconolactonase (6-PGL) using the gamma-lactone as substrate has been developed, after defining conditions under which spontaneous hydrolysis of the lactone is relatively slow and the enzymatic velocity is relatively rapid. The enzyme had no divalent cation requirement and was not significantly inhibited by a 50-fold excess of gluconolactone. It was distinct, therefore, from gluconolactonase. At 25 degrees C normal human red cells were found to contain approximately 50 IU of 6-phosphogluconolactonase/g Hb. The activity of the enzyme was independent of red cell age. Based on protein content, human lymphocytes, monocytes, granulocytes and platelets, contained approximately 10 times the activity of red blood cells. The activity of 6-PGL was stable for at least 6 d in red cells stored at 22 degrees C and for at least 20 d in red cells stored at 4 degrees C.

Preparation, quality control and application of 99mTc-gluco-ene-diolate for renal scanning

A one-step freeze-dried Sn-glucose kit was developed to be labelled with technetium-99m. TLC, paper chromatography and gel chromatography column scanning techniques (GCS) were used for the determination of the labelling yield of the complex. High radiochemical purity was obtained (98%). In vivo distribution studies were performed in white rats. Maximum uptake in kidneys (28%) was achieved in 15-90 min. The blood disappearance curve studies of the labelled Sn(II)-gluco-ene-diolate in rabbits have shown two disappearance phases of activity from blood with biological half-times of 10 and 150 min for the fast and slow component respectively.

A coupled radiometric assay for dihydrofolate reductase based on the oxidative decarboxylation of D-6-phospho-[1-14C]gluconate

The synthesis of D-6-phospho-[1-14C]gluconate and the utilization of this compound in a novel assay procedure for dihydrofolate reductase is described. This new assay method couples reductase-dependent NADP+ production to the enzymatic and NADP+-dependent decarboxylation of D-6-phospho-[1-14C]gluconate. By several criteria it is demonstrated that [14C]CO2 release is directly proportional to dihydrofolate reductase activity. This coupled radiometric assay for dihydrofolate reductase is more sensitive than the commonly used spectrophotometric assay and offers a number of advantages over earlier radiometric methods.

Preparation and quality control of 99mTc-calciumgluconate

A procedure for the labelling of lyophilised Sn-Ca-Gluconate by a 99mTc instant technique was developed. Paper and TLC chromatography and low-voltage electrophoresis were used for the determination of the labelling yield which reached between 95 to 98%. The biodistribution was followed in white (albino) rats. About 25 to 35% of the total activity of the compound was retained in the kidneys one hour after its i.v. injection.