D-isoascorbic Acid Research Articles

Enantiomerically pure 4-amino-1,2,3-trihydroxybutylphosphonic acids

(1 S,2 R,3 S)-, (1 R,2 R,3 S)- and (1 S,2 R,3 R)-4-amino-1,2,3-trihydroxybutylphosphonic acids were synthesised. The synthetic strategy involved preparation of the respective 4-azido-2,3- O-isopropylidene- l-threose or - d-erythrose, addition of dialkyl phosphites, separation of C-1 epimeric O, O-dibenzyl phosphonates, the reduction of azides and the removal of the protecting groups. The (2 R,3 S) and (2 R,3 R) configurations in the final products were secured by employing diethyl l-tartrate and d-isoascorbic acid as starting materials. The stereochemical course of the addition to the carbonyl groups in 4-azido-2,3- O-isopropylidene- l-threose or - d-erythrose followed that established earlier for 2,3- O-isopropylidene- d-glyceraldehyde and similar (3:1–4:1) diastereoselectivities were achieved.

Competing Diels–Alder intramolecular pathways from cross-conjugated trienes: Fused hydrindenones (bicyclo[4.3.0]nonenones) vs. bridged-ring (bicyclo[3.3.1]nonenones) adducts from a diene-transmissive precursor

D-Isoascorbic acid was converted to the tetraenone 12 to examine its behaviour in the intramolecular Diels–Alder reaction with pendant dienes in a diene-transmissive environment. These studies were directed toward the synthesis of the hydrindenone nucleus via a tether-controlled Diels–Alder reaction. It was anticipated that this would lead to a diene-transmissive strategy for steroids such as Desogestrel®. In contrast to our previous studies with decalins, the dominant isomer (150 °C) was the bicyclo[3.3.1]nonadieneone adduct 23, and none of fused adduct 27 was detected. These products were accompanied by two minor hydrindenone adducts 24 and 25. The isomer ratio was dependent on the temperature of the reaction.Key words: Diels–Alder, hydrindane, pentadienylation, intramolecular cycloaddition, bicyclo[3.3.1]nonenone.

Effects of Ascorbic Acid and Analogs on the Activity of Testicular Hyaluronidase and Hyaluronan Lyase on Hyaluronan

We have evaluated the inhibition of testicular hyaluronidase and hyaluronan lyase by L-ascorbic acid and chemical analogs. We observed that L-ascorbic acid, D-isoascorbic acid and dehydroascorbic acid inhibited both types of enzymes, but showed stronger effects towards hyaluronan lyase. But these compounds were observed to degrade the substrate, hyaluronan, by themselves. Of the other ascorbic acid analogs tested, saccharic acid inhibited hyaluronan lyase, while not affecting the enzymatic activity of testicular hyaluronidase, nor affecting the physic-chemical stability of hyaluronan. This is the first compound, to our knowledge, to be shown to possess such selective inhibition. Therefore, we propose that saccharic acid could serve as a lead compound for the development of potent and selective inhibitors of bacterial hyaluronan lyase or of polysaccharide lyase enzymes in general as we observed this compound to be capable of inhibiting chondroitinase ABC in addition to hyaluronan lyase.

Syntheses of (3 R,4 R,5 R,6 R)-tetrahydroxyazepane (1,6-dideoxy-1,6-imino- d-mannitol) and (3 S,4 R,5 R,6 R)-tetrahydroxyazepane (1,6-dideoxy-1,6-imino- d-glucitol)

Syntheses of 1,6-dideoxy-1,6-imino- d-mannitol ( d-mannoazepane) ( 1 ) and 1,6-dideoxy-1,6-imino- d-glucitol ( d-glucoazepane) ( 3 ) from d-isoascorbic acid and d-glucono-1,5-lactone, respectively, are described. The key step in both routes involved reductive aminative 1,6-cyclization with retention of configurations to give the corresponding lactams, which were subsequently reduced to afford compounds 1 and 3 in 24 and 28.5%, overall yield, respectively.

Salt- and glyphosate-induced increase in glyoxalase I activity in cell lines of groundnut (Arachis hypogaea).

Glyoxalase I (EC 4.4.1.5) activity has long been associated with rapid cell proliferation, but experimental evidence is forthcoming, linking its role to stress tolerance as well. Proliferative callus cultures of groundnut (Arachis hypogaea L. cv. JL24) showed a 3.3-fold increase in glyoxalase I activity during the logarithmic growth phase, correlating well with the data on FW gain and mitotic index. Inhibition of cell division decreased glyoxalase I activity and vice versa, thus further corroborating its role as a cell division marker enzyme. Cell lines of A. hypogaea selected in the presence of high salt (NaCl) and herbicide (glyphosate) concentrations, yielded 4.2- to 4.5-fold and 3.9- to 4.6-fold elevated glyoxalase I activity, respectively, in a dose dependent manner reflective of the level of stress tolerance. The stress-induced increase in enzyme activity was also accompanied by an increase in the glutathione content. Exogenous supplementation of glutathione could partially alleviate the growth inhibition of callus cultures induced by methylglyoxal and d-isoascorbic acid, but failed to recover the loss in glyoxalase I activity due to d-isoascorbic acid. The adaptive significance of elevated glyoxalase I activity in maintaining glutathione homeostasis has been discussed in view of our understanding on the role of glutathione in the integration of cellular processes with plant growth and development under stress conditions.

The effects of ascorbic acid on cartilage metabolism in guinea pig articular cartilage explants.

Ascorbic acid has been associated with the slowing of osteoarthritis progression in guinea pig and man. The goal of this study was to evaluate transcriptional and translational regulation of cartilage matrix components by ascorbic acid. Guinea pig articular cartilage explants were grown in the presence of L-ascorbic acid (L-Asc), D-isoascorbic acid (D-Asc), sodium L-ascorbate (Na L-Asc), sodium D-isoascorbate (Na D-Asc), or ascorbyl-2-phosphate (A2P) to isolate and analyze the acidic and nutrient effects of ascorbic acid. Transcription of type II collagen, prolyl 4-hydroxylase (alpha subunit), and aggrecan increased in response to the antiscorbutic forms of ascorbic acid (L-Asc, Na L-Asc, and A2P) and was stereospecific to the L-forms. Collagen and aggrecan synthesis also increased in response to the antiscorbutic forms but only in the absence of acidity. All ascorbic acid forms tended to increase oxidative damage over control. This was especially true for the non-nutrient D-forms and the high dose L-Asc. Finally, we investigated the ability of chondrocytes to express the newly described sodium-dependent vitamin C transporters (SVCTs). We identified transcripts for SVCT2 but not SVCT1 in guinea pig cartilage explants. This represents the first characterization of SVCTs in chondrocytes. This study confirms that ascorbic acid stimulates collagen synthesis and in addition modestly stimulates aggrecan synthesis. These effects are exerted at both transcriptional and post-transcriptional levels. The stereospecificity of these effects is consistent with chondrocyte expression of SVCT2, shown previously to transport L-Asc more efficiently than D-Asc. Therefore, this transporter may be the primary mechanism by which the L-forms of ascorbic acid enter the chondrocyte to control matrix gene activity.

Selective intercalation of charge neutral intercalators into GG and CG steps: implication of HOMO-LUMO interaction for sequence-selective drug intercalation into DNA.

We have synthesized naphthopyranone epoxide 4 from D-isoascorbic acid together with its three diastereoisomers. DNA alkylation of ODNs containing 5'XGT3' and 5'TGY3' by 4 (11R, 13R), where X and Y are any nucleotide bases, occurred at all G residues except at G of the 5'TGC3' sequence. In contrast, the three other diastereoisomers of 4 showed only weak G alkylation activity. Differential (1)H NMR NOE of the 4-G adduct confirmed the G-N7 alkylation at the epoxide carbon of 4 with concomitant S(N)2 ring opening of the epoxide. Quantitative HPLC analysis of G alkylation efficiency for 4 showed the order of G alkylation susceptibility as TGGT approximately CGT >> TGA > AGT > TGT >> TGC. The order was fully consistent with those reported for aflatoxin B(1) oxide and kapurimycin A(3), suggesting that the sequence selectivity observed for these DNA alkylating agents is not structure dependent but most likely due to the intrinsic property of DNA sequences. We found that the order of G alkylation susceptibility obtained for 4 completely matched the calculated HOMO energy level of G-containing sequences. These results underscore that 4 is a unique molecular probe for ranking the HOMO level of G-containing sequences by well-known G alkylation chemistry and suggests that the intercalation of charge neutral intercalators is a HOMO-controlled process.

Quantification of L-ascorbic acid and total ascorbic acid in fruits and spinach by capillary zone electrophoresis.

A standard curve for the quantification of L-ascorbic acid (L-AA) by capillary zone electrophoresis (CZE) was established, and the quantification of ascorbic acid and total ascorbic acid in fruits (lemon, Sunkist, and pineapple) and spinach were performed using D-isoascorbic acid (D-IAA) as an internal standard. The minimum detection limits (MDLs) for L-AA and D-IAA were determined to be 1 and 2 microg/mL, respectively, at 265 nm. Dehydroascorbic acid (DHAA) in fruits and spinach was quantified in the presence of DL-homocysteine. The recoveries for L-AA in these juices were between 95 and 105%.

Maintaining quality of fresh-cut mangoes using antibrowning agents and modified atmosphere packaging.

Treatments to inhibit browning and decay and prolong shelf life of fresh-cut mangoes were investigated. Combinations of antibrowning agents and modified atmosphere packaging (MAP) resulted in a reduction of browning and deterioration of fresh-cut mangoes stored at 10 degrees C. Combinations of several browning inhibitors were more effective than those applied individually. Among these treatments, solutions containing 4-hexylresorcinol (0.001 M) (HR) plus potassium sorbate (0.05 M) (KS) and HR plus KS plus D-isoascorbic acid (0.5 M) (ER) reduced changes in color (L, a, and b) and microbial growth and did not affect sensory characteristics of fresh-cut mangoes. In general, these treatments did not affect significantly the changes in organic acids and sugar content of slices during the 14 days of storage at 10 degrees C. High humidity created in the in-package atmosphere alleviated tissue dryness and was an important factor in the ability of the antibrowning solutions to prevent browning and decay. It appears that the maintenance of quality of fresh-cut mangoes is more related to particular combinations of the antibrowning agents used rather than the modified atmosphere created inside the package. HR + ER + KS treatment in combination with MAP could be used to inhibit browning, decay, and deterioration of fresh-cut mangoes.

Enantioselective Synthesis of Ethyl 4,5,7,8,9-Penta-O-acetyl-2,6-anhydro- 3-deoxy-D-erythro-L-gluca-nononate: a 2-Monodeoxygenated Derivative of `2-Keto-3-deoxy-D-glycero-D-galacto-nononic Acid'

A study aimed at developing an enantioselective synthesis of the title compound 23, a 2-monodeoxy analogue of the naturally occurring (+)-2-keto-3-deoxy-D-glycero-D-galacto-2-nononic acid (KDN), is reported. From D-mannose as starting material, the chiral 1,3-diene 10, activated by a silyloxy substituent at C(2), was prepared in six steps (Scheme 1). However, the intermediates were often contaminated with varying amounts of by-products arising from overoxidation during cleavage with periodic acid. An alternative route starting from the inexpensive and readily available D-isoascorbic acid (12), though a little longer than the first, satisfactorily circumvented the purification problem and led to the desired dienes 17 in good yields (scheme 2). The [CoII(S,S)-(+)-salen]-catalyzed hetero-Diels-Alder reactions of the aforementioned dienes with ethyl glyoxylate proceeded smoothly at room temperature, giving the dihydropyrano adducts 18 in moderate yields (Scheme 3). Dihydroxylation of 18a followed by reduction of the keto function gave the desired 4,5-trans dihydroxy moiety of the KDN framework (Scheme 4, see 21). The spectroscopic data of the penta-O-acetylated 2-deoxy-KDN ethyl ester 23 were consistent with those reported for the corresponding methyl ester derived from natural KDN.

Synthesis of both enantiomers of 4-vinyl oxazolidin-2-one from a single precursor: D-isoascorbic acid.

A convenient synthesis of (S)- and (R)-4-vinyl oxazolidin-2-one 1 and 2 from the same inexpensive starting material, D-isoascorbic acid, is described. The title compounds were obtained in 44% and 38% yield, respectively, by operationally simple steps. This approach is a suitable alternative to the literature methods and enhances the synthetic utility of these intermediates. Inc.

Synthesis of both enantiomers of 4-vinyl oxazolidin-2-one from a single precursor: D-isoascorbic acid

Synthesis of both enantiomers of 4-vinyl oxazolidin-2-one from a single precursor: D-isoascorbic acid

Human Vitamin C (l-Ascorbic Acid) Transporter SVCT1

In human, vitamin C (l-ascorbic acid) is an essential micronutrient required for an array of biological functions including enzymatic reactions and antioxidation. We describe here the molecular cloning of a novel human cDNA encoding a vitamin C transporter SVCT1. SVCT1 is largely confined to bulk-transporting epithelia (e.g., kidney and small intestine) with a putative alternative-splice product present in thymus. Applying radiotracer and voltage-clamp approaches in cRNA-injected Xenopus oocytes, we found that SVCT1 mediates saturable, concentrative, high-affinity l-ascorbic acid transport (K0.5 = 50–100 μM) that is electrogenic and can be inhibited by phloretin. SVCT1 displays exquisite substrate selectivity, greatly favoring l-ascorbic acid over its isomers d-isoascorbic acid and dehydroascorbic acid and 2- or 6-substituted analogues, whereas glucose and nucleobases are excluded. We have mapped the SLC23A2 gene (coding for SVCT1) to human chromosome 5 in band 5q31.2-31.3, within a region commonly deleted in malignant myeloid (leukemia) diseases. In addition, we have demonstrated that the human SLC23A1 gene product is a related high-affinity l-ascorbic acid transporter (SVCT2) that is widely distributed in brain, retina, and a host of endocrine and neuroendocrine tissues. The molecular identification of the human l-ascorbic acid transporters now provides the tools with which to investigate their roles in vitamin C metabolism in health and disease.

Epimeric Separation of l-Ascorbic Acid and d-Isoascorbic Acid by Capillary Zone Electrophoresis

Capillary zone electrophoresis (CZE) was used for separation of L-ascorbic acid (L-AA) and D-isoascorbic acid (D-IAA) in a model system. The effects of borate buffer concentration (0.05-0.25 M) and pH (pH 7.5-9.0) on migration time, resolution (Rs), and theoretical plates (N) were investigated. The migration times of L-AA and D-IAA increased with the increasing pH of carrier electrolyte (0.2 borate buffer), and the resolutions (Rs) of L-AA and D-IAA were calculated to be 12.98 at pH 9.0. Concentrations of borate buffer (pH 9.0) increased the Rs values of L-AA and D-IAA, and buffer concentrations >0.1 M were found to be effective for separation of L-AA and D-IAA. Methanol in the carrier electrolyte was also influential in improving the separation of L-AA and D-IAA, which increased with the increasing concentrations (0-10%) of methanol. The optimal separation conditions for L-AA and D-IAA were as follows: carrier electrolyte, 0.2 M borate buffer (pH 9.0); applied voltage, 25 kV, with an uncoated fused silica capillary, 75 microm (i.d.) x 57 cm.

Purification and Characterisation of Ascorbate Oxidase from Flour and Immature Wheat Kernels

White flour from wheat was shown to contain basic-ascorbate oxidase (AOX) enzymes (pI 7·6–9·6) and acidic-AOX enzymes (pI 5·1–6·6) in a ratio of 0·4:1, based on chromatography data. Immature wheat kernels (two weeks post-anthesis) contained about 12 times more AOX activity (units/g dry weight) than flour from mature grain, and the ratio of basic- to acidic-AOX was 5:1. Acidic-AOX was purified 90-fold from flour by hydrophobic interaction, gel filtration and anion exchange chromatography. Basic-AOX was purified 20 000-fold from immature wheat by hydrophobic interaction, anion exchange, cation exchange and gel filtration chromatography in a yield of 5%. The acid-AOX had a M of 140 k, was optimally active at pH 6·3 and 40 °C, and was stable in the pH range 5–9 and at 30 °C for 0·5 h at pH 6·2. The Km values were 0·26 m M for L-ascorbic acid and 0·93 mM for D-iso ascorbic acid. The basic-AOX had a M of 139 k and subunit M of 72 k. The enzyme was optimally active at pH 6·2 and 50 °C, and was stable in the pH range 5–9 and at 40 °C for 0·5 h at pH 6·2. The Km values were 0·30 m M for L-ascorbic acid and 0·53 m M for D-iso ascorbic acid. The absorption spectrum of basic-AOX had absorption maxima at 280 nm and 607 nm of similar magnitude to those measured in AOX fromCucurbita species (squash). This indicates that wheat AOX contains protein-bound copper similar to other plant AOX.

Synthetic Potential Inherent in D-Isoascorbic Acid as a Precursor for Pyridazine and Furo[3,2-c]pyridazine Ring Systems with Two Asymmetric Centers

Reaction of D-erythro-2,3-hexodiulosono-1,4-lactone-2,3-bis(phenylhydrazone) (2) with an iodine, triphenylphosphine and imidazole mixture afforded the furo[3,2-c]pyridazine derivative 11. Condensation of 6-bromo-6-deoxy-D-erythro-2,3-hexodiulosono-1,4-lactone with phenylhydrazine gave the bishydrazones 6, and 8 or the furo[3,2-c]pyridazine (11) depending on the reaction conditions. The lactone ring in 11 could be opened by treatment with alkali to give the pyridazine derivative 9. Lactonization of the later with simultaneous acetylation by acetic anhydride afforded the lactone derivative 14. Alkali treatment of 6 gave the pyrazolindione derivative 13 that gave upon reation with HBr/AcO H the dibromide 15. The assigned structures were based on spectral analysis. The activity of compounds 11 and 14 against hepatitis B virus has been studied.

Formal synthesis of an unusual amino acid component of cyclosporin, involving stereocontrolled nucleophilic 1,4-addition

A syn-(2 R)-amino-1,3,4-butanetriol derivative, readily available from D-isoascorbic acid, was utilized for the synthesis of MeBmt found in the immunosuppressive undecacyclopeptide cyclosporin. This new strategy involves diastereoselective nucleophilic 1,4-addition of lithium dimethylcuprate to a chiral α,β-unsaturated aldehyde, and elaboration of the terminal double bond, by Takai or Wittig method for the MeBmt or its 6 Z-isomer, respectively.

Influence of oral dosing with D-isoascorbic acid on L-ascorbic acid content in guinea pig tissues

The effect of graded doses of D-isoascorbic acid (IAA) on the tissue content of ascorbic acid (AA) in guinea pigs administered a marginal intake of ascorbic acid was studied. Thirty guinea pigs (inbred Hartley-strain) were randomly assigned to three equally sized treatment groups: 1) 1 mg AA (only); 2) 1 mg AA + 20 mg IAA, or 3) 1 mg AA + 100 mg IAA. Ascorbic acid alone or in combination with IAA was orally administered daily to all animals over 42 consecutive days, after which time the animals were sacrificed. Over the study period, animals dosed with 1 mg AA plus 100 mg IAA had a higher rate of weight gain than those dosed with 1 mg AA or 1 mg AA + 20 mg IAA. Tissue concentrations of AA, IAA, and their oxidized forms, dehydroascorbic acid (DHAA) and dehydroisoascorbic acid (DHIAA) were determined by high-pressure liquid chromatography equipped with an electrochemical detector. In guinea pigs dosed with either 20 or 100 mg IAA, AA levels in the plasma, brain, liver, adrenals, lungs, kidneys, spleen, and heart were significantly decreased (P < 0.05) compared with the nonsupplemented group. IAA content in the guinea pig tissues increased progressively after incremental dosing with IAA. DHAA levels decreased significantly in guinea pigs dosed with 20 mg IAA or 100 mg IAA compared with the corresponding controls in all tissues examined. Thus, in guinea pigs, the co-administration of graded levels of IAA with a marginal AA intake resulted in a decreased bioavailability of AA.

Organoalane-mediated isomerization of ascorbic and isoascorbic acid derivatives

Derivatives of l-ascorbic acid 2a, 10a 11a and d-isoascorbic acid 2b, 10b 11b , when treated with triisobutylaluminium, partly epimerize to give the corresponding derivatives of l-isoascorbic acid ent-2b, ent-10b or d-ascorbic acid ent-2a, ent-11a , respectively. Complete removal of the protecting groups is effected by hydrogenolysis of the benzylidene acetals ent-10 and ent-11a. This reaction leads to d-ascorbic acid ent-1a or l-isoascorbic acid ent-1b, respectively. Furthermore, the four acetonides 2 were converted by ozonolysis, transesterification and finally catalytic hydrogenation to the threonic and erythronic acid ketals 9.

Synthesis of (2S,3R)-3-amino-2-hydroxydecanoic acid and (3R,4R)-3-amino-4-hydroxyazepane from D-isoascorbic acid

Taking advantage of the high functionality of an enantiopure protected syn-2R-amino-1,3,4-triol derivative, easily available on a multigram scale from D-isoascorbic acid, several biologically active compounds have been synthesized such as the (2S,3R)-3-amino-2-hydroxydecanoic acid (AHDA), the N-terminal moiety of microginin, and the (3R,4R)-3-amino-4-hydroxyazepane, the ophiocordin and balanol core structure.