- Biocatalytic racemization of α-hydroxycarboxylic acids using a stereo-complementary pair of α-hydroxycarboxylic acid dehydrogenases
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Biocatalytic racemization of aliphatic, (aryl)aliphatic and aromatic α-hydroxycarboxylic acids was achieved via a reversible oxidation-reduction sequence using a pair of stereo-complementary Prelog- and anti-Prelog d- and l-α-hydroxyisocaproate dehydrogenases from Lactobacillus confusus DSM 20196 and Lactobacillus paracasei DSM 20008, resp., overexpressed in Escherichia coli. The mild reaction conditions ensured essential 'clean' isomerization, undesired 'over-oxidation' of the substrate forming the α-ketoacid could be suppressed by exclusion of O2 and adjustment of the NAD+/NADH-ratio.
- Bodlenner, Anne,Glueck, Silvia M.,Nestl, Bettina M.,Gruber, Christian C.,Baudendistel, Nina,Hauer, Bernhard,Kroutil, Wolfgang,Faber, Kurt
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experimental part
p. 7752 - 7755
(2009/12/04)
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- Gas chromatography/electron-capture negative ion mass spectrometry for the quantitative determination of 2- and 3-hydroxy fatty acids in bovine milk fat
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2- and 3-hydroxy fatty acids (2- and 3-OH-FAs) are bioactive substances reported in sphingolipids and bacteria. Little is known of their occurrence in food. For this reason, a method suitable for the determination of OH-FAs at trace levels in bovine milk fat was developed. OH-FAs (and conventional fatty acids in samples) were converted into methyl esters and the hydroxyl group was derivatized with pentafluorobenzoyl (PFBO) chloride to give PFBO-O-FA methyl esters. These derivatives with strong electron affinity were determined by gas chromatography interfaced to mass spectrometry using electron-capture negative ion in the selected ion monitoring mode (GC/ECNI-MS-SIM). This method proved to be highly sensitive and selective for PFBO-O-FA methyl esters. For the analysis of samples, two internal standards were used. For this purpose, 9,10-dideutero-2-OH-18:0 methyl ester (ISTD-1) from 2-OH-18:1(9c) methyl ester as well as the ethyl ester of 3-PFBO-O-12:0 (ISTD-2) was synthesized. ISTD-1 served as a recovery standard whereas ISTD-2 was used for GC/MS measurements. The whole-sample cleanup consisted of accelerated solvent extraction of dry bovine milk, addition of ISTD 1, saponification, conversion of fatty acids into methyl esters by use of boron trifluoride, separation of the methyl esters of OH-FAs from nonsubstituted FAs on activated silica, conversion of OH-FAs methyl esters into PFBO-O-FA methyl esters, addition of ISTD-2, and measurement by GC/ECNI-MS-SIM. By this method, ten OH-FAs were quantified in bovine milk fat with high precision in the range from 0.02 ± 0.00 to 4.49 ± 0.29 mg/100 g of milk fat.
- Jenske, Ramona,Vetter, Walter
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experimental part
p. 5500 - 5505
(2010/03/25)
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- Imidazole compounds
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Imidazole compounds having adenosine deaminase inhibitory activity represented by formula (I) wherein R1is hydrogen, hydroxy, protected hydroxy, or aryl optionally substituted with suitable substituent(s); R2is hydrogen or lower alkyl; R3is hydroxy or protected hydroxy; R4is cyano, (hydroxy)iminoamino(lower)alkyl, carboxy, protected carboxy, heterocyclic group optionally substituted with amino, or carbamoyl optionally substituted with suitable substituent(s); and —A— is —Q— or —O—Q—, wherein Q is single bond or lower alkylene, provided that when R2is lower alkyl, then R1is hydroxy, protected hydroxy, or aryl optionally substituted with suitable substituent(s), its prodrug, or their salt. The compounds are useful for treating and/or preventing diseases for which adenosine is effective.
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Page column 8-9
(2008/06/13)
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- BrF3, an underutilized reagent in organic chemistry: A novel C-C-N to C-N-C rearrangement
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Little is known about bromine trifluoride in organic chemistry. Under the right conditions, it can be a useful tool and generate a new and unprecedented chemistry. Thus, when reacted with oxime methyl ethers of α-ketoesters, BrF3 was able to convert the oxime group into a CF2 group and through a new type of rearrangement cause a shift of the carboxylate group to the nitrogen atom. The novel structure of the α,α-difluorocarbamate was also proven by 15N NMR as demonstrated for compounds 3, 8, 9, 12, 15, and 18. Another novel "double rearrangement" was observed during the formation of 19. Dynamic 19F NMR experiments indicate a high nitrogen inversion-rotation (NIR) barrier for these novel carbamates of about 12.5 kcal/mol.
- Rozen,Ben-David
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p. 496 - 500
(2007/10/03)
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- Oxidation of Methyl Trimethylsilyl Ketene Acetals to α-Hydroxyesters with Urea Hydrogen Peroxide Catalyzed by Methyltrioxorhenium
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In the presence of catalytic amounts of MTO, methyltrioxorhenium, methyl trimethylsilyl ketene acetals are oxidized with urea hydrogen peroxide to afford α-hydroxy and α-siloxy esters. On treatment with potassium fluoride, the α-hydroxy esters are obtained in high yields.
- Stankovic, Sasa,Espenson, James H.
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p. 5528 - 5530
(2007/10/03)
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- Regioselective deoxygenation of the cyclic thionocarbonates of 2,3- dihydroxy esters with magnesium in methanol
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Deoxygenation of the cyclic thionocarbonates of 2,3-dihydroxy esters was mediated with magnesium in methanol, which provided a facile method for the synthesis of α-hydroxy esters.
- Rho, Ho-Sik,Ko, Byoung-Seob
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p. 2875 - 2880
(2007/10/03)
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- Sulfur-based amides and bis-amides useful against skin disorders
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Novel sulfhydryl group-containing amides and disulfide group-containing bis-amides useful for treating or preventing an abnormal biological condition or a disease, and/or improving the texture or appearance of the skin, as well as compositions containing amides and bis-amides and methods for their use are described. Such types of abnormal biological conditions or diseases include skin atrophy, i.e., the thinning and/or general degradation of the dermis often characterized by a decrease in collagen and/or elastin as well as decreased number, size and doubling potential of fibroblast cells, and other maladies including, but are not limited to dry skin, severe dry skin, dandruff, acne, keratoses, psoriasis, eczema, skin flakiness, pruritus, age spots, lentigines, melasmas, wrinkles, warts, blemished skin, hyperpigmented skin, hyperkeratotic skin, inflammatory dermatoses, age-related skin changes and skin in need of cleansers.
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- Hydroxylation of carbanions with lithium teri-butyl peroxide acting as an oxenoid
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The lithium salt of terf-butyl hydroperoxide can convert alkyl, vinyl, aryl carbanions, acetylides and various enolates into the corresponding hydroxylated derivatives in good yields and under mild conditions. Eisevier.
- Julia, Marc
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- A convenient route for the homologation of saturated esters to α,β-unsaturated esters
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Methyl hexanoate (1a) is transformed to methyl 2-hydroxyheptanoate (5a) employing the following sequence of reactions (Scheme 1); (i) reaction with sodium hydride-dimethyl sulfoxide, (ii) Pummerer rearrangement with acetic anhydride-sodium acetate, (iii) alkaline hydrolysis and (iv) esterification with diazomethane.The α-hydroxy ester (5a) is converted into methyl 2E-heptenoate (7a) employing the following reactions (Scheme 2); (i) reaction with phosphorous tribromide and (ii) elimination using DBU.Thus, the sequence of reactions given in Schemes 1 and 2 provide aconvenient route for the one carbon homologation of saturated esters to α,β-unsaturated esters.
- Mohan, H Rama,Rao, A S
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p. 698 - 700
(2007/10/02)
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- A New and Facile Method for the Direct Preparation of α-Hydroxycarboxylic Acid Esters from α,β-Unsaturated Carboxylic Acid Esters with Molecular Oxygen and Phenylsilane Catalyzed by Bis(dipivaloylmethanato)manganese(II) Complex
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In the presence of a catalytic amount of bis(dipivaloylmethanato)manganese(II) complex, the oxygenation of benzyl crotonate with molecular oxygen and phenylsilane proceeds smoothly under a mild condition to give benzyl 2-hydroxybutyrate in high yield.The reaction provides a new and convenient method for the direct preparation of various α-hydroxycarboxylic acid esters starting from α,β-unsaturated carboxylic acid esters.The influence of substituents of olefins on regioselectivity is also studied.
- Inoki, Satoshi,Kato, Koji,Isayama, Shigeru,Mukaiyama, Teruaki
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p. 1869 - 1872
(2007/10/02)
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- Synthesis of S-Methyl 2-Hydrxyalkanethioates, 2-Hydroxyalkanoic Acids and Related Compounds via the Addition Reaction of Tris(methylthio)methanide Ion to Alkanals
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In connection with the studies on biological activities on myrmicacin and related compounds, the synthetic method for 2-hydroxyalkanoic acids and the corresponding 1,2-diols was studied.The addition reaction of tris(methylthio)methyllithium to the aldehydes (propanal-dodecanal) gave the corresponding 1,1,-tris(methylthio)-2-alkanols 1a-j.Treatment of 1 with mercury(II) chloride-mercury(II) oxide in water-acetone afforded S-methyl 2-hydroxyalkanethioates 2a-j, and in methanol methyl 2-hydroxyalkanoates 3c-j were obtained.Reduction of the thioates 2 with lithium aluminium hydride gave 1,2-diols 4c-j and saponification produced the corresponding 2-hydroxyalkanoic acids 5c-j.
- Orito, Kazuhiko,Seki, Yoshikatsu,Suginome, Hiroshi,Iwadare, Tsukasa
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p. 2013 - 2017
(2007/10/02)
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- α-HYDROXYLATION OF CARBOXYLIC ACIDS AND AMIDES USING BIS(TRIMETHYLSILYL)PEROXIDE
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Bis(trimethylsilyl)peroxide is shown to react with enolate anions derived from carboxylic acids and amides to give the corresponding α-hydroxy derivatives.
- Pohmakotr, Manat,Winotai, Chanchai
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p. 2141 - 2146
(2007/10/02)
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