- Racemic Structure and Optical Resolution by Preferential Crystallization of (+/-)-Organic Ammonium Hydrogen Malates
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Gibbs energies of formation of racemate, binary melting point diagrams, and ternary solubility diagrams indicate that (+/-)-propylammonium ((+/-)-PA salt) and (+/-)-1,1,3,3-tetramethylbutylammonium ((+/-)-TMB salt) hydrogen malates are conglomerates at room temperature, whereas (+/-)-TMB salt forms a racemic compound at its melting point.Free energies of critical nucleation in supersaturated solutions were examined to resolve (+/-)-PA and -TMB salts efficiently by preferential crystallization.Successive preferential crystallization of (+/-)-PA salt in methanol at 10 deg C and that of (+/-)-TMB salt in water give (+)- and (-)-PA and -TMB salts with about 90percent optical purity.Optically pure (+)- and (-)-malic acids are obtained from purified (-)- and (+)-salts.
- Shiraiwa, Tadashi,Sado, Yujin,Inoue, Mitsuo,Sakamoto, Keiji,Miyazaki, Hideya,Kurokawa, Hidemoto
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- STEREOCHEMICAL STUDIES ON BORONOLIDE, AN α-PYRONE FROM TETRADENIA BARBERAE
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Key Word Index-Tetradenia barberae; Lamiaceae; α-pyrone; boronolide. The structure of boronolide isolated from Tetradenia barberae has been confirmed as 6R--5,6-dihydro-2H-pyran-2-one by chemical degradation.
- Davies-Coleman, Michael T.,Rivett, Douglas E. A.
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- Sesquiterpene dimers esterified with diverse small organic acids from the seeds of Sarcandra glabra
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11 new sesquiterpene dimers, sarglabolides A-K (1-11), and five known ones were isolated from the seeds of Sarcandra glabra. Their structures were elucidated by spectroscopic data analysis and chemical evidence. Sarglabolide A (1) was verified to exclusively possess a seventeen-membered macrocyclic ester ring formed by the scaffold of the sesquiterpene dimer and small organic acids, different from the eighteen-membered rings of the other reported analogues. The chiral small organic acid moieties were assigned to l-malic acid, d-malic acid, and d-tartaric acid based on the combination of spectroscopy, chemical derivatization and HPLC analysis. Dimers 1, 12 and 13 can significantly inhibit NO production in LPS-induced macrophages with IC50 values at 3.04, 4.65 and 2.33 μmol/L, respectively.
- Wang, Peng,Luo, Jun,Zhang, Yang-Mei,Kong, Ling-Yi
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p. 5362 - 5370
(2015/07/15)
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- Discovery and characterization of a thermostable D-lactate dehydrogenase from Lactobacillus jensenii through genome mining
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The demand on thermostable D-lactate dehydrogenases (d-LDH) has been increased for d-lactic acid production but thermostable d-DLHs with industrially applicable activity were not much explored. To identify a thermostable d-LDH, three d-LDHs from different Lactobacillus jensenii strains were screened by genome mining and then expressed in Escherichia coli. One of the three d-LDHs (d-LDH3) exhibited higher optimal reaction temperature (50 °C) than the others. The T5010 value of this thermostable d-LDH3 was 48.3 °C, much higher than the T5010 values of the others (42.7 and 42.9 °C) and that of a commercial D-lactate dehydrogenase (41.2 °C). The Tm values were 48.6, 45.7 and 55.7 °C for the three d-LDHs, respectively. In addition, kinetic parameter (k cat/Km) of d-LDH3 for pyruvate reduction was estimated to be almost 150 times higher than that for lactate oxidation at pH 8.0 and 25 °C, implying that D-lactate production from pyruvate is highly favored. These superior thermal and kinetic features would make the d-LDH3 characterized in this study a good candidate for the microbial production of D-lactate at high temperature from glucose if it is genetically introduced to lactate producing microbial.
- Jun, Chanha,Sa, Young Seung,Gu, Sol-A,Joo, Jeong Chan,Kim, Seil,Kim, Kyung-Jin,Kim, Yong Hwan
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p. 109 - 117
(2013/04/10)
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- An approach to the chemotaxonomic differentiation of two European Dog's mercury species: Mercurialis annua L. and M. perennis L.
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Mercurialis annua and M. perennis are medicinal plants used in complementary medicine. In the present work, analytical methods to allow a chemotaxonomic differentiation of M. annua and M. perennis by means of chemical marker compounds were established. In addition to previously published compounds, the exclusive presence of pyridine-3-carbonitrile and nicotinamide in CH2Cl2 extracts obtained from the herbal parts of M. annua was demonstrated by GC/MS. Notably, pyridine-3-carbonitrile was identified for the first time as a natural product. Further chromatographic separation of the CH2Cl2 extracts via polyamide yielded a MeOH fraction exhibiting a broad spectrum of side-chain saturated n-alkylresorcinols. While the n-alkylresorcinol pattern was similar for both plant species, some specific differences were observed for particular n-alkylresorcinol homologs. Finally, the investigation of H2O extracts by LC/MS/MS revealed the presence of depside constituents. Whereas, in M. perennis, a mixture of mercurialis acid (=(2R)-[(E)-caffeoyl]-2-oxoglutarate) and phaselic acid (=(E)-caffeoyl-2-malate) could be detected, in M. annua solely phaselic acid was found. By comparison with synthesized enantiomerically pure (2R)- and (2S)-phaselic acids, the configuration of the depside could be determined as (2S) in M. annua and as (2R) in M. perennis.
- Lorenz, Peter,Duckstein, Sarina,Conrad, Juergen,Knoedler, Matthias,Meyer, Ulrich,Stintzing, Florian C.
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experimental part
p. 282 - 297
(2012/05/04)
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- Substrate specificity determinants of the methanogen homoaconitase enzyme: Structure and function of the small subunit
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The aconitase family of hydro-lyase enzymes includes three classes of proteins that catalyze the isomerization of a-hydroxy acids to β-hydroxy acids. Besides aconitase, isopropylmalate isomerase (IPMI) proteins specifically catalyze the isomerization of α,β-dicarboxylates with hydrophobic y-chain groups, and homoaconitase (HACN) proteins catalyze the isomerization of tricarboxylates with variable chain length y-carboxylate groups. These enzymes' stereospecific hydro-lyase activities make them attractive catalysts to produce diastereomers from unsaturated precursors. However, sequence similarity and convergent evolution among these proteins lead to widespread misannotation and uncertainty about gene function. To find the substrate specificity determinants of homologous IPMI and HACN proteins from Methanocaldococcus jannaschii, the small-subunit HACN protein (MJ1271 ) was crystallized for X-ray diffraction. The structural model showed characteristic residues in a flexible loop region between α2 and α3 that distinguish HACN from IPMI and aconitase proteins. Site-directed mutagenesis of MJ1271 produced loop-region variant proteins that were reconstituted with wild-type MJ1003 large-subunit protein. The heteromers formed promiscuous hydro-lyases with reduced activity but broader substrate specificity. Both R26K and R26V variants formed relatively efficient IPMI enzymes, while the T27A variant had uniformly lower specificity constants for both IPMI and HACN substrates. The R26V T27Y variant resembles the MJ1277IPMI small subunit in its flexible loop sequence but demonstrated the broad substrate specificity of the R26V variant. These mutations may reverse the evolution of HACN activity from an ancestral IPMI gene, demonstrating the evolutionary potential for promiscuity in hydro-lyase enzymes. Understanding these specificity determinants enables the functional reannotation of paralogous HACN and IPMI genes in numerous genome sequences. These structural and kinetic results will help to engineer new stereospecific hydro-lyase enzymes for chemoenzymatic syntheses.
- Jeyakanthan, Jeyaraman,Drevland, Randy M.,Gayathri, Dasara Raju,Velmurugan, Devadasan,Shinkai, Akeo,Kuramitsu, Seiki,Yokoyama, Shigeyuki,Graham, David E.
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scheme or table
p. 2687 - 2696
(2011/03/20)
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- Process for preparing R-(-) -carnitine from S-(-)-chlorosuccinic acid or from a derivative thereof
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An inner salt of L-carnitine is prepared by reduction, with a suitable reducing agent, of a compound of formula (I): where X1and X2, which may be the same or different, are hydroxy, C1-C4alkoxy, phenoxy, halogen, or X1and X2, when taken together are an oxygen atom and the resulting compound is a derivative of succinic anhydride; Y is halogen, the mesyloxy or the tosyloxy group: and subsequent treatment with water, then with a base and then with trimethylamine.
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Page column 9
(2008/06/13)
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- Preparation of Both Enantiomers of Malic and Citramalic Acid and Other Hydroxysuccinic Acid Derivatives by Stereospecific Hydrations of cis or trans 2-Butene-1,4-dioic Acids with Resting Cells of Clostridium formicoaceticum
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(R)-Malic, (S)-malic, (R)-citramalic, (S)-citramalic, (2R,3S)-2-hydroxy-3-methylsuccinic and (2R,3S)-2,3-dimethyl-2-hydroxysuccinic acid were prepared on scales up to 25 mmol by stereospecific addition of water to different 2-butene-1,4-dioic acid derivatives catalyzed by resting cells of Clostridium formicoaceticum (Scheme 1).The (3R)-monodeuterio (R)- and (S)-malic acid as well as (R)- and (S)-citramalic acid were prepared using freeze-dried cells in 2H2O-buffer.The stereochemical purity of the products was in most cases >/= 99percent.
- Eck, Richard,Simon, Helmut
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p. 13641 - 13654
(2007/10/02)
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- Antiviral purine derivatives and process for their preparation
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Compounds of formula (I), and a pharmaceutically acceptable salts thereof: wherein:, R1 is hydrogen or CH2OH;, R2 is hydrogen or, (when R1 is hydrogen), hydroxy or CH2OH;, R3 is CH2OH or, (when R1 and R2 are both hydrogen), CH(OH)CH2OH;, R4 is hydrogen, hydroxy, amino or OR5 wherein, R5 is C1-6alkyl, phenyl or phenyl C1-2alkyl either of which phenyl moieties may be substituted by one or two halo, C1-4alkyl or C1-4alkoxy groups;, and in which any OH groups in R1, R2 and/or R3 may be in the form of O-acyl, phosphate, cyclic acetal or cyclic carbonate derivatives thereof; having antiviral activity, processes and intermediates for their preparation and their use as pharmaceuticals.
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- The Absolute Configuration of 4-(Trichloromethyl)oxetan-2-one; A Case of Double Anchimeric Assistance with Inversion
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It has been shown that the absolute configuration of the oxetan-2-one (1) is opposite to that of its hydrolysis product, S-(-)-malic acid (3).
- Wynberg, Hans,Staring, Emiel G. J.
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p. 1181 - 1182
(2007/10/02)
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- AMINO-ACIDS AS CHIRAL SYNTHONS : SYNTHESIS OF ENANTIOMERICALLY PURE α-HYDROXY ESTERS.
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Reaction of lithium homocuprates with α-hydroxy β-bromo ester derivated from aspartic acid affords α-hydroxy esters of high enantiomerical purity.
- Larcheveque, Marc,Petit, Yves
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p. 3705 - 3706
(2007/10/02)
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- Synthesis and Stereochemistry of Hypusine, a New Amino Acid in Bovine Brain
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Hypusine, a new basic amino acid occurring in the homogenate of bovine brain tissue, was synthesized to determine the absolute structure.Nα-Benzyloxycarbonyl-L-lysine benzyl ester was coupled with (S)- or (R)-4-benzyloxycarbonylamino-1-bromo-2-butanol derived from L- or D-malic acid, respectively.The products were deprotected by catalytic dehydrogenation.One of the synthetic compounds, i.e., (2S,9R)-2,11-diamino-9-hydroxy-7-azaundecanoic acid, was completely identical with natural hypusine in all respects.
- Shiba, Tetsuo,Akiyama, Hitoshi,Umeda, Isao,Okada, Satoshi
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p. 899 - 903
(2007/10/02)
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- Asymmetric Synthesis of (S)- and (R)-Malic Acid from Ketene and Chloral
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Quinidine (5) catalyzes the addition of ketene (1) to chloral (2) at -50 deg C in toluene.The β-(trichloromethyl)-β-propiolactone 3 is formed virtually optically pure (98percent enantiomeric excess).A mechanism for this reaction, accounting for the high enantiomeric excess, is proposed.Known hydrolytic procedures convert the lactone 3 to malic acid (6).By proper choice of catalyst both (R)- and (S)-malic acid can be obtained optically pure.
- Wynberg, Hans,Staring, Emiel G. J.
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p. 166 - 168
(2007/10/02)
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