- Synthesis and solid-state polymerization of l-alanine derivatives with a (1-pyrenyl)butadiynyl group
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(1-Pyrenyl)butadiyne derivatives 5 and 6 with a methylene chain and a L-alanine moiety as a chiral group were synthesized, and the end group of 5 and 6 was ethyl ester and carboxylic acid, respectively. These compounds could be polymerized in the crystals by UV irradiation at 365 nm. The regular solid-state polymerization was confirmed for 5 although 6 showed irregular polymerization. Their nanoaggregate water dispersions were obtained by the reprecipitation method. Morphology of their nanoaggregates was studied by SEM, and helical nanoribbons and circle domains were observed for 5 and 6, respectively.
- Tatewaki, Yoko,Sato, Akinori,Ito, Shoya,Inayama, Satoshi,Okada, Shuji
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Read Online
- Carbocyclization of Heterosubstituted Alkynes via the Memory of Chirality: Access to Cα-Substituted Proline Derivatives
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An efficient strategy for the asymmetric synthesis of Cα-substituted proline derivatives from acyclic α-amino acids has been established. The 5-exo-dig asymmetric cyclization of α-amino ester enolates onto heterosubstituted alkynes provided a product with excellent enantioselectivity via the memory of chirality concept. Density functional theory calculations indicated that a heteroatom is crucial for the success of the asymmetric cyclization because a more stabilized vinyl carbanion is produced. This new method has the potential to enable the rapid asymmetric construction of bioactive molecules containing the pyrrolidine skeleton.
- Tan, Shenpeng,Li, Feng,Park, Soojun,Kim, Sanghee
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Read Online
- Reductive Alkylation of Amines with Carboxylic Ortho Esters
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We have demonstrated for the first time that carboxylic ortho esters could be used as an alkylating agent in the reductive alkylation of amines. A variety of amines, including amino acid esters, were alkylated affording mono-alkylated products with high selectivity in practical to high yields using standard heterogeneous catalysts. By applying acyclic ortho esters alkylation was completed at room temperature. (Figure presented.).
- Kadyrov, Renat,Moebus, Konrad
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supporting information
p. 3352 - 3357
(2020/07/04)
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- Stereospecific Synthesis of 3,4-Dihydro-2 H-naphtho-1,4-oxazin-2-ones by Unification of Benzoxepine-4-carboxylates with Chiral Amino Acid Ethyl Esters
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A novel and efficient stereocontrolled method has been developed for the preparation of chiral 3,4-dihydro-2H-naphtho[1,2-b][1,4]oxazin-2-ones by the reaction of benzoxepine-4-carboxylates with chiral amino acid ethyl esters for the first time. The chiral 3,4-dihydro-2H-naphtho-1,4-oxazinones have been achieved in one step by the formation of C-N, C-C, and C-O bonds.
- Bhimapaka, China Raju,Kasagani, Veera Prasad,Kurma, Siva Hariprasad
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supporting information
p. 2976 - 2983
(2020/03/23)
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- Design, synthesis and biological evaluation of novel 2-(5-aryl-1H-imidazol-1-yl) derivatives as potential inhibitors of the HIV-1 Vpu and host BST-2 protein interaction
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Novel ethyl 2-(5-aryl-1H-imidazol-1-yl)-acetates 17 and propionates 18, together with their acetic acid 19 and acetohydrazide 20 derivatives, were designed and synthesized using TosMIC chemistry. Biological evaluation of these newly synthesized scaffolds in the HIV-1 Vpu- Host BST-2 ELISA assay identified seven hits (17a, 17b, 17c, 17g, 18a, 20f and 20g) with greater than 50% inhibitory activity. These hits were validated in the HIV-1 Vpu- Host BST-2 AlphaScreen and six of the seven compounds were found to have comparable percentage inhibitory activities to those of the ELISA assay. Compounds 17b and 20g, with consistent percentage inhibitory activities across the two assays, had IC50 values of 11.6 ± 1.1 μM and 17.6 ± 0.9 μM in a dose response AlphaScreen assay. In a cell-based HIV-1 antiviral assay, compound 17b exhibited an EC50 = 6.3 ± 0.7 μM at non-toxic concentrations (CC50 = 184.5 ± 0.8 μM), whereas compound 20g displayed antiviral activity roughly equivalent to its toxicity (CC50 = 159.5 ± 0.9 μM). This data suggests that compound 17b, active in both cell-based and biochemical assays, provides a good starting point for the design of possible lead compounds for prevention of HIV-1 Vpu and host BST-2 protein binding in new anti-HIV therapeutics.
- Bode, Moira L.,Coyanis, E. Mabel,Mosebi, Salerwe,Njengele, Zikhona,Rashamuse, Thompho J.,Sayed, Yasien
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- Synthesis, insecticidal activities and SAR studies of novel anthranilic diamides containing trifluoroethoxyl substituent and chiral amino acid moieties
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Ryanodine receptors (RyRs) activator has become one class of popular insecticide because of its unique mode of action. In order to find more new RyRs activators as insecticidal agents, a series of 18 novel chiral anthranilic diamides were designed by introducing the D-alanine acid and D-serine acid esters as well as trifluoroethoxyl group into the anthranilic diamide skeleton and synthesized successfully based on anthranilic diamide and FKI-1033 structures. The structures of the title compounds Ia–i and IIa–i were confirmed by melting points, 1H NMR, 13C NMR, elemental analysis and specific optical rotation analysis. The preliminary bioassay results indicated that most of the title compounds exhibited considerable larvicidal activities against oriental armyworm at 10 mg/L, especially Ib, Ie and IIh showed remarkable insecticidal activities at 0.5 mg/L. The larvicidal activity against diamondback moth of Ia and IId were 80% and 90% respectively at 0.0001 mg/L, which was similar to that of chlorantraniliprole. The relationship between structure and insecticidal activity was analyzed to reveal a possible co-regulated effect of the chiral amino acid ester, halogen atom or cyano group, and trifluoroethyloxyl group of the skeleton structures of the title compounds, which will provide useful information for guiding the design and discovery of new RyRs activators and insecticidal agrochemicals.
- Zhou, Shaa,Zhou, Sha,Xie, Yongtao,Meng, Xiangde,Wang, Baolei,Xiong, Lixia,Yang, Na,Li, Zhengming
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supporting information
p. 1254 - 1256
(2017/11/24)
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- Characterization and cytotoxicity evaluation of biocompatible amino acid esters used to convert salicylic acid into ionic liquids
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The technological utility of active pharmaceutical ingredients (APIs) is greatly enhanced when they are transformed into ionic liquids (ILs). API-ILs have better solubility, thermal stability, and the efficacy in topical delivery than solid or crystalline drugs. However, toxicological issue of API-ILs is the main challenge for their application in drug delivery. To address this issue, 11 amino acid esters (AAEs) were synthesized and investigated as biocompatible counter cations for the poorly water-soluble drug salicylic acid (Sal) to form Sal-ILs. The AAEs were characterized using 1H and 13C NMR, FTIR, elemental, and thermogravimetric analyses. The cytotoxicities of the AAE cations, Sal-ILs, and free Sal were investigated using mammalian cell lines (L929 and HeLa). The toxicities of the AAE cations greatly increased with inclusion of long alkyl chains, sulfur, and aromatic rings in the side groups of the cations. Ethyl esters of alanine, aspartic acid, and proline were selected as a low cytotoxic AAE. The cytotoxicities of the Sal-ILs drastically increased compared with the AAEs on incorporation of Sal into the cations, and were comparable to that of free Sal. Interestingly, the water miscibilities of the Sal-ILs were higher than that of free Sal, and the Sal-ILs were miscible with water at any ratio. A skin permeation study showed that the Sal-ILs penetrated through skin faster than the Sal sodium salt. These results suggest that AAEs could be used in biomedical applications to eliminate the use of traditional toxic solvents for transdermal delivery of poorly water-soluble drugs.
- Moshikur, Rahman Md.,Chowdhury, Md. Raihan,Wakabayashi, Rie,Tahara, Yoshiro,Moniruzzaman, Muhammad,Goto, Masahiro
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- The reactions of α-amino acids and α-amino acid esters with high valent transition metal halides: synthesis of coordination complexes, activation processes and stabilization of α-ammonium acylchloride cations
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Titanium tetrachloride smoothly reacted with a selection of α-amino acids (aaH) in CH2Cl2 affording yellow to orange solid coordination compounds, 1a-d, in 70-78% yields. The salts [NHEt3][TiCl4(aa)], 2a-b, were obtained from TiCl4/aaH/NEt3 (aa = l-phenylalanine, N,N-dimethylphenylalanine), in 60-65% yields. The complex , 3, was isolated from the reaction of l-proline with NbCl5/NHiPr2, performed in CH2Cl2 at room temperature. The X-ray structure of 3 features a bridging (E)-1,2-bis(3,4-dihydro-2H-pyrrol-5-yl)ethene-1,2-diolate ligand, resulting from the unprecedented C-C coupling between two proline units. Unusually stable α-ammonium acyl chlorides were prepared by the reactions of PCl5/MCln (MCln = NbCl5, WCl6) with l-proline, N,N-dimethylphenylalanine, sarcosine and l-methionine. MX5 (M = Nb, Ta; X = F, Cl) reacted with l-leucine methylester and l-proline ethylester to give ionic coordination compounds, [MX4L2][MX6] (M = Nb, L = Me2CHCH2CH(NH2)CO2Me, X = F, 9; Cl, 11a; M = Nb, X = Cl, , 11c; Ta, 11d), in moderate to good yields. [NbCl5(Me2CHCH2CHNH3CO2Me)][NbCl6], 12, was isolated as a co-product of the reaction of NbCl5 with l-leucine isopropylester, and crystallographically characterized. The reaction of NbCl5 with l-serine isopropylester afforded NbCl3(OCH2CHNHCO2iPr), 13, in 66% yield. The activation of the ester O-R bond was observed in the reactions of l-leucine methyl ester with NbF5 and l-proline ethyl ester with MBr5 (M = Nb, Ta), these reactions proceeding with the release of EtF and EtBr, respectively. All the metal products were characterized by analytical and spectroscopic methods, while DFT calculations were carried out in order to provide insight into the structural and mechanistic aspects.
- Biancalana, Lorenzo,Bortoluzzi, Marco,Ferretti, Eleonora,Hayatifar, Mohammad,Marchetti, Fabio,Pampaloni, Guido,Zacchini, Stefano
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p. 10158 - 10174
(2017/02/15)
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- Stereochemistry and conformation of skyllamycin, a non-ribosomally synthesized peptide from streptomyces sp. Acta 2897
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Skyllamycin is a non-ribosomally synthesized cyclic depsipeptide from Streptomyces sp. Acta 2897 that inhibits PDGF-signaling. The peptide scaffold contains an N-terminal cinnamoyl moiety, a β-methylation of aspartic acid, three β-hydroxylated amino acids and one rarely occurring α-hydroxy glycine. With the exception of α-hydroxy glycine, the stereochemistry of the amino acids was assigned by comparison to synthetic reference amino acids applying chiral GC-MS and Marfey-HPLC analysis. The stereochemistry of α-hydroxy glycine, which is unstable under basic and acidic conditions, was determined by conformational analysis, employing a combination of data from NOESY-NMR spectroscopy, simulated annealing and free MD simulations. The simulation procedures were applied for both R- and S-configured α-hydroxy glycine of the skyllamycin structure and compared to the NOESY data. Both methods, simulated annealing and free MD simulations independently support S-configured α-hydroxy glycine thus enabling the assignment of all stereocenters in the structure of skyllamycin and devising the role of two-component flavin dependent monooxygenase (Sky39) as S-selective.
- Schubert, Vivien,Di Meo, Florent,Saaidi, Pierre-Loic,Bartoschek, Stefan,Fiedler, Hans-Peter,Trouillas, Patrick,Suessmuth, Roderich D.
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p. 4948 - 4955
(2014/05/06)
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- Substrate profile of an ω-transaminase from Burkholderia vietnamiensis and its potential for the production of optically pure amines and unnatural amino acids
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A new (S)-enantioselective ω-transaminase (ω-TA) gene from Burkholderia vietnamiensis G4 was functionally expressed in Escherichia coli BL21 (DE3), and the purified recombinant N-terminal His-tagged ω-TA (HBV-ω-TA) had a dimeric structure with optimum pH and temperature of 8.4 and 40 C, respectively. The enzyme showed higher activities toward aromatic amines than aliphatic amines and (S)-1-methylbenzylamine ((S)-α-MBA) was the most active amino donor. For amino acceptor, keto acids, keto esters and aldehydes were more reactive than ketones with pyruvate ethyl ester being most active. Several chiral amines and unnatural amino acids or esters were synthesized using HBV-ω-TA as the catalyst and isopropylamine or (S)-α-MBA as amino donor. Notably, HBV-ω-TA catalyzed the amino transfer to β-keto esters to give optically pure β-amino acid esters. In addition, glyoxylate was used as amino acceptor for the first time in the kinetic resolution of racemic amines and optically pure amines, such as (R)-1-methylbenzylamine, (R)-1-phenylpropylamine, (R)-2-amino-4-phenylbutane and (R)-1-aminotetraline, were obtained.
- Jiang, Jinju,Chen, Xi,Feng, Jinhui,Wu, Qiaqing,Zhu, Dunming
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- Friedel-Crafts alkylation of natural amino acid-derived pyrroles with CF3-substituted cyclic imines
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Natural amino acid-derived ethyl 2-(1-pyrrolyl)alkanoates react with 2-trifluoromethyl-1-azacycloalkenes selectivity at the β-position of the pyrrole moiety to afford ethyl 2-[3-(1-trifluoromethyl-2-azacycloalkyl)pyrrol-1- yl]alkanoates.
- Shmatova, Olga I.,Shevchenko, Nikolay E.,Balenkova, Elizabeth S.,R?schenthaler, Gerd-Volker,Nenajdenko, Valentine G.
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- N-alkylcarbonyl-amino acid ester compounds and their use for cough and pharyngitis
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The present invention generally relates to refreshing, soothing, and cooling compounds that affect sensory processes. More particularly, the present invention pertains to certain N-alkylcarbonyl-amino acid esters compounds as described herein; compositions and articles comprising such compounds; and methods of treatment, for example, methods of reducing cough and pharyngeal irritation, itch, and/or pain.
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- Enantioselective benzoylation of α-amino esters using (S)-1-benzoyl-2-(α-acetoxyethyl)benzimidazole, a chiral benzimidazolide
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(Chemical Equation Presented) A new chiral benzimidazolide is developed as a nonenzymatic acylating agent for enantioselective benzoylation of racemic α-amino esters. The process is highly efficient, which exhibits uniformly high enantioselectivity for α-amino esters with or without aryl substituents under mild reaction conditions. The chiral benzimidazolide is inexpensive and is easily accessible.
- Karnik, Anil V.,Kamath, Suchitra S.
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p. 7435 - 7438
(2008/02/11)
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- A vaulted biaryl phosphoric acid-catalyzed reduction of α-imino esters: The highly enantioselective preparation of α-amino esters
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A new method for the chiral phosphoric acid-catalyzed reduction of α-imino esters using Hantzsch ester is described. A series of 11 α-imino esters were evaluated, and it was shown that imino substrates derived from substituted aryl and alkyl keto esters could be reduced to the corresponding α-amino ester in excellent yield and in enantiomeric excesses from 94 to 99%. Catalyst loading was 5 mol % in each case, and the reactions were run with toluene as the solvent. Copyright
- Li, Guilong,Liang, Yuxue,Antilla, Jon C.
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p. 5830 - 5831
(2008/02/10)
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- Methods and compositions for treating amyloid-related diseases
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Methods, compounds, pharmaceutical compositions and kits are described for treating or preventing amyloid-related disease.
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Page/Page column 135
(2010/11/24)
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- Inhibitors of alpha l beta 2 mediated cell adhesion
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The present invention relates to small molecules according to formula (I) that are potent inhibitors of αLβ2 mediated cell adhesion and which could be useful for the treatment of inflammatory diseases:
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- Small molecules useful in the treatment of inflammation disease
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Novel compounds of the formula I which are useful for treating or preventing inflammatory and immune cell-mediated diseases. Exemplary compounds are:1-acetyl-5-(R)-(4-bromobenzyl)-3-(2,6-dichloropyridin-4-yl)-5-methylimidazoline-2,4-dione;5-(R)-(4-bromobenzyl)-3-(2,6-dichloropyridin-4-yl)-1-ethyl-5-methylimidazoline-2,4-dione; and,5-(R)-(4-bromobenzyl)-3-(2,6-dichloropyridin-4-yl)-5-methylimidazoline-2,4-dione.
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Page column 27
(2010/02/05)
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- Rapid microwave-assisted deprotection of N-Cbz and N-Bn derivatives
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Catalytic-transfer hydrogenation in iso-propanol under microwave irradiation has been performed to rapidly deprotect N-Cbz and N-Bn derivatives. The method is particularly suitable for the synthesis of short peptides and can also be carried out on supported molecules. The rapid cleavage of chiral molecules derived from (S)-1-phenylethylamine can be very useful for asymmetric synthesis of nitrogen containing compounds.
- Daga, Maria Caterina,Taddei, Maurizio,Varchi, Greta
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p. 5191 - 5194
(2007/10/03)
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- Asymmetric α-substitution versus aza Diels-Alder reaction of electron deficient N-sulfonyl imines
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Several N-arylsulfonylglycine esters have been brominated under photolytic conditions to provide the corresponding α-bromoglycine. These bromo esters can be treated with a range of bases to generate N-sulfonyl imino esters in situ; attempts to isolate the imines in a pure state were universally unsuccessful. Once generated, the imines can be trapped with cyclopcntadiene to provide the corresponding aza Diels-Alder adducts in varying yields, depending upon the base used. In addition, if organometallic bases were employed (alkyllithiums and alkylaluminium reagents), not only were aza Diels-Alder adducts formed, but addition to the imine was also observed. In the case of organoaluminium reagents, imine addition was the major product. This process could be transformed into a stoichiometric asymmetric version, by generating a chiral aluminium reagent in situ to form a trialkyl (or trialkoxy) aluminium reagent, which when reacted with an N-sulfonyl bromoglycinate resulted in 19 to 62% enantiomeric excess of the corresponding substituted glycinate product. The Royal Society of Chemistry 2000.
- Morgan, Paul E.,McCague, Ray,Whiting, Andrew
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p. 515 - 525
(2007/10/03)
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- N-carboalkoxy-2-nitrobenzenesulfonamides: A practical preparation of N- Boc-, N-Alloc-, and N-Cbz-protected primary amines
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N-Carboalkoxy-2-nitrobenzenesulfonamides, readily prepared by acylation of 2-nitrobenzenesulfonamide (o-NsNH2), can be alkylated by either conventional or Mitsunobu protocols. Since the o-nosyl group can be deprotected under mild conditions, a variety of N-carboalkoxy derivatives of primary amines may be prepared in excellent yields from the corresponding alcohols and/or halides. In addition, allyloxycarbonyl (Alloc), t- butoxycarbonyl (t-Boc), and benzyloxycarbonyl (Cbz) groups can be deprotected in the presence of the o-nosyl group, allowing the resultant N-alkylated 2- nitrobenzenesulfonamides to be used for further preparation of secondary amines.
- Fukuyama, Tohru,Cheung, Mui,Kan, Toshiyuki
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p. 1301 - 1303
(2007/10/03)
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- Synthesis of Tc-D,D-HMPAO and Tc-L,L-HMPAO and their comparison of chemical and biological properties
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Tc-D,D- and Tc-L,L-HMPAO were synthesized. The stability of Tc-D,D- and Tc-L,L-HMPAO in vitro is similar to that of d,l-isomers by the spectrophotometric and three strips methods. Cerebral uptake (%D in brain) for the L,L-isomer is higher than the D,D- and d,l-isomer in rats. Delayed studies shows that Tc-L,L-HMPAO reveals less washout and reflects a higher cerebral deposition properties than the D,D- and d,l-isomer.
- Ding, Hueisch-Jy,Huang, Ying-Fong,Tzeng, Cherng-Chyi,Wei, Li-Mei,Yeh, Si-Jung
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p. 3199 - 3202
(2007/10/03)
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- Synthesis and anticholinesterase activity of some benzo-1,3,2-dioxaphospholene, oxazaphospholine and diazaphospholine 2-ones containing 2-amino acid substitution
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Synthesis of the titled compounds has been described. 1H NMR, IR band frequencies and MS fragmentation and rearrangement peaks were analyzed and discussed in detail. Studying the inhibitory effect of these compounds on acetylcholinesterase (AChE) showed that dioxaphospholenes were stronger inhibitors than oxazaphospholines and diazaphospholines. This was explained by increasing the number of nitrogen atoms around the phosphorus atom in the later two series, which reduces the electrophilic character of the phosphorus atom by the overlapping between the dπ - pπ orbitals of the phosphorus and the neighboring nitrogen atoms, and hence reducing the electrophilic attack of the phosphorus atom on a nucleophilic center at the esteratic site of the enzyme. Steric factor of the amino acid moiety showed stronger effect than the electronic factor on the inhibition activity, the observed order was glycine > glutamic > methaionine > phenylalanine > alanine.
- Ali, Hussein M.
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p. 157 - 166
(2007/10/03)
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- Enantioselective hydrogenation of ethyl pyruvate over Pt/alumina modified by (R)-1-(1-naphthyl)ethylamine derivatives
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A new chiral modifier, (R)-1-(1-naphthyl)ethylamine, has been tested in the enantioselective hydrogenation of ethyl pyruvate to ethyl lactate over 5 wt% Pt/Al2O3. The influence of catalyst (2-28 g liter-1) and modifier concentration (0-20 mM), temperature (282-333 K), pressure (1-75 bar), and solvents was studied in a slurry reactor. The 82% enantiomeric excess (ee) at full conversion was achieved in acetic acid after optimizing the reaction parameters. Under mild conditions the new modifier affords ee's better than that achieved with cinchona alkaloids. A drop in ee at pressures higher than 10 bar and temperatures above 288 K is attributed to partial hydrogenation of the naphthalene ring, which hinders the adsorption of the modifier parallel to a flat Pt surface. Maximum rate acceleration by a factor of 12, compared to the racemic reaction, was observed after thermal treatment of the catalyst in flowing hydrogen at 673 K, followed by aerobic treatment at 273-298 K in acetic acid. It is shown that naphthylethylamine is only a precursor of the actual modifier, which is a secondary amine formed in situ from naphthylethylamine and ethyl pyruvate by condensation to the corresponding imine and subsequent reduction of the C=N bond. Several other derivatives of naphthylethylamine were prepared by reductive alkylation and tested as modifiers. The results indicate that the presence of an oxygen function such as a hydroxy or methoxy group, as in previously used modifiers, is not an indispensable requirement for obtaining high ee in the hydrogenation of α-ketoesters.
- Minder,Schueren,Mallat,Baiker,Heinz,Pfaltz
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p. 261 - 268
(2007/10/03)
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- (3R)- AND (3S)-METHYLPIPERAZINE-2,5-DIONE DERIVATIVES AS USEFUL INTERMEDIATES IN THE ENANTIOSELECTIVE SYNTHESIS OF α-AMINO ESTERS
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Treatment of (3S)-3-methylpiperazine-2,5-dione 1 with lithium hexamethyldisilazide (LHMDS) followed by alkylation with several alkyl bromides affords (3S,6S)-3-methyl-6-alkyl derivatives 3 (a-e) in d.e. greater than 98percent.The same reaction sequence carried out on the (3R)-derivative 2 leads to a diastereoisomeric mixture of (3R,6S)-4 (a-e) and (3R,6R)-5 (a-e), the ratio 5 : 4 depending on the alkylating reagent.The configuration at C-6 (of 3, 4 and 5) has been assigned on the basis of 1H-NMR spectroscopic data and conformational analysis performed by the MMPMI program.Cleavage of the heterocyclic ring of 3 (b, d) and 5 (b, d) leads to the corresponding (S)- and (R)-α-amino esters respectively.
- Orena, Mario,Porzi, Gianni,Sandri, Sergio
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p. 2125 - 2152
(2007/10/02)
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- A New Chiral Glycine Synthon. Synthesis, X-Ray Structure of (-)-(2S,4R)-2-Ethoxycarbonyl-4-phenyl-1,3-oxazolidine and Diastereoselective Nucleophilic Ring Opening to (R)-Ethyl α-Amino Carboxylates.
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Condensation of (R)-N-benzyl-2-phenylglycinol 1 with the methyl hemiacetal of ethyl glyoxylate leads to (2S,4R)-2-ethoxycarbonyl-4-phenyl-1,3-oxazolidine 2 as the major product, obtained as a pure enantiomer after column chromatography.Compound 2 is stereoselectively cleaved by dialkylzinc reagents, prepared from alkylmagnesium iodides and ZnCl2, with moderate to good d.e. (72-94 percent).These compounds, after separation by column chromatography and debenzylation by hydrogenolysis in the presence of 10percent Pd on carbon, lead to enantiomerically pure ethyl α-amino carboxylates with good chemical yields. Key words: Chiral Oxazolidines, alpha-amino Esters, Chiral Glycine Synthon, Ring Opening, Asymmetric Synthesis
- Andres, Celia,Gonzalez, Alfonso,Pedrosa, Rafael,Perez-Encabo,Garcia-Granda, Santiago,et al.
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p. 4743 - 4746
(2007/10/02)
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- ENANTIOSELECTIVE SYNTHESES OF α-AMINO ACIDS FROM 10-SULFONAMIDO-ISOBORNYL ESTERS AND DI-t-BUTYL AZODICARBOXYLATE
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Successive treatment of chiral esters 7 with LDA/Me3SiCl and di-t-butyl azodicarboxylate/TiCl4 and Ti(OiPr)4 gave N,N-di-t-butoxycarbonylhydrazinoesters 11 which on deacylation, hydrogenolysis, transesterification and acidic hydrolysis furnished (2S)-α-amino acid hydrochlorides 13 in good overall yields, high enantiomeric purity and with efficient recovery of the alcohol auxiliary 4.Experimental evidence for the configuration and conformation of the intermediate O-silyl ketene acetals 1 is provided.
- Oppolzer, Wolfgang,Moretti, Robert
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p. 5541 - 5552
(2007/10/02)
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- OLIGONUCLEOTIDES AND NUCLEOTIDYLPEPTIDES. XXXII. SYNTHESIS AND HYDROLYTIC STABILITY OF AMINO ACID DERIVATIVES OF ADENOSINE 5'-DI(TRI)PHOSPHATES
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The synthesis has been effected of the ethyl esters of adenosine -5'-diphospho(Pβ --> N)- and adenosine-5'-triphospho(Pγ --> N)-alanine.It has been shown that under the conditions of synthesis the serine analogues of ATP and ADP decompose.An investigation of the hydrolytic stability of the compounds synthesized has shown that they are unstable in acid and alkaline media.In an acid medium the phosphoramide bond is cleaved more rapidly than the phosphoric anhydride bond (in the case of ADP analogue), while in an alkaline medium the ester bond is saponified and the p hosphoric anhydride bond is cleaved.The ATP analogue is more labile both in acid and in alkaline media.
- Yuodka, B. A.,Sasnauskene, S. I.
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p. 479 - 483
(2007/10/02)
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- Water soluble 3,5-diacetamido-2,4,6-triiodobenzoic acid derivatives
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The invention relates to novel water soluble 3,5-diacetamido-2,4,6-triiodobenzoic acid derivatives, the method for making the same and their use as X-ray contrast agents for vasography, urography, myelography, artrography, fistulography and salpingography.
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- Metal Complexes of Salical-N-α-Alanino Hydroxamic Acid (Schiff Base)
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Schiff base, salical-N-α-alaninohydroxamic acid, (RH2), has been prepared and its complexes with Ni(II), Cu(II), Co(II), Mn(II), Cr(III) and UO2(II) have been isolated in the solid state.All the products are found insoluble in water or common organic solvents.The general formula for the complexes is except for the Cr(III) complex, *H2O and the UO2(II) complex, .Attempts have been made to characterise the complexes with the help of the magnetic moment values, reflectance visible spectra, ir spectra and thermogravimetric analysis.
- Ghosh, M. K.,Sur, B.,Chakraburtty, A. K.
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p. 282 - 285
(2007/10/02)
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