- Chiral tetraaryl-and tetraalkynylborates as chiral solvating agents for tetraalkylammonium salts
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The application of tetracarbon-substituted chiral borate sodium salts (NaBR*4) as NMR chiral solvating agents for various tetraalkylammonium salts (R4NX) has been successfully demonstrated. Ion exchange between R4NX and NaBR*4 proceeded in excellent yields and provided the corresponding dia-stereomeric salts (R4NBR*4). The ee values of the R4NX salts were determined by1H NMR analysis of R4NBR*4. Two types of chiral borates, tetraaryl-and tetraalkynylborates with optically active 1,1′-binaphthyl components were used. At the beginning of this research, we investigated the efficacy of a known chiral tetraar-ylborate developed by Pommerening et al. for R4NX. To expand the possibility of further structural design of the chiral borate, we designed chiral tetraalkynylborates as a new structure. Their synthesis and application are also described.
- Tayama, Eiji,Sugawara, Takeshi
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supporting information
p. 803 - 811
(2019/01/18)
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- Tertiary-butoxycarbonyl (Boc) – A strategic group for N-protection/deprotection in the synthesis of various natural/unnatural N-unprotected aminoacid cyanomethyl esters
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A number of cyanomethyl esters of natural/unnatural aminoacids with un-protected amino functionality were synthesized because of their synthetic and medicinal importance. Critical N-Boc deprotection methods in the presence of labile (hydrolytic sensitivity) cyanomethyl functionality were screened thoroughly and it was found that readily available 4M HCl in 1,4-dioxane solution (2–4 equiv); acetonitrile, 0 °C, 2–4 h was a suitable condition. This condition was generalized and successfully applied to a variety of alkyl, alkynyl, aryl, heteroaryl, benzyl, azido, spiro amino acid cyanomethylesters irrespective of the nature of the amine (primary or secondary) and the distance between the amine and ester group to achieve final deprotected amino esters with high yield, and purity compared to other commonly known N-protecting groups (Cbz, Fmoc, Ac, Bn, Bz etc.). It was also demonstrated that N-Boc protected aminoacid cyanomethylesters are stable enough to carry out further functionalization compared to N-unprotected counterparts.
- Karmakar, Ananta,Basha, Mushkin,Venkatesh Babu,Botlagunta, Murali,Malik, Noormohamed Abdul,Rampulla, Richard,Mathur, Arvind,Gupta, Arun Kumar
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p. 4267 - 4271
(2018/11/03)
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- Synthesis, screening and docking of small heterocycles as Glycogen Phosphorylase inhibitors
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A series of morpholine substituted amino acids (phenylalanine, leucine, lysine and glutamic acid) was synthesized. A fragment-based screening approach was then used to evaluate a series of small heterocycles, including morpholine, oxazoline, dihydro-1,3-oxazine, tetrahydro-1,3-oxazepine, thiazoline, tetrahydro-1,3-pyrimidine, tetrahydro-1,3-diazepine and hexahydro-1H-benzimidazole, as potential inhibitors of Glycogen Phosphorylase a. Thiazoline 7 displayed an improved potency (IC50 of 25 μM) and had good LE and LELP values, as compared to heterocycles 1, 5, 9e13 and 19 (IC50 values of 1.1 mM e23.9 mM). A docking study using the crystal structure of human liver Glycogen Phosphorylase, provided insight into the interactions of heterocycles 5, 7, 9e13 and 19 with Glycogen Phosphorylase.
- Schweiker, Stephanie S.,Loughlin, Wendy A.,Lohning, Anna S.,Petersson, Maria J.,Jenkins, Ian D.
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p. 584 - 594
(2015/03/14)
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- Synthesis of enantiopure free and N-benzyloxycarbonyl-protected 3-substituted homotaurines from naturally occurring amino acids
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Enantiopure N-benzyloxycarbonyl-protected and free 3-substituted homotaurines were synthesized from naturally occurring amino acids via N-benzyloxycarbonyl protection, Arndt-Eistert homologation, reduction, esterification with thioacetic acid, and oxidation with performic acid. The current method is a convenient, practical, and salt-free method for the synthesis of enantiopure 3-substituted homotaurine with moderate to good yields.
- Zheng, Yongpeng,Xu, Jiaxi
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p. 5197 - 5206
(2014/12/10)
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- Resolution of non-proteinogenic amino acids via microbial lipase-catalyzed enantioselective transesterification
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A number of non-proteinogenic amino acids bearing aliphatic side chains were resolved with moderate to good enantioselectivities (E = 15-42) through the Burkholderia cepacia lipase-catalyzed enantioselective transesterification of the 2,2,2-trifluoroethyl esters of their N-benzyloxycarbonyl derivatives with methanol as a nucleophile in diisopropyl ether.
- Miyazawa, Toshifumi,Mio, Motoe,Watanabe, Yuko,Yamada, Takashi
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p. 219 - 224
(2008/09/20)
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- Inhibitors interacting with the magnesium binding site of reverse transcriptase: Synthesis and biological activity studies of 3′-(Ω- amino-acyl) amino-3′-deoxy-thymidine
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Active site of reverse transcriptase contains carboxylate groups involved in the magnesium binding. We prepared some nucleoside analogs which could bind to these carboxylates preventing the binding of nucleotides. To the 3′-amino-3′-deoxy-thymidine, different N-protected ω-amino-acids were bound, the protection removed to give the 3′-(ω-amino-acyl-) amino-3′-deoxy-thymidines in good yield. Some showed moderate to low activity in HIV 1 replication test. Copyright Taylor & Francis Group, LLC.
- Goud, Thirumani Venkateshwar,Aubertin, Anne-Marie,Biellmann, Jean-Francois
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p. 495 - 505
(2008/09/21)
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- A Stereoselective entry into functionalized 1,2-diamines by zinc-mediated homologation of α-aminoacids
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A general, stereoselective synthsis of 4,5-disubstituted imidazolidines-2-ones from α-aminoacids has been developed: the key steps are a Biaise reaction of bromoacetate on α-aminonitriles and further reduction. Although reduction with sodium cyanoborohydride afforded a mixture of cis and trans isomers 6a-e with moderate to good stereoselectivity, reduction with sodium in liquid ammonia gave the trans isomers 8a-e with complete stereoselectivity. Acidic hydrolysis of the urea gave 4-amino-pyrrolidinones, which can be precursors to β,γ-diaminoacids or 3-aminopyrrolidines.
- Hoang, Cam Thuy,Alezra, Valerie,Guillot, Regis,Kouklovsky, Cyrille
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p. 2521 - 2524
(2008/02/05)
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- α-Chymotrypsin-catalyzed peptide synthesis in frozen aqueous solution using N-protected amino acid carbamoylmethyl esters as acyl donors
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A kinetically controlled peptide synthesis catalyzed by α-chymotrypsin was performed in frozen aqueous solution (ice, -24 °C). The yield of the peptide was significantly improved by the use of the carbamoylmethyl (Cam) ester as the acyl donor instead of the conventional ethyl ester. The peptide yield increased up to ca. 90% when N-benzyloxycarbonyl (CBZ)-Phe-OCam and H-Phe-NH2 were used as the acyl donor and nucleophile, respectively. Such an improvement of the peptide yield in ice was also observed in the coupling of other CBZ-amino acid Cam esters as acyl donors. Furthermore, this approach was applied to the synthesis of peptides containing d-amino acids. The peptides such as CBZ-d-Phe-Phe-NH2, CBZ-Phe-d-Phe-NH2 and CBZ-d-Phe-d-Phe-NH2 were also obtained in excellent to moderate yields in ice. A high diastereoselectivity towards the l-l peptide was observed when the racemic amino acid Cam ester was used as the acyl donor in ice.
- Salam, Sayed Mohiuddin Abdus,Kagawa, Ken-Ichi,Kawashiro, Katsuhiro
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- Potassium trimethylsilanolate-mediated conversion of dialkyl phosphonates to their anhydrous potassium monoalkyl phosphonates under mild, non-aqueous conditions
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Anhydrous potassium monoalkyl phosphonates have been prepared from the corresponding dialkyl phosphonates and potassium trimethylsilanolate under non-aqueous conditions in good to excellent yields. Simple workup procedure has been developed to afford high purity products.
- Dziemidowicz, Joanna,Witt, Dariusz,Sliwka-Kaszynska, Magdalena,Rachon, Janusz
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p. 569 - 574
(2007/10/03)
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- The use of cellulose (chromatography paper) as a cheap, versatile and non-covalent support for organic molecules during multi-step synthesis
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Cellulose chromatography paper provides a novel non-covalent support for synthesis and in-situ purification of multi-dimensional arrays.
- Shanahan, Stephen E.,Byrne, Douglas D.,Inglis, Graham G. A.,Alam, Mahbub,Macdonald, Simon J. F.
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p. 2554 - 2555
(2007/10/03)
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- A novel concept in combinatorial chemistry in solution with the advantages of solid-phase synthesis: Formation of N-betaines by multicomponent domino reactions
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Advantages of solid-phase and liquid-phase synthesis are combined in a new concept of combinatorial chemistry: a domino sequence comprising Knoevenagel and hetero-Diels-Alder reactions, with subsequent hydrogenation starting from protected aminoaldehydes, 1.3-dicarbonyl compounds, and enol ethers leads to N-heterocycles of high diversity with a betaine structure, which are isolated in highly pure form by precipitation with diethyl ether (see scheme), Cbz = benzylocycarbonyl, Bn = benzyl.
- Tietze, Lutz F.
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p. 903 - 905
(2007/10/03)
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- α-chymotrypsin-catalysed peptide synthesis via the kinetically controlled approach using activated esters as acyl donors in organic solvents with low water content: Incorporation of non-protein amino acids into peptides
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The α-chymotrypsin-catalyzed peptide synthesis via the kinetically controlled approach using activated esters as acyl donors in orgnanic solvents with low water content was presented. The methyl esters of N-Z derivatives of racemic non-protein amino acids were chosen as carboxy components. They allowed the peptide-bond formation and optical resolution simultaneously to yield homochiral peptides. This method is useful for the incorporation of non-protein amino acids into peptides.
- Miyazawa, Toshifumi,Nakajo, Shin'ichi,Nishikawa, Miyako,Hamahara, Kazumi,Imagawa, Kiwamu,Ensatsu, Eiichi,Yanagihara, Ryoji,Yamada, Takashi
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- HYDRAZIDE COMPOUNDS
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Compounds of formula (I):R—NH—A—CO—NH—NH—(W) n—Z (I) wherein:n is 0 or 1, W represents —CO— or S(O) r wherein r is 0, 1 or 2,Z represents a group selected from aryl, arylalkyl, heteroaryl and heteroarylalkyl, each optionally substituted,R represents a grouping selected from:Z 1—T—CO—, Z 1—O—T—CO—, Z 1—T—O—CO—, Z 1—T— S(O) q—wherein Z 1, T and q are as defined in the description,A represents alkylene, alkenylene or alkynylene each having from 3 to 8 carbon atoms, alkylenecycloalkylene, cycloalkylenealkylene, alkylenecycloalkylenealkylene, alkylenearylene, arylenealkylene, alkylenearylenealkylene a grouping whereinB 1 is as defined in the description, or A forms with the adjacent nitrogen atom a grouping as defined in the description, andmedicinal products containing the same which are useful as Neuropeptide Y receptors ligands.
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- Sonoelectroreduction of metallic salts: A new method for the production of reactive metallic powders for organometallic reactions and its application in organozinc chemistry
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The reactivity of ultrafine zinc powders, produced by a new electrochemical method coupled to the use of ultrasound, has been evaluated for various organometallic reactions such as the Reformatsky reaction, Barbier allylation, alkyne reduction, reductive dehalogenation and p- nitroester cleavage. The results show that zinc powders produced by sonoelectrochemistry are highly reactive. Particle-size effects, reactivity of zinc-copper alloys and metal-waste recycling procedures have also been studied. The production of highly reactive zinc powder by sonoelectrochemical methods appears to be an interesting alternative to conventional methods used in organozinc chemistry and may be especially important in medium- or large- scale processes.
- Durant, Alex,Delplancke, Jean Luc,Libert, Valery,Reisse, Jacques
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p. 2845 - 2851
(2007/10/03)
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- Design and synthesis of a targeted set of aromatic amino acid derivatives for identification of new lead compounds.
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A targeted set of 256 aromatic α-amino acid derivatives is described to provide new lead compounds for biological screening. The utility is exemplified by identification of ligands for the human neuromedin B (hNMB) receptor, such as compound 3 (Ki hNMB 37nM).
- Horwell,Kneen,Pritchard,Ratcliffe,Roberts,Suman-Chauhan,Steiner,Betche
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p. 1957 - 1962
(2007/10/03)
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- Porcine Pancreatic Lipase Catalyzed Enantioselective Hydrolysis of Esters of N-Protected Unusual Amino Acids
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Porcine pancreatic lipase catalyzed the highly enantioselective hydrolysis of a kind of α-substituted carboxylic esters, i.e., the 2,2,2-trifluoroethyl esters of the N-benzyloxycarbonyl derivatives of unusual amino acids.
- Miyazawa, Toshifumi,Iwanaga, Hitoshi,Ueji, Shinichi,Yamada,Takashi,Kuwata, Shigeru
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p. 2219 - 2222
(2007/10/02)
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- MECHANISM OF HYDROLYSIS OF p-NITROPHENYL ESTERS OF N-BENZYLOXYCARBONYLAMINO ACIDS CATALYZED BY IMIDAZOLE
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The kinetics of the imidazole hydrolysis of the p-nitrophenyl esters of some N-benzyloxycarbonylamino acids (glycine, phenylalanine, β-alanine), acetic acid, and chloroacetic acid in ethanol-water solutions at 25 deg C were studied.For all the above-menti
- Alebyan, G.P.,Topuzyan, V.O.,Mndzhoyan, O.L.
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p. 1712 - 1715
(2007/10/02)
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