- Solvent-freeN-Boc deprotection byex situgeneration of hydrogen chloride gas
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An efficient, scalable and sustainable method for the quantitative deprotection of thetert-butyl carbamate (N-Boc) protecting group is described, using down to near-stoichiometric amounts of hydrogen chloride gas in solvent-free conditions. We demonstrate theex situgeneration of hydrogen chloride gas from sodium chloride and sulfuric acid in a two-chamber reactor, introducing a straightforward method for controlled and stoichiometric release of HCl gas. The solvent-free conditions allow deprotection of a wide variety ofN-Boc derivatives to obtain the hydrochloride salts in quantitative yields. The procedure obviates the need for any work-up or purification steps providing an uncomplicated green alternative to standard methods. Due to the solvent-free, anhydrous conditions, this method shows high tolerance towards acid sensitive functional groups and furnishes expanded functional group orthogonality.
- De Borggraeve, Wim M.,Gilles, Philippe,Van Mileghem, Seger,Verschueren, Rik H.
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supporting information
p. 5782 - 5787
(2021/07/12)
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- A chiral bis-L - leucine hydrochloride preparation and synthetic method
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The invention discloses a preparation method of chiral double L-leucine hydrochloride. The chiral double L-leucine hydrochloride has a chemical formula shown in the description; a synthesis method of the chiral double L-leucine hydrochloride comprises the following steps: weighing 0.03 mol of L-leucine (3.9354 g) into a 100 ml round-bottom flask; adding 40 ml of absolute methanol into L-leucine, performing stirring to ensure that L-leucine dissolves in absolute methanol and obtain a solution I; weighing 0.01 mol of CuCl2.2H2O (1.7048 g) into the solution to obtain a solution II; heating the solution II for a 48 hours' reflux reaction; after the reaction, and filtering a reaction solution when the reaction solution is hot to obtain a saturated solution, so that a filtrate naturally volatilizes, and green crystals are separated out after two days. The chiral double L-leucine hydrochloride has good catalytic performance in a nitrile silicification reaction of benzaldehyde, and has the yield rate of being as high as 75%.
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Paragraph 0080-0020
(2017/08/25)
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- LAT-1 activity of meta-substituted phenylalanine and tyrosine analogs
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The transporter protein Large-neutral Amino Acid Transporter 1 (LAT-1, SLC7A5) is responsible for transporting amino acids such as tyrosine and phenylalanine as well as thyroid hormones, and it has been exploited as a drug delivery mechanism. Recently its role in cancer has become increasingly appreciated, as it has been found to be up-regulated in many different tumor types, and its expression levels have been correlated with prognosis. Substitution at the meta position of aromatic amino acids has been reported to increase affinity for LAT-1; however, the SAR for this position has not previously been explored. Guided by newly refined computational models of the binding site, we hypothesized that groups capable of filling a hydrophobic pocket would increase binding to LAT-1, resulting in improved substrates relative to parent amino acid. Tyrosine and phenylalanine analogs substituted at the meta position with halogens, alkyl and aryl groups were synthesized and tested in cis-inhibition and trans-stimulation cell assays to determine activity. Contrary to our initial hypothesis we found that lipophilicity was correlated with diminished substrate activity and increased inhibition of the transporter. The synthesis and SAR of meta-substituted phenylalanine and tyrosine analogs is described.
- Augustyn, Evan,Finke, Karissa,Zur, Arik A.,Hansen, Logan,Heeren, Nathan,Chien, Huan-Chieh,Lin, Lawrence,Giacomini, Kathleen M.,Colas, Claire,Schlessinger, Avner,Thomas, Allen A.
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supporting information
p. 2616 - 2621
(2016/05/09)
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- LAT1 activity of carboxylic acid bioisosteres: Evaluation of hydroxamic acids as substrates
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Large neutral amino acid transporter 1 (LAT1) is a solute carrier protein located primarily in the blood–brain barrier (BBB) that offers the potential to deliver drugs to the brain. It is also up-regulated in cancer cells, as part of a tumor's increased metabolic demands. Previously, amino acid prodrugs have been shown to be transported by LAT1. Carboxylic acid bioisosteres may afford prodrugs with an altered physicochemical and pharmacokinetic profile than those derived from natural amino acids, allowing for higher brain or tumor levels of drug and/or lower toxicity. The effect of replacing phenylalanine's carboxylic acid with a tetrazole, acylsulfonamide and hydroxamic acid (HA) bioisostere was examined. Compounds were tested for their ability to be LAT1 substrates using both cis-inhibition and trans-stimulation cell assays. As HA-Phe demonstrated weak substrate activity, its structure–activity relationship (SAR) was further explored by synthesis and testing of HA derivatives of other LAT1 amino acid substrates (i.e., Tyr, Leu, Ile, and Met). The potential for a false positive in the trans-stimulation assay caused by parent amino acid was evaluated by conducting compound stability experiments for both HA-Leu and the corresponding methyl ester derivative. We concluded that HA's are transported by LAT1. In addition, our results lend support to a recent account that amino acid esters are LAT1 substrates, and that hydrogen bonding may be as important as charge for interaction with the transporter binding site.
- Zur, Arik A.,Chien, Huan-Chieh,Augustyn, Evan,Flint, Andrew,Heeren, Nathan,Finke, Karissa,Hernandez, Christopher,Hansen, Logan,Miller, Sydney,Lin, Lawrence,Giacomini, Kathleen M.,Colas, Claire,Schlessinger, Avner,Thomas, Allen A.
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supporting information
p. 5000 - 5006
(2016/10/05)
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- Tumescenamide C, an antimicrobial cyclic lipodepsipeptide from Streptomyces sp.
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Tumescenamide C, a new cyclic lipodepsipeptide, was isolated from a culture broth of an actinomycete Streptomyces sp. KUSC-F05. Tumescenamide C was a congener of tumescenamides A and B, representing a sixteen-membered ring system, consisting of two proteinogenic and three non-proteinogenic amino acids, to which a methyl-branched fatty acid was attached. The planar structure was determined by spectroscopic analysis, while its absolute stereochemistry was determined by chemical degradation and asymmetric synthesis. Tumescenamide C exhibited antimicrobial activity with high selectivity against Streptomyces species.
- Kishimoto, Shinji,Tsunematsu, Yuta,Nishimura, Shinichi,Hayashi, Yutaka,Hattori, Akira,Kakeya, Hideaki
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experimental part
p. 5572 - 5578
(2012/09/08)
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- Hydration of amino acids from ultrasonic measurements
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In this paper the results of compressibility of aqueous solutions of amino acids in water and in aqueous HCl and NaOH solutions at 25 °C are presented. The effect of the charged protonated amino groups and deprotonated carboxylic groups on the hydration number was tested. The idea of additivity of the hydration number with the constituents of the solute molecule was successfully applied and discussed.
- Burakowski, Andrzej,Gliński, Jacek
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experimental part
p. 12157 - 12161
(2011/01/11)
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- Resolution of DL-racemic mixtures
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The present invention relates to a process for the resolution of DL-racemic mixtures of compounds which crystalize in the form of a conglumerate. Both, the D and L-enantiomers are obtained according to the invention in a industrially feasable process by adding chiral enantioselective polymers to the supersaturated solution of the racemat to inhibit crystalization of one enantiomer. Next a DL-racemic mixture of said compound is suspended in about twice the amount of the crystallized enantiomer. Consequently, the opposite enantiomer could be recovered by said suspension by physical separation.
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Page column 7-8
(2008/06/13)
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- Methods and compositions for controlled polypeptide synthesis
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Methods and compositions for the generation of polypeptides having varied material properties are disclosed herein. Methods include means for initiating the polymerization of aminoacid-N-carboxyanhydride (NCA) monomer by combining the monomer with an amido-containing metallacycle, for making self assembling amphiphilic block copolypeptides and related protocols for adding oligo(ethyleneglycol) functionalized aminoacid-N-carboxyanhydrides (NCAs) to polyaminoacid chains. Additional methods include means of adding an end group to the carboxy terminus of a polyaminoacid chain by reacting an alloc-protected amino acid amide with a transition metal-donor ligand complex to forming an amido-amidate metallacycle for use in further polymerization reactions. Novel compositions for use in peptide synthesis and design including five and six membered amido-containing metallacycles and block copolypeptides are also disclosed.
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- Methods and compositions for controlled polypeptide synthesis
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Methods and compositions for the generation of polypeptides having varied material properties are disclosed herein. Methods include means for making self assembling amphiphilic block copolypeptides and related protocols adding oligo(ethyleneglycol) functionalized aninoacid-N-carboxyanhydrides (NCAs) to polyaminoacid chains. Additional methods include means of adding an end group to the carboxy terminus of a polyaminoacid chain by reacting an alloc-protected amino acid amide with a transition metal-donor ligand complex, thereby forming an amido-amidate metallacycle for use in further polymerization reactions. Novel compositions for use in peptide synthesis and design including five and six membered amido-containing metallacycles and block copolypeptides are also disclosed.
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- Methods and compositions for controlled polypeptide synthesis
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Methods and compositions for the generation of polypeptides having varied material properties are disclosed herein. Methods include means for initiating the polymerization of aminoacid-N-carboxyanhydride (NCA) monomer by combining the monomer with an amido-containing metallacycle, for making self assembling amphiphilic block copolypeptides and related protocols for adding oligo(ethyleneglycol) functionalized aminoacid-N-carboxyanhydrides (NCAs) to polyaminoacid chains. Additional methods include means of adding an end group to the carboxy terminus of a polyaminoacid chain by reacting an alloc-protected amino acid amide with a transition metal-donor ligand complex to forming an amido-amidate metallacycle for use in further polymerization reactions. Novel compositions for use in peptide synthesis and design including five and six membered amido-containing metallacycles and block copolypeptides are also disclosed.
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- Conjugate additions of organocuprates to a 3-methylene-6-isopropyldiketopiperazine acceptor for the asymmetric synthesis of homochiral α-amino acids
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Addition of a range of organocuprates to (S)-N,N′-bis(p-methoxybenzyl)-3-methylene-6-isopropylpiperazine-2, 5-dione 8 affords cis-3-isopropyl-6-alkyldiketopiperazines in excellent yield and >95% de. Subsequent deprotection and hydrolysis of these cis-3-isopropyl-6-alkyldiketopiperazines affords homochiral (S)-α-amino acids in excellent yield.
- Bull,Davies,Garner,O'Shea
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p. 3281 - 3287
(2007/10/03)
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- Asymmetric amino acid synthesis: Mitsunobu reaction on chiral cyanohydrins
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BOC(SES)NH was reacted with chiral cyanohydrins using the Mitsunobu reaction to give good yields of protected α-aminonitriles, which were converted to chiral amino and imino acids.
- Decicco, Carl P.,Grover, Paul
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p. 529 - 530
(2007/10/03)
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- CHLOROTRIMETHYLSILANE-PHENOL AS A MILD DEPROTECTION REAGENT FOR THE TERT-BUTYL BASED PROTECTING GROUPS IN PEPTIDE SYNTHESIS
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Efficient deprotection of the tertbutyl urethane group by 1 M Me3SiCl- 1 M and 3 M-phenol reagents is described.
- Kaiser, Emil,Tam, James P.,Kubiak, Teresa M.,Merrifield, R. B.
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p. 303 - 306
(2007/10/02)
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- A STEREOSELECTIVE SYNTHESIS OF N-BOC-α-AMINO ALCOHOLS AND α-AMINO ACIDS
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A sterteoselective synthesis of N-Boc-α-amino alcohols and α-amino acids via the addition of Grignard reagents to the chiral electrophilic glycine equivalent α-bromo-N-Boc-glycine(-)phenylmenthylester is described.
- Ermert, Philipp,Meyer, Jsabella,Stucki, Christoph,Schneebeli, Joerg,Obrecht, Jean-Pierre
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p. 1265 - 1268
(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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- Enantioselective Synthesis of α-Amino Acids from 10-(Aminosulfonyl)-2-bornyl Esters and Di(tert-butyl) Azodicarboxylate
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Successive treatment of chiral esters 1 with LiN(i-Pr)2/Me3SiCl and di(tert-butyl) azodicarboxylate/TiCl4/Ti(i-PrO)4 gave N,N'-dihydrazino esters 9 which on deacylation, hydrogenolysis, transesterification, and acidic hydrolysis furnished (2S)-α-amino acids 6 in high enantiomeric purity with efficient recovery of the auxiliary alcohol 7.
- Oppolzer, Wolfgang,Moretti, Robert
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p. 1923 - 1926
(2007/10/02)
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