- Active Controlled and Tunable Coacervation Using Side-Chain Functional α-Helical Homopolypeptides
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We report the development of new side-chain amino acid-functionalized α-helical homopolypeptides that reversibly form coacervate phases in aqueous media. The designed multifunctional nature of the side-chains was found to provide a means to actively control coacervation via mild, biomimetic redox chemistry as well as allow response to physiologically relevant environmental changes in pH, temperature, and counterions. These homopolypeptides were found to possess properties that mimic many of those observed in natural coacervate forming intrinsically disordered proteins. Despite ordered α-helical conformations that are thought to disfavor coacervation, molecular dynamics simulations of a polypeptide model revealed a high degree of side-chain conformational disorder and hydration around the ordered backbone, which may explain the ability of these polypeptides to form coacervates. Overall, the modular design, uniform nature, and ordered chain conformations of these polypeptides were found to provide a well-defined platform for deconvolution of molecular elements that influence biopolymer coacervation and tuning of coacervate properties for downstream applications.
- Barun, Ehab,Bell, Alexandra G.,Deming, Timothy J.,Evans, Declan,Gharakhanian, Eric G.,Houk, K. N.,Scott, Wendell A.
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supporting information
p. 18196 - 18203
(2021/11/12)
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- The: Ortho -substituent on 2,4-bis(trifluoromethyl)phenylboronic acid catalyzed dehydrative condensation between carboxylic acids and amines
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2,4-Bis(trifluoromethyl)phenylboronic acid is a highly effective catalyst for dehydrative amidation between carboxylic acids and amines. Mechanistic studies suggest that a 2:2 mixed anhydride is expected to be the only active species, and the ortho-substituent of boronic acid plays a key role in preventing the coordination of amines to the boron atom of the active species, thus accelerating the amidation. This catalyst works for α-dipeptide synthesis.
- Wang, Ke,Lu, Yanhui,Ishihara, Kazuaki
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supporting information
p. 5410 - 5413
(2018/05/30)
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- Synthesis of chiral TFA-protected α-amino aryl-ketone derivatives with friedel-crafts acylation of α-amino acid n-hydroxysuccinimide ester
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Chiral N-protected α-amino aryl-ketones are one of the useful precursors used in the synthesis of various biologically active compounds and can be constructed via Friedel-Crafts acylation of N-protected α-amino acids. One of the drawbacks of this reaction
- Tachrim, Zetryana Puteri,Oida, Kazuhiro,Ikemoto, Haruka,Ohashi, Fumina,Kurokawa, Natsumi,Hayashi, Kento,Shikanai, Mami,Sakihama, Yasuko,Hashidoko, Yasuyuki,Hashimoto, Makoto
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supporting information
(2017/11/07)
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- Synthesis of dipeptides based on valine and threonine
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Val-Val, Val-Thr, and Thr-Val dipeptides were synthesized using trifluoroacetyl protecting group. The optical rotations of the products were similar to those of samples synthesized using Boc protection, which indicated the absence of racemization in the course of introduction and removal of trifluoroacetyl protection. Pleiades Publishing, Ltd., 2012.
- Sorokina, Yu. M.,Sladkova,Popova,Shadyro,Knizhnikov
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p. 1297 - 1301
(2013/02/21)
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- Trifluoroacetylation of amino acids under aqueous conditions using a readily prepared non-odoriferous reagent
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The synthesis of S-dodecyltrifluorothioacetate and its application to trifluoroacetylation of amino acids under aqueous conditions are described. This reagent afforded good isolated yields (71-92%) of the N-trifluoroacetyl derivatives via an operationally simple and odor free procedure.
- Hickey, Matthew R.,Nelson, Todd D.,Secord, Elizabeth A.,Allwein, Shawn P.,Kress, Michael H.
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p. 255 - 258
(2007/10/03)
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- Employing the structural diversity of nature: Development of modular dipeptide-analogue ligands for ruthenium-catalyzed enantioselective transfer hydrogenation of ketones
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A library of novel dipeptideanalogue ligands based on the combination of tert-butoxycarbonyl(N-Boc)-protected a-amino acids and chiral vicinal amino alcohols were prepared. These highly modular ligands were combined with [{RuCl2(p-cymene)}2 and the resulting metal complexes were screened as catalysts for the enantioselective reduction of acetophenone under transfer hydrogenation conditions using 2-propanol as the hydrogen donor. Excellent enantioselectivity of 1-phenylethanol (up to 98% ee) was achieved with several of the novel catalysts. Although most of the ligands contained two stereocenters, it was demonstrated that the absolute configuration of the product alcohol was determined by the configuration of the amino acid part of the ligand. Employing ligands based on L-amino acids generated S-configured products, and catalysts based on Damino acids favored the formation of the R-configured alcohol. The combination N-Boc-L-alanine and (R)-phenylglycinol (Boc-L-Ab) or its enantiomer (N-Boc-D-alanine and (S)-phenylglycinol, Boc-D-Aa) proved to be the best ligands for the reduction process. Transfer hydrogenation of a number of aryl alkyl ketones were evaluated and excellent enantioselectivity, up to 96 % ee, was obtained.
- Pastor, Isidro M.,Vaestilae, Patrik,Adolfsson, Hans
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p. 4031 - 4045
(2007/10/03)
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- Efficient large (ca. 40 g) laboratory scale preparation of (S)- and (R)-valine tert-butyl esters
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A large laboratory scale (ca. 40 g) method for the preparation of enantiomerically pure (S)- and (R)-valine tert-butyl esters has been developed. The method involves three steps: preparation of N-TFA-valines, preparation of valine tert-butyl esters using 2-methylpropene in dioxane in the presence of sulfuric acid, and isolation of the target compounds as the acetate derivative. The overall yield is up to 70% relative to the starting valine, ee being more than 98% (by HPLC).
- Krasnov, Victor P.,Levit, Galina L.,Bukrina, Iraida M.,Demin, Alexander M.,Chupakhin, Oleg N.,Yoo, Ji Uk
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p. 1911 - 1914
(2007/10/03)
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- Coupling of N-trifluoroacetyl amino acids under 'neutral' conditions.
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The possibility of using the trifluoroacetyl group as a base-labile N-protection in peptide synthesis is discussed.Under normal coupling conditions, a very high level of racemization is observed.However, when 'neutral' coupling conditions (by silylation of amino acids or peptides) were used, the coupling racemization decreased as much as 1-2percent. - Key words: peptide coupling; N-protection; N-trifluoroacetyl amino acid; racemization, silylated amino acid
- Benouargha, Amina,Verducci, Jean,Jacquier, Robert
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p. 824 - 828
(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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- Effect of N-trifluoroacetyl derivatives of amino acids and amino acid analogs on microbial antitumor screen
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Eighteen trifluoroacetyl derivatives of amino acids and of amino acid analogs were prepared and tested for growth-inhibitory activity. Of the compounds tested, the trifluoroacetyl derivatives of o-, m-, and p-fluorophenylalanine and β-3-thienylalanine showed modest activity; trifluoroacetyl derivatives of phenylalanine and of β-2-thienylalanine showed marginal activity. The activity exhibited by the active trifluoroacetyl compounds was equal to that noted for most active chloroacetyl derivatives reported previously, as judged by comparison of their activity with that of chloroacetyl-m-fluorophenylalanine. No reversal of inhibition was noted when a representative of these inhibitors was challenged with a corresponding natural metabolite, both as free amino acid and as a noninhibitory acylated compound.
- Otani,Briley
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p. 496 - 499
(2007/10/05)
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- N-perfluoroacyl-amino acids and derivatives thereof
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An N-perfluoroacyl-L-α-amino acid is converted to the corresponding acid halide which is useful as a resolving agent for the resolution of racemic amines.
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