- Leveraging Peptaibol Biosynthetic Promiscuity for Next-Generation Antiplasmodial Therapeutics
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Malaria remains a worldwide threat, afflicting over 200 million people each year. The emergence of drug resistance against existing therapeutics threatens to destabilize global efforts aimed at controlling Plasmodium spp. parasites, which is expected to leave vast portions of humanity unprotected against the disease. To address this need, systematic testing of a fungal natural product extract library assembled through the University of Oklahoma Citizen Science Soil Collection Program has generated an initial set of bioactive extracts that exhibit potent antiplasmodial activity (EC50 25 μM, selectivity index > 250). The unique chemodiversity afforded by these fungal isolates serves to unlock new opportunities for translating peptaibols into a bioactive scaffold worthy of further development.
- Lee, Jin Woo,Collins, Jennifer E.,Wendt, Karen L.,Chakrabarti, Debopam,Cichewicz, Robert H.
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supporting information
p. 503 - 517
(2021/03/01)
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- High-chirality method for selectively synthesizing alpha-disubstituted alpha-amino acid
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The invention discloses a high-chirality method for selectively synthesizing alpha-disubstituted alpha-amino acid. The high-chirality method for selectively synthesizing alpha-disubstituted alpha-amino acid is characterized by comprising the following steps: step one, reacting S-tert-butanesulfinyl amide or R-tert-butanesulfinyl amide, R-beta substituted ethyl pyruvate and tetraethyl titanate in atetrahydrofuran solvent to obtain a compound C; step two, reacting the compound C with alkyl substituted magnesium bromide under the catalyzing effect of zinc dimethyl in tetrahydrofuran to obtain acompound E; step three, reacting the compound E under the effect of ammonium chloride and anhydrous hydrogen chloride to obtain a compound F; and step four, hydrolyzing the compound F in an ethanol aqueous solution of sodium hydroxide to obtain hydrochloride of a compound G, and carrying out ion exchange to obtain the compound G. The chiral selective reaction is greatly improved, and the method issimple in process, uses cheap and easily obtained raw materials, is simple and convenient to operate, is quite suitable for industrial mass production, and has quite extensive industrial applicationprospect and market value.
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Paragraph 0056; 0058; 0066
(2018/09/13)
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- A practical chemoenzymatic synthesis of (R)-isovaline based on the asymmetric hydrolysis of 2-ethyl-2-methyl-malonamide
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(R)-Isovaline has potential applications in drug development, and therefore the development of an efficient method for the production of (R)-isovaline is desired. Herein we have investigated the asymmetric hydrolysis of 2-ethyl-2-methyl-malonamide into (S)-2-ethyl-2-methyl-malonamic acid, a useful synthetic intermediate in the production of (R)-isovaline, using CsAM, which is a recombinant amidase originally derived from Cupriavidus sp. KNK-J915. The produced (S)-2-ethyl-2-methyl-malonamic acid (98.6% ee) could be easily converted into (R)-isovaline by the Hofmann rearrangement. Starting from diethyl 2-methylmalonate, we obtained (R)-isovaline (99.1% ee) in 58.6% yield over eight steps, including the CsAM-catalyzed asymmetric hydrolysis of 2-ethyl-2-methyl-malonamide.
- Nojiri, Masutoshi,Yoshida, Fumi,Hirai, Yoshinori,Nishiyama, Akira,Yasohara, Yoshihiko
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- PROCESS FOR PRODUCING SOLID AMINO ACID
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The problem to be solved by the present invention is to ea lily and efficiently produce an amino acid having 2 to 7 carbon atoms as a high-purity solid without complicated operation, which is useful as a synthetic intermediate for medicines or agrochemicals. The present invention is characterized in comprising a step of precipitating solid amino acid with high purity. In the present invention, the by-produced salt composed of the sulfonic acid and the amine was removed to the mother liquor by reacting an amine with a sulfonic acid salt of amino acid in an aprotic polar solvent, or by reacting a sulfonic acid with an amine salt of amino acid in an aprotic polar solvent. The sulfonic acid salt of amino acid, for example, may be produced by reacting a N-(tert-butoxycarbonyl) amino acid with a sulfonic acid, or by reacting an amino acid tert-butyl ester with a sulfonic acid.
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Paragraph 0076; 0077
(2014/12/09)
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- A new type of oxidation-reduction condensation by the combined use of phenyl diphenylphosphinite and oxidant
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A new type of oxidation-reduction condensation of alcohols with sulfur, nitrogen, and oxygen nucleophiles by the combined use of phenyl diphenylphosphinite (PhOPPh2) and oxidants such as azides or diethyl azodicarboxylate (DEAD) are described. In these reactions, chiral secondary and tertiary alcohols are converted into the corresponding chiral sulfides, azides, esters and ethers under mild and neutral conditions with almost complete inversion of stereochemical configuration.
- Mukaiyama, Teruaki,Kuroda, Kiichi,Maruyama, Yuji
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scheme or table
p. 63 - 82
(2010/04/23)
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- Mitsunobu approach to the synthesis of optically active α,α-disubstituted amino acids
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Chiral tertiary α-hydroxy esters of known stereochemical configuration were transformed to α-azido esters by Mitsunobu reaction with HN3. Optimization of this reaction was shown to proceed at room temperature with high chemical yield using 1,1-(azodicarbonyl)dipiperidine (ADDP) and trimethylphosphine (PMe3). Complete inversion of configuration was observed at the α-carbon. Several α,α- disubstituted amino acids were synthesized in high overall chemical yield and optical purity.
- Green, Jonathan E.,Bender, David M.,Jackson, Stona,O'donnell, Martin J.,Mccarthy, James R.
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supporting information; experimental part
p. 807 - 810
(2009/08/08)
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- Chiral salen-metal complexes as novel catalysts for the asymmetric synthesis of α-amino acids under phase transfer catalysis conditions
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Chiral salen-metal complexes have been tested as catalysts for the C-alkylation of Schiff's bases of alanine and glycine esters with alkyl bromides under phase-transfer conditions (solid sodium hydroxide, toluene, ambient temperature, 1-10 mol% of the catalyst). The best catalyst, which was derived from a Cu(II) complex of (1R, 2R or 1S,2S)-[N,N′-bis(2′-hydroxybenzylidene)]-1,2-diaminocyclohexane, gave α-amino and α-methyl-α-amino acids with enantiomeric excesses of 70-96%.
- Belokon, Yuri N,North, Michael,Churkina, Tatiana D,Ikonnikov, Nikolai S,Maleev, Victor I
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p. 2491 - 2498
(2007/10/03)
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- Chiral 3,6-dihydro-2H-1,4-oxazin-2-ones as alanine equivalents for the asymmetric synthesis of α-methyl α-amino acids (AMAAs) under mild reaction conditions
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3,6-Dihydro-2H-1,4-oxazin-2-ones 1 act as very reactive chiral cyclic alanine equivalents and can be diastereoselectively alkylated or allylated using mild reaction conditions: potassium carbonate under phase-transfer catalysis (PTC) conditions when using activated alkyl halides, organic bases such as tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2- diazaphosphorine (BEMP) or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) when using unactivated alkyl halides, and neutral Pd(0)-catalysis when allylic carbonates are used. In most cases, the diastereoselectivity under all these different reaction conditions is excellent although the reactions are always carried out at room temperature. Hydrolysis of the obtained alkylated or allylated oxazinones allows the preparation of enantiomerically enriched (S)- α-methyl α-amino acids (S)-AMAAs. The PTC and organic base methodologies have also been applied to the synthesis of (R)-α-methyl α-amino acids starting from (R)-alanine. When dihalides are used as electrophiles under PTC or BEMP conditions, a spontaneous N-alkylation also takes place giving bicyclic oxazinones, which can be hydrolyzed to enantiomerically pure cyclic (S)-AMAAs.
- Chinchilla, Rafael,Galindo, Nuria,Nájera, Carmen
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p. 704 - 717
(2007/10/03)
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- Stereocontrolled synthesis of α,α-disubstituted α-aminoaldehydes and α-aminoacids using a [3,3] allylic trichloracetimidate rearrangement
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Sigmatropic rearrangement of trichloracetimidates derived from syn monoprotected allylic diols 3 resulting from the condensation of vinylalanes or cuprates with α-alkoxyaldehydes afforded diastereomerically pure allylic amines 6. The oxidative cleavage of these amines allowed the access to α,α-disubstituted α-aminoacids in high enantiomeric purity.
- Imogai, Hassan,Petit, Yves,Larcheveque, Marc
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p. 2573 - 2576
(2007/10/03)
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- Enantioselective Synthesis of α-Branched α-Amino Acids with Bulky Substituents
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Enantiopure 5,5-disubstituted t-butyl 2-t-butyl-3-methyl-4-oxoimidazolidine-1-carboxylates readily available by diastereoselective double alkylation of the parent compound (Boc-BMI) can be converted to α-branched α-amino acids with two bulky substituents (PhCH2/Et, PhCH2/i-Pr, PhCH2/CH2C6H11) in four simple steps: hydrolysis to the amino acid amides, N-benzoylation, cleavage of the amino acid amide group, and debenzoylation (Scheme 3, products 6-10, overall yields >50percent).This procedure constitutes an extension of the scope of amino acid synthesis from (R)- and (S)-Boc-BMI. - Key Words: Amino acids, α-branched/ Highly hindered amides/ Hydrolysis of amino acid amides/ Anchimeric effect/ Phenylalanine, 2-ethyl, 2-i-propyl- and 2-cyclohexylmethyl-
- Studer, Armido,Seebach, Dieter
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p. 217 - 222
(2007/10/02)
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- Synthesis of (R)- and (S)-2-amino-2-methylbutanoic acid (Iva) in enantiomerically pure form
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A new strategy for the preparation of both enantiomers of 2-amino-2-methylbutanoic acid (Iva) based on diastereoselective alkylation of (1S,2R,4R)-10-dicyclohexylsulfamoylisobornyl 2-cyanoesters and the corresponding degradation process is described.
- Cativiela, Carlos,Diaz-de-Villegas, Maria D.,Galvez, Jose A.
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p. 1445 - 1448
(2007/10/02)
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- Enzymatic resolution of α,α-disubstituted α-amino acid esters and amides
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The scope and limitations of the enzymatic resolution of α,α-disubstituted α-amino acid amides by an amino acid amidase from Mycobacterium neoaurum and of the corresponding ethyl esters with Pig liver esterase (PLE) have been studied. Moderate enantiomeric excesses were obtained with PLE, with only a narrow substrate specificity. Mycobacterium neoaurum on the contrary yields a broad range of S-α,α-disubstituted α-amino acids 1 and the corresponding R-amides 2.
- Kaptein,Boesten,Broxterman,Peters,Schoemaker,Kamphuis
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p. 1113 - 1116
(2007/10/02)
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- Stereoselective Alkylierung an C(α) von Serin, Gycerinsaeure, Thereonin und Weinsaeure ueber heterocyclische Enolate mit exocyclischer Doppelbindung
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The chiral, non-racemic title acids are converted to methyl dioxalene- (cf. 13), oxazoline- (4) and oxazolidine-carboxylates (cf. 9).Deprotonation by Li(i-Pr)2N at dry-ice temperature gives solutions of the litium enolates A-D with exocyclic enolate double bonds.These are stable enough with respect to β-elimination (Scheme 1) to be alkylated with or without cosolvents such as HMPA or DMPU.The products are formed in good to excellent yields and, with the exception of the tartrate derived acetonide (see Schemem 2), with diastereoselectivities above 90percent.While the tartrate- and threonine-derived enolates (A and B, resp.) are chiral due to the second stereogenic center of the precursors, the serine- and glyceric-acid-derived enolates are non-racemic due to a tert butyl-substituted (pivalaldehyde-derived) acetal center (C and D, resp.).The products of alkylation can be hydrolyzed to give α-branched tartaric acid (Scheme 2), allothreonine (Scheme 3), serine (Scheme 4), and glycerine-acid derivatives (Scheme 5) with quaternary stereogenic centers.The configurations of the products are determined by NOE-NMR measurements and by chemical correlation.These show taht the dioxolane-derived enolates A and D are alkylated preferentially from that face of the ring which is alredy substituted ('syn'-attack).The 'syn'-attack is postulated to arise from strong folding of the heterocyclic ring due to elelctronic repulsion between the enolate ?-system and non-bonding elelctron pairs on the heteroatoms (see Scheme 6).
- Seebach, Dieter,Aebi, Johannes D.,Gander-Coquoz, Marlyse,Naef, Reto
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p. 1194 - 1216
(2007/10/02)
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- Asymmetric Syntheses via Heterocyclic Intermediates, V. - Asymmetric Synthesis of α-Methyl Amino Acids by Alkylation of the Lithiated Lactim Ether of cyclo-(L-Ala-L-Ala)
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The (3S,6S)-2,5-dimethoxy-3,6-dimethyl-3,6-dihydropyrazine (7) is obtained from cyclo-(L-Ala-L-Ala) 5 (93-95percent optically pure) and trimethyloxonium tetrafluoroborate.With butyllithium the lithio derivative 8 is formed which reacts with alkyl halides in good chemical yields and with more than 90percent diastereoselectivity, whereby R-configuration is induced at C-3.A model concept is discussed, which explains the remarkably high asymmetric induction. - Hydrolysis (0.25 N HCl, room temp.) gives L-alanine methyl ester (4) and the (R)-α-methyl amino acid methyl esters 13.The two amino acid esters are separable by distillation or chromatography.
- Schoellkopf, Ulrich,Hartwig, Wolfgang,Groth, Ulrich,Westphalen, Karl-Otto
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p. 696 - 708
(2007/10/02)
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