- Palladium-catalyzed transprotection of allyloxycarbonyl-protected amines: Efficient one-pot formation of amides and dipeptides
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The synthetic utility of the N-(allyloxycarbonyl) (Alloc) substituent in α-amino acid derivatives is substantially extended beyond its well-known function as an amine protecting group. When the palladium-catalyzed deprotection is carried out by using tributyltin hydride as nucleophile (the Guibe method) in the presence of an active acylating agent a new acyl group is introduced on nitrogen. Successful acylating agents include carboxylic acid anhydrides, acid chlorides, and activated esters. A useful example of this methodology is the removal of the Alloc group in the presence of tert-butyl dicarbonate, which in essence amounts to a 'transprotection' to a Boc-protected α-amino acid derivative. More importantly, the use of activated N-protected α-amino ester derivatives (e.g., pentafluorophenyl esters) leads to dipeptides. This new method for peptide coupling proceeds very fast under mild conditions, in good to excellent yields, and without noticeable racemization.
- Roos,Bernabe,Hiemstra,Speckamp,Kaptein,Boesten
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- Urethanes synthesis from oxamic acids under electrochemical conditions
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Urethane synthesis via oxidative decarboxylation of oxamic acids under mild electrochemical conditions is reported. This simple phosgene-free route to urethanes involves an in situ generation of isocyanates by anodic oxidation of oxamic acids in an alcoholic medium. The reaction is applicable to a wide range of oxamic acids, including chiral ones, and alcohols furnishing the desired urethanes in a one-pot process without the use of a chemical oxidant.
- Ogbu, Ikechukwu Martin,Lusseau, Jonathan,Kurtay, Gülbin,Robert, Frédéric,Landais, Yannick
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supporting information
p. 12226 - 12229
(2020/10/26)
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- Substrate-directed lewis-acid catalysis for peptide synthesis
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A Lewis-acid-catalyzed method for the substrate-directed formation of peptide bonds has been developed, and this powerful approach is utilized for the new "remote" activation of carboxyl groups under solvent-free conditions. The presented method has the following advantages: (1) the high-yielding peptide synthesis uses a tantalum catalyst for any amino acids; (2) the reaction proceeds without any racemization; (3) the new substrate-directed chemical ligation using the titanium catalyst is applicable to convergent peptide synthesis. These advantages overcome some of the unresolved problems in classical peptide synthesis.
- Muramatsu, Wataru,Hattori, Tomohiro,Yamamoto, Hisashi
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supporting information
p. 12288 - 12295
(2019/08/20)
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- Synthetic studies towards cyclic peptides. Concise synthesis of thiazoline and thiazole containing amino acids
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Concise and efficient syntheses of optically pure thiazoline and thiazole containing amino acids of the constitution (26) and (27), based on simple condensation reactions between cysteine esters and N-protected imino ethers (22) and (25) derived from chir
- North, Michael,Pattenden, Gerald
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p. 8267 - 8290
(2007/12/18)
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