94744-50-0Relevant articles and documents
Radical-Mediated Activation of Esters with a Copper/Selectfluor System: Synthesis of Bulky Amides and Peptides
Matsumoto, Akira,Wang, Zhe,Maruoka, Keiji
, p. 5401 - 5411 (2021/04/12)
Herein, we describe a new approach for the activation of esters via a radical-mediated process enabled by a copper/Selectfluor system. A variety of para-methoxybenzyl esters derived from bulky carboxylic acids and amino acids can be easily converted into the corresponding acyl fluorides, directly used in the one-pot synthesis of amides and peptides. As a proof of concept, this method was applied to the iterative formation of sterically hindered amide bonds.
A one-pot procedure for the preparation of N-9-fluorenylmethyloxycarbonyl- α-amino diazoketones from α-amino acids
Siciliano, Carlo,De Marco, Rosaria,Guidi, Ludovica Evelin,Spinella, Mariagiovanna,Liguori, Angelo
, p. 10575 - 10582 (2013/02/22)
The study describes a new "one-pot" route to the synthesis of N-9-fluorenylmethyloxycarbonyl (Fmoc) α-amino diazoketones. The procedure was tested on a series of commercially available free or side-chain protected α-amino acids employed as precursors. The conversion into the title compounds was achieved by masking and activating the α-amino acids with a single reagent, namely, 9-fluorenylmethyl chloroformate (Fmoc-Cl). The resulting N-protected mixed anhydrides were reacted with diazomethane to lead to the α-amino diazoketones, which were isolated by flash column chromatography in very good to excellent overall yields. The versatility of the procedure was verified on lipophilic α-amino acids and further demonstrated by the preparation of N-Fmoc-α-amino diazoketones also from α-amino acids containing side-chain masking groups, which are orthogonal to the Fmoc one. The results confirmed that tert-butyloxycarbonyl (Boc), tert-butyl (tBu), and 2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl (Pbf), three acid-labile protecting groups mostly adopted in the solution and solid-phase peptide synthesis, are compatible to the adopted reaction conditions. In all cases, the formation of the corresponding C-methyl ester of the starting amino acid was not observed. Moreover, the proposed method respects the chirality of the starting α-amino acids. No racemization occurred when the procedure was applied to the synthesis of the respective N-Fmoc-protected α-amino diazoketones from l-isoleucine and l-threonine and to the preparation of a diastereomeric pair of N-Fmoc-protected dipeptidyl diazoketones.
Highly selective deprotection of tert-butyl esters using ytterbium triflate as a catalyst under mild conditions
Sridhar, P. Ramu,Sinha, Surajit,Chandrasekaran
, p. 157 - 160 (2007/10/03)
Ytterbium triflate catalyses the deprotection of tert-butyl esters selectively in the presence of other esters under mild conditions in almost quantitative yields. The reactions are carried out in nitromethane (45°-50°C) using 5 mole percent of the catalyst.
