Relevant articles and documents
All total 13 Articles be found
All total 13 Articles be foundEnantioselective radical addition to ketimines: A synthetic route towards α,α-disubstituted α-amino acids
Kim, Sang Yoon,Kim, Sung Jun,Jang, Doo Ok
supporting information; experimental part, p. 13046 - 13048 (2011/02/21)
A radical attack: In the presence of a protonated cinchonine derivative, radical addition reactions proceeded efficiently, providing a general approach to the synthesis of a diverse range of enantioenriched α,α- disubstituted α-amino acids.
Enantioselective synthesis and enantiomeric amplification of amino acids under prebiotic conditions
Levine, Mindy,Kenesky, Craig Scott,Mazori, Daniel,Breslow, Ronald
supporting information; experimental part, p. 2433 - 2436 (2009/05/27)
(Chemical Equation Presented) A plausible origin of biomolecular homochirality is advanced, where α-methyl amino acids found on meteorites transfer their chirality in the synthesis of normal amino acids. This asymmetry can be amplified to nearly homochiral levels, thus providing the necessary prerequisite for life to start on this planet and elsewhere in the universe.
L-phenylalanine cyclohexylamide: A simple and convenient auxiliary for the synthesis of optically pure α,α-disubstituted (R)- and (S)-amino acids
Obrecht,Bohdal,Broger,Bur,Lehmann,Ruffieux,Schonholzer,Spiegler,Muller
, p. 563 - 580 (2007/10/02)
This work describes L-phenylalanine cyclohexylamide (5c) as a simple, cheap, and powerful chiral auxiliary for the synthesis of a series of optically pure α,α-disubstituted (R)- and (S)-amino acids of type 1, such as (R)- and (S)-2-methyl-phenylalanine (1a), (R)- and (S)-2-methyl-2-phenylglycine (1b), and (R)- and (S)-2-methylvaline (1c). These amino acids were efficiently transformed into the suitably protected and activated amino-acid building blocks (R)- and (S)-12b and (R)- and (S)-12c which are ready for incorporation into peptides by solution or solid-phase techniques. Based on the crystal structures of 6b, 6c, and 7a belonging to the diastereoisomeric peptides series 6 and 7, the absolute configurations of each member of the series were determined. β-Turn geometries of type II' and I were observed for 6b and 7a, respectively, whereas 6c crystallized in an extended conformation. The impacts of side-chain variation on conformation and crystal packing of these triamides are discussed.
