3850-31-5Relevant articles and documents
Design of radical-resistant amino acid residues: A combined theoretical and experimental investigation
Croft, Anna K.,Easton, Christopher J.,Radom, Leo
, p. 4119 - 4124 (2007/10/03)
Ab initio calculations have been used to design radical -resistant amino acid residues. Optimized structures of free and protected amino acids and their corresponding β-carbon-centered radicals were determined with B3-LYP/6-31G(d). Single-point RMP2/6-31G
Preparation of α-(N-Trimethylsilyl)imino Esters and Their Use ih the Synthesis of α-Amino Esters and 2-Alkoxycarbonylimidazol-4(2H)-ones
Matsuda, Yoshihiko,Tanimoto, Shigeo,Okamoto, Tadashi,Ali, Syed Mashhood
, p. 279 - 281 (2007/10/02)
The reaction of α-keto esters with lithium 1,1,1,3,3,3-hexamethyldisilazanide afforded α-(N-trimethylsilyl)imino esters in good yields, which were reduced to the corresponding α-amino esters by reducing agents such as NaBH3CN. α-(N-Trimethylsilyl)imino esters were treated with methanol to afford 2-alkoxycarbonylimidazole-4(2H)-ones via dimerization of the intermediate α-imino esters.
Molecular Structure of a Chiral 3,5-Bridged Pyridine and the Effect of Structure on Circular Dichroic Spectra
Speelman, Johanna C.,Talma, Auke G.,Kellogg, Richard M.,Meetsma, A.,Boer, J. L. de,et al.
, p. 1055 - 1062 (2007/10/02)
The crystal structure of the 3,5-bridged chiral macrocyclic pyridine (4S,14S)-4,14-di(2-propyl)-6,9,12-trioxa-3,15,19-triazabicycloheneicosa-1(21),17,19-triene-2,5,13,16-tetrone (5a) has been determined by crystallographic means.Each unit cell contains two nonequivalent molecules.In each molecule the amide groups are twisted out-of-plane in a conrotatory fashion righ-handedly with respect to the molecular C2 axis viewed along the line from C4 to N1 of the pyridine ring.This twist allows avoidance of potential interaction between the amide nitrogen bonded protons and that bonded to C4 of the pyridine ring.The macrocyclic framework is inherently dissymmetric as a result of this helical twist.This is reflected in the circular dichroism spectrum of 5a, which has two strongly negative effects in the 200-400-nm region, at 218 nm, -58800 and 273 nm, -45600.Very similar CD effects are found for analogues of 5a with at the chiral atoms at the 4,14-positions, methyl groups (6a), tert-butyl groups (6b), and proline (7).Comparison are also made with compounds (8b) derived (in thought) from 5a by transposition of the macrocyclic bridge from the 3,5- to the 2,6-positions.Compound 8a is analogous to 8b save that it is a benzene rather than a pyridine derivative.Several nonmacrocyclic analogues of 5a have also been examined as well as the thiamide derivative of 5a (compound 9) for which a synthesis has been developed.The longer wavelength CD effect in 5a is assigned to the pyridine n-?* transition and the shorter wavelength effect to ?-?* transitions.Attempts to correlate the absolute signs with a recently postulated model fail.A method for synthesis of the unnatural amino acids, (S)-(+)-2-amino-3,3,-dimethylbutanoic acid (13), in enantiomerically pure form is described as well as an NMR method for the determination of the enantiomeric purity of samples of 13.
Asymmetric Syntheses via Heterocyclic Intermediates, XXXI.- Asymmetric Synthesis of Various Non-Proteinogenic Amino Acid Methyl Esters (Functionalized in the Carbon Chain) and Amino Acids by the Bislactim Ether Method
Schoellkopf, Ulrich,Busse, Ulrich,Lonsky, Ralph,Hinrichs, Rolf
, p. 2150 - 2163 (2007/10/02)
The lithiated bislactim ethers 5, 10, 12, and 23 were alkylated with a variety of alkylating agents 6 to give the alkylated bislactim ethers 7, 11, 13, and 24 with a high degree of asymmetric induction (up to 99percent).Upon hydrolysis these furnished the optically active amino acid methyl esters of type 8, 14, or 25.Some of these amino acid esters were further hydrolyzed to yield the amino acids.
