New Amino Acids for the Topographical Control of Peptide Conformation: Synthesis of All the Isomers of .alpha.,.beta.-Dimethylphenylalanine and .alpha.,.beta.-Dimethyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic Acid of High Optical Purity
摘要:
The synthesis of all four diastereoisomers of alpha,beta-dimethylphenylalanine (4) as well as those of alpha,beta-dimethyl-1 ,2,3,4,-tetrahydroisoquinoline-3-carboxylic acid (5 and 6) have been accomplished in high yield and high optical purity. Molecular mechanics calculations on the N-alpha-acetyl and N- methylcarboxamide derivatives of (3R,4R)-6 and (3R,4S)-5 indicate large and moderate energy stabilization for the gauche(-) but not the gauche(+) side-chain conformers of (3R,4S)-5 and (3R,4R)-6, respectively. By symmetry rules, the same holds for (3S,4R)-5 and (3S,4S)-6, respectively. Thus, these amino acids are potential building blocks for the topographical design of peptides (Kazmierski et al., J. Am. Chem. Sec. 1991, 113, 2275-2283) by providing acylated 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives in which a gauche(-) and not a gauche(+) side-chain conformation is energetically more stable for the L amino acid. Synthetic details and implications of these new amino acids for peptide and protein design are discussed.
New Amino Acids for the Topographical Control of Peptide Conformation: Synthesis of All the Isomers of .alpha.,.beta.-Dimethylphenylalanine and .alpha.,.beta.-Dimethyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic Acid of High Optical Purity
摘要:
The synthesis of all four diastereoisomers of alpha,beta-dimethylphenylalanine (4) as well as those of alpha,beta-dimethyl-1 ,2,3,4,-tetrahydroisoquinoline-3-carboxylic acid (5 and 6) have been accomplished in high yield and high optical purity. Molecular mechanics calculations on the N-alpha-acetyl and N- methylcarboxamide derivatives of (3R,4R)-6 and (3R,4S)-5 indicate large and moderate energy stabilization for the gauche(-) but not the gauche(+) side-chain conformers of (3R,4S)-5 and (3R,4R)-6, respectively. By symmetry rules, the same holds for (3S,4R)-5 and (3S,4S)-6, respectively. Thus, these amino acids are potential building blocks for the topographical design of peptides (Kazmierski et al., J. Am. Chem. Sec. 1991, 113, 2275-2283) by providing acylated 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives in which a gauche(-) and not a gauche(+) side-chain conformation is energetically more stable for the L amino acid. Synthetic details and implications of these new amino acids for peptide and protein design are discussed.
Asymmetric Synthesis of (2<i>S</i>,3<i>S</i>)- and (2<i>R</i>,3<i>R</i>)-α,β-Dialkyl-α-amino Acids via Alkylation of Chiral Nickel(II) Complexes of Aliphatic α-Amino Acids with Racemic α-Alkylbenzyl Bromides
This studv has demonstrated that the stereochemical outcome of the direct alkylation of nickel(II) complexes derived from chiral Schiffbases of glycine, alanine, 2-aminobutyric acid, and leucine with racemic α-methylbenzyl bromide depends on the steric bulk of the corresponding aminoacid residue. In particular, the alkylation of the alanine complex was found to proceed with a synthetically useful level
该研究表明,由甘氨酸、丙氨酸、2-氨基丁酸和亮氨酸的手性席夫碱衍生的镍 (II) 配合物与外消旋 α-甲基苄基溴的直接烷基化的立体化学结果取决于相应氨基的空间体积。酸残渣。特别是,发现丙氨酸络合物的烷基化以合成有用水平 (90% de) 的立体选择性进行,提供了对映体纯 (2S,3S)- 或 (2R,3R)-α,β-二甲基苯丙氨酸的简明合成.
Asymmetric Synthesis of β-Substituted α-Amino Acids Using 2<i>H</i>-Azirine-2-carboxylate Esters. Synthesis of 3,3-Disubstituted Aziridine-2-carboxylate Esters