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首页> 外文期刊>Chemistry: A European journal >Stereoconversion of Amino Acids and Peptides in Uryl-Pendant Binol Schiff Bases
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Stereoconversion of Amino Acids and Peptides in Uryl-Pendant Binol Schiff Bases

机译：尿烷垂体二元醇席夫碱中氨基酸和肽的立体转化

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(S)-2-Hydroxy-2'-(3-phenyl-uryl-benzyl)-1,1'-binaphthyl-3-carboxal- dehyde (1) forms Schiff bases with a wide range of nonderivatized amino acids, including unnatural ones. Multiple hydrogen bonds, including resonance-assisted ones, fix the whole orientation of the imine and provoke structural rigidity around the imine C=N bond. Due to the structural difference and the increase in acidity of the cc proton of the amino acid, the imine formed with an L-amino acid (1-L-aa) is converted into the imine of the Damino acid (1-D-aa), with a D/L ratio of more than 10 for most amino acids at equilibrium. N-terminal amino acids in dipeptides are also predominantly epimerized to the D form upon imine formation with 1. Density functional theory calculations show that 1-D-Ala is more stable than 1-L-Ala by 1.64 kcal mol(-1), a value that is in qualitative agreement with the experimental result. Deuterium exchange of the alpha proton of alanine in the imine form was studied by H-1 NMR spectroscopy and the results support a stepwise mechanism in the L-into-D conversion rather than a concerted one; that is, de-protonation and protonation take place in a sequential manner. The deprotonation rate of L-Ala is approximately 16 times faster than that Of D-Ala. The protonation step, however, appears to favor L-amino acid production, which prevents a much higher predominance of the D form in the imine. Receptor I and the predominantly D-form amino acid can be recovered from the imine by simple extraction under acidic conditions. Hence, I is a useful auxiliary to produce D-amino acids of industrial interest by the conversion of naturally occurring L-amino acids or relatively easily obtainable racemic amino acids.
机译：（S）-2-羟基-2'-（3-苯基-尿酰基-苄基）-1,1'-联萘-3-羧酸-醛（1）形成席夫碱，具有多种非衍生氨基酸，包括非天然氨基酸那些。多个氢键（包括共振辅助的氢键）固定了亚胺的整个方向，并引起亚胺C = N键周围的结构刚性。由于氨基酸的cc质子的结构差异和酸度的增加，由L-氨基酸（1-L-aa）形成的亚胺被转化为D氨基酸（1-D-aa）的亚胺。 ），对于大多数处于平衡状态的氨基酸，D / L比率大于10。亚胺形成后，二肽中的N末端氨基酸也主要差向D形式。密度泛函理论计算表明，在1.64 kcal mol（-1）下，1-D-Ala比1-L-Ala更稳定，该值与实验结果在质量上一致。通过H-1 NMR光谱研究了亚胺形式丙氨酸的α质子的氘交换，结果支持L-to-D转换中的逐步机理，而不是协同的机理。即，去质子化和质子化依次发生。 L-Ala的去质子速率比D-Ala的去质子速率快大约16倍。然而，质子化步骤似乎有利于L-氨基酸的产生，这阻止了亚胺中D形式的更高的优势。可以通过在酸性条件下简单提取从亚胺中回收受体I和主要为D型氨基酸。因此，I是通过转化天然存在的L-氨基酸或相对容易获得的外消旋氨基酸来生产工业上感兴趣的D-氨基酸的有用助剂。

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