Madsen U, Frydenvang K, Ebert B, Johansen T N, Brehm L, Krogsgaard-Larsen P
Department of Medicinal Chemistry, Royal Danish School of Pharmacy, Copenhagen, Denmark.
J Med Chem. 1996 Jan 5;39(1):183-90. doi: 10.1021/jm950393q.
(R,S)-2-Amino-2-(3-hydroxy-5-methyl-4-isoxazolyl)acetic acid [(R,S)-AMAA, 4] is a potent and selective agonist at the N-methyl-D-aspartic acid (NMDA) subtype of excitatory amino acid receptors. Using the Ugi "four-component condensation" method, the two diastereomers (2R)- and (2S)-2-[3-(benzyloxy)-5-methyl-4-isoxazolyl]N-tert-butyl-2- [N-[(S)-1-phenylethyl]benzamido]-acetamide (16 and 17, respectively) were synthesized and separated chromatographically. The absolute stereochemistry of 16 was confirmed by an X-ray analysis. Deprotection of these intermediates did, however, provide (R)- (8) and (S)- (9) AMAA, respectively, in extensively racemized forms. N-BOC-protected (R,S)-AMAA (21) was successfully resolved via diastereomeric salt formation using cinchonidine. The stereochemical purity and stability of 8 and 9 obtained via this resolution were determined using chiral HPLC. (R)-AMAA (8) showed peak affinity for [3H]AMPA receptor sites (IC50 = 72 +/- 13 microM) and was shown to be a more potent inhibitor of [3H]CPP binding (IC50 = 3.7 +/- 1.5 microM) than (S)-AMAA (9) (IC50 = 61 +/- 6.4 microM). Neither enantiomer of AMAA affected [3H]kainic acid receptor binding significantly. In electrophysiological studies using rat brain tissue, 8 (EC50 = 7.3 +/- 0.3 microM) was 1 order of magnitude more potent than 9 (EC50 = 75 +/- 9 microM) as an NMDA receptor agonist.
（R，S）-2-氨基-2-（3-羟基-5-甲基-4-异恶唑基）乙酸[（R，S）-AMAA，4]是兴奋性氨基酸受体N-甲基-D-天冬氨酸（NMDA）亚型的一种强效且选择性激动剂。采用乌吉“四组分缩合”方法，合成了两种非对映异构体（2R）-和（2S）-2-[3-（苄氧基）-5-甲基-4-异恶唑基]N-叔丁基-2-[N-[(S)-1-苯乙基]苯甲酰胺基]乙酰胺（分别为16和17），并通过色谱法进行分离。16的绝对立体化学结构通过X射线分析得以确证。然而，这些中间体脱保护后分别以广泛外消旋的形式提供了（R）-（8）和（S）-（9）AMAA。N-BOC保护的（R，S）-AMAA（21）通过使用辛可宁形成非对映体盐成功拆分。通过该拆分得到的8和9的立体化学纯度和稳定性使用手性高效液相色谱法进行测定。（R）-AMAA（8）对[3H]AMPA受体位点显示出峰值亲和力（IC50 = 72±13μM），并且被证明是比（S）-AMAA（9）（IC50 = 61±6.4μM）更强效的[3H]CPP结合抑制剂。AMAA的两种对映体均未对[3H] kainic酸受体结合产生显著影响。在使用大鼠脑组织的电生理研究中，作为NMDA受体激动剂，8（EC50 = 7.3±0.3μM）比9（EC50 = 75±9μM）的效力高1个数量级。
