Synthesis of Various 3-Substituted 1,2,4-Oxadiazole-Containing Chiral β<sup>3</sup>- and α-Amino Acids from Fmoc-Protected Aspartic Acid
作者:Abdallah Hamzé,、Jean-François Hernandez、Pierre Fulcrand、Jean Martinez
DOI:10.1021/jo0345953
日期:2003.9.1
ester). These compounds represent new series of nonnatural amino acids, which could be used in combinatorial synthesis. A simple protocol has been developed to generate the 1,2,4-oxadiazole ring. Indeed, common methods resulted in cleavage of the Fmoc group or required long reaction times. We found that sodium acetate in refluxing ethanol/water (86 degrees C) was a convenient and efficient catalyst to promote
从Fmoc-(l或d)-Asp(OtBu)-OH和Fmoc-1-Asp合成了各种3-取代的含手性1,2,4-恶二唑的Fmoc-beta(3)-和-α-氨基酸-OtBu分别在三个步骤中进行(即,天冬氨酰衍生物与差异取代的a胺肟的缩合,1,2,4-恶二唑的形成以及叔丁酯的裂解)。这些化合物代表了一系列新的非天然氨基酸,可用于组合合成。已经开发出一种简单的方案来生成1,2,4-恶二唑环。实际上,常规方法导致Fmoc基团的裂解或需要较长的反应时间。我们发现乙酸钠在回流的乙醇/水(86摄氏度)中是促进Fmoc-氨基酰基a基肟转化为1,2,4-恶二唑的便捷有效的催化剂,并且该过程证明与Fmoc保护兼容。结果表明,可以制备这些化合物而对映体纯度没有明显损失。此外,用于从这些化合物上裂解Fmoc保护基的碱性条件没有诱导其手性中心的差向异构化。