An Efficient Synthesis of Aryl Phenaceturates Using Acid Catalyzed Dicyclohexylcarbodiimide Esterification and Transient<i>N</i>-<i>trent</i>-Butoxycarbonylation
作者:Daniel Cabaret、Jie Liu、Michel Wakselman
DOI:10.1055/s-1994-25507
日期:——
Application of the Holmberg procedure (DCC/pyridine/p-TSAcat) improves the yield of the direct condensation of phenols with phenylacetylglycine (1). Moreover, N-tert-butoxycarbonylation of 1 impedes an intramolecular reaction leading to an oxazolone, and allows the formation of stable aryl N-Boc phenaceturates. Then, mild cleavage of the Boc group with four equivalents of trifluoroacetic acid furnishes the aryl phenylacetylglycinate. This indirect method is more efficient than its direct analog in the case of phenols possessing electron-withdrawing substituents.
Holmberg 程序(DCC/吡啶/p-TSAcat)的应用提高了酚与苯乙酰甘氨酸直接缩合的产率 (1)。此外,1的N-叔丁氧基羰基化阻碍了产生恶唑酮的分子内反应,并允许形成稳定的芳基N-Bocphenaceturates。然后,用四当量的三氟乙酸温和裂解 Boc 基团,得到芳基苯乙酰甘氨酸酯。对于具有吸电子取代基的酚类,这种间接方法比其直接类似方法更有效。