Application of the ‘Direct Amide Cyclization’ to Peptides Containing an Anthranilic Acid Residue
作者:Irena Philipova、Anthony Linden、Heinz Heimgartner
DOI:10.1002/hlca.200590135
日期:2005.7
acid-catalyzed ‘direct amide cyclization’. Unfortunately, all attempts to isolate the ten-membered cyclotripeptides, by starting with different precursors, failed. Instead of the expected cyclotripeptides, the corresponding 1,3a,7-triazabenz[e]azulene-3,6-diones 12 and 17 (Schemes 2 and 3) were obtained in up to 44% yield. Most likely, these products were formed by a transannular ring contraction of the desired
2,2-二取代的2 H-叠氮基-3-胺7a - 7c被用作氨基酸合成子,以制备衍生自邻氨基苯甲酸的线性肽。这些线性肽,其含有α,α二取代的α -氨基酸,通过用“氮杂环丙烯/恶唑酮的方法”(合成方案2 - 5),并对其进行酸催化“直接酰胺环化”。不幸的是,所有通过从不同的前体开始分离十元环三肽的尝试都以失败告终。代替预期的环三肽,相应的1,3a,7-三氮杂并[ e ] azulene -3,6-diones 12和以高达44%的产率获得了17(方案2和3)。这些产物最有可能是通过所需产物的环环形收缩,然后脱水而形成的。在线性前体24的情况下,以50%的产率形成20元环二聚体25,以及痕量的1,3a,7-三氮杂[ e ] azulene -3,6-dione 27和完全出乎意料的喹唑啉酮26(方案5)。在线性前体30和34的情况下,在“直接酰胺环化”的条件下未观察到闭环,这表明该方法的局限性。