14-Membered cyclodepsipeptides with alternating β-hydroxy and α-amino acids by cyclodimerization
作者:Boyan Iliev、Anthony Linden、Roland Kunz、Heinz Heimgartner
DOI:10.1016/j.tet.2005.11.002
日期:2006.2
cyclodimer 10. In all cases, when starting with racemic material, only the trans-substituted cyclodepsipeptides were isolated. Simple molecular modeling revealed that the formation of the cyclodimer is thermodynamically slightly more favorable than that of the cyclomonomer. The proposal that cyclodimer formation is preferred because of the presence of intramolecular H-bonds could not be confirmed by X-ray
描述了在“直接酰胺环化”(DAC)条件下1型β-羟基酰胺的环二聚(孪生)。尽管其他偶联方法也可得出中等结果,但通过DAC可获得最佳收率,环二聚体10可达88%。在所有情况下,当从外消旋物质开始时,仅分离出反式取代的环二肽。简单的分子模型表明,环二聚体的形成在热力学上比环聚单体的形成稍微更有利。由于分子内氢键的存在,优选形成环二聚体的提议不能通过X射线晶体学证实。还研究了取代基在氨基酸和羟基酸部分中的影响。结果表明,仅当羟基酸部分被α,α-二取代时,环二聚作用才成功。