作者:Shingo Makino、Eiji Nakanishi、Takashi Tsuji
DOI:10.1055/s-2003-38757
日期:——
The synthesis of 2,3,5-triketopiperadines on solid-support has been achieved for the first time. Cyclization of 4 using oxalyl diimidazole proceeded excellently with N-methyl amino acids except for Sarcosine (Sar). On the other hand, this cyclization did not proceed well when amino acids without N-methyl substitution were used. This can be explained by the lower energy difference between the trans and cis configurations of oxalyl amide 5 by the introduction of N-methyl substitution, because cis conformation is necessary for the cyclization to proceed. This cyclization also worked well with amino acids with a six-membered ring such as tetrahydroisoquinoline-3-carboxylic acid (Tic) and piperidine-2-carboxylic acid (Pic), which are N-alkylated amino acids. Although the purity of the target compounds was found to be low in the case of Sar and amino acids with a five-membered ring such as proline (Pro) and thiazolidine-4-carboxylic acid (Thz) under the same cyclization conditions, we were able to successfully optimize the reaction conditions to give the target compounds with good purity. Furthermore, it was demonstrated that 2,3,5-triketopiperadines with three points diversity could be prepared on solid-support with high purity, showing the generality of this method.
首次实现了在固相载体上合成2,3,5-三酮哌啶。使用草酰二咪唑进行的4的环化反应在除肌氨酸(Sar)以外的N-甲基氨基酸中表现优异。另一方面,当使用没有N-甲基取代的氨基酸时,这种环化反应进展不佳。这可以解释为通过引入N-甲基取代,草酰胺5的顺反构型之间的能差降低,因为顺式构象是环化反应所必需的。这种环化反应对于具有六元环的氨基酸如四氢异喹啉-3-羧酸(Tic)和哌啶-2-羧酸(Pic)也同样有效,这些是N-烷基化的氨基酸。尽管在同样环化条件下,肌氨酸和具有五元环的氨基酸如脯氨酸(Pro)和噻唑烷-4-羧酸(Thz)的目标化合物纯度较低,但我们成功地优化了反应条件,得到了纯度良好的目标化合物。此外,证明了可以在固相载体上以高纯度制备具有三点多样性的2,3,5-三酮哌啶,显示了该方法的普遍性。