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目的合成叔丁氧羰基(Boc)保护的环状氨基酸Acc5、Acc6,并将这类构型限制型氨基酸用于多肽的固相合成,考察环状氨基酸在多肽固相合成中的应用以及在强酸条件下的稳定性。方法环状氨基酸通过相应的环酮与KCN和铵盐反应得到含有氰基的环状化合物,再通过氰基的酸性水解而得到,最后在弱碱性条件下与二碳酸二叔丁酯(Boc2O)反应,得到Boc保护的环状氨基酸;通过1H NMR和ESI-MS表征其结构;采用对甲基二苯甲基氨基树脂,通过Boc、芴甲氧羰基(Fmoc)的氨基保护策略,对肽序列进行固相合成,最后在强酸HF条件下裂解,通过HPLC对粗肽进行纯度分析,ESI-MS表征其结构。结果1H NMR和ESI-MS图谱显示环状氨基酸Acc5和Acc6均为目标化合物。HPLC结果显示,得到的2个促性腺激素释放激素类似物(GnRH),粗肽纯度良好,且易于纯化;ESI-MS图谱确证肽序列结构正确。结论环状氨基酸在固相合成工艺中有很好的缩合效率,并且能够在强酸裂解条件下保持稳定。
OBJECTIVE: To synthesize cyclic amino acids Acc5 and Acc6 protected by t-butoxycarbonyl (Boc), and to use these constitutively restricted amino acids for the solid-phase synthesis of polypeptides. The application of cyclic amino acids in the solid-phase synthesis of polypeptides, Under the conditions of stability. Methods Cyclic amino acids were obtained by reaction of the corresponding cyclic ketones with KCN and ammonium salts to obtain cyclic compounds containing cyano groups which were obtained by acidic hydrolysis of cyano groups and finally reacted with di-tert-butyl dicarbonate (Boc2O ) To give the Boc-protected cyclic amino acids. The structures were characterized by 1H NMR and ESI-MS. The p-methyldibenzyl amino resin was used to protect the peptide against the peptide by the amino protection strategy of Boc and fluorenylmethoxycarbonyl (Fmoc) Sequence, and finally cleaved under the condition of strong acid HF. The purity of the crude peptide was analyzed by HPLC, and its structure was characterized by ESI-MS. Results The 1H NMR and ESI-MS spectra showed that both the cyclic amino acids Acc5 and Acc6 were the target compounds. HPLC results showed that the obtained two gonadotropin-releasing hormone analogs (GnRH), the crude peptide purity and easy purification; ESI-MS map confirmed the peptide sequence structure is correct. CONCLUSION Cyclic amino acids have good condensation efficiency in the solid-phase synthesis process and remain stable under strong acid cleavage conditions.