Improvement of Thioester Method by Using Pac Ester for Synthesis of Cyclopentapeptides

Thioester method was improved by using Pac (phenacyl group) ester as protecting group of 3-mercaptopropionic acid. Two cyclopentapeptides c(Ala-Tyr-Leu-Ala-Gly) and c(Pro-Tyr-Leu- Ala-Gly) were synthesized successfully by this method.

两个Galaxamide类似物的合成及其抗肿瘤活性初探

以D-苯丙氨酸和D-亮氨酸为起始原料,采用液相合成法,经典的"3+2"合成策略,通过对氨基酸N端的保护及脱保护、C端的脱保护、氨基酸的甲基化、缩合等步骤,以混合缩合试剂DEPBT/HATU/TBTU关环,合成了两个环五肽HW-1和HW-2,化合物结构通过1HNMR,13CNMR,MS和ICP-MS进行表征。采用MTT法对目标产物HW-1和HW-2进行抗肿瘤活性筛选,结果显示其具有良好的活性,尤其对Hep G2的IC50值分别为3.14和9.2 mg/L。

两个C2轴对称环十肽的合成

以亮氨酸和苯丙氨酸为原料,通过氨基酸的保护以及脱保护、氨基酸的甲基化和耦合,最后以O-苯并三氮唑-N,N,N'N'-四甲基脲四氟硼酸酯(TBTU)/2-(7-偶氮苯并三氮唑)-N,N,N',N'-四甲基脲六氟磷酸酯(HATU)/3-(二乙氧基磷酰氧基)-1,2,3-苯并三嗪-4-酮(DEPBT)为环合试剂,合成2个C2轴对称环十肽化合物Q10-1与Q10-2,最后环合收率分别为31.6%和39%。通过HPLC进行分离纯化,经HPLC检测产物纯度均在98%以上,通过1HNMR,13CNMR和ESI-MS对两个化合物进行表征。

两个Galaxamide类似物的固相合成及抗肿瘤活性研究

以N-芴甲氧羰基-L-亮氨酸(Fmoc-Leu-OH)和N-芴甲氧羰基脯氨酸(Fmoc-Pro-OH)为原料,采用经典的Fmoc固相合成法,通过对氨基酸N端的保护及脱保护、氨基酸的甲基化、缩合等步骤合成线性五肽,以缩合试剂六氟磷酸苯并三唑-1-基氧基三吡咯烷基磷(Py \BOP)关环,分别以59.5%和41.1%的环合收率得到了两个新的环五肽化合物G_1和G_2,结构通过~1HNMR、^(13)CNMR、ESI-MS进行确认。采用MTT法对目标化合物G_1和G_2进行了体外抗肿瘤活性的研究。结果表明:含有脯氨酸片段的Galaxamide类似物G_2具有良好的活性,尤其对人乳腺癌细胞株(MCF-7)具有较好的细胞毒性,其IC_(50)值为5.85 mg/L。

Application of Pac Ester in Thioester Method for the Synthesis of Cyclopentapeptides

Thioester method for the synthesis of cyclopeptides is improved by using Pac (Pac = phenacyl, CH2COC6H5) ester as a protecting group of 3-mercaptopropionic acid. The Pac group is easy to be removed from C-terminal with zinc in acetic acid. The protected glycine thioester and peptide thioesters synthesized by the unproved method, are easy to be purified, so the final linear peptides are pure enough for the following cyclization. Furthermore, this method is flexible for peptide chain elongation, either from C-terminal or from N-terminal. So it is an efficient and practical method for synthesis of bioactive peptides. Two N-protected pentapeptide thioesters, Boc-Pro-Tyr-Leu-Ala-GlySCH2CH2COOPac and Boc-Ala-Tyr-Leu-Ala-Gly-SCH2CH2-COOPac were synthesized by the improved thioester method. After deprotecting Pac ester with zinc in aqueous acetic acid and Boc group with trifluoroacetic acid in CH2C12, two free pentapeptide thioesters were obtained. Ag+ -assisted cyclization in acetate buffered solution afforded two cyclic pentapeptides c(Pro-Tyr-Leu-Ala-Gly) and c(Ala-Tyr-Leu-Ala-Gly). Effects of different buffer pH, different Ag+ concentrations, etc. on the cyclization were studied.