The Isolation And Synthesis Of Galaxamide, The Synthesis Of Its Analogue And The Anti-tumor Activity Of These Compounds.

In recent years,scientists have obtained a number of marine cyclic peptides from sponges,blue bacteria,sea squirts,sea hares and other marine organisms;most of these cyclic peptides have unique chemical structure and exhibit a variety of activities, including insecticidal,antibacterial,antiviral,anti-tumor,tumor promoting-agents, anti-inflammatory and immunosuppressive effects.In this dissertation,we described the isolation,structure determination and synthesis of Galaxamide(dl),a rare cytotoxic cyclic pentapeptide from a marine alga Galaxaurafilamentosa.In addition, we demonstrated the synthesis of its analogue and the anti-tumor activity of these compounds.In the Chapter 2 of this thesis,we described the isolation of Galaxamide from a marine alga Galaxaura filamentosa collected from the Xisha Island of South China Sea.The structure of cyclopeptide was determined as c(Leu-N-MeLeu-Leu-Leu-N -MeLeu) by using spectral methods,including IR,¹HNMR,¹³CNMR,TOF-MS-ES+, TOF-MSMS ES+,HSQC,TOCSY and HMBC.All leucines of Galaxamide were assigned to L-configuration by Marfey's method.In Chapter 3,the dipeptide fragment a1 was synthesized by the commercially available tertbutyl-L-leucine with N-methyl-L-leucine benzyl ester.After removal of the Boc group in al using TFA,the product was coupled with Boc-L-leucine leading to the tripeptide b1.Boc group of b1 was removed using TFA to e1 and benzyl was taken off from a1 to e2,respectively.The synthesis of pentapeptide e1 was achieved by coupling of e1 and e2.After the Boc group and benzyl in pentapeptide e1 were removed using TFA and hydrogen reduction in Pd/C,respectively.The dried,crude, free amine/free acid linear pentapeptide was cyclizated using TBTU/HATU/DEPBT as a coupling reagent in three steps with a yield of 42.5%.We found,upon completion, each reaction was concentrated,needed not carry out the postproccessing,and directly subjected to silica gel column chromatography using n-hexane/acetone(20:1) isocratic elution when we prepared the all linear peptide using DEPBT as a coupling reagent.In addition,we synthesized five analogues of Galaxamide in cyclization yield of 36.4%-56.9%.In Chapter 4,the filtration of anti-tumor activity was determined by MTT assay for Galaxamide,its analogues and synthesis intermediates on four tumor cells, including human breast cancer cell MCF-7,human cervical carcinoma cell Hela and human hepatoma carcinoma cell Bel-7402 and HepG2.The results show that eight compounds obviously inhibit the growth of different tumor cells.Biological activity of the compounds is enhanced with increasing the number of N-methyl in compounds and there were evident differences among different configuration cyclopeptides(d1, d5,d6).In addition,we examined the preliminary mechanism underlying the inhibition of Galaxamide on human hepatoma carcinoma cell Bel-7402.The results indicated that the compounds could evidently inhibit Bel-7402 cell,induce the cell aptotosis and kill cells at last through arousing G2/M arrest of the cell cycle,and reduce mitochondria membrane potential.