The Research Of Octreotide Synthesis Method

The peptide is the biology information transmission activematerial which is composed by the amino acids, they act as animportant role in life activities, therefore is also called the bioactivitypeptide. As a kind of important chemical substance, presently, theresearch of bioactive peptides is very popular, which particularlyfocuses on the aspect of pharmaceutical. The research anddevelopment of peptide drugs has been the new focus ofpharmaceutical because of the technological maturation of chemistrypeptide synthesis and the progress of solid-phase peptide synthesisespecially. Comparing with the enzymatic and gene engineeringmethod on the synthesis of peptide, chemistry peptide synthesis hasmore advantage about the syntheses of short and middle peptide chains,and which attracts more interests.Many new drugs with more advantages than native analogueshave been synthesized by using the technique of chemistry peptidesynthesis, such as octreotide. Octreotide, an analogue of synthetichormone somatostatin, has been used as a clinical therapeutic agent totreat VI-Pomasyndrome , carcinoid syndrome , glucagonomagastrinoma/Zollinger Ellison,insulinoma ,GRFoma and esophagus-varicosity bleeding. Somatostatin, a cyclic peptide consisting of 14amino acids, plays an inhibitory role in the hormonal regulation of atleast three organ systems in humans: (i) the central nervous system, thehypothalamus, and pituitary gland, (ii) the gastrointestinal tract, and(iii) the exocrine and endocrine pancreas. Because of the "growthinhibitory" effect obtained in most tissues by the stimulation ofsomatostatin receptors, a large number of human tumors are alsosomatostatin receptor positive. The pharmacological properties ofsomatostatin have generated an interest in the use of this peptide fortherapeutic purposes. Somatostatin is unsuitable for in vivo used due toits very short biological half-life, however an eight-amino acid peptideanalogue of somatostatin , octreotide, has a longer half-life as well asinhibitory properties more potent than the native somatostatin.Because of its growth hormone inhibitory effects, octreotide has beenused as a clinical therapeutic agent to treat a wide variety of tumorswhich contain somatostatin receptors. It was firstly approved by USAFDA as an agent to treat tumors of gastrointestinal tract endocrine andhypophysis and acromegaly in 1988, then approved byUSA FDA totreat acromegaly in 1998 again.In the solid phase peptide synthesis, the Fmoc/tBu strategy hadbeen used, and H-Threoninol(tBu)-2-Cl Trt resin was also applied,BOP, HOBt reagent as coupling reagent , and the kaiser test was usedto examine the coupling completeness , so the coupling production ratewas all above 97%. In the disulphide bond formation, we had selectedtwo methods: firstly, DMSO recommendation oxidation, we found theoptimum condition, which is in the pH8.0 condition, in the 1%DMSOwatery solution , the concentration of Octreotide is 3mg/ml, the time ofreaction is 100min, the oxidation is complete, the effect is the best, theimpurity are few, easy to separate, the radio of product and impurityis 43.12%。So the method mostly suited the mass productions and thepreparation. Secondly, the oxidation directly on the resin with theiodine in dichloromethane, then octreotide on resin was cut with TFA.In HPLC examination , the main peak is in evidence and its area rate isalso good (30%), the method easy to carry on.In the liquid phase peptide synthesis, we used the ethylchloroformate, trichloro three cyanogen and BOP to active Fmoc-Thrand then it was reducted by boron sodium hydride. The reaction rate isrespectively 32%,45%,58%. Using BOP and the trichloro threecyanogen as activation is the good method for amino-alcoholpreparation, but generally speaking ,production rate of the threereagent is not too high. Under the pyridine existence condition, weprotected the amino-alcohol with Trt-Cl, for preventing the sidereaction in coupling, the production rate is 70%.However, When weuse the one-pot method to couple, we cannot get final production. Ithink because the anhydrous condition was insufficient and thepiperidine was not pulled out entirely. That Leaves behind somewhatregret in the present paper.In protectation on the base the aspect, because has used the Fmocprotection base protected the ɑ-amino of Trp , we avoided the dangerof the acidity removing to form the by-product under the acidcondition;Simultaneously cleavaging the protectation with the TFAsystem, which avoid reacting in the fierce condition which threefluorine methylsulfonic acid brought.The method described in this paper provided a simplified syntheticroute and resulted in dramatically improved yield of octreotide,moreover , reduced the cost of material drug. It may be supplied for avast of tumor patients. Therefore, the reach and development ofoctreotide will be greatly economic and societal significances.