Method for preparing bremelanotide by solid-liquid combination

Abstract

The invention relates to the field of chemical synthesis of peptide drugs, in particular to a method for preparing bremelanotide by solid-liquid combination. The method for preparing bremelanotide bysolid-liquid combination comprises the following steps that S1, Fmoc-Trp(Boc)-OH is connected to a 2-CTC Resin carrier to synthesize hexapeptide full protection fragments; S2, in a liquid phase system, the synthetic hexapeptide full protection fragments are subjected to fragment condensation with an amino acid through a condensing agent to obtain a heptapeptide methyl ester with a side chain witha protecting group; S3, the side chain protecting group of the full protection heptapeptide methyl ester is split by using cutting fluid, and drying is carried out to obtain a methyl ester ring; and S4, methyl ester cyclic peptide is dissolved in an ACN / H2O solution, a product is precipitated and filtered, and then MTBE or ether is used for beating and then washing the solid product, and drying iscarried out to obtain a bremelanotide crude product. The method for preparing bremelanotide by solid-liquid combination is mild in reaction conditions, simple and convenient to operate, short in production cycle, low in the cost and small in environmental pollution, is convenient to produce on a large scale, and has wide application prospects and good economic and social value.

Description

technical field [0001] The invention belongs to the field of chemical synthesis of polypeptide drugs, and relates to a method for preparing bremelanotide by solid-liquid combination. Background technique [0002] The peptide sequence of Bremelanotide PT 141 is: Ac-Nle-Cyclo(-Asp-His-D-Phe-Arg-Trp-Lys)-OH, molecular formula: C50H68N14O10, molecular weight is 1025.18, and its structural formula is as follows: [0003] [0004] Bremelanotide PT 141, also known as bremelanotide, is a melanocortin receptor-4 (MC4r) agonist that regulates libido and sexual response by activating endogenous pathways in the brain, helping concomitant Premenopausal women with hypoactive sexual desire disorder maintain normal libido. This peptide is a new drug for the treatment of female sexual dysfunction developed by Palatin Technologies Pharmaceutical Company in the United States. It has completed clinical phase III research and was released on June 21, 2019. Approved by the FDA for marketing. ...

AI Technical Summary

Problems solved by technology

[0005] At present, the domestic situation about the synthesis of bremelanotide is roughly as follows: as reported in the patent CN106589111A, 5+2 fragments are used for synthesis, Lys(IvDde) ​​is expensive and a large amount is not easy to obtain, and hydrazine hydrate is used for removing the side chain protecting group IvDde It is highly toxic, difficult to operate, difficult to dispose of waste liquid, and highly polluting to the environment. Among them, Ac-Nle-Asp-OtBu in the 5+2 fragment requires a lot of liquid phase synthesis steps and it is not easy to obtain high-purity fragments. The overall design is cumbersome to operate , low efficiency, unfavorable for large-scale production, adopted expensive Asp (O-2-Phipr) in the patent CN101280005B, on the Lys (MMt) resin selective deprotection ring formation, the yield is only about 17%, large-scale high production cost

[0006] In the patents of foreign original research companies such as US6579968, US6794489, US7176279, US7235625, US7417027 and US7473760, the Lys side chain in the peptide sequence uses Adpoc, Alloc, Mtt unconventional protecting groups, and is gradually coupled in Wang resin. This method is a special protecting group for the Lys side chain , raw materials are expensive and not easy to obtain in large quantities in the market, use low concentration of TFA to selectively cleave the Lys side chain protecting group (Adpoc, Alloc, Mtt) and the Asp side chain protecting group tBu without cleaving the polypeptide from Wang resin. After forming a ring on the 2-Phipr resin, use high-concentration TFA to cleave the polypeptide chain from Wang resin to obtain the crude product of Bremelanotide (PT114). It is not clean and needs to be repeated many times. The removal of Alloc requires the use of expensive tetrakis(triphenylphosphine) palladium. The operation is cumbersome and the product is easy to introduce heavy metal palladium. The low concentration of TFA on the resin selectively cleaves the side chain protecting group and cannot detect the carboxyl group. Whether the protecting group tBu is completely removed, and the entire polypeptide chain is easily cleaved from the resin, which is not conducive to controlling the reaction, which will increase the cost and is not conducive to mass production. Therefore, a solid-liquid combination is required to prepare Bremelanotide The method to improve the above problems

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