The current situation involves the ligation of melanocytes, especially type 4 melanocytes, which is helpful for the treatment of sensitive diseases caused by this receptor, such as obesity, diabetes and sexual dysfunction. 1. Requirement 1: the compound represented by formula (1) has the property that X1 is the remaining part (2) of the formula；X2 is another formula (3)；A¹ is Cys； A² is a Glu, D-Ala； A³ is His； A⁴ is D-2-Nal, D-Phe； A⁵ is Arg； A⁶ is Trp； A⁷ is Cys, Pen； R¹ is H, C₁₋₁₀ alkyl or substituted C₁₋₁₀ alkyl； R² and R³ are each, independently, H, C₁₋₁₀ alkyl,C₁₋₁₀ heteroalkyl substituted with NRᵃRᵇ or cyclohexyl where Rᵃ and Rᵇ is hydrogen or R² and R³ can be joined to form a cyclohexyl； R⁴ is OH or NH₂；R83099 and r8310s are respectively c83218c833128320； 8320a is an independent class H.C₁₋₁₀ heteroalkyl substituted with NRᵃRᵇ or cyclohexyl where Rᵃ and Rᵇ is hydrogen or R⁵ and R⁶ can be joined to form cyclohexyl； R⁷ and R⁸ are each, independently, H, C₁₋₁₀ alkyl,C₁₋₁₀ heteroalkyl substituted with NRᵃRᵇ or cyclohexyl where Rᵃ and Rᵇ is hydrogen； or R⁷ and R⁸ can join to form a cyclohexyl； R⁹ is H； and n is 0, characterized in that they are selected from the group consisting of: Hydantoin (C (O) - (Arg-Gly)) - cycle (Cys-Glu-His-D-Phe-Arg-Trp-Cys) -NH₂ ( SEQ ID No. 13)；Hidanto na (C (O) - (Nle-Gly)) - ciclo (Cys-Glu-His-D-Phe-Arg-Trp-Cys) -NH (SEQ ID N 14)Hidanto na (C (O) - (Gly-Gly)) - ciclo (Cys-Glu-His-D-Phe-Arg-Trp-Cys) -NH (SEQ ID N 15)Hidanto na (C (O) - (Nle-Gly)) - ciclo (Cys-D-Ala-His-D-Phe-Arg-Trp-Cys) -NH (SEQ ID N 16)Hidanto na (C (O) - (Gly-Gly)) - ciclo (Cys-D-Ala-His-D-Phe-Arg-Trp-Cys) -NH (SEQ ID N 17)Hidanto na (C (O) - (Nle-Gly)) - ciclo (Cys-D-Ala-His-D-Phe-Arg-Trp-Pen) -NH (SEQ ID N 18)Hidanto na (C (O) - (Gly-Gly)) - ciclo (Cys-D-Ala-His-D-Phe-Arg-Trp-Pen) -NH (SEQ ID N 19)Hidanto na (C (O) - (Ala-Gly)) - ciclo (Cys-D-Ala-His-D-Phe-Arg-Trp-Cys) -NH (SEQ ID N 20)Hidanto na (C (O) - (D-Ala-Gly)) - ciclo (Cys-D-Ala-His-D-Phe-Arg-Trp-Cys) -
