Melanotan II (CAS NO.121062-08-6) was first synthesized at the University of Arizona. Researchers decided to find a more potent and stable alternative, one that would be more practical to defenses against skin cancer.
The researchers headed by Victor Hruby, found a peptide, [Nle⁴, D-Phe⁷]-α-MSH, that was approximately 1,000 times more potent than natural α-MSH after synthesizing and screening hundreds of molecules. They dubbed this new peptide, "Melanotan" (later Melanotan I, now known as afamelanotide). They subsequently developed another analog, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂), which they named "Melanotan ⅡAcetate". Since their discovery, numerous studies dating back to the mid-1980s have found no obvious toxic effects of the Melanotan peptides. The scientists hoped to use Melanotan peptides to combat melanoma by stimulating the body's natural tanning mechanism to create a tan without first needing exposure to harmful levels of UV radiation. This in turn, they hypothesized, could reduce the potential for skin damage that can eventually lead to skin cancer.
The scientists licensed their patented peptides, via a technology transfer company, to a number of biotechnology companies who intend to develop them into drugs.

The Melanotan II, with the CAS registry number 121062-08-6.It belongs to the product Pharmaceutical Intermediates. This chemical's molecular formula is C₅₀H₆₉N₁₅O₉ and molecular weight is 1024.17.What's more,Its systematic name is L-Lysinamide,N-acetyl-L-norleucyl-L-alpha-aspartyl-L-histidyl-D-phenylalanyl-L-arginyl-L-tryptophyl-,cyclic (2-7)-peptide. The Melanotan II with the capable of stimulating melanin synthesis & promoting rapid tanning of skin.Currently it is in trials for use in the prevention of sunlight-induced skin cancer. 

Physical properties about Melanotan II are: (1)Density: 1.43 g/cm³ ; (2)Index of Refraction: 1.683 ; (3)Molar Refractivity: 269.94 cm³ ; (4)Molar Volume: 711.6 cm³ ; (5)Surface Tension: 63 dyne/cm ; (6)Storage Temp.: -20 °C; (7)Water Solubility: 5 mg/mL, soluble; (8)Form: solid; (9)H-Bond Donor: 13 ; (10)H-Bond Acceptor: 13 ; (11)Rotatable Bond Count: 17 ; (12)Tautomer Count: 1000 ; (13)Exact Mass: 1023.540269 ; (14)MonoIsotopic Mass: 1023.540269 ; (15)Topological Polar Surface Area: 385 ; (16)Heavy Atom Count: 74 ;

You can still convert the following datas into molecular structure:
(1)SMILES:O=C(N[C@H](C(=O)N[C@@H]1C(=O)N[C@H](C(=O)N[C@@H](C(=O)N[C@H](C(=O)N[C@H](C(=O)N[C@H](C(=O)N)CCCCNC(=O)C1)Cc3c2ccccc2nc3)CCC/N=C(\N)N)Cc4ccccc4)Cc5cncn5)CCCC)C;
(2)Std. InChI:InChI=1S/C50H69N15O9/c1-3-4-16-36(59-29(2)66)44(69)65-41-25-42(67)55-20-11-10-18-35(43(51)68)60-47(72)39(23-31-26-57-34-17-9-8-15-33(31)34)63-45(70)37(19-12-21-56-50(52)53)61-46(71)38(22-30-13-6-5-7-14-30)62-48(73)40(64-49(41)74)24-32-27-54-28-58-32/h5-9,13-15,17,26-28,35-41,57H,3-4,10-12,16,18-25H2,1-2H3,(H2,51,68)(H,54,58)(H,55,67)(H,59,66)(H,60,72)(H,61,71)(H,62,73)(H,63,70)(H,64,74)(H,65,69)(H4,52,53,56)/t35-,36-,37-,38+,39-,40-,41-/m0/s1;
(3)Std. InChIKey:JDKLPDJLXHXHNV-MFVUMRCOSA-N.