Table 1.

Analytical Data for the New Melanotropin Peptides

		TLC Rfa			HPLC	HR-MSc
	peptide sequence	A	B	C	kb	obsd	calcd
1	Ac-c[Cys-His-d-Phe-Nα-guanidinylbutyl-Cys]-Trp-NH2	0.64	0.43	0.18	9.98	847.3517	847.3496
2	Ac-c[Cys-His-d-Phe-Nα-guanidinylbutyl-d-Cys]-Trp-NH2	0.66	0.47	0.21	10.41	847.3510	847.3496
3	Ac-c[Cys-His-d-Phe-Cys]-Nα-guanidinylbutyl-Trp-NH2	0.63	0.43	0.18	10.66	847.3502	847.3496
4	Ac-c[Cys-His-d-Phe-Cys]-Nα-guanidinylbutyl-d-Trp-NH2	0.64	0.44	0.20	9.58	847.3510	847.3496
5	Ac-c[Glu-His-d-Phe-Nα-guanidinylbutyl-Dab]-Trp-NH2	0.37	0.18	0.07	8.79	854.4442	854.4426
6	Ac-c[Glu-His-d-Phe-Nα-guanidinylbutyl-Orn]-Trp-NH2	0.38	0.19	0.07	8.58	868.4592	868.4582
7	Ac-c[Cys-His-d-Nal(2)′-Cys]-Nα-guanidinylbutyl-d-Trp-NH2	0.71	0.54	0.26	13.09	897.3669	897.3652
8	Ac-c[Glu-His-d-Nal(2)′-Nα-guanidinylbutyl-Orn]-Trp-NH2	0.48	0.28	0.11	12.24	918.4725	918.4739

^aR_f values were obtained using thin-layer silica gel chromatography in the following three solvent systems: (A) water/HOAc/tert-butyl alcohol/EtOAc (1:1:1:1); (B) water/HOAc/tert-butyl alcohol/EtOAc (1:1:1:2); and (C) water/HOAc/tert-butyl alcohol/EtOAc (1:1:2:2).

^bHPLC k′ = [(peptide retention time – solvent retention time)/solvent retention time] in the solvent system (A: 0.1% aqueous TFA; B: acetonitrile). A linear gradient from 10% to 40% of solvent B over 30 min was applied. An analytical Waters C₁₈ column (3.5 μm, 4.6 × 75 mm) was used with a flow rate of 1 mL/min. c High-resolution MS.

^cHigh-resolution MS.