Table 1. Analytical data of monovalent and bivalent ligands for hMC4R.

	liganda	molecular formula	no of atoms present in the linker	Estimated linker length (Å)	MSb		HPLCc (tR, min)
					calcd	observed
					1			C96 H131 N27 O21	36	10-20	1999.2	2000.1a	11.9
2		C117 H161 N33 O27	54	15-30	2460.2	2461.2a	11.9
3		C140 H196 N39 O33	72	20-40	2922.5	2924.1a	11.9
4		C103 H153 N25 O27	58	13-46	2173.5	2174.4a	12.3
5		C68 H97 N17 O15	20	4-18	1392.5	1393.6b	12.5
6		C82 H123 N19 O21	40	8-36	1709.9	1710.6b	12.5
7		C148 H197 N41 O29	36	10-20	3014.4	3016.4a	N.D
8		C169 H227 N47 O35	54	15-30	3476.9	3478.5a	13.2
9		C194 H267 N53 O41	72	20-40	3997.5	3940.9a	13.1
10		C155 H219 N39 O35	58	13-46	3186.6	3188.1a	13.6
11		C120 H163 N31 O23	20	4-18	2407.7	2407.3a	14.0
12		C134 H189 N33 O29	40	8-36	2726.1	2727.0a	13.9
13		C144 H197 N40 O31	36	10-20	2955.3	2955.0a	12.0
14		C165 H227 N46 O37	54	15-30	3417.0	3417.0a	12.0
15		C186 H257 N52 O43	72	20-40	3880.2	3880.7a	12.0
16		C151 H219 N38 O37	58	13-46	3129.4	3129.2a	12.2
17		C116 H163 N30 O25	20	4-18	2348.6	2348.6a	12.4
18		C130 H189 N32 O31	40	8-36	2665.4	2666.8a	12.5

- SHU9119; - MSH(7); - PEGO moiety; - (Pro-Gly)₃

^aN-terminus: acetylated; C-terminus: amidated.

^b(M + H)⁺, ESI method (Finnigan, Thermoelectron, LCQ classic).

^cPerformed on a Waters Alliance 2695 HPLC using a reverse-phase column (Jupiter 5U C18 300A; 2.2 × 2.5 cm) in gradient system (10-40% of acetonitrile containing 0.1% TFA within 30 min, 1 mL/min).