Table 1. Opioid Receptor Binding Affinity of LP1 (2) Derivatives 7a–e, 11a–e, and 14a–c.

						Ki (nM) ± SEMa,b
Cmp	R	R1	R2	R3	R4	MOR	DOR	KOR
7a	H	CH3	H	H	CH3	7.4 ± 0.75	277 ± 12	252 ± 10
7b	H	CH3	CH3	H	CH3	43.7 ± 2	>2,000	313 ± 15
7c	H	CH3	CH3	H	H	20.8 ± 1	474 ± 20	340 ± 13
7d	H	CH3	H	H	C2H5	14.9 ± 0.92	198 ± 8	320 ± 11
7e	H	CH3	H	CH3	H	7.9 ± 0.65	478 ± 22	480 ± 22
11a	Bn	H	H	H	H	606 ± 34	>5,000	>5,000
11b	Bn	CH3	H	H	CH3	400 ± 24	>5,000	>3,000
11c	Bn	CH3	CH3	H	CH3	504 ± 27	>5,000	444 ± 24
11d	Bn	CH3	CH3	H	H	165 ± 7	>5,000	>2,000
11e	Bn	CH3	H	H	C2H5	1,540 ± 59	>5,000	151 ± 6
14a	Bn	H	H	H	H	244 ± 12	>1,000	>3,000
14b	H	CH3	CH3	H	H	129 ± 10	>5,000	>1,000
14c	H	CH3	H	CH3	H	182 ± 13	>5,000	>2,000
1c						6.1 ± 0.50	147 ± 5.70	31 ± 1.30
2 (LP1)d						0.83 ± 0.05	29 ± 1.00	110 ± 6.00
DAMGO						0.90 ± 0.04	-	-
Naltrindole						-	0.83 ± 0.04	-
U50,488						-	-	0.27 ± 0.03

^aValues are means ± SEM of three separate experiments, each carried out in duplicate.

^bK_i values were obtained as [³H]DAMGO displacement for MOR, [³H]DPDPE displacement for DOR, and [³H]U69,593 displacement for KOR.

^cReference (16).

^dReference (17).