Table 1.

Binding affinities of known ligands derived from diprenorphine (2).

compound	R1=	K i [nM]
		μ	κ	δ
2 33	H	0.14	2.0	0.73
4 37	H	2.19±0.65	4.15±1.3	3.66±0.92
5 34	H	0.7±0.25	2.6±0.0	0.7±0.05
6 38	Me	14.4	0.15	89.3
7 38	Me	1.91	25.8	1753
8 38	Me	1.87	0.74	–