Table 8.

Binding affinities at the opioid receptors of N-methylmorphinans 22, 1, 2 and 4, and their N-phenethyl substituted analogues 22b, 1b, 2b and 4b.

	Binding Affiniy Ki (nM) a
	MOP	DOP	KOP	Ki Ratios MOP/DOP/KOP
Morphine (22)	3.35	195	96.4	1/58/29
22b	0.25	24.5	93.5	1/98/374
Oxymorphone (1)	1.41	79.1	32.6	1/56/23
1b	0.12	10.7	42.2	1/89/352
2	0.27	9.08	10.3	1/34/38
2b	0.19	1.81	15.8	1/9.5/83
4	0.25	18.6	12.8	1/74/51
4b	0.24	1.45	35.3	1/6.0/147

^a Determined in competition binding assays using membranes from CHO cells stably expressing human opioid receptors. Data from [94,116]. For compound structures, refer to Figure 3.