Table 1.

Compound	X1	X2	R	Apparent IC50 (nM)	Ki (pM) estimate
1a	O	CH	H	0.07	6.3
1b	O	CH	4-CN	0.14	12.8
1c	O	CH	3-CN	0.03	2.5
1d	O	CH	4-Cl	0.08	7.2
1e	O	CH	4-CF3	0.36	33.6
1f	O	CH	2-CL	0.06	5.3
1g	O	CH	3,5-CH3	42	3962
1h	O	CH	2-CH3	0.04	3.4
1i	O	CH	2,5-CH3	35	3302
1j	O	CH	3-CL	0.41	38.3
1k	O	CH	2,6-CH3	2000	188,680
1l	O	CH	3-CH3	0.6	56.3
1m	O	CH	4-CH3	0.2	18.5
1n (notea)	O	CH	H	29	2735
1o (noteb)	O	CH	H	0.02	INDh
1p	O	CH	4-OCH3	0.01	INDh
2a	NH	CH	2-CH3	600	56,603
2b (notec)	NH	CH	H	222	20,943
2c	NH	CH	H	190	17,924
2d (noted)	NH	CH	NAg	382	36,037
2e (notee)	NH	CH	H	9.8	924
2f (notef)	NH	CH	H	25	2358
3a	O	N	H	1.56	147
3b	O	N	4-CN	0.09	8.1
3c	O	N	3-CN	0.2	18.5
3d	O	N	4-CL	0.01	INDh
3e	O	N	4-CF3	0.16	14.7
3f	O	N	4-NO2	0.2	18.5

^afragment Z =

^bfragment A =

^cfragment A =

^dfragment A =

^efragment A =

^ffragment A =

^gNA(not applicable)

^hIND(indeterminable)

IC50 values were determined as described in Experimental Procedures. Reactions were measured over 40 min, but because inhibition was time dependent, only initial linear rates were used (0 to about 25min).