Table 1. Structures and actual pIC₅₀ (CDK4) and log[IC₅₀ (CDK2)/IC₅₀ (CDK4)] values of thieno[2,3-d]pyrim-idin-4-yl hydrazone analogues.

Compound	R1	R2	R3	R4	Actual
					pIC50 (CDK4)	log[IC50 (CDK2)/IC50 (CDK4)]
1	Et	H	H		5.584	0.166
2	Me	H	H		5.159	−0.048
3	i-Pr	H	H		6.781	0.845
4	t-Bu	H	H		6.421	0.669
5	Me	Et	H		4.276	−0.125
6	i-Pr	H	Me		5.053	0.502
7	Et	H	H	t-Bu	4.775	−0.064
8	Et	H	H		4.886	0.108
9	i-Pr	H	H		5.528	0.547
10	i-Pr	H	H		5.732	0.105
11	i-Pr	H	H		6.093	0.138
12	i-Pr	H	H	Phenyl	5.799	0.272
13	i-Pr	H	H		5.871	0.149
14	t-Bu	H	H		5.539	0.493
15	t-Bu	H	H		5.794	0.0492
16	t-Bu	H	H		5.567	1.135
17	t-Bu	H	H		5.796	1.123
18	t-Bu	H	H		5.762	0.785
19	t-Bu	H	H		6.152	1.453
20	t-Bu	H	H		6.818	1.398
21	t-Bu	H	H		6.382	1.51
22	t-Bu	H	H		5.989	0.778
23	t-Bu	H	H		5.558	−0.4
24	t-Bu	H	H		5.929	−0.187
25	t-Bu	H	H		7.15	1.626
26	t-Bu	H	H		6.678	0.892
27	t-Bu	H	H		7.152	1.015
28	t-Bu	H	H		7.209	1.882
29	t-Bu	H	H		6.969	1.253
30	t-Bu	H	H		6.627	0.797
31	t-Bu	H	H		6.58	1.018
32	t-Bu	H	H		6.691	1.574
33	t-Bu	H	H		7.032	0.724
34	t-Bu	H	H		6.984	1.226
35	t-Bu	H	H		6.888	0.688
36	t-Bu	H	H		5.552	0.398
37	t-Bu	H	H		6.785	0.041
38	t-Bu	H	H		7.026	1.46
39	t-Bu	H	H		6.934	0.919
40	t-Bu	H	H		6.939	1.513
41	t-Bu	H	H		6.586	0.623
42	t-Bu	H	H		7.279	1.64
43	t-Bu	H	H		6.812	1.382
44	t-Bu	H	H		7.006	1.473
45	t-Bu	H	H		6.708	1.137
46	t-Bu	H	H		6.743	1.41
47	t-Bu	H	H		7.457	2.084
48	t-Bu	H	H		7.157	0.903
49	i-Pr	H	H		6.777	1.413
50		H	H		6.902	1.493
51		H	H		7.095	1.182
52		H	H		7.097	1.67
53		H	H		7.287	1.607
54		H	H		7.232	1.602
55		H	H		6.737	1.417
56		H	H		6.421	1.111
57		H	H	e4r	6.904	1.167