Table 2. SAR of the Stereoisomers of 2 and Simplified Analogs^a.

						enzyme assay (kinact/KI × 10–3/s–1 μM–1)			NanoBRET (EC50, μM)
compound	5a	R6	R6′	R7	R7′	CDK2	CDK1	CDK7	CDK2	CDK1	CDK7
1 (5aS,6S,7R)	(S)	Me	OMe	H	OH	0.92	0.018	0.18	0.90	2.89	5.36
2 (5aS,6S,7S)	(S)	Me	OMe	OH	H	23	1.1	9	0.14	0.61	0.30
24 (5aR,6R,7S)	(R)	OMe	Me	OH	H	rev (70 μM)	rev (>100 μM)	rev	>33	>33	>33
27 (5aS,6R,7S)	(S)	OMe	Me	OH	H	1.1	0.11	0.08	0.33	1.6	4.0
28 (5aS,6R,7R)	(S)	OMe	Me	H	OH	0.16	0.012	0.007	3.0	8.0	11.6
29 (5aR,6S,7R)	(R)	Me	OMe	H	OH	rev (9 μM)	rev (19 μM)	rev	22	>33	>33
38	(S)	H	H	H	H	0.0002			26.6
39	(S)	H	Me	H	OH	0.14		0.01	1.62	16.35	30.2
40	(S)	H	Me	OH	H	0.10	0.0057	0.01	0.87	35	55.5

^aStereochemistry indicated for stereoisomers of 2. Rev = Reversible. Enzyme and NanoBRET activity assays were assessed on the active CDK/cyclin holoenzyme as follows: CDK2/cyclin E1, CDK1/cyclin B1, CDK7/cyclin H/MAT1. Mean values calculated from at least two independent replicates for enzyme assays and NanoBRET; exception: NanoBRET compounds 24 and 38 were run n = 1 and inactive.