Table 1.

Structure and enzymatic inhibition activity evaluation of compounds X1–X23.^a

	Structure				Inhibition (%) at 1 μM
Compds.	Formula	R	L	n	CDK4	CDK6	CDK9
Ribociclib	–	–	–	–	101 ± 0	85 ± 1.2	84 ± 0
X1	I	H	S	3	35 ± 0.5	63 ± 1.2	76 ± 0
X2	I	CH3	S	3	29 ± 2.1	17 ± 1.2	80 ± 0
X3	I	OCH3	S	3	8 ± 2.1	5 ± 0.8	33 ± 2.5
X4	I	CF3	S	3	9 ± 1.6	8 ± 3.3	41 ± 0.8
X5	I	CF3	SO	3	91 ± 0.8	48 ± 1.2	97 ± 0.4
X6	I	CF3	SO2	3	35 ± 2.4	14 ± 1.2	75 ± 0.4
X7	I	H	SO	3	99 ± 0	87 ± 1.6	99 ± 0
X8	I	H	S	1	70 ± 2.4	64 ± 0.8	97 ± 0.4
X9	I	H	SO2	1	94 ± 1.6	92 ± 1.2	97 ± 0
X10	I	H	SO2	2	90 ± 0.8	88 ± 0.8	98 ± 0.4
X11	I	H	SO2	3	89 ± 0.4	82 ± 0.8	98 ± 0.4
X12	I	H	SO2	4	83 ± 0	75 ± 0.4	97 ± 0.4
X13	I	H	SO2	5	74 ± 0	68 ± 0.4	96 ± 0.4
X14	II	H	S	1	95 ± 0	86 ± 1.2	97 ± 0.4
X15	II	H	S	2	83 ± 0.8	76 ± 0.8	96 ± 0
X16	II	H	S	3	71 ± 0.8	73 ± 0	94 ± 0.4
X17	II	H	S	4	61 ± 2.1	52 ± 0.4	94 ± 1.6
X18	II	H	S	5	82 ± 1.2	52 ± 0.8	95 ± 0.4
X19	II	H	SO2	1	98 ± 0	94 ± 0.8	98 ± 0.4
X20	II	H	SO2	2	99 ± 0.4	94 ± 0.4	98 ± 0.4
X21	II	H	SO2	3	98 ± 0.4	93 ± 0	98 ± 0
X22	II	H	SO2	4	97 ± 0.4	91 ± 0	98 ± 0
X23	II	H	SO2	5	95 ± 0.5	77 ± 1.6	97 ± 0

^aInhibition activities were determined using the KinaseProfiler of Eurofins. The data represent the mean values of two independent experiments.