CDK INHIBITORS

1 . A compound of formula:

or a pharmaceutically acceptable salt thereof, wherein:

Z is —(CH 2 ) x — wherein x is 1, 2, 3 or 4;

each X is independently CH or N;

each R 1 is independently aryl, alkyl, or cycloalkyl, wherein two R 1 s on adjacent ring atoms or on the same ring atom together with the ring atom(s) to which they are attached optionally form a 3-8-membered cycle;

y is 0, 1, 2, 3 or 4;

R 2 is -(alkylene) m -heterocyclo, -(alkylene) m -heteroaryl, -(alkylene) m -NR 3 R 4 , -(alkylene) m -C(O)—NR 3 R 4 ; -(alkylene) m -C(O)—O-alkyl; -(alkylene) m -O—R 5 , -(alkylene) m -S(O) n —R 5 , or -(alkylene) m -S(O) n —NR 3 R 4 any of which may be optionally independently substituted with one or more R x groups as allowed by valance,

m is 0 or 1;

n is 1 or 2;

R 3 and R 4 at each occurrence are independently:

(i) hydrogen or

(ii) alkyl, cycloalkyl, heterocyclo, aryl, heteroaryl, cycloalkylalkyl, heterocycloalkyl, arylalkyl, or heteroarylalkyl, or R 3 and R 4 together with the nitrogen atom to which they are attached may combine to form a heterocyclo ring;

R 5 is:

(i) hydrogen or

(ii) alkyl, alkenyl, alkynyl, cycloalkyl, heterocyclo, aryl, heteroaryl, cycloalkylalkyl, heterocycloalkyl, arylalkyl, or heteroarylalkyl;

R x at each occurrence is independently, halo, cyano, nitro, alkyl, haloalkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocyclo, aryl, heteroaryl, arylalkyl, heteroarylalkyl, cycloalkylalkyl, or heterocycloalkyl; and

R 6 is a lower alkyl or absent.

2 . The compound of claim 1 having formula:

3 . The compound of claim 1 having formula:

4 . The compound of claim 1 having formula:

5 . The compound of claim 1 having formula:

6 . The compound of claim 1 having formula:

7 . The compound of claim 1 having formula:

8 . The compound of claim 1 having formula:

9 . The compound of claim 1 having formula:

10 . The compound of claim 1 having formula:

11 . The compound of claim 1 having formula:

12 . The compound of claim 1 , wherein x is 1 or 2.

13 . The compound of claim 1 , wherein y is 0, 1, or 2.

14 . The compound of claim 1 , wherein R 2 is -(alkylene) m -heterocyclo, -(alkylene) m -NR 3 R 4 , -(alkylene) m -C(O)—NR 3 R 4 ; -(alkylene) m -C(O)—O-alkyl, or -(alkylene) m -O—R 5 .

15 . The compound of claim 1 , wherein R 2 is -(alkylene) m -heterocyclo or -(alkylene) m -heteroaryl.

16 . The compound of claim 1 , wherein R 2 is -(alkylene) m -heterocyclo.

17 . The compound of claim 16 , wherein m is 0.

18 . The compound of claim 1 , wherein R 2 is substituted with one R x group.

19 . The compound of claim 1 , wherein R x is selected from alkyl, cycloalkyl, and heterocycle.

20 . The compound of claim 1 , wherein R 6 is absent.