Table 1.

Comparison of hydroxamate and carboxylate MAP/ERK kinase inhibitors in a cell-free kinase cascade assay.^[15]

Compd	X	R	IC50 [nm]
1	OH	H	15
2	OH	F	5.8
3	NHOH	H	7.9
4	NHOCH2cPr	F	7.0