series of novel indolin-2-ones inhibitors against p90ribosomalS6proteinkinase2 (RSK2) were designed and synthesized and their structure–activity relationship (SAR) was studied. The most potent inhibitor, compound 3s, exhibited potent inhibition against RSK2 with an IC50 value of 0.5 μM and presented a satisfactory selectivity against 23 kinases. The interactions of these inhibitors with RSK2 were