ine (1), a histoneacetyltransferaseinhibitor previously identified by our research group and active at the sub‐millimolar/millimolar level, led to compounds bearing higher alkyl groups at the C2‐quinoline or additional side chains at the C6‐quinoline positions. Such compounds displayed at least threefold improved inhibitory potency toward p300 protein lysine acetyltransferaseactivity; some of them