p300 and CBP are important histone acetyltransferases (HATs) that regulate gene expression and may be anti-cancer drug targets. Based on a previous lead compound, Lys-CoA, we have used solid phase synthesis to generate a series of 11 new analogues and evaluated these compounds as HAT inhibitors. Increased spacing between the CoA moiety and the lysyl moiety generally decreases inhibitory potency. We have found two substituted derivatives that show about 4-fold increased potency compared to the parent compound Lys-CoA. These structure-activity studies allow for a greater understanding of the optimal requirements for potent inhibition of HAT enzymes and pave the way for a novel class of anti-cancer therapeutics.