Inhibiting the histone H3–ASF1 (anti‐silencing function 1) protein–protein interaction (PPI) represents a potential approach for treating numerous cancers. As an α‐helix‐mediated PPI, constraining the key histone H3 helix (residues 118–135) is a strategy through which chemical probes might be elaborated to test this hypothesis. In this work, variant H3118–135 peptides bearing pentenylglycine residues at the i and i+4 positions were constrained by olefin metathesis. Biophysical analyses revealed that promotion of a bioactive helical conformation depends on the position at which the constraint is introduced, but that the potency of binding towards ASF1 is unaffected by the constraint and instead that enthalpy–entropy compensation occurs. Histones diss organisation: Inhibiting the histone H3–anti‐silencing function 1 (ASF1) interaction could potentially be used to treat numerous cancers. Biophysical analyses revealed that the binding affinity of hydrocarbon‐constrained histone H3 towards ASF1 protein is unaffected by pre‐organisation; instead enthalpy–entropy compensation occurs.