Herein, we report the synthesis of gold nanoclusters (AuNCs) functionalized by peptide dendron thiolate ligands forming a hydrogen bonding supramolecular reaction field. The prepared AuNCs act as efficient photocatalysts that promote the oxidative cyclization of an amino alcohol to afford the oxazolidine product. Circular dichroism (CD) spectroscopy and1H NMR titration experiments revealed that the dynamic transformation of interdendron hydrogen bonds into intermolecular hydrogen bonds between the ligand and the substrate is the key to accelerating the photocatalytic reaction. This work introduces a concept for tuning the reactivities and selectivities of metal nanocluster catalysts that use supramolecular reaction fields created with dendritic thiolate ligands.