Abstract
The resorcinolic macrolide (RM) family comprises over 50 natural products with diverse biological activities, including the potent natural Hsp90 inhibitor radicicol. Here, we report a modular and enantioselective synthetic strategy featuring a biomimetic macrocyclization-aromatization cascade that enables rapid access to natural and unnatural RMs. Using this route, we generated a small panel of minimal RMs, introducing covalent warheads, double bonds for macrocycle rigidification, and modifications at the C15 position, a position that has not been modified before. We also synthesized macrocyclic peptide-RM hybrids, offering a platform for rapid diversification. We evaluated all analogs for inhibitory activity against Hsp90α and Hsp90β and for disruption of the KRas(G12C)-CRAF protein-protein interaction (PPI). We found that introduction of polar groups at C15 improved Hsp90 activity relative to the representative RM de-O-methyllasiodiplodin, dependent on stereochemistry, whereas introduction of larger groups at C15 or introduction of a trans double bond into the macrocycle reduced activity. Two analogs with poor Hsp90 inhibitory activity exhibited dose-dependent inhibition of the KRas(G12C)-CRAF PPI. This work demonstrates that strategic modifications of a minimal RM scaffold through modular chemical insight can provide foundational structure-activity relationships for the class.