Concise, Convergent Syntheses of (±)-Trichostatin A Utilizing a Pd-Catalyzed Ketone Enolate α-Alkenylation Reaction

Two concise, convergent syntheses of (+/-)-trichostatin A (1), a potent histone deacetylase inhibitor, have been accomplished. The key step in both is a Pd-catalyzed alpha-alkenylation reaction between ketone 2 and either dienyl bromide 3 or alkenyl bromide 9 using a modification of cross-coupling conditions described by Negishi and Hartwig. A brief investigation has shown the potential utility of a Ni-catalyzed version of this reaction. The overall synthetic routes are short and amenable to scaleup, providing access to trichostatin A via trichostatic acid as a direct precursor.