Reagent for an improved 2-step introduction of the 1,1-dimethylallyl (DMA) ester protecting group for carboxylic acids. Reaction with the acid in the presence of copper(I) iodide and cesium carbonate in DMF affords the 1,1-dimethylpropargyl ester. Hydrogenation with Pd/barium sulfate/quinoline affords the 1,1-dimethylallyl ester. The DMA group is resistant to nucleophilic attack, but readily cleaved under non-acidic conditions with Pd(0), which is an advantage compared with the tert-butyl ester in solid-phase peptide synthesis: Org. Lett., 7, 1473 (2005).
