The Role of the Amino Protecting Group during Parahydrogenation of Protected Dehydroamino Acids

A series of, dehydroamino acids endowed with different protective groups at the amino and carboxylate moieties and with different substittents at the double bond have been reacted with parahydrogen. The observed Para Hydrogen Inchiced-Polarization (PHIP) effects in the H-1 NMRspectra are strongly dependent on the amino protecting group. DFT calculations allowed us to establish a relationship betWeen the structures of the reaction intermediates (whose energies depend on the amido substitution) and the observed PHIP patterns.