Raising the HOMO: 2,4‐Dienals can react with nitroalkenes in trienamine‐catalyzed asymmetricDiels–Alderreactions (see scheme). Crucial for the success is raising the HOMO energy of the diene through the introduction of appropriate substituents. The reaction exhibits unusually high enantioselectivity and exo selectivity; endo addition is possibly disfavored because of the electrostatic repulsion shown
The synthesis and structure-stability relationships of a series of novel FK409 derivatives (1, 2, and 3) are described. The rates of decomposition in aqueous solution (pH 8.0, 30 degrees C) were parallel with those of spontaneous NO release measured by ESR spectroscopy using carboxy-PTIO. The compounds can cover a wide range of NO releasing rates by appropriate modification of the molecule.