Oxygenated monoterpenes as dipolarophiles for nitrilimine cycloadditions

A variety of naturally-occurring oxygenated monoterpenes, namely (S)-cis-verbenol, (1R)-(-)-myternol, (1S)-(-)-verbenone, (1R)-(-)-myternal, (S)-(-)-perillyl alcohol, and (S)-(-)-perillaldehyde have been submitted to nitrilimine cycloaddition. These processes were fully regio- and stereoselective for four dipolarophiles. In contrast, regioselective but non-stereoselective cycloadditions occurred in the case of two of the monoterpene derivatives. The configurations of the newly-formed stereocentres of the cycloadducts were assigned on the basis of NOE and NOESY experiments.