Chiroptical properties of n-nitrosopyrrolidines and n-nitrosamino acids : Implications for the nitrosamine sector rule

CD data for a variety of N-nitrosamino acids and N-nitrosopyrrolidines are presented. The effects of nitrosamino group conformation, pyrrolidine ring geometry, different perturbing substituents, and especially intramolecular H-bonding upon the n → π^* CD band are discussed. Stereochemical conclusions can be made with confidence in many cases, although no sector diagram, as yet published, successfully correlates all the available chiroptical data in this series of compounds. However, a negative CD band due to the π → π* transition was observed tor all N-nitrosamines having the L-proline configuration at C-2, regardless of nitroso group conformation; it is suggested that this band be used whenever possible for stereochemical correlations.