摘要:
By Swern oxidation of the hydroxamic acid 3, prepared from the homochiral imidazolidin-2-one 1, the transient C-nitroso derivative 4 is obtained, and its cycloaddition to either cyclohexadiene or cyclopentadiene proceeds with high diastereoselection, owing to the conformational stability of 4. The stereochemical outcome of the reaction is determined from H-1 NMR data and further confirmed by the specific rotation value of 7, obtained by cleavage of the major cycloadduct 5a.