The N-benzoyl derivatives of 2-oxa-5-azabicyclo[2.2.1]heptane (7) and of 2-oxa-5-azabicyclo [2.2.1]heptane-3-one (8) have been prepared from hydroxy-L-proline. The NMR spectra of these compounds have been analyzed with the aid of variable temperature studies. It was found that ΔG‡ for NCO rotation in 7 is ≈ 2 Kcal/mole higher than for 8. Possible explanations for the difference in ΔG‡ are discussed.
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