STRUCTURAL STUDY OF ETHYL 3-METHYL-9-OXO-3-AZABICYCLO[3.3.1]NONANE-1-CARBOXYLATE BY 2-DIMENSIONAL NMR-SPECTROSCOPY

Ethyl 3-methyl-9-oxo-3-azabicyclo[3.3.1]nonane has been studied by 1(H), C-13 and 2D NMR spectroscopy in order to establish its conformational behaviour. The combined use of COSY and H-1-C-13 correlation spectra helped in the unambiguous and complete assignment of the bicyclic carbon and proton resonances, It is found that the piperidone ring displays a slightly fattened chair conformation with the N-methyl group in the equatorial position, while a twist-chair form seems to be favoured for the cyclohexanone one. Two preferred orientations migth be proposed for the ethoxycarbonyl moiety.