Synthesis and Spectral Study of Some Novel Oxime Esters Derived from 3-azabicyclo[3.3.1]nonan-9-one Oxime

Ten substituted 3-azabicyclo[3.3.1]nonan-9-one oxime ester derivatives 3-12 were synthesized from the starting material 3-azabicyclo[3.3.1]nonan-9-one oxime 2 with activated carboxylic acids in POCl3/pyridine. A wide range of carboxylic acids were used to produce the corresponding oxime esters up to 85% yield. The synthesized compounds were confirmed by FT-IR, NMR (1H, 13C and NOESY) and mass spectrometry. The chemical shift values were assigned unambiguously using one- and two-dimensional NMR spectroscopic data. The nuclear overhauser enhancement study suggests that the compounds exist in twin-chair conformation with equatorial orientation of the bulky substituents. The single crystal structure of compound 4 was determined to elucidate the structure unambiguously.