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.
Keywords: Azabicyclo[3.3.1]nonane, carboxylic acid, Mannich reaction, NOESY, ring conformation.
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