Abstract The synthesis and conformational analysis of a “bridged” anabasine, 5,8,9,10,11,11a-hexahydro-6H-pyrido[2,1-f][1,6] naphthyridine ( 5), and related compounds are reported. Conformational assignments were made using NMR data (including coupling constants, homonuclear Overhauser effects, and 2D correlations) and the results of molecular mechanics (MM2) calculations. The tricyclic compounds have trans-quinolizidine ring fusion with a chair-shaped piperidine ring. The center ring shows a half-chair conformation for the title compound, and a half-boat shape for its 6-oxo derivative. Calculated vicinal coupling constants are in good agreement with those obtained experimentally.