Beschreibung:
<jats:title>Abstract</jats:title>
<jats:p> Two isomers of 7-methyl-9-oxo-2,4-diphenyl-3-oxa-7-aza-bicyclo[3.3.1]nonan-1,5-ethyl dicarboxylate (1a and 1b) were obtained by condensation of 2,6-diphenyl-1-oxa-4-oxo-cyclohexan-3,5-ethyl dicarboxylate with methylamine and formaldehyde. Their crystal structures were determined by X-ray diffraction. They crystallize in the triclinic space group P1̄ with (for 1a) a = 12.907(5), b = 11.223(4), c = 8.993(4) Å, α = 105.82(4), β = 100.14(5), γ = 97.35(4)°, and (for 1b) a = 16.400(7), b = 13.062(4), c = 11.336(2) Å, α = 94.19(3), β = 94.74(3), γ = 102.56(4)°. This investigation has shown that isomer 1a has the boat-chair conformation, and isomer 1b has the chair-chair conformation. The formation of la causes a configurational change of the phenyl substituents. The two species are characterized by NMR spectroscopy. - Another comparable bicyclononanone with a bulky substituent at the nitrogen atom has been synthesized and was investigated spectroscopically. This compound should have chair-boat conformation (with the boat conformation in the N-heterocyclic ring) whereas 1a has the boat conformation in the O-heterocyclic ring.</jats:p>