THE OCTANT RULE. XVI. CONFORMATION AND CIRCULAR DICHROISM OF SYN AND ANTI 2-METHYLBICYCLOHEXAN-3-ONES, THUJONE AND ISOTHUJONE

Article abstract of DOI:10.1016/S0040-4020(01)97203-5

(1S,5S)-exo-2(R)-Methylbicyclo<3.1.0>hexan-3-one (1) and (1S,5S)-endo-2(S)-methylbicyclo<3.1.0>hexan-3-one (2) were synthesized and their circular dichroism (CD) spectra run.Conformational analysis based on molecular mechanics calculations and Karplus equation analyses of vicinal H/H NMR coupling constants indicate boat-like sofa conformations for both 1 and 2, with very little ring distortion from the symmetry of the parent bicyclo<3.1.0>hexan-3-one.The lone dissymmetric ψ-axial and ψ-equatorial methyl groups of 1 and 2, respectively, are both octant consignate.The natural product analogs of 1 and 2, (-)-3-isothujone (3) and (+)-3-thujone (4) were prepared and examined similarly.Their α-methyl perturbers dominate the CD n-?* Cotton effects.