Synthesis and Circular Dichroism of Optically Pure (±)‐(1 S ,2 S ,5 S )‐5‐Methoxy‐3,4,6,7‐tetramethylidenebicyclo[3.2.1]oct‐2‐yl Derivatives. Baker's Yeast Reduction of 4‐Methoxy‐5,6,7,8‐tetramethylidenebicyclo[2.2.2]octan‐2‐one

Baker's yeast reduction of 4‐methoxy‐5,6,7,8‐tetramethylidenebicyclo[2.2.2]octan‐2‐one ( 11 ) under fermenting conditions afforded (−)‐(1 S ,2 S ,4 R )‐4‐methoxy‐5,6,7,8‐tetramethylidenebicyclo[2.2.2]octan‐2‐ol ((−)‐ 13 ) in 60% yield with an e.e. > 99.5%. Its methanesulfonate (−)‐ 14 was hydrolyzed and rearranged with high stereo‐selectivity into (+)‐(1 S ,2 S ,5 S )‐5‐methoxy‐3,4,6,7‐tetramethylidenebicyclo[3.2.1]octan‐2‐ol ((+)‐ 15 ). The absolute configuration of (−)‐ 13 was deduced from the CD spectrum of its 4‐(dimethylamino)benzoate ((+)‐ 22 ) applying the chiral exciton‐coupling method. The CD spectrum of (+)‐ 15 and of its ( tert ‐butyl)dimethylsilyl ether ((+)‐ 23 ) showed exciton‐split type of Cotton effects attributed to through‐space interactions between the s‐ gauche ‐buta‐diene and s‐ cis ‐butadiene chromophores of these systems.