SYNTHESIS AND CIRCULAR-DICHROISM OF OPTICALLY PURE (+/-)-(1S,2S,5S)-5-METHOXY-3,4,6,7-TETRAMETHYLIDENEBICYCLO[3.2.1]OCT-2-YL DERIVATIVES - BAKERS-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 (−)‐(1S,2S,4R)‐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 (+)‐(1S,2S,5S)‐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. Copyright © 1990 Verlag GmbH & Co. KGaA, Weinheim