Synthesis of optically active polycyclic compounds by Diels-Alder reactions of (+)-nopadiene

4-Oxo-2-cyclopentenylacetate 1 underwent a tandem Diels-Alder reaction with (+)-nopadiene 3 to lead to C-2-symmetric optically active polycyclic ketone 4. All attempts to carry out similar processes with acetoxy ketone 1 and two different dienes, that is, (+)-nopadiene 3 and isoprene 6 or 2,3-dimethyl-1,3-butadiene 7 were unsuccessful. Enantiomerically pure polycyclic ketones 8 and 9 were prepared by Diels-Alder cycloaddition between optically active alpha,beta-unsaturated ketone 5 and dienes 6 and 7. (C) 2004 Elsevier Ltd. All rights reserved.