Biogenetically patterned enantioselective synthesis

Biogenetically orientated enantioselective syntheses of the bicyclic-ether substructure of Azadirachtin and of the spirocyclohexenone building block f or the Agelorines are communicated. In the first case the kinetic resolutio n of a cyclopentenone starting material is exercised in a high pressure Die ls-Alder cycloaddition and in the second case the cycloadduct of a prochira l spirocyclohexadienone is used for the differentiation of enantiotopic gro ups.