A facile and efficient route to the bicyclo[3.2.1]octane system. Application to the enantioselective approach to cyclopentanoids

Abstract

The reaction of (4R,5R)-1-acetoxy-4-(1,2-epoxy-1-methyl-ethyl)-5-methylcyclohex-1-ene 8 with BF₃·Et₂O provides, in one chemical operation, (1R,4R,5R,7S)-7-acetoxy-4,6-dimethylbicyclo[3.2.1]octan-2-ones 9a,b which are then transformed to (2R,3R)-2-methyl-3-[(R)-1-methyl-3-oxobutyl]-cyclopentanone 16 with the same absolute configuration as that of the steroid D ring.