Synthesis and odor of optically active 2-n-hexyl- and 2-n-heptylcyclopentanone and the corresponding δ-lactones

Enantiomeric 2-n-hexyl- and 2-n-heptylcyclopentanones ( 3 ) and ( 4 ) have been synthesized by asymmetric hydrogenation of 2-n-hexylidene and 2-n-heptylidenecyclopentanones ( 1 ) and ( 2 ) with Ru2Cl4[p-tolyl-binap]2NEt3 complexes. The differences in odor qualities between enantiomeric pairs of the ketones 3 and 4 have been found to be small, and the same odor threshold values have been observed between the enantiomeric pairs, although the corresponding δ-undeca- and δ-dodecalactones ( 6 ) and ( 7 ), synthesized by Baeyer–Villiger oxidation of the chiral ketones 3 and 4 , showed a fairly large difference in the threshold values between the enantiomeric pairs.