PREPARATION OF OPTICALLY-ACTIVE CYCLOHEXENONES - CHIRONS FOR THE LIPOPHILIC MOIETY OF FLOWERY-LIKE AND WOODY-LIKE ODORANT KETONES

Optically active 2,5,6,6- and 2,4,4,5-tetraalkylcyclohex-2-en-1-ones ((+)-2a-d and (-)-5a-d), important building blocks for flowery- and woody-like odorants, have been prepared. Compounds (+)-2a-d and (-)-5a-d were obtained by ozonolysis of the corresponding cyclopentenic precursors, followed by intramolecular aldol condensation. Alternatively, enones (+)-2a-d were reduced to the corresponding allylic alcohols and converted to enones (-)-5a-d via acidic isomerization and oxidation. C-13-NMR assignments are presented.