b-Damascenone (I) and b-damascone (II) were synthesized from the same intermediate, the bisepoxide III, derived from the photooxidn. of allylic b-cyclogeraniol. Protection of the carbonyl group of III with o-nitrophenyl glycol, reduction, photodeprotection and dehydration gave II while I was obtained by means of acid catalytic ring-opening of the epoxy groups of III, protection, reduction and photodeprotection. It was the first time to observe epoxidn. of terminal double bond under photooxidn.

Key words: PHOTOCHEMICAL REACTION, INFRARED SPECTROPHOTOMETRY, PHOTOOXIDATION, NITROBENZENE P, PROTON MAGNETIC RESONANCE SPECTROMETRY, DAMMARAN, KETONE, CYCLOHEXADIENE P, CYCLOHEXENE P, KETENE