PREPARATION OF OPTICALLY-ACTIVE FLOWERY AND WOODY-LIKE ODORANT KETONES VIA COREY-CHAYKOVSKY OXIRANYLATION - IRONES AND ANALOGS

Alpha-, beta-, and gamma-Irones and analogues have been prepared from optically active ketones (+)-1, (+)-6a,b, and (+)-17, via a Corey-Chay kovsky oxiranylation (Me2S, Me2SO4, Me2SO, NaOH) followed by isomerisa tion (SnCl4 or MgBr2). (+)-Dihydrocyclocitral (19a), obtained from (-) -citronellal, and analogue (+)-19b, were condensed with various ketone s to afford (+)-21a-f, and after hydrogenation (+)-22a-f. A mild oxida tive degradation of aldehydes (+)-trans- and (-)-cis-8a,b to ketones ( -)-16a,b, as well as olfactive evaluations, C-13-NMR assignments, and absolute configurations of the intermediate epoxides, aldehydes, and a lcohols are presented.