Preparation of chiral hydroxy carbonyl compounds and diols by ozonolysis of olefinic isoborneol and fenchol derivatives: Characterization of stable ozonides by H-1-,C-13-, and O-17-NMR and electrospray ionization mass spectrometry

The allylic and homoallylic alcohols 1-8, prepared from (+)-camphor and (-) -fenchone, were ozonized in Et2O at -78 and treated with Et3N or LiAlH4 to give the chiral hydroxy carbonyl compounds 9-16 and the diols 17-24, respec tively (Scheme I). In the case of the diols 19 and WI the formation of new chiral centers proceeded with high diastereoselectivity. These diols were p repared highly diastereoselectively also by LiAlH4 reduction of the hydroxy carbonyl compounds 11 and 16a, respectively (Scheme 2). The absolute confi guration of the new chiral centers in 19 and 24 was determined by X-ray and NMR methods. The ozonization of compounds 2, 3, 7, and 8 provided the rela tively stable hydroxy-substituted 1,2,4-trioxolane derivatives (ozonides) 3 7-40 (Scheme 5) which were characterized by H-1- and C-13-NMR spectra. ESI- MS, and natural-abundance O-17-NMR spectra.