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
K. Kostova et al., 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, HELV CHIM A, 82(9), 1999, pp. 1385-1399
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.