Preparation of Chiral Hydroxy Carbonyl Compounds and Diols by Ozonolysis of Olefinic Isoborneol and Fenchol Derivatives: Characterization of Stable Ozonides by1H-,13C-, and17O-NMR and Electrospray Ionization Mass Spectrometry

Abstract

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, respectively (Scheme 1). In the case of the diols 19 and 24, the formation of new chiral centers proceeded with high diastereoselectivity. These diols were prepared highly diastereoselectively also by LiAlH4 reduction of the hydroxy carbonyl compounds 11 and 16a, respectively (Scheme 2). The absolute configuration 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 relatively stable hydroxy‐substituted 1,2,4‐trioxolane derivatives (ozonides) 37 – 40 (Scheme 5) which were characterized by 1H‐ and 13C‐NMR spectra, ESI‐MS, and natural‐abundance 17O‐NMR spectra.

Synthesis of a Carbon Analogue of N-Acetylmannosamine via Acetolysis on a Relatively Stable Ozonide

“…Surprisingly, a 1.5:1 mixture of the diastereomeric ozonides 12 was obtained after flash column chromatography, which may be due in part to the low reactivity of dimethyl sulfide. 17 Each of these two compounds exhibited 13 C NMR signals at ∼108 and ∼94 ppm, values that are consistent with literature values of similar ozonides. 16 While no effort was taken to separate the two isomers, formation of diastereomers was reasonable given the chiral environment imposed by the carbohydrate motif.…”

“…Sugar 11 was treated with ozone and then with dimethyl sulfide for 6 h at room temperature. Surprisingly, a 1.5:1 mixture of the diastereomeric ozonides 12 was obtained after flash column chromatography, which may be due in part to the low reactivity of dimethyl sulfide . Each of these two compounds exhibited 13 C NMR signals at ∼108 and ∼94 ppm, values that are consistent with literature values of similar ozonides …”

Oxygen-17 NMR spectroscopy: Basic principles and applications (Part I)

“…and ring stress in bicyclic ozonides result in deshielding of the AO-O-nuclei and, to larger extent, of the -O-nuclei.Dimitrov, Hesse and co-workers[519] investigated ozonization of a series of allylic and homoallylic alcohols prepared from (+)-camphor and (À)-fenchone. They were able to isolate a number of ozonides and to obtain the 17 O NMR spectrum, at natural isotopic abundance, of the diastereomeric mixture of the derivative shown in Scheme 29 (the 17 O NMR chemical shifts(d, ppm) are also indicated).…”

“…It was not possible to differentiate between the two diastereoisomers because of the large line-widths of the signals. Nevertheless, the relatively deshielded d( 17 O) values of the peroxide oxygen atoms were interpreted with the hypothesis of a relatively small C-O-O-C dihedral angle in the trioxolane ring[519].…”

An Efficient Synthesis of Five-membered Cyclic Ethers from 1,3-Diols Using Molecular Iodine as a Catalyst

“…A total of 410 mg (2.28 mmol; 91% yield) of 5,6,6-trimethyl-4-oxatricyclo[5.2.1.0 1,5 ]decane ( ) was obtained. The spectroscopic data of the product agreed with those of 24) . …”