Configurational analysis of diastereomeric open-chain and cyclic nitro-substituted diols by NMR spectroscopy

✍ Scribed by P. Sohár; Gy. Mikite; I. Pelczer; Á. Kovács; A. Kis-Tamás

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: English
• Weight: 625 KB
• Volume: 22
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270221109

✦ Synopsis

Nitro-substituted 1,3-dioxanes and pyrans with potential biological activity were synthesized. The relative configurations of the threo and erythro isomers of 2-nitro-l-phenylpropane-1,3-diol (the starting materials) and of 5-nitro-2,4-diphenyl-1,3-dioxane, the products formed with benzaldehyde, were determined by 'H and =C NMR spectroscopy. Ciamaldehyde and nitroethanol give a homologue of nitrophenylpropanediol, which exists as a mixture of two diastereomeric cyclic hemiacetals. After dissolving in CDCI,, the ratio of these components changes &om approximately 10 : 1 to 3 : 2 in a few days. The ethyl acetal of the hemiacetal is stereohomogeneous, and the ethoxy group is axial to the pyran ring owing to the anomeric effect. This configuration was proved by two-dimensional NMR measurement, permitting separate observation of the originally overlapping mnltiplets and direct reading of the H,H coupling constants.