On the basis of 1,2,3-triols la∼d, 1,2,3,4-tetraols 2a∼h, and 1,2,3,4,5-pentaols 3a∼p, NMR databases with four types of profile-descriptors (13C-, 1H-, and 1H(OH)-chemical shifts and vicinal spincoupling constants) for contiguous polyols are reported. To systematically assess the relative values of these databases, a case study has been conducted on heptaols 4a∼d, through which the γ- and δ- effects have been recognized to refine the 13C and 1H chemical shift profile predicted via an application of the concept of self-contained nature. The magnitudes of γ- and δ- effects depend on a specific stereochemical arrangement of the functional groups present in both the inside and outside of a self-contained box and are significant only for the stereoisomers belonging to a specific sub-group. With the exception of the stereochemical arrangement of functional groups belonging to a specific sub-group, the γ- and δ- effects can, at the first order of approximation, be ignored for the stereochemical analysis of unknown compounds. For the stereoisomers belonging to a specific sub-group, it is necessary to refine, with incorporation of the γ- and δ- effects, the profile predicted at the first order of approximation. With use of heptaols 4a∼d, the values of 3JH, H profiles have been assessed. Two methods, one using profiles consisting of three contiguous 3JH,H constants and the other using profiles consisting of two contiguous 3J H,H constants, have been developed. A stereochemical analysis based on three, or two, contiguous 3JH, H profiles is operationally simplerthan one based on 13C and 1H chemical shift profiles. Therefore, it is recommended to use a 3JH,H profile as the primary device to predict the stereochemistry of unknown polyols and 13C and 1H chemical shift profiles as the secondary devices to confirm the predicted stereochemistry.
ASJC Scopus subject areas
- 化学 (全般)