Analytical Chemistry and Spectroscopy
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
A complete and unambiguous assignment of the 1H and 13C NMR spectra of peracetylated catechin-(4α-8)-catechin-(4α-8)-catechin procyandin trimer was accomplished by reverse two-dimensional chemical shift correlation methods. An HMBC spectrum showed, for the first time, evidence of the sites of condensation between the interflavan units of a trimer. The 2,3-trans stereochemistry of the C- and F-rings are easily deduced from measurement of 3J coupling constants. The multiplicity analysis of the protons of the i-ring in the terminal unit does not lead to such an assignment. A ROESY experiment is needed to confirm the 2,3-trans relationship. Molecular mechanics calculations explain the unexpected coupling constants of these protons.
Type of Medium: