DETECTION OF CONNECTIVITY BETWEEN EQUIVALENT CARBONS IN A C2 MOLECULE USING ISOTOPOMERIC ASYMMETRY - IDENTIFICATION OF HOPEAPHENOL IN CAREX-PUMILA

In the structure determination of the C2 symmetrical tetrastilbene hopeaphenol, isolated from Carex pumila, the elucidation of the C-C connectivity between equivalent carbons was needed. From an isotopomeric point of view, three isotopomers, C-12-C-12, C-12-C-13 and C-13-C-13, are present with respect to the equivalent carbons connecting each other. Among them, the C-12-C-12 Species is undetectable and the C-13-C-13 Species is excluded owing to its low natural abundance. Therefore, only the C-12-C-13 isotopomer is detected in C-13 NMR and this species is not symmetrical. In the H-C-12-C-13-H system, the separate detection of 1J(CH) and 2J(CH) was achieved by the INEPT-LSPD, COLOC and HMBC methods to demonstrate the connectivity between the equivalent carbons from the viewpoint of isotopomeric asymmetry.