Oenothein B, a dimeric, hydrolysable tannin with macrocyclic structure, and accompanying tannins from Oenothera erythrosepala

A new dimeric, hydrolysable tannin which we have named oenothein B (1), and eight accompanying compounds, including oenothein C (2), were isolated from the leaves of Oenothera erythrosepala. The macrocyclic structure of compound (1) was established from chemical and spectroscopic data. The previously assigned structure of compound (2) was also confirmed by two-dimensional NMR spectroscopy.