Procyanidin C2 is found in grape seeds (Vitis vinifera)[1][2] and wine,[3] in barley (Hordeum vulgare),[4] malt[5] and beer,[6] in Betula spp., in Pinus radiata, in Potentilla viscosa, in Salix caprea or in Cryptomeria japonica.

[7][8][9] The contents in barley grain of trimeric proanthocyanidins, including procyanidin C2, range from 53 to 151 μg catechin equivalents/g.

[11] Experiments showed that both procyanidin C2 and Pycnogenol (French maritime pine bark extract) increase TNF-α secretion in a concentration- and time-dependent manner.

[16] A coupling utilising a C8-boronic acid as a directing group was developed in the synthesis of natural procyanidin B3 (i.e., 3,4-trans-(+)-catechin-4α→8-(+)-catechin dimer).

The key interflavan bond is forged using a Lewis acid-promoted coupling of C4-ether with C8-boronic acid to provide the α-linked dimer with high diastereoselectivity.