According to the papers, acid hydrolysis should yield products like the monomers. I assume the mechanism is the same either in i-propanol/acid or butanol/acid. Is it an oxidative reaction? I can't quite draw the curved arrows correctly nor find the correct one by google. I need to know the exact structures of the hydrolysed products.
Actually it is not an hydrolysis, so it will not work if you try to draw the arrows to add H and OH. Look up Beart, J. E.; Lilley, T. H.; Haslam, E. Polyphenol interactions.2. Covalent binding of procyanidins to proteins during acid-catalysed decomposition, observation on some polymeric proathocyanidins. J. Chem. Soc., Perkin Trans. 2 1985, No. 9, 1439−1443.
The acid cleavage leaves a highly reactive carbocation that may oxidise to an anthocyan (as in the butanol/HCl method) or react with other polyphenols (much studied in wines) or with nucleophilic functions such as various thiols as used in analysis of proanthocyanidins (toluen-alpha-thiol, cysteine...), or with amines (reaction with proteins), ...
The end monomer of the procyanidin however ends up as a simple monomeric flavanol.
Thank you so much Catherine for this paper! A proton was added to the C8 position, and the rest can be worked out.
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