Synthesis of condensed tannins. Part 13. The first 2,3-trans-3,4-cis-procyanidins: sequence of units in a “trimer” of mixed stereochemistry. - Delcour,J.A.; Serneels,E.J.; Ferreira,D.; Roux,D.G. (J Chem Soc [Perkin I], 1985)