Planta Med 2010; 76 - TC_3
DOI: 10.1055/s-0030-1264183

A novel approach towards the syntheses of proanthocyanidins and biflavonoids

J van der Westhuizen 1, T Mosoabisane 1
  • 1University of the Free State, Chemistry, Nelson Mandela Avenue, 9301 Bloemfontein, South Africa

Oxidative condensation of tetra-O-methyl-3-oxocatechin and tetra-O-methylcatechin with silver tetrafluoroborate readily affords procyanidin B-3 analogues with the 3,4-cis diastereomers predominating. The 3-oxo-group deactivates the 8-position and no self condensation or oligomerisation was observed [1]. This condensation suggests the oxidative biosynthesis of proantocianidins from flavan-3-ol precursors [2].

Fig.1: Lewis acid catalysed condensation of tetra-O-methyl-3-oxocatechin and tetra-O-methylcatechin with tin chloride readily affords the first synthetic access to optically active 3-coupled biflavonoids.

Acknowledgements: 1. Mimosa Central Co-Op, 2. THRIP.

References: 1. Achilonu, M. et al. (2008) Org. Lett.10 (17): 3865–3868.

2. Weinges, K. et al. (1968) Annalen 711:184–186.