Tetrahedron zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Vol. 48, No. 10. pp. 1743-1803.1992 Printed in Chat Britain 0040-4020192 $3.OO+.M) l’crgamm press plc TETRAHEDRON REPORT NUMBER 308 DIVERSlTY OF STRUCTURE AND FUNCTION IN OLIGOMERIC FLAVANOIDS Daneel Ferreira’, Jan P, Steynberg, David C. Roux, and E. Vincent Brandt. Department of Chemistry, University of the Orange Free State, P.O. Box 339, Bloemfontein, 9300 South Africa (Received 10 August 1991) Contents 1. Introduction 2. Synthesis of Oligo~av~oi~ 2.1. Selection of precursors to synthetic oligoflavanoids 2.2. FIavan-JP-dials as incipient electrophiles 2.3. Nucleophilic flavanoids 2.4. Bonding positions at nucleophilic centres 2.5. Conditions for C-C in~~av~oid bonding, stereochemical course of condensation, and methods for determining the absolute configuration at C-4 3. Biomimetic Synthesis of the Different Classes of Oligoflavanoids 3.1. Procyanidins 3.2. ~~~tini~ns and pro~binetinidins 3.3. ~ogui~~ni~ns 3.4. Proteracacidins and promelacacidins 3.5, A-Type proanthocyanidins 4. Flavan-3-01 Oligomers via Phenol Oxidative Coupling 5. Mis~~ilaneous OIigo~avanoids and Techniques for StructuraI Elu~i~tion 6. Conformation of Oligoflavanoids 7. Phlobatannins via Base-catalyzed Conversions of Oligoflavanoids 7.1. Introduction 7.2. Base-catalyzed rearrangement of profisetinidin-type oligoflavanoids 7.2.1 Fi~tinidoI-(i)-cat~hin bi~avanoi~ 7.2.2 (-)-Fisetinidoi-(-)-epicatechins 7.2.3 Bis-fisetinidols 7.2.4 Bis-(-)-fisetinidol-(+)-catechin triflavanoids 7.2.5 Proguibourtinidin bi-and tritlavanoids 7.2.6 Base-catalyzed ~~nge~nt of p~yanidins 7.2.7 Conclusion 1744 1744 1744 1746 1748 1750 1753 1756 1756 1760 1765 1766 1768 1770 1772 1772 1776 1776 1777 1777 1784 1784 1787 1789 1791 1793 1743