Theoretically, there are at least four ways of forming the C6 C3 —C6 flavonoid skeleton from simple starting materials, but only two have achieved importance for the laboratory synthesis (Geissman, 1962, p. 409): (1) Condensation of a C6C2 unit (2-hydroxyacetophenone) with a C6C! unit (aromatic aldehyde) according to scheme A; and (1i) Acylation of phenols (C6 unit) with a cinnamic acid derivative or its equivalent (C6C3 unit) according to scheme B (Geissman, 1962, p. 409), which also corresponds to the biosynthetic pathway (Fig. 4.1). In addition, many flavonoids can be prepared by modifying existing C1 5 structures by oxidation, reduction, isomerization, partial O- and C-alkylation, dealkylation, selective glycosylation or partial hydrolysis.

Synthesis of Flavonoids

This article provides generalized and systematic overview of data on the synthesis, stereoisomerism, and reactivity of aurones (2-benzylidenebenzofuran-3(2Н)-ones) published between the years 1910 and 2018. Analysis of the literature data shows that the most common precursors for the synthesis of aurones are 2'-hydroxychalcones, benzofuran-3(2Н)-ones, and 1-(2-hydroxyphenyl)-3-phenylprop-2-yn-1-ones. Reactions involving electrophiles, nucleophiles, as well as reduction reactions have been reviewed.

E. Berényi

Papers

Aurones and aurone glucosides—XI: Synthesis of hispidol and its glucosides