2′-Hydroxy-6′-methoxychalcone epoxide reacts in neutral aqueous acetonitrile solution to give a 6: 1 ratio of the α-and β-cyclisation products, erythro-4-methoxyaurone hydrate [erythro-2-(α-hydroxybenzyl)-4-methoxycoumaran-3-one] and trans-3-hydroxy-5- methoxyflavanone: the dominance of α-cyclisation may be associated with a stereoelectronic preference for a conformation favourable for α-but not β-cyclisation when ...