Acid-catalysed hydrolysis of 2,2-dimethoxy-3,4-dihydropyrans ( ) yields mixtures of δ-keto esters ( ) and 3,4-dihydro-α-pyrones ( ). The amount of increases with increasing alkyl substitution in the 3-, 5- and 6-position of and when the hydrolysis is carried out in a two-phases system ...