The intermediate alkoxide is treated with a benzyloxyaicetyl chloride, wherein Bn is a protecting group such as benzyl or asubstituted derivative thereof, to provide an intermediate diester of the formula, ##STR9## wherein Aryl, R and Alk are as hereinbefore defined; (b) Intramolecular Claisen cyclization of the diester of formula IV to the tetronic cid of the formula,##STR10## wherein Aryl, R and