A method of producing a compound represented by the formula: ##STR1## wherein R.sup.1 stands for hydrogen or an optionally substituted alkyl or acyl group, which comprises reacting a compound represented by the formula: ##STR2## wherein R.sup.1 is of the same meaning as defined above, and R.sup.2 stands for an optionally halolgenated alkyl group or an optionally substituted phenyl group with a compound represented by the formula: ##STR3## in a lower alcohol in the presence of an alkali metal or alkaline earth metal carbonate; the compound (III) being useful as starting compounds for producing thiazolidinedione derivatives having hypoglycemic and hypolipidemic activities.