Careful hydrolysis of (+/-)-cis- or (+/-)-trans-tetrahydro-2,5-dimetho
xy-2-furaldehyde dimethyl acetal proceeded via 5,5-dimethoxy-4-oxopent
anal to give (+/-)-trans-4-hydroxy-5-methoxy-2-cyclopentenone. and (+/
-)-trans-4,5-dihydroxy-2-cyclopentenone. The latter product did not is
omerize to 2,3-dihydroxy-2-cyclopentenone (reductic acid) on prolonged
reaction.