3,4-Dihydroxybenzaldehyde

3,4-Dihydroxybenzaldehyde, also known as protocatechuic aldehyde, is a phenolic aldehyde, a compound released from cork stoppers into wine. It is an isomer of 2,4-dihydroxybenzaldehyde.

This molecule can be used as a precursor in the vanillin synthesis by biotransformation by cell cultures of Capsicum frutescens, a type of Chili pepper. It is also found in the mushroom Phellinus linteus.