(6S)-5-Formyl-5,6,7,8-tetrahydropteroic acid is the chiral derivative of 5-Formyl-5,6,7,8-tetrahydropteroic acid (F700980). 5-Formyl-5,6,7,8-tetrahydropteroic acid along with its glutamate esters can be used as a subtrate for binding to methyenyltetrahydrofolate synthetase.