Catalyzes the conversion of cyclic dehypoxanthine futalosine (cyclic DHFL) into 1,4-dihydroxy-6-naphthoate, a step in the biosynthesis of menaquinone (MK, vitamin K2). Quinol/quinone metabolism; menaquinone biosynthesis. The tartarate seen in the active site in the crystallographic structure may partially mimic the substrate; it is suspected that the tartarate may resemble the open-chain form of the ribose part of the substrate, cyclic dehypoxanthine futalosine. Belongs to the MqnA/MqnD family. MqnD subfamily.