Synthesis of 3- and 3,6-Substituted Pyranocoumarins as Starting Structures Towards Compounds Having Neuroprotective Activity

Pyranocoumarins—a mixture of (+)-visnadine and (+)-dihydrosamidine—isolated from the roots of Phlojodicarpus sibiricus were subjected to chemical modification. The reactions of halogenation and selenylation of natural pyranocoumarins were studied, and a mechanism for the observed transformations was proposed. Selective methods for the synthesis of the corresponding 3- and 3,6-halogen- and -organylselanyl-substituted derivatives were developed, and their neuroprotective activity (inhibition of butyrylcholinesterase) was studied. Despite moderate activity, the synthesized 3- and 3,6-substituted pyranocoumarins are promising synthons for further functionalization, aimed at obtaining new neuroprotective drugs based on chemically modified plant material.