Synthesis of Parvisoflavones A and B

Abstract

Parvisoflavone B (2', 4', 5-trihydroxy-2", 2"-dimethylpyrano[5", 6"-g]isoflavone) (2) was synthesized by regioselective reduction of 7-[2, 4-bis(benzyloxy)phenyl]-2, 3-dihydro-5-methoxy-2, 2-dimethyl-4H, 6H-benzo[1, 2-b : 5, 4-b']dipyrano-4, 6-dione (7) with sodium borohydride and dehydration of the resultant alcohol, followed by dealkylation with boron trichloride. Its angular isomer, parvisoflavone A (2', 4', 5-trihydroxy-2", 2"-dimethylpyrano[6", 5"-h]isoflavone) (1) was also synthesized from 3-[2, 4-bis(benzyloxy)phenyl]-8, 9-dihydro-5-methoxy-8, 8-dimethyl-4H, 10H-benzo[1, 2, -b : 3, 4-b']-dipyran-4, 10-dione (15) in a similar manner.