Synthetic Potential Inherent in D-Isoascorbic Acid as a Precursor for Pyridazine and Furo[3,2-c]pyridazine Ring Systems with Two Asymmetric Centers

Reaction of D-erythro-2,3-hexodiulosono-1,4-lactone-2,3-bis(phenylhydrazone) (2) with an iodine, triphenylphosphine and imidazole mixture afforded the furo[3,2-c]pyridazine derivative 11. Condensation of 6-bromo-6-deoxy-D-erythro-2,3-hexodiulosono-1,4-lactone with phenylhydrazine gave the bishydrazones 6, and 8 or the furo[3,2-c]pyridazine (11) depending on the reaction conditions. The lactone ring in 11 could be opened by treatment with alkali to give the pyridazine derivative 9. Lactonization of the later with simultaneous acetylation by acetic anhydride afforded the lactone derivative 14. Alkali treatment of 6 gave the pyrazolindione derivative 13 that gave upon reation with HBr/AcO H the dibromide 15. The assigned structures were based on spectral analysis. The activity of compounds 11 and 14 against hepatitis B virus has been studied.