On the other hand, the reaction path leading to 80 is assumed to proceed as follows: first. the hydrazino nitrogen atom of 1 nucleophilically attacks the positive C-2 atom of compound 71 producing the intermediate 76. After sodium acetateinduced deprotonation, the ring opens, thereby forming the intermediate 77, followed by phenolate group elimination to give sultone 78 and subsequent hydrolytic cleavage of cyano acetic acid to 79. Finally, the ring closes, thereby producing the final isotable product 80 (Scheme 29) .