Mikio Honjo: Studies on the Active Components of Digenea simplex AG. and Related Compounds. LXI. The Formation of ct-Allokainic Acid ry-Lactone. ( 2 ). (Research Laboratories, Takeda Pharmaceutical Industries, Ltd.) It has been found that L-a-kainic acid (III), L-L -allokainic acid (VI), L-o-isokainsc acid (V), L-a-kainic acid s-lactone (VII), and L-a-allokainic acid S-lactone (VII) all tran sit to the most stable c~-allokainic acid -y-lactone (IV), m.p. 284°(decomp. ), on heating with

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... ic acid for a long period of time. These reaction routes were clarified and considerations were made on its reaction mechanism based on the new observa tion that S-lactone changes into y-lactone by the action of acid. The same treatment of D-/3-kainic acid (X) or its derivative (XI) with hydrobromic acid was found to form (IV) with retro-kainic inversion10) while heating of (III) with hydrochloric or sulfuric acid failed to form (IV). Heating of (VII) with hydrochloric acid, however, was found to cause transition of a part of it to (V).