Dimethyl kainate (II) and dimethyl dihydrokainate (V) were each submitted to reduction with lithium aluminum hydride and derived respectively to kaininediol (III) and dihydrokaininediol (VI). From the analyses of the infrared curves of (III) and (VI) and of kainic acid (I) and dihydrokainic acid (IV) with fluorinated paraffine as the solvent, the double bond in (I) was attributable to the isopropenyl group. Oxidation of N-acetylkainic acid (VII) with potassium permanganate yielded formic acid as the volatile matter, and saponification of the non-volatile portion afforded C9H13O5N (IX), m.p. 205° (decomp.). Ozonization of (VII) yielded formaldehyde (identified as the dimedone) and C11H15ON (VIII), m.p. 185°, whose saponification gave a product (IX), identical with that obtained with formaldehyde by the ozonization of (I). (IX), m.p. 205° (decomp.), forms a polymorphic crystals of m. p. over 280°. It gives yellow coloration by the ninhydrin reaction, does not discolor bromine, gives a positive iodoform reaction, and shows single ketone absorption in the ultraviolet region. It absorbs 1 mole of hydrogen on catalytic reduction and forms a semicarbazone (X), m.p. 235-236° (decomp.), C10H16O5N4. From the foregoing results, it was concluded that (I) and (VII) possessed an isopropenyl side chain and formed (IX) and (VIII) possessing the methyl ketone group, together with formic acid or formaldehyde, by the oxidation. It follows, therefore, that (I) is 2-carboxy-4-isopropenylpyrrolidine, with -CH2-COOH group outside the ring.
