海人草有効成分ならびに関連化合物の研究 第11報

Abstract

Ethyl isobutyrylisonitrosoacetate (II) was prepared by the isonitrosation of ethyl isobutyrylacetate (I), used by Miyazaki et al. for the preparation of 2-methyl-4-isopropylpyrrole (V), the substance assumed by them as the zinc dust-distillation product of kainic acid. Condensation of (II) and ethyl acetoacetate yielded 2-methyl-4-isopropyl-3, 5-diethoxycarbonylpyrrole (III), C14H21O4N. Hydrolysis of (III) with 10% sodium hydroxide solution or conc. sulfuric acid followed by treatment with 10% potassium hydroxide solution afforded the same crystals (IV), m.p. 134°, in either case, and agreed with 2-methyl-3-carboxy-4-isopropylpyrrole, m.p. 134°, prepared by a different route. It follows, therefore, that in both cases the ester at the α-position was saponified and decarboxylated and this is a different behavior from that of 2-methyl-4-propyl-3, 5-diethoxycarbonylpyrrole (VIII) and Knorr's pyrrole. Decarboxylation of (IV) hereby obtained gave the objective (V), b.p15 84°, C8H13N.