駆虫薬の研究 (第6報)

Ethyl Pyrrole-2-carboxylate誘導体の接触還元

抄録

Ethyl pyrrole-2-carboxylate derivatives, 3-ethoxycarbonylmethyl-4-acetyl-5-methyl (Ia), 3-ethoxycarbonylmethyl-4-ethyl-5-methyl (Ib), 3, 5-dimethyl-4-acetyl (Ic), 3, 4-dimethyl (Id), 3, 5-dimethyl (Ie), and 3-ethoxycarbonylmethyl-4-ethyl-5-bromo (If) compounds were derived to N-ethoxycarbonyl compounds and submitted to catalytic reduction with platinum catalyst, at ordinary temperature and pressure. (Ia, b, c) afforded the corresponding ethyl pyrroline-1, 2-dicarboxylate derivatives (IIIa, b, c) and (Id, e, f) afforded the corresponding ethyl pyrrolidine-1, 2-dicarboxylate derivatives (III′d, e, f). In these cases, the 4-acetyl group is reduced at the same time to 4-ethyl group and 5-bromo group in (If) is liberated. Saponification with hydrobromic acid of (III) and (III′) afforded pyrroline-2-carboxylic acid derivatives (IV) and proline derivatives (IV′). It was concluded that the double bond in pyrroline is not conjugated but is in the 3-position because the imino group in (IVa) gives pK′ value of 10.25 and the infrared absorption of the carboxylic ester group at 2-position is identical with that of the carboxylic acid ester at 2-position of pyrrolidine.