1957 年 77 巻 6 号 p. 575-579
Diethyl 1, 2-diethoxycarbonyl-4-isopropyl-3-pyrrolidinemalonate (XIII) was derived from diethyl 3-acetoxy-4-isopropyl-1, 2-pyrrolidinedicarboxylate and the important question in this reaction is the effect of steric relationship of the acetoxyl and isopropyl groups on the steric configuration of the diethoxycarbonylmethyl group introduced against the isopropyl group present. Therefore, reduction of diethyl 3-oxo-4-isopropyl-1, 2-pyrrolidinedicarboxylate (V) was carried out under various conditions and reduction products were examined. It was thereby found that the steric configuration of the hydroxyl and isopropyl groups was different in the hydroxy compound (IX-i) obtained by reduction with platinum or Raney nickel catalyst and that (IX-ii) obtained by reduction with sodium borohydride. The hydroxy compounds were derived respectively to the acetoxy compounds, (X-i) from (IX-i) and (X-ii) from (IX-ii), proving that the steric configuration of the acetoxyl radical differs in (X-i) and (X-ii). Moreover, substitution of the acetoxyl radical in (X-i) and (X-ii) with diethoxycarbonylmethyl group afforded the same (XIII) whose hydrolysis to 2-carboxy-4-isopropyl-3-pyrrolidineacetic acid (XV) and its optical resolution yielded L-α-dihydroallokainic acid (XVI-i). It was thereby found that (XIII), with sterically stable trans configuration, forms in this reaction irrespective of the configuration of the acetoxyl group to the isopropyl group. This has confirmed the appropriateness of the proposed structure for L-α-dihydroallokainic acid obtained by the reduction of natural L-α-allokainic acid.