海人草有効成分ならびに関連化合物の研究 第36報

Kainic Acidの異性化ならびに異性体に関する研究 (15) Kainic Acidおよびその諸異性体の立体構造 その3

抄録

Treatment of α-kainic acid (α-I) and α-allokainic acid (α-alto-I) with conc. sulfuric acid, under the same conditions, affords a stable α-kainic acid lactone (α-VII) from (α-I) but a labile α-allokainic acid lactone (α-allo-VII) from (α-allo-I), which easily undergoes hydrolysis in aqueous solution to change to α-allohydroxy acid (α-allo-VIII). These results suggest that (α-VII) is a stable cis-lactone compound and (α-alto-VII) the labile trans-lactone compound. It follows, therefore, that the isopropenyl and acetic acid groups in kainic acid and its stereoisomers are cis in α- and β-series, and trans in α-allo- and β-allo-series. Summarizing the results herein obtained and the steric configuration of the α-carbon atom and the relationship between the carboxyl and acetic acid groups as reported in Part XXVI of this series, it seems that these steric structures are more correctly represented by those shown in Fig, 4 and Table I in the present paper, rather than those proposed in Part XXVII.