Abstract
A spiro-type ring was found to be attached to the 3-position of the oxindole ring in uncarine-A and -B from the fact that lithium aluminum hydride reduction of these compounds afforded indoline derivatives and that the application of methyl iodide in the presence of sodium methoxide afforded 1-methyluncarine-A and 1-methyluncarine-B methiodide. Examination was made as to which carbon in the uncarine molecule this spiro bonding existed and the possibilities of the formulae (XIV) and (XV) were considered. However, measuremnt of pK revealed that Nb and the carbonyl in the oxindole were in very close proximity in the uncarine-A molecule. Relationship between uncarine-A and -B would be well explainable by assuming 4-epimeric structures and conformational formulae (XXI) for uncarine-A and (XXII) for uncarine-B were for warded.
