Cyclic tautomers of tryptamines and tryptophans. V. Formation and reactions of cyclic tautomers of cyclo-L-tryptophanyl-L-proline

Two stereoisomeric cyclic tautomers ($\text{5}$ and $\text{6}$ of cyclo-L-tryptophanyl-L-proline whose stereochemistry was established by x-ray analysis, gave 5- and 6-hydroxytryptophanyl derivatives ($\text{10}$), $\text{11}$, and $\text{19}$) on the hydroxylation with lead tetraacetate in trifluoroacetic acid.