A new method for the preparation of delta 1-pyrroline 5-carboxylic acid and proline.

Hydroxylysine was oxidized with sodium metaperiodate and the major product characterized as Δ¹-pyrroline 5-carboxylic acid by the visible spectrum of its o-aminobenzaldehyde complex and by its reduction to proline by subsequent treatment with sodium borohydride. The reduction product was positively identified as proline by proton nuclear magnetic resonance spectroscopy and mass spectral analysis. The pH dependence for the preparation of Δ¹-pyrroline 5-carboxylic acid was determined by a study of the yields of proline obtained by variation of the pH values of the oxidative step. These observations support the hypothesis of intramolecular cyclization of α-aminoglutaric γ-semialdehyde as the second step in the reaction mechanism.