10.1021/jo00331a016
The study presents a chemical method for converting folic acid to pteroic acid, a valuable intermediate for synthesizing folic acid analogues and derivatives. The process involves treating folic acid with acetic anhydride to form a mixture of acetylated azlactones, which are then cleaved with mild base to yield mainly acetylated pteroic acids. Further treatment with hot base removes the acetyl groups, resulting in pteroic acid with a yield of 55-60% contaminated with folic acid. The study also discusses various side reactions and byproducts, including the formation of a pyrazine derivative from the hydrolysis of the glutamic acid moiety and the opening of the pyrimidine ring. The authors detail the experimental procedures, including HPLC analysis, UV absorption spectra, mass spectrometry, and proton NMR spectra, and provide a method for separating folic and pteroic acids using column chromatography. The research was supported by a grant from the National Cancer Institute, National Institutes of Health.