PTERIDINES .106. ISOLATION AND CHARACTERIZATION OF LIMIPTERIN (1-O-(L-ERYTHRO-BIOPTERIN-2'-YL)-BETA-N-ACETYLGLUCOSAMINE) AND ITS 5,6,7,8-TETRAHYDRO DERIVATIVE FROM GREEN SULFUR BACTERIUM CHLOROBIUM-LIMICOLA F THIOSULFATOPHILUM NCIB-8327

A new pteridine compound was isolated from green sulfur photosynthetic bacteria, Chlorobium limicola f. thiosulfatophilum NCIB 8327. The structure of this pterin derivative was established to be 1-O-(L-erythro-5,6,7,8-tetrahydropterin-2'-yl)-beta-N-acetylglucosamine (1) from H-1-NMR and CD spectra as well as from various mass-spectrometric techniques and chemical-cleavage techniques. Upon acid hydrolysis of 1, equimolar amounts of biopterin (2) and N-acetylglucosamine were produced. The structure of the hydrolysis product 2 was confirmed by comparing its NMR, UV, CD, and MS and its chromatographical behavior with those of an authentic specimen. N-Acetylglucosamine was identified by an enzymatic hydrolysis experiment as well as by NMR and thin layer chromatography. Electrospray (ES), fast-atom-bombardment (FAB), and thermospray (TS) mass spectrometry of 1 yielded an MH(+) at m/z 441. Periodate-oxidation experiments of the intact molecule 1 and of its hydrolysis product 2 are consistent with the proposed structure. Differential I-2 oxidation experiments with the native compound showed that the in vivo oxidation state of this pterin is its tetrahydro form. We propose the trivial name 'limipterin' for this new compound.