Reumycin

The transformation sequence of reumycin in aqueous (D2O) solutions with various pD was studied by NMR spectroscopy and the structures of the yielding products were determined. It was shown that formation of 6-(3-methylureido)-1,2,4-triazine-5-carboxylic acid was the first stage of reumycin alkaline hydrolysis. The subsequent cyclization of this compound resulted in obtaining 5-methyl-5H-imidazo [4,5-e]-1,2,4-triazin-6 (7H) one-4a-carboxylic acid in mono-,di- or trianionic form which depended on the medium pH and was due to dissociation of the carboxylic group, N(4)H group of the triazine ring and N(7)H group of the imidazolidinone ring.

Toxoflavin (1), fervenulin (2), and reumycin (3), known to be produced by plant pathogen Burkholderia glumae BGR1, are structurally related 7-azapteridine antibiotics. Previous biosynthetic studies revealed that N-methyltransferase ToxA from B. glumae BGR1 catalyzed the sequential methylation at N6 and N1 in pyrimido[5,4-e]-as-triazine-5,7(6H,8H)-dione (4) to generate 1. However, the N8 methylation of 4 in the biosynthesis of fervenulin remains unclear. To explore the N-methyltransferases required for the biosynthesis of 1 and 2, we identified and characterized the fervenulin and toxoflavin biosynthetic gene clusters in S. hiroshimensis ATCC53615. On the basis of the structures of intermediates accumulated from the four N-methyltransferase gene inactivation mutants and systematic enzymatic methylation reactions, the tailoring steps for the methylation order in the biosynthesis of 1 and 2 were proposed. The N-methylation order and routes for the biosynthesis of fervenulin and toxoflavin in S. hiroshimensis are more complex and represent an obvious departure from those in B. glumae BGR1.

IR and electron spectra of an uracil derivative (antitumor antibiotic reumycin) were studied by low temperature spectroscopy. The experimental data corresponded to the quantum chemistry calculations of electron transmission. On the basis of the spectra interpretation the molecular structure of the reumycin isolated molecules was suggested. pKa of reumycin in aqueous medium was determined by UV spectroscopy.