Structure of Wyosine, the Condensed Tricyclic Nucleoside of Torula Yeast Phenylalanine Transfer Ribonucleic Acid.

Large-scale isolation of the minor nucleoside wyosine of torula yeast tRNAPhe was accomplished by a combination of enzymatic digestion and reversed-phase chromatography: the wyosine-containing nucleotide fraction, which was obtained by partial digestion of unfractionated tRNA (1 g) with nuclease P1, was concentrated by reversed-phase column chromatography followed by complete digestion with nuclease P1/alkaline phosphatase. The nucleoside mixture thus obtained was purified by reversed-phase HPLC, providing wyosine (70 μg). Comparison of this nucleoside with a chemically synthesized authentic sample has unambiguously established that the structure of wyosine is 4,6-dimethyl-3-β-D-ribofuranosyl-3,4-dihydro-9H-imidazo[1,2-a]purin-9-one (2).