Methylation of desmethyl analogue of Y nucleosides. Wyosine from guanosine.

Wyosine la, one of the fluorescent hypermodified Y nucleosides found in tRNAsPhe, was synthesized chemically from its biogenetic precursor guanosine 2. The route involved transformation of 2 into the tricyclic structure 3a and subsequent methylation at N-4. The major products of various methylation procedures were isomers of wyosine, methylated at N-5 (3b) or at N-1 (4). Mesoionic compound 4 is a new analogue of 7-methylguanosine 5, modified nucleoside occurring in the unique positions in transfer, messenger and ribosomal RNAs. The chromatographic and spectral characteristics of wyosine and its isomers is given.