SYNTHESIS AND N-15-NMR AND O-17-NMR SPECTRA OF 5-METHYL(N-15(2))[O-2,O-4-O-17(2)]URIDINE (=(N-15(2))[O-2,O-4-O-17(2)]RIBOSYLTHYMINE)

The 5-methyl(N-15(2))[O-2,O-4-O-17(2)]uridine (=(N-15(2))[O-2,O-4-O-17 (2)]ribosylthymine; 15) was synthesized and analyzed by N-15- and O-17 -NMR spectroscopy. (N-15(2))Urea was condensed with 2,3-dibromo-2-meth ylpropanoyl chloride (3) and cyclized to form ((15)N(2)thymine (5). Af ter glycosidation, the O-17 isotopes were introduced in two separate s teps: hydrolytic ring opening of 2,5'-anhydro derivative 9 and hydroly sis of 3-nitro-1H-1,2,4-triazole derivative 12 with labelled water in the presence of a strong base. The N-15- and O-17-NMR spectra (Fig.) o f 15 in phosphate-buffered water serve as references for heteronuclear NMR spectra of labelled RNA fragments.