O6-methylguanosine:m.p. 113-115℃. 1H NMR (D2O), δ=7.87 (s, 1H), 5.7 (d, J=6.03 Hz, 1H), 4.6 (s, 2H), 4.60~4.66 (m, 1H), 4.26~4.28 (M, 1H), 4.10~4.11 (m, 1H), 3.89 (s, 3H), 3.65~3.77 (m, 2H) ppm. ESI-HRMS calcd for [C11H16N5O5+H+] 298.1151, found: 298.1150.
这里面的5.7 (d, J=6.03 Hz, 1H), J是怎么看出来的?是算出来的,还是只能在核磁图中看出来。怎么才能知道J的值?
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