Table 2. 15N Chemical Shifts (δ) of Compounds 3 and 4 in D2O and 5 in 4:1 (v/v) DMSO-d6/D2O as a Function of pDa.
| pD 1 |
pD 4 |
|||||||
|---|---|---|---|---|---|---|---|---|
| compound | Nγ | Nα | Nβ | NO2 | Nγ | Nα | Nβ | NO2 |
| 3b | 120 | 402 | 238 | 75 | 481 | 454 | ||
| 4 | 128 | 410 | 254 | 370 | 76 | 449 | 497 | 370 |
| 5 | 67(65) | d | (489) | 370 | 65 | d | d | 369 |
| methyl yellowb,c | 86(78) | 450(463) | 369(398) | 59 | 499 | 472 | ||
a
15N NMR δ were determined by 1H–15N correlations in gHMBC spectra.
b
The nitro substituent is absent.
c
1H–15N gHMBC spectra recorded in DMSO-d6.
d
Not observed. Values in parentheses measured in the presence of Cr3+ relaxant.