Table 2. 1H NMR and 13C NMR spectroscopic data of PREPi, methyl gallate, syringic acid, and butanedioic acid. δH: Proton (1H) NMR chemical shift. δC: Carbon (13C) NMR chemical shift. s, d, m: Singlet, doublet, multiplet, respectively. Numbers in parentheses represent the number of protons.
| Position | PREPi | Methyl gallate | Syringic acid | Butanedioic acid |
|---|---|---|---|---|
| 1 | δ H: 119.3, δC: 120.6, δH: 173.9, δC: 3.50, δH: 72.0 | δ H: 7.02, δC: 108.5 | δ H: 7.15, δC: 106.9 | δ H: 7.02, δC: 108.5 |
| 2 | δ H: (1H, m) | δ H: (1H, s) | δ H: (1H, d, 0.6) | δ H: (1H, m) |
| 3 | δ H: 145.7, δC: 147.3, δH: 2.55 (2H, s), δC: 28.9 | δ H: 145.7, δC: 147.3 | δ H: 145.7, δC: 137.4 | δ H: 137.4, δC: 137.5 |
| 4 | δ H: 1.47, δC: 22.75 | δ H: 2.55 (2H, s), δC: 28.9 | δ H: 1.47, δC: 22.75 | δ H: 1.47, δC: 25.65 |
| 5 | δ H: 22.75, δC: 22.68 | δ H: 1.47, δC: 22.68 | δ H: 1.47, δC: 22.68 | δ H: 1.47, δC: 22.68 |
| 6 | δ H: (1H, m) | δ H: 7.02, δC: 108.5 | δ H: (1H, d, 0.6) | δ H: (1H, m) |
| 7 | δ H: 7.02, δC: 108.5 | δ H: 7.15, δC: 106.9 | δ H: 7.15, δC: 106.9 | δ H: 7.15, δC: 106.9 |
| 8 | δ H: 166.4, δC: 167.9 | δ H: 166.4, δC: 167.9 | δ H: 166.4, δC: 167.9 | δ H: 166.4, δC: 167.9 |
| 9 | δ H: 3.80, δC: 52.3 | δ H: 3.80, δC: 52.3 | δ H: 3.86, δC: 56.2 | δ H: 3.86, δC: 56.2 |
| 10 | δ H: (3H, s), δC: 56.2 | δ H: (3H, s), δC: 56.2 | δ H: (3H, s), δC: 56.2 | δ H: (3H, s), δC: 56.2 |
| 11 | δ H: 3.83, δC: 56.2 | δ H: 3.83, δC: 56.2 | δ H: 3.83, δC: 56.2 | δ H: 3.83, δC: 56.2 |
| 12 | δ H: 56.2 | δ H: 56.2 | δ H: 56.2 | δ H: 56.2 |
| 13 | δ H: 1.18, δC: 29.67 | δ H: 1.18, δC: 29.67 | δ H: 1.18, δC: 29.67 | δ H: 1.18, δC: 29.67 |
| 14 | δ H: 29.67 | δ H: 29.67 | δ H: 29.67 | δ H: 29.67 |
| 15 | δ H: 0.81, δC: 14.10 | δ H: 0.81, δC: 14.10 | δ H: 0.81, δC: 14.10 | δ H: 0.81, δC: 14.10 |
| 16 | δ H: 14.10 | δ H: 14.10 | δ H: 14.10 | δ H: 14.10 |