TABLE 1.
Chemical shifts and coupling constants for [13C]citrinin and RE with labeled [1,2-13C2]acetatea
| Carbon atom | Chemical shift (ppm) | 1J(13C-13C) (Hz) | Enrichment | REb |
|---|---|---|---|---|
| 1 | 162.9 | 69.6 | a | 3.1 |
| 3 | 81.8 | 37.6 | a | 0.6 |
| 4 | 34.7 | 40.7 | b | 0.7 |
| 4a | 139.2 | 40.7 | a | 1.3 |
| 5 | 123.2 | 57.0 | b | 2.1 |
| 6 | 183.9 | 57.0 | a | 2.4 |
| 7 | 100.4 | 63.9 | b | 2.0 |
| 8 | 177.3 | 63.9 | a | 2.5 |
| 8a | 107.5 | 69.6 | b | 1.6 |
| 9 | 18.3 | 37.6 | b | 1.1 |
| 10 | 9.6 | s | 1.0 | |
| 11 | 18.4 | s | ||
| 12 | 174.7 | s |
a
a, incorporation of [1-13C]acetate; b, incorporation of [2-13C]acetate; s, singlet.
b
RE was calculated by the following equation: α · IC-XE/IC-XN, where α is determined by the equation IC-10N/IC-10E, C-X is the carbon number, C-10 is the reference carbon, IC-XN is the intensity of the NMR signal of carbon X naturally enriched, and IC-XE is the intensity of the NMR signal of carbon X enriched in the presence of [1,2-13C2]acetate. The calculation takes into account the experimental 13C NMR conditions.