Table 2.
The 400 MHz 1H and 100 MHz 13C NMR data of 1 and 4 in CDCl3. a
| Proton | 1 | Position | 4 | ||
|---|---|---|---|---|---|
| δH (J in Hz) of 1a | δH (J in Hz) of 1b | δH (J in Hz) | δC | ||
| 3 | 3.25 (dd, 12.0, 6.0) | 3.54 (dd, 11.3, 7.0) | 1 | 4.94 (dt, 6.8, 1.5) | 79.5 d |
| 4 | 4.78 (d, 6.0) | 4.98 (d, 7.0) | 2α | 2.14 (dddd, 14.0, 8.6, 2.6, 1.5) | 27.8 t |
| 8 | 6.71 (s) | 6.70 (s) | β | 2.31 (dddd, 14.0, 9.4, 7.4, 6.8) | |
| 10 | 6.63 (s) | 6.63 (s) | 3α | 3.17 (dddd, 18.0, 8.6, 7.4, 1.5) | 30.3 t |
| 15 | 2.38 (s) | 2.37 (s) | β | 2.77 (ddd, 18.0, 9.4, 2.6) | |
| 16 | 3.82 (s) | 3.90 (s) | 4 | — | 174.0 s |
| 3′ | 2.78 (ddd, 12.7, 12.0, 4.0) | 3.93 (td, 11.3, 5.1) | 6 | — | 157.5 s |
| 4′α | 2.94 (dd, 17.0, 12.7) | 2.75 (dd, 17.6, 11.9) | 7 | 6.70 (br s) | 107.8 d |
| β | 2.84 (dd, 17.0, 4.0) | 3.05 (dd, 17.6, 5.1) | 8 | — | 146.8 s |
| 8′ | 6.78 (s) | 6.73 (s) | 9 | 6.63 (br s) | 112.8 d |
| 10′ | 6.71 (s) | 6.70 (s) | 10 | — | 161.2 d |
| 15′ | 2.43 (s) | 2.43 (s) | 11 | — | 109.2 d |
| 16′ | 3.80 (s) | 3.85 (s) | 12 | — | 181.3 d |
| 11–OH | 12.12 (s) | 11.89 (s) | 13 | — | 120.1 d |
| 2′–OH | 4.60 (br s) | 4.49 (s) | 14 | 2.39 (s) | 22.4 q |
| 11′–OH | 12.37 (s) | 12.34 (s) | 15 | 3.49 (s) | 57.5 q |
| — | — | — | 10-OH | 12.55 (s) | — |
a 1H and 13C NMR signals were recorded as δ values using the solvent CDCl3 signals (δH 7.26 and δC 77.16) as references, respectively. Remisporine B (1) existed in dynamic isomerism between major isomer 1a and minor isomer 2b in CDCl3, and the signals of 1a and 1b were assigned by comparison with the data of 1a in DMSO, given in Table 1. The ratio of 1a and 1b was determined approximately to be 1:0.8 by the standard integrals of their H-4 signals.