Table 3.
The 400 MHz 1H NMR data (δ, J in Hz) of 2 and 3 in CDCl3. a
| Proton | 2 | 3 | ||
|---|---|---|---|---|
| 2a | 2b | 3a | 3b | |
| 3 | 3.93 (t, 9.0) | 3.86–3.82 (masked by H-16/16′) | 3.95 (t, 9.0) | 3.90 (t, 9.0) |
| 4 | 5.19 (d, 9.0) | 5.22 (d, 9.0) | 5.21 (d, 9.0) | 5.22 (d, 9.0) |
| 8 | 6.70 (s) | 6.70 (s) | 6.70 (s) | 6.70 (s) |
| 10 | 6.60 (s) | 6.60 (s) | 6.60 (s) | 6.60 (s) |
| 15 | 2.32 (s) | 2.30 (s) | 2.33 (s) | 2.32 (s) |
| 16 | 3.79 (s) | 3.82 (s) | 3.79 (s) | 3.84 (s) |
| 3′ | 3.01 (ddd, 11.7, 9.0, 5.8) | 2.93 (ddd, 12.8, 8.2, 5.2) | 2.98 (ddd, 11.9, 9.0, 5.7) | 2.92 (ddd, 12.7, 9.0, 5.4) |
| 4′α | 2.87 (dd, 16.7, 5.8) | 2.81 (dd, 15.9, 5.2) | 2.88 (dd, 16.6, 5.7) | 2.81 (dd,15.9, 5.4) |
| β | 2.62 (dd, 16.7, 11.7) | 2.46 (dd, 15.9, 12.8) | 2.62 (dd, 16.6, 11.9) | 2.49 (dd,15.9, 12.7) |
| 8′ | 6.71 (s) | 6.70 (s) | 6.72 (s) | 6.71 (s) |
| 10′ | 6.68 (s) | 6.68 (s) | 6.69 (s) | 6.69 (s) |
| 15′ | 2.42 (s) | 2.42 (s) | 2.42 (s) | 2.42 (s) |
| 16′ | 3.87 (s) | 3.85 (s) | 4.37-4.29 (m) | 4.35-4.27 (m) |
| 17′ | — | — | 1.35 (t, 7.1) | 1.37 (t, 7.0) |
| 11–OH | 12.04 (s) | 11.95 (s) | 12.06 (s) | 11.98 (s) |
| 2′–OH | 4.64 (br s) | 4.64 (br s) | 4.64 (br s) | 4.64 (br s) |
| 11′–OH | 12.35 (s) | 12.30 (s) | 12.36 (s) | 12.31 (s) |
a The chemical shift was recorded as δ value using the solvent CDCl3 signal (δH 7.26) as reference. Both 2 and 3 existed in dynamic isomerism between the major and minor isomers, 2a/2b and 3a/3b, in CDCl3, respectively. The signals for each isomer were assigned by comparison with their data in DMSO given Table 1, respectively. The ratio of 2a/2b and 3a/3b were approximately determined both to be 1:0.8 by the standard integrals of H-4, HO-11 and HO-11′ signals for 2 and Hβ-4 signals for 3, respectively.