Table 3. 1H NMR Data of Compounds 5–9a.
| position | 5 | 6 | 7 | 8 | 9 |
|---|---|---|---|---|---|
| 1 | 6.69 d (12.6) | 4.89b | 4.86b | 4.28 d (2.0) | 4.38 d (3.0) |
| 2a | 5.97 d (12.6) | 3.50 br d (16.0) | 3.47 br d (15.8) | 2.81 dd (17.0, 3.3) | 2.85 dd (17.0, 3.7) |
| 2b | 3.05 dd (16.0, 7.5) | 3.05 dd (7.4, 15.8) | 2.49 br d (17.5) | 2.53 br d (17.0) | |
| 5 | 2.57b | 2.45b | 2.52 m | 2.70 br d (12.5) | 2.38 dd (15.0, 2.5) |
| 6a | 2.17 m | 2.13b | 2.09b | 1.68 m | 1.87 br dd (14.0, 3.3) |
| 6b | 2.07b | 2.06b | 1.98b | 2.03 m | 2.13b |
| 7 | 4.70b | 4.64 br d (2.5) | 5.17 br s | 3.56 br s | 4.70 br s |
| 9 | 2.55b | 2.92 d (3.5) | 2.63 m | 2.77 d (3.3) | 2.80 br d (3.7) |
| 11a | 5.78 m | 5.28 br dd (9.0, 4.3) | 1.62b | 5.43 dd (9.0, 4.0) | 5.53 m |
| 11b | 1.49 m | ||||
| 12a | 2.60b | 2.46b | 2.03b | 2.28 dd (14.3, 10.0) | 1.62 br d (14.0) |
| 12b | 1.61b | 1.65 dd (15.0, 5.5) | 1.61b | 1.59 dd (15.6, 4.4) | |
| 15 | 3.73 s | 3.70 s | 5.33 br s | 3.88 s | 3.70 s |
| 16a | 2.50 m | ||||
| 16b | 2.11b | ||||
| 17 | 5.49 br s | 5.52 br s | 1.97b | 5.09 s | 5.52 br s |
| 18 | 1.32 s | 1.40 s | 1.27 s | 1.33 s | 1.34 s |
| 19a | 1.57 s | 1.51 s | 1.25 s | 5.09 d (13.0) | 5.06 d (13.5) |
| 19b | 4.72 d (13.0) | 4.77 d (13.5) | |||
| 21 | 6.15 br s | –c | 3.63 br d (3.0) | 7.54b | –c |
| 22a | 6.29 br s | –c | 1.93b | 6.46 s | –c |
| 22b | 1.77 m | ||||
| 23 | 3.72 m | 7.54b | |||
| 28 | 1.37 s | 1.39 s | 1.40 s | 1.28 s | 1.30 s |
| 29 | 1.50 s | 1.58 s | 1.58 s | 1.12 s | 1.13 s |
| 30 | 1.40 s | 1.30 s | 1.24 s | 1.08 s | 1.19 s |
| AcO-1 | 2.12 s | 2.03 s | 2.10 s | ||
| AcO-7 | 2.08 s | 2.11 s | 2.09 s | ||
| AcO-11 | 2.01 s | 2.11 s | 2.11 s | 2.10 s |
a
Spectra were recorded in methanol-d4 at 600 MHz. J values are in parentheses and reported in Hz; chemical shifts are given in ppm; assignments were confirmed by 1D-TOCSY, COSY, HSQC, and HMBC experiments.
b
Overlapped signal.
c
Signal cannot be observed clearly from 1D and 2D NMR. Weak signals are due presumably to an instable hemiacetal function and tautomerism of the butenolide ring in solution.