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Table 4. Comparison of 1H NMR data for the C5--C16 degradation fragments (recorded at 500 MHz, CD3OD)
|
Proton no. |
9* |
(5S)-54a |
(5R)-54b |
|
5 |
3.90/3.92 (m) |
3.94 (m) |
3.90 (m) |
|
6a |
1.80 (m) |
1.59 (ddd, 3.2, 9.0, 14.3) |
1.81 (ddd, 6.3, 8.0, 14.2) |
|
6b |
1.50 (m) |
1.48 (ddd, 3.4, 6.1, 14.3) |
1.52 (ddd, 4.8, 6.5, 14.1) |
|
7 |
3.68 (m) |
3.73 (m) |
3.68 (m) |
|
8a |
2.61 (m) |
2.48-2.62 (ol)† |
2.62 (dd, 4.6, 15.3) |
|
8b |
2.54 (m) |
2.48-2.62 (ol)† |
2.54 (dd, 7.4, 15.3) |
|
10a |
2.57 (m) |
2.48-2.62 (ol)† |
2.56 (dd, 1.9, 17.6) |
|
10b |
2.52 (m) |
2.48-2.62 (ol)† |
2.51 (dd, 10.6, 17.6) |
|
11 |
4.53 (m) |
4.53 (ddd, 3.8, 3.8, 12.2) |
4.53 (ddd, 4.8, 4.8, 11.3) |
|
12 |
2.15 (m) |
2.15 (m) |
2.15 (m) |
|
13 |
3.49 (m) |
3.50 (ddd, 3.5, 3.5, 9.2) |
3.50 (ddd, 3.7, 3.7, 9.2) |
|
14a |
1.70 (m) |
1.73 (ddd, 3.5, 9.3, 14.6) |
1.73 (ddd, 3.5, 9.3, 14.6) |
|
14b |
1.65 (m) |
1.64 (ddd, 3.5, 9.5, 14.6) |
1.64 (ddd, 3.6, 9.3, 14.6) |
|
15 |
3.40 (m) |
3.41 (m) |
3.41 (m) |
|
16a |
3.68 (m) |
3.68 (dd, 4.4, 11.8) |
3.68 (dd, 4.4, 11.7) |
|
16b |
3.53 (m) |
3.54 (dd, 4.7, 11.8) |
3.54 (dd, 4.7, 11.7) |
|
5-Me |
1.22/1.20 (d, 6.6) |
1.21 (d, 6.7) |
1.22 (d, 6.2) |
|
7-OMe‡ |
3.37 (s) |
3.42 (s) |
3.38 (s) |
|
12-Me |
1.08 (d, 6.6)§ |
1.08 (d, 7.1) |
1.08 (d, 7.1) |
|
13-OMe‡ |
3.40 (s) |
3.41 (s) |
3.41 (s) |
|
15-OMe‡ |
3.45 (s) |
3.46 (s) |
3.46 (s) |
|
39 |
5.85 (s) |
5.86 (m) |
5.85 (m) |
Reidispongiolide A numbering is used. All data are reported in order: chemical shift (multiplicity, coupling constant in Hz).
*Ref. 1.
†Resonances observed as overlapping multiplets.
‡Assignments may be interchanged.
§The corrected chemical shift for 12-Me in the natural degradation fragment was extracted from 1H NMR spectra of this material provided to us by D’Auria (University of Naples "Federico II").
1. Zampella, A., Bassarello, C., Bifulco, G., Gomez-Paloma, L. & D’uria, M. V. (2002) Eur. J. Org. Chem., 785–790.