The total synthesis of the plant natural product altissimacoumarin D was achieved by the Mitsunobu alkylation of isofraxidin by geraniol. Isofraxidin was prepared from 2,4-dihydroxybenzaldehyde in five steps. The key reaction was the Knoevenagel condensation of an ortho-hydroxybenzaldehyde with Meldrum's acid under neutral conditions in water and one-pot acid catalyzed cyclization to the coumarin.
Keywords:
natural products; epigenetics; sirtuins; coumarins
| δH, natural product | δH, synthetic sample | δC, natural product | δC, synthetic sample |
|---|---|---|---|
| 1.59 (s) | 1.52 (s) | 16.4 | 16.4 |
| 1.67 (s) | 1.60 (s) | 17.6 | 17.6 |
| 1.69 (s) | 1.63 (s) | 25.6 | 25.6 |
| 2.05, 2.08 (m) | 1.99 (m) | 26.3 | 26.3 |
| 3.89 (s) | 3.82 (s) | 39.6 | 39.6 |
| 4.03 (s) | 3.96 (s) | 56.3 | 56.2 |
| 4.68 (d, J7 Hz) | 4.62 (d, J7 Hz) | 61.7 | 61.7 |
| 5.06 (t, J7 Hz) | 5.00 (t, J8 Hz) | 70.3 | 70.2 |
| 5.56 (t, J7 Hz) | 5.49 (t, J8 Hz) | 103.5 | 103.5 |
| 6.34 (d, J10 Hz) | 6.28 (d, J8 Hz) | 114.4 | 114.4 |
| 6.66 (s) | 6.58 (s) | 115.1 | 115.1 |
| 7.61 (d, J10 Hz) | 7.54 (d, J12 Hz) | 119.6 | 119.6 |
| 123.8 | 123.8 | ||
| 131.7 | 131.7 | ||
| 141.8 | 141.8 | ||
| 142.5 | 142.5 | ||
| 142.9 | 143.0 | ||
| 143.5 | 143.4 | ||
| 144.9 | 144.9 | ||
| 150.7 | 150.7 | ||
| 160.6 | 160.5 |
