Table 3.
Isoxazolidines 33, 34, 35 and 36 produced viaScheme 3.
| Nitrone | Nucleobase B | Reaction time (h)a | Ratio of isomers 33:34:35:36 | Yield [%] |
|---|---|---|---|---|
| 20a |  |
3 | 62:31:5:2 |
33a – 14b; 33a + 34a + 35a + 36a – 38c; |
| 20b |  |
6 | 62:31:6:1 |
33b–33b; 33b + 34b + 35b + 36b–41c; |
| 20c |  |
3 | 60:32:6:2 |
33c – 24b; 33c + 34c + 35c + 36c – 16c; 34c – 10b; |
| 20d |  |
6 | 50:39:7:4 |
33d – 2b; 33d + 34d + 35d + 36d – 8c; 34d – 1b; |
| 20e |  |
8 | 64:30:5:1 |
33e + 34e – 10c; 33e + 34e + 35e + 36e – 45c; |
a
Cycloaddition under MW irradiation.
b
Yield of the pure diastereoisomer.
c
Yield of the pure mixture of two, three or four diastereoisomers.