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Competitive activations of S-ethyl glycosyl donors: 1c (armed) vs. 2c (superarmed)
 | |||||
|---|---|---|---|---|---|
| Entry | Temp. | Time | Ratio 4:5 a | Yield 4 b (α:β) | Yield 5 b (α:β)b |
| 1 | rt | 1 h | 1:0.8 | 53% (1:1.7) | 45% (β only) |
| 2 | −10 °C | 1 h | 1:2.4 | 22% (1:4) | 51% (β only) |
| 3 | −25 °C | 3 h | 1:4 | 14% (1:4) | 62% (β only) |
| 4 | −35 °C | 24 h | 1:1.5 | 11% (1:5) | 26% (β only) |
– determined by comparing integral intensities of the corresponding signals in the NMR spectra recorded for the crude reaction mixtures;
– isolated yields
