Table 1.
Preliminary experiments using ent-15, obtained by TEMPO/PhI(OAc)2 oxidation of ent-14.
| Entry 1 | Solvent | Additive (equiv.) | Temperature (°C) | Yield (%) | anti-20a:syn-20a 2 |
|---|---|---|---|---|---|
| 1 3 | CH2Cl2 | none | r.t. | 67 | 61:39 |
| 2 3 | CH2Cl2/THF | ZnBr2 (0.4) | r.t. | 51 | 76:24 |
| 3 4 | CH2Cl2/THF | ZnBr2 (0.4) | r.t. | 55 | 71:29 |
Notes: 1 1.1 equivalents of isocyanide. 2 Determined by 1H-NMR; the relative configuration of compounds 20a was determined as reported in the Supplementary Materials; 3 no drying procedure of the aldehyde. 4 In the presence of 3 Å MS.