反应详情

N-Carbobenzyloxy-β-phenyl isoserine methyl ester (Preparation No. 19, 3C, 0.375 g, 1.14 mM) is dissolved in dry THF (10 mL) and the solution treated with 2,4-dimethoxy benzaldehyde dimethyl acetal (4, 0.300 g, 1.42 mM) and pyridinium p-toluenesulfonate (10 mg) and the solution heated to distill off the THF and methanol. After ½ the THF is distilled off, THF (10 mL) is added and the reaction distilled to ½ volume again. The process is repeated three times. The reaction is then concentrated in vacuo and the residue chromatographed over 75 g silica gel packed and eluted in acetone-hexane (300 mL of 20-80 and 300 mL of 25-75). Fractions of 20 mL are collected and analyzed by TLC. The following fractions are combined and evaporated under vacuum.

1. temperaturethe solution heated
2. distillationto distill off the THF and methanol
3. distillationis distilled off
4. additionTHF (10 mL) is added
5. distillationthe reaction distilled
6. concentrationThe reaction is then concentrated in vacuo
7. customthe residue chromatographed over 75 g silica gel
8. washeluted in acetone-hexane (300 mL of 20-80 and 300 mL of 25-75)
9. customFractions of 20 mL are collected
10. customevaporated under vacuum