1: 1.61 g / dimethylformamide / 2 h / 0 °C 2: p-TsOH; Girard-P / methanol / 0.5 h / 20 °C View Scheme

1: dimethylformamide / 8 h / 0 °C 2: 1.93 g / dimethylformamide / 2 h / 0 °C 3: p-TsOH; Girard-P / methanol / 0.5 h / 20 °C View Scheme