1.1: silica gel; pyridinium chlorochromate / dichloromethane / 3 h / 20 °C / Inert atmosphere 2.1: n-butyllithium / tetrahydrofuran; hexane / 0.25 h / -78 °C / Inert atmosphere 2.2: -78 - 20 °C / Inert atmosphere 3.1: methanol; acetyl chloride / 20 °C / Inert atmosphere 4.1: silica gel; pyridinium chlorochromate / dichloromethane / Inert atmosphere View Scheme