1: acetic anhydride / 0.5 h / 110 °C / |Inert atmosphere 2: (9S)-6'-methoxycinchonan-9-ol / toluene / 168 h / -30 °C / |Inert atmosphere 3: triethylamine; diphenyl phosphoryl azide / toluene / 0.5 h / |Inert atmosphere; |Heating 4: toluene / 110 °C / |Inert atmosphere View Scheme

1: acetic anhydride / 0.5 h / 110 °C / |Inert atmosphere 2: QNH / toluene / 72 h / -30 °C / |Inert atmosphere 3: triethylamine; diphenyl phosphoryl azide / 95 °C / |Inert atmosphere 4: 110 °C View Scheme