1: With trifluoroacetic acid in dichloromethane T=20°C; 2: With sodium cyanoborohydride; acetic acid in ethanol 1 h; 3: With sodium hydrogencarbonate in ethanol; water; ethyl acetate

1.1: n-butyllithium / hexane; tetrahydrofuran / 0.25 h / -78 °C 1.2: 1 h / -78 - 20 °C 1.3: 20 °C 2.1: trifluoroacetic acid / dichloromethane / 20 °C 2.2: 1 h View Scheme