1: With trifluoroacetic acid in toluene T=140°C; Pictet-Spengler cyclisation; 0.5 h; Microwave irradiation; 2: With sodium hydroxide in water pH=8;

sodium hydroxide

1: With (2R,3R)-(-)-di-O-(p-toluoyl)-tartaric acid in methanol T=28°C; 720 h; Resolution of racemate; 2: With ammonium hydroxide in water

1.1: titanium tetraethoxide / dichloromethane / 4 h / Reflux; Inert atmosphere 2.1: lithium diisopropyl amide / tetrahydrofuran; hexane / 1 h / -78 °C / Inert atmosphere 2.2: -78 - 20 °C / Inert atmosphere 3.1: trifluoroacetic acid / methanol / 3 h / 0 °C / Inert atmosphere 4.1: trifluoroacetic acid / toluene / 0.5 h / 140 °C / Microwave irradiation 4.2: pH 8 View Scheme

1.1: lithium diisopropyl amide / tetrahydrofuran; hexane / 1 h / -78 °C / Inert atmosphere 1.2: -78 - 20 °C / Inert atmosphere 2.1: trifluoroacetic acid / methanol / 3 h / 0 °C / Inert atmosphere 3.1: trifluoroacetic acid / toluene / 0.5 h / 140 °C / Microwave irradiation 3.2: pH 8 View Scheme

1.1: trifluoroacetic acid / methanol / 3 h / 0 °C / Inert atmosphere 2.1: trifluoroacetic acid / toluene / 0.5 h / 140 °C / Microwave irradiation 2.2: pH 8 View Scheme

1.1: chloroformic acid ethyl ester; potassium carbonate / tetrahydrofuran / 24 h / -78 - 20 °C / Inert atmosphere 2.1: sodium tetrahydroborate / tetrahydrofuran / 18 h / Reflux; Inert atmosphere 3.1: lithium diisopropyl amide / tetrahydrofuran; hexane / 1 h / -78 °C / Inert atmosphere 3.2: -78 - 20 °C / Inert atmosphere 4.1: trifluoroacetic acid / methanol / 3 h / 0 °C / Inert atmosphere 5.1: trifluoroacetic acid / toluene / 0.5 h / 140 °C / Microwave irradiation 5.2: pH 8 View Scheme

1.1: sodium tetrahydroborate / tetrahydrofuran / 18 h / Reflux; Inert atmosphere 2.1: lithium diisopropyl amide / tetrahydrofuran; hexane / 1 h / -78 °C / Inert atmosphere 2.2: -78 - 20 °C / Inert atmosphere 3.1: trifluoroacetic acid / methanol / 3 h / 0 °C / Inert atmosphere 4.1: trifluoroacetic acid / toluene / 0.5 h / 140 °C / Microwave irradiation 4.2: pH 8 View Scheme

1.1: lithium diisopropyl amide / tetrahydrofuran; hexane / 1 h / -78 °C / Inert atmosphere 1.2: -78 - 20 °C / Inert atmosphere 2.1: trifluoroacetic acid / methanol / 3 h / 0 °C / Inert atmosphere 3.1: trifluoroacetic acid / toluene / 0.5 h / 140 °C / Microwave irradiation 3.2: pH 8 View Scheme

1.1: n-butyllithium / tetrahydrofuran; hexane / 2 h / 0 - 5 °C / Inert atmosphere 1.2: 4 h / 20 °C / Inert atmosphere 2.1: chloroformic acid ethyl ester; potassium carbonate / tetrahydrofuran / 24 h / -78 - 20 °C / Inert atmosphere 3.1: sodium tetrahydroborate / tetrahydrofuran / 18 h / Reflux; Inert atmosphere 4.1: lithium diisopropyl amide / tetrahydrofuran; hexane / 1 h / -78 °C / Inert atmosphere 4.2: -78 - 20 °C / Inert atmosphere 5.1: trifluoroacetic acid / methanol / 3 h / 0 °C / Inert atmosphere 6.1: trifluoroacetic acid / toluene / 0.5 h / 140 °C / Microwave irradiation 6.2: pH 8 View Scheme