1: (4R,5S)-4-hydroxy-5-(hydroxymethyl)dihydrofuran-2(3H)-one With 2-methyl-but-2-ene; dimethylsulfide borane complex in tetrahydrofuran T=20°C; 20 h; 2: aniline in ethanol; water T=5°C; 3 h;

1: CF3COOH, H2O / 3 h / Ambient temperature 2: 1.) disiamylborane / 1.) THF, RT, 20 h, 2.) ethanol, water View Scheme

1.1: 96 percent / sulfuric acid / 1,2-dichloro-ethane; H2O / 5 h / Heating 2.1: borane-dimethylsulfide complex; 2-methyl-2-butene / tetrahydrofuran / 20 h / 20 °C 2.2: 56 percent / H2O; ethanol / 3 h / 5 °C View Scheme

1: disiamylborane<(Sia2BH)2> / tetrahydrofuran / 22 h / Ambient temperature 2: ethanol; H2O / 5 °C / overnight View Scheme

in ethanol; water T=5°C; overnight; Yield given;