1: (R)-4,4-dimethoxytetrahydro-2H-pyran-3-ol With sodium t-butanolate in tetrahydrofuran; water 2: dimethyl sulfate in tetrahydrofuran; water T=36°C; 4.33333 h; 3: With hydrogenchloride; water; sodium hydrogencarbonate more than 3 stages;

1: tetrahydro-pyran-4-one With t-butyldimethylsiyl triflate; triethylamine in dichloromethane T=20°C; 2: With potassium osmate(VI); 4-methylmorpholine N-oxide; 1,4-bis(9-O-dihydroquinidine)phthalazine in water; acetone T=0 - 20°C; 3: dimethyl sulfate Further stages;

1.1: (S)-3,3-diphenyl-1-methyltetrahydro-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborol; dimethylsulfide borane complex / tetrahydrofuran / 25 h / 40 °C / |Inert atmosphere 2.1: potassium tert-butylate / tetrahydrofuran / 0.75 h / 0 °C / |Inert atmosphere 2.2: 2.25 h / 0 - 20 °C 3.1: hydrogenchloride; water / tetrahydrofuran / 2.25 h / 0 - 3 °C View Scheme

1.1: potassium tert-butylate / tetrahydrofuran / 0.75 h / 0 °C / |Inert atmosphere 1.2: 2.25 h / 0 - 20 °C 2.1: hydrogenchloride; water / tetrahydrofuran / 2.25 h / 0 - 3 °C View Scheme

1.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 1 h / -70 °C 1.2: 18 h / -70 - 20 °C 2.1: (S)-3,3-diphenyl-1-methyltetrahydro-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborol; dimethylsulfide borane complex / tetrahydrofuran / 25 h / 40 °C / |Inert atmosphere 3.1: potassium tert-butylate / tetrahydrofuran / 0.75 h / 0 °C / |Inert atmosphere 3.2: 2.25 h / 0 - 20 °C 4.1: hydrogenchloride; water / tetrahydrofuran / 2.25 h / 0 - 3 °C View Scheme

1.1: potassium hydroxide / 1.5 h / 0 - 5 °C 1.2: 19.5 h / 5 - 20 °C 2.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 1 h / -70 °C 2.2: 18 h / -70 - 20 °C 3.1: (S)-3,3-diphenyl-1-methyltetrahydro-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborol; dimethylsulfide borane complex / tetrahydrofuran / 25 h / 40 °C / |Inert atmosphere 4.1: potassium tert-butylate / tetrahydrofuran / 0.75 h / 0 °C / |Inert atmosphere 4.2: 2.25 h / 0 - 20 °C 5.1: hydrogenchloride; water / tetrahydrofuran / 2.25 h / 0 - 3 °C View Scheme