boron trifluoride diethyl etherate in acetone T=23°C; 2 h; Inert atmosphere;

1: 2,2-dimethyloxazolidine-(4R)-3,4-dicarboxylic acid 3-tert-butyl ester 4-methyl ester With LiOH*H2O in methanol; water T=20°C; 4 h; Inert atmosphere; 2: O,N-dimethyl-hydroxylamine hydrochloride With (benzotriazo-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate; triethylamine in dichloromethane T=20°C; 3 h; Inert atmosphere;

1: N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, N-methylmorpholine / CH2Cl2 / 1 h / -15 °C 2: BF3*Et2O / acetone / 1.5 h / Ambient temperature View Scheme

1: NaOH / dioxane; H2O / 48 h / 0 - 20 °C 2: N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, N-methylmorpholine / CH2Cl2 / 1 h / -15 °C 3: BF3*Et2O / acetone / 1.5 h / Ambient temperature View Scheme

1: boron trifluoride diethyl etherate / acetone / 2 h / 20 °C 2: water; lithium hydroxide hydrate / methanol / 4 h / 20 °C 3: (benzotriazo-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate; triethylamine / 3 h / 20 °C View Scheme

1: water; lithium hydroxide hydrate / methanol / 4 h / 20 °C 2: (benzotriazo-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate; triethylamine / 3 h / 20 °C View Scheme

(benzotriazo-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate; triethylamine T=20°C; 3 h;

lithium aluminium tetrahydride in tetrahydrofuran T=0°C; 0.5 h;