ethylmagnesium bromide in tetrahydrofuran; diethyl ether T=0°C; 2.33333 h; Inert atmosphere;

potassium carbonate in methanol T=0 - 20°C; 3 h; Inert atmosphere;

1: (2-oxo-propyl)-phosphonic acid dimethyl ester With 4-Acetylaminobenzenesulfonyl Azide; potassium carbonate in chloroform T=0 - 10°C; 48 h; Inert atmosphere; 2: 1,1-Dimethylethyl (R)-4-formyl-2,2-dimethyl-3-oxazolidinecarboxylate in methanol; chloroform T=0°C; Bestmann-Ohira reaction; 24 h; Inert atmosphere;

1: 2,2-dimethyloxazolidine-(4R)-3,4-dicarboxylic acid 3-tert-butyl ester 4-methyl ester With diisobutylaluminium hydride in n-heptane; dichloromethane T=-78°C; 2: (1-Diazo-2-oxo-propyl)-phosphonic acid dimethyl ester With potassium carbonate in methanol; n-heptane; dichloromethane T=20°C; Further stages.;

n-butyllithium in tetrahydrofuran 1) -78 deg C, 30 min; 2) -15 deg C, 15 min;

1: 1.) PPh3, 2.) Et3N / 1) CH2Cl2, -20 deg C, 30 min; 2) CH2Cl2, -60 deg C, 30 min, rt, overnight 2: 58 percent / BuLi / tetrahydrofuran / 1) -78 deg C, 30 min; 2) -15 deg C, 15 min View Scheme

1: (L)-3-tert.butoxycarbonyl-2,2-dimethyl-oxazolidine-4-carboxylic acid-N-methoxy-N-methyl-amide With lithium aluminium tetrahydride in tetrahydrofuran T=20°C; 0.5 h; Inert atmosphere; 2: (1-Diazo-2-oxo-propyl)-phosphonic acid dimethyl ester in methanol T=0°C; 0.5 h; Inert atmosphere; 3: With potassium carbonate in methanol T=20°C; 15 h; Inert atmosphere;

p-toluenesulfonic acid monohydrate in methanol; water