pyridinium p-toluenesulfonate in toluene 0.5 h; Reflux;

pyridinium p-toluenesulfonate; paraformaldehyde in toluene

potassium carbonate in acetonitrile 1 h; Heating;

chloro-trimethyl-silane; sodium cyanoborohydride in acetonitrile 0.0833333 h; Ambient temperature;

sodium tetrahydroborate in methanol 3 h; 0 deg C -> r.t.;

1: (4S)-4-Benzyl-N-tert-butyloxycarbonyl-1,3-oxazolidin-5-one With lithium tri-t-butoxyaluminum hydride in tetrahydrofuran T=-10 - 0°C; 2: Methyltriphenylphosphonium bromide With potassium tert-butylate in tetrahydrofuran T=0 - 55°C;