1: water; toluene-4-sulfonic acid / tetrahydrofuran / 12 h / 45 °C 2: sodium tetrahydroborate / ethanol / 3 h / 0 °C View Scheme

1: 1,3-Dithiane With n-butyllithium in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide T=-78°C; 1 h; 2: 2-bromoacetaldehyde diethyl acetal in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide T=-78 - -30°C; 1 h;

in tetrahydrofuran; water; acetic acid 8 h; Heating;