1: 2-(trimethylsilyl)-1,3-dithiane With n-butyllithium in tetrahydrofuran; hexane T=-78 - 0°C; Peterson olefination; 2: pentanal in tetrahydrofuran; hexane T=20°C; 20 h;

N,N,N',N,-tetramethylethylenediamine; titanium tetrachloride; zinc in tetrahydrofuran T=25°C; 0.75 h;

potassium hydroxide in benzene 2 h; Heating;