1: propionic acid methyl ester With lithium diisopropyl amide in tetrahydrofuran; hexane T=-78°C; 0.5 h; 2: tert-butyldimethylsilyl chloride With N,N,N',N',N'',N''-hexamethylphosphoric triamide in tetrahydrofuran; hexane T=-78 - 20°C; Title compound not separated from byproducts;