1: diazomethyl-trimethyl-silane With lithium diisopropyl amide in tetrahydrofuran T=-78°C; 0.5 h; 2: furan-3-carboxaldehyde in tetrahydrofuran T=-78 - 20°C; Peterson olefination; 1.5 h; Further stages.;

in pentane T=20°C;

tetrabutyl ammonium fluoride in tetrahydrofuran