1: 75 percent / n-BuLi / tetrahydrofuran; hexamethylphosphoric acid triamide / -78 °C / under N2 2: 96 percent / 30percent H3PO4 / methanol / 5 h / Ambient temperature 3: 74 percent / CrO3, conc H2SO4 / H2O; acetone / 0.5 h / 0 °C View Scheme

1: n-BuLi / tetrahydrofuran; hexamethylphosphoric acid triamide / -78 °C / under N2 2: 30percent H3PO4 / methanol / 5 h / Ambient temperature 3: CrO3, conc H2SO4 / H2O; acetone / 0.5 h / 0 °C 4: LCA(long chain aldehydes)-forming activity in Ulva pertusa fronds solubilized by Triton X-100, 2,4-dinitrophenylhydrazone / 0.25 h / 35 °C View Scheme

1: n-BuLi / tetrahydrofuran; hexamethylphosphoric acid triamide / -78 °C / under N2 2: 30percent H3PO4 / methanol / 5 h / Ambient temperature 3: CrO3, conc H2SO4 / H2O; acetone / 0.5 h / 0 °C View Scheme

1: With n-butyllithium in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide; hexane T=0°C; 2 h; 2: With toluene-4-sulfonic acid in methanol T=20°C; 1 h;

1: n-BuLi / tetrahydrofuran; hexamethylphosphoric acid triamide / 2 h / 0 °C 2: TsOH / methanol View Scheme

1: n-BuLi / tetrahydrofuran; hexamethylphosphoric acid triamide / -78 °C / under N2 2: 30percent H3PO4 / methanol / 5 h / Ambient temperature 3: CrO3, conc H2SO4 / H2O; acetone / 0.5 h / 0 °C View Scheme

1: 1.) n-butyllithium / 1.) THF-HMPA, -78 deg C, 1 h 2: potassium carbonate / methanol / 3 h / 23 °C View Scheme

1: 1.) n-butyllithium / 1.) THF-HMPA, -78 deg C, 1 h 2: potassium carbonate / methanol / 3 h / 23 °C 3: triphenylphosphine / CH2Cl2 / 1 h / 0 °C View Scheme

1: 75 percent / n-BuLi / tetrahydrofuran; hexamethylphosphoric acid triamide / -78 °C / under N2 2: 96 percent / 30percent H3PO4 / methanol / 5 h / Ambient temperature 3: 80 percent / CrO3 / pyridine; CH2Cl2 / 0.33 h / Ambient temperature View Scheme

1: n-BuLi / tetrahydrofuran; hexamethylphosphoric acid triamide / -78 °C / under N2 2: 30percent H3PO4 / methanol / 5 h / Ambient temperature 3: CrO3, conc H2SO4 / H2O; acetone / 0.5 h / 0 °C View Scheme