1: 99 percent / 1) lithium diisopropylamide / tetrahydrofuran; various solvent(s) / 1) -5 to -15 deg C, 40 min. 2) warming to 10 deg C, 3 h 2: 98 percent / polyphosphoric acid, water / 0.5 h / 140 °C 3: 97 percent / NaOH, NaBH4 / ethanol; H2O / 2 h / Ambient temperature 4: 86 percent / conc. H2SO4 / acetic acid / 1 h / 55 - 75 °C 5: 95 percent / sodium perborate tetrahydrate / acetic acid / 1 h / 60 - 115 °C View Scheme

1: 99 percent / 1) lithium diisopropylamide / tetrahydrofuran; various solvent(s) / 1) -5 to -15 deg C, 40 min. 2) warming to 10 deg C, 3 h 2: 98 percent / polyphosphoric acid, water / 0.5 h / 140 °C 3: 1) ethyl chloroformate, triethylamine 2) sodium borohydride / 1) tetrahydrofuran, 5 deg C, 15 min.; 15 deg C, 45 min. 2) water, 40 deg C, 4 h; 20 deg C, 18 h View Scheme

Multi-step reaction with 2 steps 1: 99 percent / 1) lithium diisopropylamide / tetrahydrofuran; various solvent(s) / 1) -5 to -15 deg C, 40 min. 2) warming to 10 deg C, 3 h2: 98 percent / polyphosphoric acid, water / 0.5 h / 140 °C  

Multi-step reaction with 3 steps 1: 99 percent / 1) lithium diisopropylamide / tetrahydrofuran; various solvent(s) / 1) -5 to -15 deg C, 40 min. 2) warming to 10 deg C, 3 h2: 98 percent / polyphosphoric acid, water / 0.5 h / 140 °C3: 97 percent / NaOH, NaBH4 / ethanol; H2O / 2 h / Ambient temperature  

Multi-step reaction with 3 steps 1: 99 percent / 1) lithium diisopropylamide / tetrahydrofuran; various solvent(s) / 1) -5 to -15 deg C, 40 min. 2) warming to 10 deg C, 3 h2: 98 percent / polyphosphoric acid, water / 0.5 h / 140 °C3: 1) ethyl chloroformate, triethylamine 2) sodium borohydride / 1) tetrahydrofuran, 5 deg C, 15 min.; 15 deg C, 45 min. 2) water, 40 deg C, 4 h; 20 deg C, 18 h  

Multi-step reaction with 4 steps 1: 99 percent / 1) lithium diisopropylamide / tetrahydrofuran; various solvent(s) / 1) -5 to -15 deg C, 40 min. 2) warming to 10 deg C, 3 h2: 98 percent / polyphosphoric acid, water / 0.5 h / 140 °C3: 1) ethyl chloroformate, triethylamine 2) sodium borohydride / 1) tetrahydrofuran, 5 deg C, 15 min.; 15 deg C, 45 min. 2) water, 40 deg C, 4 h; 20 deg C, 18 h4: conc. H2SO4 / 18 h / 40 °C