1: 1,4-dioxa-spiro[4.5]decane-8-carboxylic acid ethyl ester With lithium diisopropyl amide 2: chloro-trimethyl-silane

1: 81 percent / 4-MeC6H4SO3H / Heating 2: 1.) LDA / 1) THF, -20 deg C, 1 h, 2) THF, -20 deg C, 30 min, -20 deg C --> rt, 1 h View Scheme

lithium diisopropyl amide 1) THF, -20 deg C, 1 h, 2) THF, -20 deg C, 30 min, -20 deg C --> rt, 1 h; Yield given. Multistep reaction;

1: N-(2-naphthalenesulfonyl)-D-valine, BH3*THF / various solvent(s) / 3 h / -78 °C 2: n-Bu4NF / tetrahydrofuran / 1 h / Ambient temperature 3: 1.) Me3Al / 1) CH2Cl2, toluene, rt, 30 min; 2) CH2Cl2, toluene. 50-55 deg C, 2 d View Scheme

1: N-(2-naphthalenesulfonyl)-D-valine, BH3*THF / various solvent(s) / 3 h / -78 °C 2: n-Bu4NF / tetrahydrofuran / 1 h / Ambient temperature 3: 1.) Me3Al / 1) CH2Cl2, toluene, rt, 30 min; 2) CH2Cl2, toluene. 50-55 deg C, 2 d 4: BnNEt3Cl, (EtO)2P(O)Cl, aq. NaOH / CH2Cl2 / 2 h / Ambient temperature 5: toluene; various solvent(s) / 1.5 h / 48 - 52 °C / further solvents and temperatures View Scheme

1: N-(2-naphthalenesulfonyl)-D-valine, BH3*THF / various solvent(s) / 3 h / -78 °C 2: n-Bu4NF / tetrahydrofuran / 1 h / Ambient temperature 3: 1.) Me3Al / 1) CH2Cl2, toluene, rt, 30 min; 2) CH2Cl2, toluene. 50-55 deg C, 2 d 4: BnNEt3Cl, (EtO)2P(O)Cl, aq. NaOH / CH2Cl2 / 2 h / Ambient temperature View Scheme