1: L-methyl-Val With chloro-trimethyl-silane in dichloromethane 3 h; Inert atmosphereReflux; 2: (9H-Fluoren-9-yl)-methyl chloroformate With N-ethyl-N,N-diisopropylamine T=0°C;

sodium chlorite; sodium dihydrogenphosphate; 2-methyl-but-2-ene in tert-butyl alcohol T=20°C;

1.1: 520 mg / 110 °C 2.1: O3 / CH2Cl2 / -78 °C 2.2: methyl sulfide / CH2Cl2 / 6 h / -78 - 20 °C 3.1: 2-methyl-2-butene; aq. NaClO2; aq. NaH2PO4 / 2-methyl-propan-2-ol / 20 °C View Scheme

1.1: 85 percent / Jones reagent / acetone / 6 h / 0 °C 2.1: diphenylphosphoryl azide; Et3N / toluene / 1 h / Heating 3.1: 520 mg / 110 °C 4.1: O3 / CH2Cl2 / -78 °C 4.2: methyl sulfide / CH2Cl2 / 6 h / -78 - 20 °C 5.1: 2-methyl-2-butene; aq. NaClO2; aq. NaH2PO4 / 2-methyl-propan-2-ol / 20 °C View Scheme

1.1: diphenylphosphoryl azide; Et3N / toluene / 1 h / Heating 2.1: 520 mg / 110 °C 3.1: O3 / CH2Cl2 / -78 °C 3.2: methyl sulfide / CH2Cl2 / 6 h / -78 - 20 °C 4.1: 2-methyl-2-butene; aq. NaClO2; aq. NaH2PO4 / 2-methyl-propan-2-ol / 20 °C View Scheme

1.1: O3 / CH2Cl2 / -78 °C 1.2: methyl sulfide / CH2Cl2 / 6 h / -78 - 20 °C 2.1: 2-methyl-2-butene; aq. NaClO2; aq. NaH2PO4 / 2-methyl-propan-2-ol / 20 °C View Scheme