1: 2-carboxy-2,5,5-trimethyl-1,3-dioxane With triethylamine; isobutyl chloroformate in dichloromethane T=-20°C; 0.0833333 h; 2: diazomethane in diethyl ether; dichloromethane T=-20 - 20°C; 16 h; Further stages.;

1: 85 percent / NaOH / tetrahydrofuran; H2O / 5 h / 20 °C 2: Et3N / CH2Cl2 / 0.08 h / -20 °C 3: 550 mg / CH2Cl2; diethyl ether / 16 h / -20 - 20 °C View Scheme

1.1: 72 percent / BF3*OEt2 / acetonitrile / 16 h / 20 °C 2.1: 85 percent / NaOH / tetrahydrofuran; H2O / 5 h / 20 °C 3.1: Et3N; isobutyl chloroformate / CH2Cl2 / 0.08 h / -20 °C 3.2: 99 percent / CH2Cl2; diethyl ether / 16 h / -20 - 20 °C View Scheme

1: Et3N / tetrahydrofuran / -15 °C 2: tetrahydrofuran; diethyl ether / -5 °C View Scheme

in diethyl ether; dichloromethane T=-20 - 20°C; Arndt-Eistert synthesis; 16 h;

in tetrahydrofuran; diethyl ether T=-5°C;