1: 2,2-Dimethyl-1,3-dioxan-5-one With L-proline in N,N-dimethyl-formamide T=20°C; 0.5 h; 2: cyclohexanecarbaldehyde in N,N-dimethyl-formamide T=2°C; aldol reaction; Title compound not separated from byproducts;

1: benzene / 80 °C 2: 1.) t-BuLi / 1.) Et2O, pentane, -80 deg C, 40 min, 2.) Et2O, pentane, from -100 deg Cto RT, 14 h 3: 84 percent / O3 / CH2Cl2 / -78 °C 4: 1.) dicyclohexylboron chloride, EtMe2N / 1.) Et2O, a) -80 deg C, 15 min, b) from -80 deg C to 0 deg C, 1 h, 2.) Et2O, a) -80 deg C, 1 h, b) from -80 deg C to -20 deg C, 10-14 h 5: 67 percent / Et3N*3HF / tetrahydrofuran / 10 h / -20 °C View Scheme

1: 1.) t-BuLi / 1.) Et2O, pentane, -80 deg C, 40 min, 2.) Et2O, pentane, from -100 deg Cto RT, 14 h 2: 84 percent / O3 / CH2Cl2 / -78 °C 3: 1.) dicyclohexylboron chloride, EtMe2N / 1.) Et2O, a) -80 deg C, 15 min, b) from -80 deg C to 0 deg C, 1 h, 2.) Et2O, a) -80 deg C, 1 h, b) from -80 deg C to -20 deg C, 10-14 h 4: 67 percent / Et3N*3HF / tetrahydrofuran / 10 h / -20 °C View Scheme

1: 1.) dicyclohexylboron chloride, EtMe2N / 1.) Et2O, a) -80 deg C, 15 min, b) from -80 deg C to 0 deg C, 1 h, 2.) Et2O, a) -80 deg C, 1 h, b) from -80 deg C to -20 deg C, 10-14 h 2: 67 percent / Et3N*3HF / tetrahydrofuran / 10 h / -20 °C View Scheme