Dowex-50(H+) resin in water 0.5 h; steam bath;

1: 92 percent / Dowex-50(H+) resin / H2O / 0.5 h / steam bath 2: DCC / dimethylformamide View Scheme

1: 93 percent / H2SO4 / CH2Cl2 / Ambient temperature 2: 1) sodium formate, 2) KOH / 1) DMF, a) 110 deg C, 4h, b) RT, 2 days, 2) H2O, 30-40 deg C, 4h 3: 1) triethylamine, 2) pyridine, H2O / 1) RT, 1h, 2) RT 4: 40 percent / CHCl3 / 8 h / Heating View Scheme

1: 1) sodium formate, 2) KOH / 1) DMF, a) 110 deg C, 4h, b) RT, 2 days, 2) H2O, 30-40 deg C, 4h 2: 1) triethylamine, 2) pyridine, H2O / 1) RT, 1h, 2) RT 3: 40 percent / CHCl3 / 8 h / Heating View Scheme

1: 1) triethylamine, 2) pyridine, H2O / 1) RT, 1h, 2) RT 2: 40 percent / CHCl3 / 8 h / Heating View Scheme

in chloroform 8 h; Heating;