1: KHMDS / tetrahydrofuran; toluene / 0.5 h / -78 °C 2: 82 percent / HMPA / tetrahydrofuran / 0.5 h / -78 °C 3: 90 percent / pyridinium p-toluenesulfonate / methanol / 1.5 h / 20 °C 4: 90 percent / 1N LiOH; CO2 / methanol; tetrahydrofuran / 2.5 h / 0 °C View Scheme

1: KHMDS / tetrahydrofuran; toluene / 0.5 h / -78 °C 2: HMPA / tetrahydrofuran / 0.5 h / -78 °C 3: 85 percent / H2; Lindlar catalyst / hexane; pyridine / 36 h 4: 84 percent / pyridinium p-toluenesulfonate / methanol / 1.5 h / 20 °C 5: 85 percent / 1N LiOH; CO2 / methanol; tetrahydrofuran / 2.5 h / 0 °C View Scheme