(3-(4-chlorobenzyl)-4-methyl phenyl)((3aS,5R,6S,6aS)-6-hydroxy-2,2-dimethyltetrahydrofuro[2,3-d][1,3]dioxol-5-yl)methanone (4, 26.1 g, 64.9 mmol) and CeCl3.7 H2O (29.0 g, 77.9 mmol) were suspended in 520 mL of MeOH. Sodium borohydride (982 mg, 26.0 mmol, dissolved in 10 mL of 1N aqueous NaOH) was added and the reactants slowly went into solution over about 5 minutes. Another 100 mg (2.6 mmol) of sodium borohydride was added to push the reaction to completion. The reaction was stirred for 10 minutes and quenched with 500 mL of saturated aqueous NH4Cl. Most of the MeOH was removed in vacuo and the residual solvents were diluted with a 1:1 (v:v) solution of saturated aqueous NH4Cl:brine. The aqueous layer was extracted three times with 500 mL of EtOAc. The combined organic layers were washed with brine, dried over MgSO4, filtered, and concentrated under vacuum. The crude product was used without further purification in the next step (26.2 g, 99% yield, >10:1 d.r.). 1H NMR (400 MHz, CHLOROFORM-d) δ ppm 7.14-7.31 (m, 5 H), 7.04 (d, J=8.3 Hz, 2 H), 6.04 (d, J=3.8 Hz, 1 H), 5.24 (t, J=3.4 Hz, 1H), 4.51 (d, J=3.8 Hz, 1 H), 4.14-4.21 (m, 2 H), 4.04 (d, J=1.5 Hz, 1 H), 3.97 (s, 2 H), 2.77 (d, J=3.0 Hz, 1 H), 2.20-2.27 (m, 3 H), 1.46 (s, 3 H), 1.33 (s, 3 H). MS (ES+) [M+NH4]+=422.
