Acetone → (R)-isopropylidenebutane-1,2,4-triol

(R)-(+)-1,2,4-Butanetriol (0.7 g, 6.6 mmol), prepared as described in step a) above, was stirred for 1.5 h in acetone (50 ml) containing 3 drops of conc. perchloric acid, a satured solution of sodium bicarbonate in water (5 ml) was added and the stirring was continued for additional 10 min. The precipitate was filtered off and the filtrate evaporated under reduced pressure (2.7 kPa, 30° C.). The residue was taken up in ethyl acetate, washed with saturated aqueous sodium bicarbonate (5 ml) and brine (5 ml), and dried over magnesium sulphate. Evaporation of the solvent and distillation gave the title compound as a colourless oil (0.3 g, 2.05 mmol, 31%): b.p. 104°-106° C. at~2.7 kPa. nD20 =1.4390.