An oven-dried, 3-L, three-necked flask equipped with a mechanical stirrer, a Friedrich condenser, and a nitrogen-inlet tube is flushed with nitrogen, and then charged with a suspension of lithium aluminum hydride (47.9 g, 1.26 mol) in 1200 mL of tetrahydrofuran (THF) (Note 1). The mixture is cooled (10°C, ice bath) and L-valine (100 g, 0.85 mol) is added in portions over a 30-min period from a 200-mL round-bottomed flask connected to the reaction flask via a flexible plastic sleeve so as not to produce too vigorous an evolution of hydrogen (Note 2). After the addition is complete, the plastic sleeve is replaced by a stopper, the ice bath is removed, and the reaction mixture is warmed to room temperature and then refluxed for 16 hr. The reaction mixture is then cooled again (10°C, ice bath) and diluted with ethyl ether (1000 mL) (Note 3). The reaction is quenched over a 30-min period with water (47 mL) (Caution! See (Note 4), aqueous 15% sodium hydroxide (47 mL, over 20 min), and water (141 mL, over 30 min). The solution is stirred for 30 min and the white precipitate is filtered. The filter cake is washed with ethyl ether (3 × 150 mL) and the organic filtrates are combined, dried with anhydrous sodium sulfate, and concentrated under reduced pressure. Distillation of the residue under vacuum affords L-valinol (63.9–65.7 g, 73–75%) (Note 5) as a clear liquid: bp 63–65°C (0.9 mm) (Note 6): [α]_D20 + 14.6° (neat); n_D20 1.455; IR (neat) cm¹: 3300, 1590; ¹H NMR (CDCl₃) δ: 0.92 (d, 6 H), 2.38–2.74 (m, 4 H), 3.13–3.78 (m, 2 H).

B. Caution! Because of the foul odor of the methyl sulfide given off, this procedure, up to the methanol quench, should be carried out in a hood.

A 2-L, three-necked, round-bottomed flask is equipped with a mechanical stirrer, heating mantel, 250-mL graduated addition funnel, and an 8-in., air-cooled reflux condenser (West type) topped with a water-cooled distillation head and a 1-L receiving flask. It is connected to a nitrogen line through the still head. The glassware is either oven-dried and cooled in a desiccator or flame-dried and assembled while still hot. The assembly is flushed with nitrogen and charged with 200 g of L-valine (1.7 mol), 400 mL of tetrahydrofuran (THF) (Note 1), and 210 mL of freshly distilled boron trifluoride etherate (242 g, 1.7 mol). The mixture is heated at a rate sufficient to cause the THF to reflux gently (Note 7) and 188 mL (1.88 mol) of borane–methyl sulfide complex (BMS) (Note 8) is added dropwise over the course of 2 hr (Note 9). The solution is then refluxed for 18 hr. The methyl sulfide that has collected at the stillhead is discarded (Note 10), and the reaction mixture is cooled to 0°C and quenched by the slow addition of 200 mL of methanol. The addition funnel is replaced by a glass stopper, and the air-cooled condenser is removed, leaving the flask equipped for distillation of solvent through the distillation head. The reaction mixture is concentrated under reduced pressure with heating and stirring. The distillation head is replaced by a water-cooled reflux condenser, and the residue is dissolved in 1 L of 6 M sodium hydroxide and refluxed for 4 hr. The mixture is saturated with potassium carbonate (ca. 400 g); cooled; filtered through a Celite pad on a coarse, fritted funnel; and extracted with three 1-L portions of chloroform. The combined extracts are washed with three portions of saturated sodium chloride (500 mL each), stirred over anhydrous potassium carbonate for 24 hr, and concentrated under reduced pressure to give a yellow oil. The crude material is vacuum distilled to give 77.5 g (44%) of purified L-valinol, bp 62–67°C/2.5 mm(Note 6); [α]_D20 + 14.6° (neat), n_D20 1.455; IR (neat film) cm⁻¹: 3300 (OH), and 1590 (NH₂); NMR δ: 0.92 (d, 6 H), 1.54 (m, 1 H), 2.38–2.74 (m, 4 H), 3.13–3.78 (m, 2 H).