(-)-2-tert-butyl-(4S)-benzyl-(1,3)-oxazoline could be produced through the following synthetic routes.

(-)-2-tert-butyl-(4S)-benzyl-(1,3)-oxazoline (2). In a two-necked 500-mL round-bottomed flask are placed 12 g of molecular sieves. (2S)-(-)-2-Amino-3-phenyl-1-propanol ((S)-phenylalaninol) (5.20 g, 0.0344 mol) and trimethylacetaldehyde (2.96 g, 0.0344 mol, 1.0 equiv) are dissolved in 150 mL of dichloromethane. The resulting slightly turbid solution is added to the flask containing the molecular sieves. The flask is fitted with a glass stopper and a CaCl₂-filled drying tube. The reaction mixture is stirred at room temperature for 18 h. Subsequently the glass stopper is replaced by a thermometer, the drying tube is removed and N- (6.19 g, 0.0348 mol, 1.01 equiv) is added. The resulting yellow-orange reaction mixture is stirred for 60 min at room temperature. The orange mixture is filtered and the filtrate was transferred to a 500-mL separatory funnel where it is extracted with 50 mL of 0.5 m aq. Na₂S₂O₃ solution, 50 mL of sat. aq. Na₂CO₃ solution and 50 mL of water. The combined aqueous phases are then extracted with 50 mL of CH₂Cl₂ in a 500-mL separatory funnel and the combined organic phases are washed with 50 mL of brine in a 500-mL separatory funnel, then are dried over MgSO₄ (7 g) and are filtered through a glass funnel with a cotton wool plug. The filtrate is transferred to a 500-mL, round-bottomed flask and is treated with Celite (10 g) and the solvent is removed on a rotary evaporator under reduced pressure. The resulting solid is transferred to a column (17 cm × 5 cm, h × d) containing 150 g of silica gel. Elution with pentane/MTBE (10:1 to 7:1 to 5:1) affords 5.57-5.72 g (74-76%) of a pale yellow liquid.