N-Hydroxy-(S)-1-phenylethylamine oxalate (CAS NO.: 78798-33-1) could be produced through the following synthetic routes.

A. (S)-[(1-Phenylethyl)amino]acetonitrile (CAS NO.: 35341-76-5). A 1-L, round-bottomed flask equipped with a -coated magnetic stirrer bar, rubber septum and argon gas inlet is charged with (S)-1-phenylethylamine (10.17 g, 83.92 mmol), acetonitrile (MeCN) (170 mL), and diisopropylethylamine (i-Pr₂NEt) (29.2 mL, 168 mmol). After stirring the solution for 5 min, bromoacetonitrile (6.43 mL, 92.3 mmol) is added via syringe over 10 min. The reaction mixture is stirred at ambient temperature until completion of the reaction. The mixture is then concentrated on a rotary evaporator to give a white solid, to which is added saturated aqueous sodium bicarbonate (NaHCO₃) solution (100 mL); the suspension is extracted with dichloromethane (CH₂Cl₂) (100 mL). The organic phase is washed with brine (100 mL), and the combined aqueous phases are back-extracted with CH₂Cl₂ (3 × 100 mL). The combined organic extracts are dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to give a slightly yellow oil (21.6 g). To the crude oil is added CH₂Cl₂ (10 mL) and the resulting solution is passed through a short column of silica gel (5 cm i. d. × 10 cm, 100 g of SiO₂). A forerun was obtained by elution with 400 mL of 9:1 hexanes:ethyl acetate, followed by collection of the desired fractions with 100 mL of 9:1 hexanes:ethyl acetate, then 700 mL of 7:3 hexanes:ethyl acetate. Concentration of the appropriate fractions on a rotary evaporator and then under high vacuum gives (S)-[(1-phenylethyl)amino]acetonitrile as a colorless oil (13.62 g, 101%).

B. [(1S)-1-Phenylethyl]imino]acetonitrile N-oxide (CAS NO.: 300843-73-6). A 1-L, three-necked flask equipped with a mechanical stirrer, argon gas inlet, and thermometer is charged with (S)-[(1-phenylethyl)amino]acetonitrile (10.34 g, 64.54 mmol) and CH₂Cl₂ (200 mL), and the resulting solution is cooled in an ice bath. m-Chloroperbenzoic acid (MCPBA) (ca. 77%, 34.3 g, 153 mmol) is added in portions over 30 min. After completion of the addition, the ice bath is removed and the mixture is stirred at ambient temperature. When the reaction is complete, the mixture is cooled in an ice bath again, and aqueous sodium thiosulfate (Na₂S₂O₃) (16.0 g, 129 mmol, in 60 mL of H₂O) and saturated NaHCO₃ (200 mL) are added. The resulting slurry is stirred vigorously for 15 min until the white solid completely dissolves. The two-phase solution is separated using a separatory funnel. The aqueous phase is extracted with CH₂Cl₂ (100 mL). The organic layer is washed with brine (100 mL), and the combined aqueous phases are back-extracted with CH₂Cl₂ (3 × 100 mL). The combined organic extracts are dried over anhydrous sodium sulfate, filtered, and concentrated on a rotary evaporator to afford crude nitrone (11.5 g) as slightly yellow crystals.

C. N-Hydroxy-(S)-1-phenylethylamine oxalate (CAS NO.: 78798-33-1). A 1-L, round-bottomed flask equipped with a reflux condenser, Teflon-coated magnetic stirrer bar, and argon gas inlet is charged with crude nitrone (11.5 g) and methanol (MeOH) (130 mL). After addition of hydrochloride (20.8 g, 323 mmol) in one portion at ambient temperature, the mixture is warmed to 60°C (55°C internal) and is stirred at that temperature for 2 hr. The reaction mixture is cooled to room temperature and diluted with CH₂Cl₂ (260 mL). After stirring for 5 min, the resulting precipitate is collected by filtration and the filter cake is washed with CH₂Cl₂ (40 mL). The filtrate is neutralized with saturated NaHCO₃ (150 mL) and partitioned. The aqueous phase is extracted with CH₂Cl₂ (100 mL). The organic phase is washed with brine (100 mL), and the combined aqueous phases are back-extracted with CH₂Cl₂ (3 × 100 mL). The combined organic extracts are dried over anhydrous sodium sulfate, filtered and concentrated to a minimum volume at a temperature below 25°C under reduced pressure. To the residue is added a MeOH (25 mL) solution of oxalic acid (11.6 g, 129 mmol) and ether (Et₂O) (100 mL), precipitating white crystals, which are collected by filtration and washed with Et₂O (3 × 20 mL). After drying under reduced pressure, (S)-N-1- phenylethylhydroxylamine oxalate (12.6 g, 86% for two steps) is obtained as white crystals. The oxalate salt was recrystallized from hot ethanol (110 mL) and washed with Et₂O (50 mL) to provide analytically pure material (10.45, 71% for two steps). Concentration and recrystallization of the mother liquor provides additional (S)-N-1-phenylethylhydroxylamine oxalate (0.85 g, 6%).

Notice: Reactions and subsequent operations involving peracids and peroxy compounds should be run behind a safety shield. Peroxy compounds should be added to the organic material, never the reverse. For relatively fast reactions, the rate of addition of the peroxy compound should be slow enough so that it reacts rapidly and no significant unreacted excess is allowed to build up. The reaction mixture should be stirred efficiently while the peroxy compound is being added, and cooling should generally be provided since many reactions of peroxy compounds are exothermic. New or unfamiliar reactions, particularly those run at elevated temperatures, should be run first on a small scale. Reaction products should never be recovered from the final reaction mixture by distillation until all residual active oxygen compounds (including unreacted peroxy compounds) have been destroyed. Hydroxylamines may cause explosions under certain conditions. Careful handling and proper safety equipment are needed especially when they are heated or have not been converted to salts with acids.