Benzyl chloroformate → 1-Benzyl 4-(tert-butyl) (2R,5R)-2-(hydroxymethyl)-5-methylpiperazine-1,4-dicarboxylate

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Reaction Steps

To (2R,5R)-5-hydroxymethyl-2-methyl-piperazine-1-carboxylic acid tert-butyl ester (21 g, 90 mmol) in THF (210 mL) at 3-4° C. (ice bath) was added 1 M aqueous NaOH (99.5 mL) and benzyl chloroformate (12.9 mL, 90.43 mmol). After stirring for 1 h at the same temperature, the mixture was left to stir for another 1 h and then warmed to RT. The organic layer was separated and the aqueous phase extracted with EtOAc (2×50 mL). The combined organic extracts were washed with saturated brine solution (150 mL), then dried over sodium sulfate, filtered and concentrated. The crude oil was purified by column chromatography on silica gel (gradient elution, 0-100%, EtOAc/petrol), to give the title compound (26 g) as a pale yellow oil, used directly in Preparation 11. 1H NMR (Me-d3-OD): 7.47-7.15 (5H, m), 5.26-5.07 (2H, m), 4.25 (2H, s), 4.04-3.88 (1H, m), 3.83 (1H, d), 3.61 (2H, bs), 3.31-3.09 (2H, m), 1.48 (9H, s), 1.14 (3H, t).

Provenance & Evidence