(2S)-5-azido-2-[(2-methylpropan-2-yl)oxycarbonylamino]pentanoic acid

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: N,N-Diisopropylethylamine (111 μL, 0.639 mmol) and subsequently bromoacetonitrile (203 μL, 2.90 mmol) were added to a solution of (S)-5-azido-2-((tert-butoxycarbonyl)amino)pentanoic acid (Compound tk69) (150 mg, 0.581 mmol) in acetonitrile (0.8 mL) at room temperature under a nitrogen atmosphere. The reaction mixture was stirred at the same temperature for 4 hours and then concentrated under reduced pressure, and the resulting crude product was purified by normal-phase silica gel column chromatography (hexane/ethyl acetate) to afford (S)-cyanomethyl 5-azido-2-((tert-butoxycarbonyl)amino)pentanoate (Compound tk70) (185 mg, quant.). concentrated under reduced pressure the resulting crude product was purified by normal-phase silica gel column chromatography (hexane/ethyl acetate)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Sodium bicarbonate (1.99 g, 23.68 mmol) was added to a mixture of Boc-Orn-OH (Compound tk56) (1.0 g, 4.31 mmol) and copper sulfate pentahydrate (21 mg, 0.086 mmol) in methanol (20 mL)-water (6 mL) at room temperature, followed by addition of 1H-imidazole-1-sulfonyl azide hydrochloride synthesized by the method described in the literature (Org. Lett., 2007, 9, 3797) (1.08 g, 5.17 mmol). The reaction mixture was stirred at room temperature for 24 hours. The reaction mixture was cooled in an ice bath, followed by addition of a saturated aqueous potassium bisulfate solution (8 mL). The resulting mixture was extracted with ethyl acetate (three times), and the organic phase was concentrated under reduced pressure. The resulting residue was purified by reverse-phase silica gel column chromatography (0.05% aqueous trifluoroacetic acid solution/0.05% trifluoroacetic acid-acetonitrile solution) to afford (S)-5-azido-2-((tert-butoxycarbonyl)amino)pentanoic acid (Compound tk69) (1.19 g, quant.). synthesized by the method The reaction mixture was cooled in an ice bath The resulting mixture was extracted with ethyl acetate (three times) the organic phase was concentrated under reduced pressure The resulting residue was purified by reverse-phase silica gel column chromatography (0.05% aqueous trifluoroacetic acid solution/0.05% trifluoroacetic acid-acetonitrile solution)