Ammonium Chloride → methyl 3-((E)-2-((1S,2S,5R)-2-benzyloxycarbonylamino-5-(tert-butoxycarbonylamino)cyclohexyl)vinyl)benzoate

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Reaction Steps

A suspension of 3-(methoxycarbonyl)benzyltriphenylphosphonium bromide (1.8 g, see J. Chem. Soc. 1961, 5015) in tetrahydrofuran (5 mL) was stirred on an ice bath and treated dropwise over 10 min with a solution of potassium bis(trimethylsilyl)amide (0.5 M in toluene, 7.3 mL). The resulting yellow suspension was stirred on ice for 15 min, then was treated with a solution of (1R,2S,5R)-tert-butyl 2-(benzyloxycarbonylamino)-7-hydroxy-6-aza-bicyclo[3.2.1]octane-6-carboxylate (460 mg) in tetrahydrofuran (3 mL). After allowing to stir on an ice bath for 75 min, the mixture was stirred at rt for 3 h. Saturated aqueous NH4Cl was added, the mixture was stirred rapidly until colorless, then was extracted three times with ethyl acetate. The combined organic phases were washed with 1.0 M aqueous HCl, then with brine, dried over Na2SO4 and concentrated under vacuum. The residue was purified by flash column chromatography on silica gel, eluting with 2:1 v/v hexane-ethyl acetate, to provide methyl 3-((E)-2-((1S,2S,5R)-2-benzyloxycarbonylamino-5-(tert-butoxycarbonylamino)cyclohexyl)vinyl)benzoate as a glassy foam (365 mg). MS found: (M+H)+=509.3.

Provenance & Evidence