Hydrochloric Acid → [1-Benzyl-3-(benzyloxycarbonyl-isobutyl-amino)-2-hydroxy-propyl]-carbamic Acid hexahydro-furo[2,3-b]furan-3-yl Ester

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Reaction Steps

(3-tert-Butoxycarbonylamino-2-hydroxy-4-phenyl-butyl)-isobutyl-carbamic acid benzyl ester 16 (7.54 g, 15 mmol) and 35 ml of 4M HCl in dioxane were stirred 30 min under an argon atmosphere. The mixture was concentrated in vacuo, and co-evaporated twice with dichloromethane. The residue was dissolved in dichloromethane (50ml) and N,N-diisopropylethylamine (6.1 ml, 35 mmol), and carbonic acid 2,5-dioxo-pyrrolidin-1-yl ester hexahydro-furo[2,3-b]furan-3-yl ester 17 (4.88g, 18 mmol) was added. The reaction mixture was stirred overnight, and then concentrated in vacuo. The residue was diluted with dichloromethane, and sequentially washed with brine, 10% KHSO4, brine, saturated NaHCO3, and brine, then dried over MgSO4, and concentrated in vacuo. The oily residue was purified by flash chromatography using 70:30 ethyl acetate hexane as eluant, to give [3-(Hexahydro-furo[2,3-b]furan-3-yloxycarbonylamino)-2-hydroxy-4-phenyl-butyl]-isobutyl-carbamic acid benzyl ester 18 (5.8 g, 73%) as a white solid. TLC: Rf 0.56 (7:3 ethyl acetate: hexane). MS m/z 527 (MH)+.

Provenance & Evidence