3,4-dihydro-2H-pyran → (1R,3S,5S)-5-(Tetrahydro-pyran-2-yloxymethyl)-2-aza-bicyclo[3.1.0]hexane-2,3-dicarboxylic acid 2-tert-butyl ester 3-ethyl ester

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Reaction Steps

A mixture of (1R,3S,5S)-5-hydroxymethyl-2-aza-bicyclo[3.1.0]hexane-2,3-dicarboxylicacid 2-tert-butyl ester 3-ethyl ester (500 mg, 1.75 mmol), 3,4-dihydro-2H-pyran (176 μL, 1.93 mmol) and TsOH.H2O (33 mg, 0.17 mmol) in CH2Cl2 (6 mL) was stirred 3 h at RT. Then poured into a saturated aqueous solution of NaHCO3 and extracted with CH2Cl2 (×2). The combined organic extracts were dried (Na2SO4), filtered and concentrated. The crude residue was purified by flash column chromatography on silica gel (c-hexane to c-hexane/EtOAc 1:1). Colorless oil. TLC, Rf (EtOAc)=0.85; MS (UPLC/MS): 370.4 [M+H]+, 387.4 [M+H2O]+; tR (HPLC conditions f): 2.28 min.

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