Triphenylphosphine → (2R)-Methyl 2-(tert-butoxycarbonylamino)-(4-((S)-2-methyl-butoxy)-phenyl)acetate

Participants

Reaction Steps

A 0° C. solution of (R)-Methyl 2-(tert-butoxycarbonylamino)-2-(4-hydroxyphenyl)acetate (2.8 g, 10 mmol), (S)-2-methyl-1-butanol (1.1 mL, 10 mmol), triphenylphosphine (2.6 g, 10 mmol), and tetrahydrofuran (100 mL) was treated dropwise with diisopropylazodicarboxylate (1.9 mL, 10 mmol) via syringe. The resulting reaction mixture was allowed to warm to room temperature and maintained overnight. The reaction was concentrated and the residue was purified by column chromatography on silica gel (5%→10% ethyl acetate in hexanes) to afford (2R)-methyl 2-(tert-butoxycarbonylamino)-(4-((S)-2-methyl-butoxy)-phenyl)acetate (2.8 g, 80% yield) as a clear, colorless oil: 1H NMR (400 MHz, CDCl3) δ 7.27 (d, J=7.3 Hz, 2H), 6.88 (d, J=8.6 Hz, 2H), 5.49 (d, J=6.6 Hz, 1H), 5.26 (d, J=7.3 Hz, 1H), 3.81 (dd, J=9.1, 6.1 Hz, 1H), 3.73 (s, 3H), 3.69-3.76 (m, 1H), 1.86 (dq, J=13.1, 6.5 Hz, 1H), 1.52-1.61 (m, 1H), 1.45 (s, 9H), 1.22-1.33 (m, 2H), 1.02 (d, J=6.8 Hz, 3H), 0.95 (t, J=7.5 Hz, 3H); LRMS (ESI) m/e 352.2 [(M+H)+, calcd for C19H30NO5 352.5].

Provenance & Evidence