Citric Acid → tert-butyl (1S)-1-benzyl-2-oxobut-3-enylcarbamate

HRID 654304Notes

Reaction equation

[CH:1]([Mg]Br)=[CH2:2].[C:5]([O:9][C:10]([NH:12][C@H:13]([C:21]([OH:23])=O)[CH2:14][C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1)=[O:11])([CH3:8])([CH3:7])[CH3:6].C(O)(=O)CC(CC(O)=O)(C(O)=O)O>CCOCC>[C:5]([O:9][C:10]([NH:12][C@@H:13]([CH2:14][C:15]1[CH:16]=[CH:17][CH:18]=[CH:19][CH:20]=1)[C:21](=[O:23])[CH:1]=[CH2:2])=[O:11])([CH3:6])([CH3:7])[CH3:8]

Participants

Conditions

Temperature: -10 °C

Procedure

Vinylmagnesium bromide (1M in tetrahydrofuran) was cooled under N2 atmosphere to -10° C. and treated in portions with 10 g (37.7 mmol) of N-(t-butyloxycarbonyl)-L-phenylalanine. The resulting solution was stirred at -10° C. for 5 h, and poured into a rapidly stirring mixture of ice, 10% aqueous citric acid and ether. The mixture was separated, and the organic phase was washed sequentially with water, two portions of aqueous NaHCO3, and saturated brine; dried over MgSO4 ; and concentrated in vacuo. Silica gel chromatography of the residue using 4:1 hexane:ethyl acetate provided 3.63 g (35%) of the desired compound (Rf 0.33, 3:1 hexane:ethyl acetate). 1H NMR (CDCl3) δ 1.41 (s, 9 H), 2.98 (dd, J=14, 6 Hz, 1 H), 3.15 (dd, J=14, 6 Hz, 1 H), 4.86 (q, J=8 Hz, 1 H), 5.23 (br d, 1 H), 5.85 (dd, J=9, 2 Hz, 1 H), 6.35 (dd, J=18, 2 Hz, 1 H), 6.45 (dd, J=18, 9 Hz, 1 H), 7.10 (br d, 2 H), 7.25 (m, 3 H). Mass spectrum: (M+H)+ =276.

Workup

additionpoured into
stirringa rapidly stirring
customThe mixture was separated
washthe organic phase was washed sequentially with water, two portions of aqueous NaHCO3, and saturated brine
dry with materialdried over MgSO4
concentrationand concentrated in vacuo

Sources & evidence

ORD record: ord-0755a79915dc44129a66a33d1d91e0af
Source dataset: uspto-grants-1992_07
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US05130468

Reaction notes

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