反应详情

Adapting a literature procedure (Jandeleit et al., U.S. Pat. No. 8,168,617 (2012)), tert-butyl(3S)-3-(tert-butoxycarbonylamino)-5-(2-methyl-5-nitro-phenyl)pent-4-enoate (18b) is prepared from [(2S)-4-tert-butoxy-2-(tert-butoxycarbonylamino)-4-oxo-butyl]-triphenyl-phosphonium iodide (18a) (1.30 g, 2.0 mmol), 2-methyl-5-nitro-benzaldehyde (1b) (495 mg, 3.0 mmol) (commercial or prepared in two steps from commercial 2-methyl-5-nitro benzoic acid (i) BH3.SMe2, THF, reflux, ii) MnO2, DCM, room temperature) as described in Example 1) with a commercial ˜1.0 M solution of potassium tert-butoxide (KOtBu) (3.0 mL, 3.0 mmol) in anhydrous tetrahydrofuran (THF) (10 mL) at with gradual warming from 0° (ice bath) to room temperature for 24 hours. Aqueous work and purification by silica gel column chromatography furnish the title compound (18b) as a mixture of geometric isomers ((E)/(Z)-isomers).

1. customAqueous work and purification by silica gel column chromatography