Thionyl Chloride → (2R)-2-((2-(tert-butoxycarbonylamino)ethyl)amino)-3-(2-naphthyl)propionic acid methylester

Participants

Reaction Steps

##STR196## (2R)-2-Amino-3-(2-naphthyl)propionic acid (5, 0 g, 23 mmol) was added to methanol (150 ml) and thionylchloride (2.0 ml; 23 mmol) was added dropwise and the mixture was stirred overnight and then refluxed for 2.5 h. The solvent was removed in vacuo and the residue was dissolved in a mixture of methanol (95 ml) and acetic acid (5 ml). (2-Oxoethyl)carbamic acid tert-butyl ester (3.4 g, 23 mmol, prepared as in Dueholm et al. Org. Prep. Proced. Int. (1993), 457), sodium cyanoborohydride (1.9 g, 31 mmol) and molecular sieves (50 g, Fluka, 3Å) were added and the mixture was left overnight. The mixture was filtered and the filtrate was added to water (200 ml) and extracted with methylene chloride (3×100 ml). The combined organic phases were dried (magnesium sulphate), and the solvent was removed in vacuo. The residue was chromatographed on silica (3×30 cm) to afford 3.55 g of (2R)-2-((2-(tert-butoxycarbonylamino)ethyl)amino)-3-(2-naphthyl)propionic acid methylester.

Provenance & Evidence