1,4-Dioxane → N-tert-Butoxycarbonyl-3-tert-butyl-D-alanine methyl ester

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Reaction Steps

Methyl (2Z)-2-[(tert-butoxycarbonyl)amino]-4,4-dimethylpent-2-enoate (example 4A, 60 g, 233.2 mmol) is dissolved in ethanol p.a./dioxane 3:1 (1000 ml). An argon protective gas atmosphere is passed through with a needle (˜10 min). The solution is placed in an ultrasonic bath (about 5 min) and (+)-1,2-bis[(2R,5R)-diethylphospholano]benzene(cyclooctadiene)rhodium(I) triflate (600 mg, 1% by weight) is added. The mixture is hydrogenated under a pressure of 3.5 bar of hydrogen and at RT for 3 days. The reaction mixture is filtered through kieselguhr, and the eluate is concentrated. The crude product is chromatographed (silica gel, eluent: cyclohexane/ethyl acetate 4:1). 60 g (99% of theory) of the title compound are obtained.

Provenance & Evidence