2,2-Dimethoxypropane → 3-tert-butyl 4-methyl (4R)-2,2-dimethyl-1,3-oxazolidine-3,4-dicarboxylate

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Reaktionsschritte

A solution of methyl (2R)-2-{[(tert-butoxy)carbonyl]amino}-3-hydroxypropanoate (22 g, 0.1 mol), 2,2-dimethoxypropane (20.8 g, 0.2 mol) and 4-methylbenzene-1-sulfonic acid (0.5 g) in toluene was heated with stirring at 110° C. overnight. The solvent was removed under reduced pressure. The residue was treated with ethyl acetate, washed with water and brine. The organic layer was dried over sodium sulfate, concentrated under reduced pressure. The residue distilled at 0.6 mbar to give 16.5 g of 3-tert-butyl 4-methyl (4R)-2,2-dimethyl-1,3-oxazolidine-3,4-dicarboxylate (yield was 63.6%) as an amber oil.

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