2,2-Dimethoxypropane → (4S,5R)-3-(tert-butoxycarbonyl)-2,2,5-trimethyloxazolidine-4-carboxylic acid

Participants

Reaction Steps

Boc-L-threonine (600 g, 2.74 mol) was added to methyl-tert-butyl ether (3.6 L) and THF (1.2 L) followed by 2,2-dimethoxypropane (1710 g, 16.42 mol) and pyridinium p-toluenesulfonate (171.9 g, 684 mmol) and the suspension heated to reflux for 20 hours. The reaction was cooled and diluted with water (3 L) and stirred to achieve a solution. The organic layer was collected, washed with water (1.8 L), and diluted with methyl-tert-butyl ether (4.2 L). A solution of NaOH in water (109 g in 120 mL) was added and the mixture stirred for 20 minutes. The mixture was concentrated to low volume to effect precipitation. The resulting solid was filtered and collected as the sodium salt of the title compound.

Provenance & Evidence