Water → (2S,4R)-N-t-Butoxycarbonyl-4-methyl glutamic acid

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Reaction Steps

A solution of (3R,5S)-1-t-Butoxycarbonyl-5-carboxy-3-methylpyrrolidine-2-one (6.2 g, 25.5 mmol) in THF (50 mL) was treated with lithium hydroxide monohydrate (3 eq, 3.20 g) and water (5 mL). After stirring for 16 hr at room temperature the THF was removed in vacuo and water (20 mL) was added. The pH was adjusted to 3 by the addition of glacial acetic acid, ether (100 mL) was added and the layers separated. The aqueous phase was extracted with ether (3 x 100 mL) and the combined organic phases were washed with brine (400 mL), dried over Na2SO4, filtered and evaporated to dryness, azeotroping with toluene (3 x 15 mL). The residue was dried under high vacuum to give 6.58 g of the product (99%) as a white foam which was used without further purification: Rf 0.8 (1% formic acid in ethyl acetate, developed with ninhydrin). 1H NMR (200 MHz, D2O): δ 3.80 (dd, J=10.4, 4.7 Hz, 1H), 2.45 (m, 1H), 2.0 (m, 1H), 1.60 (ddd, J=12.8, 4.2, 10.3 Hz, 1H), 1.25 (s, 9H), 1.0 (d, J=7.0 Hz, 3H).

Provenance & Evidence