Benzyl Bromide → tert-butyl(2S)-2-{4-[(benzyloxy)methyl]-2-oxo-1-pyrrolidinyl}butanoate

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Reaction Conditions

Reaction Steps

In a 100 ml 3 necked flask, fitted with magnetic stirrer and reflux condenser under inert atmosphere, 1.1 g (60%, 27.5 mmoles, 1.1 eq) of sodium hydride are suspended in 60 ml of DMF and the mixture cooled down to 0° C. 6.37 g (24.8 mmoles, 1 eq) of tert-butyl(2S)-2-[4-(hydroxymethyl)-2-oxo-1-pyrrolidinyl]butanoate 398 in 10 ml of DMF are added cautiously. After 10 min, 3.3 ml (4.75 g, 27.8 mmoles, 1 eq) of benzyl bromide in 10 ml of DMF are added, and stirring continued for 30 min at 0° C., followed by 3 hours at room temperature. The mixture is concentrated to dryness, the residue is suspended in brine/CH2Cl2, decanted and extracted with CH2Cl2. The combined organic phases are dried over MgSO4, concentrated to dryness and the residue is purified by Prep LC (1 kg SiO2, hexane/MTBE, 40:60→0:100) to give 3.2 g of a mixture of t-Bu and Benzyl esters in two fractions, 37% total yields. It is used as such for the next step 7.3.1.b. 1H NMR (250 MHz, (CDCl3): 0.85 (t, 3H), 1.44 (s, 9H), 1.55-1.95 (m, 2H), 2.10 (dd, 1H), 2.45 (dd, 1H), 2.55-2.70 (m, 1H), 3.45-3.55 (m, 1H), 4.40 (dd, 1H), 4.55 (s, 2H), 7.20-7.40 (m, 5H).

Provenance & Evidence