Diisopropylamine → (2S,3R)-3-(2-butenyl)-2-hydroxysuccinic dimethyl ester

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Reaction Steps

To a solution of diisopropylamine (14 mL, 100 mmol) in THF at 0° C. is added BuLi (2.5 M in hexane, 40 mL, 100 mmol) over 10 minutes. The mixture is stirred at rt for 30 minutes, and then added via cannula to a −78° C. solution of dimethyl malate B-1 (7.71 g, 47.6 mmol) in THF (130 mL). The mixture is warmed to −20° C. over 2 hours, and then cooled to −78° C. Crotyl bromide (8.1 g, 60 mmol) is added, then the mixture is allowed to warm to rt and then stirred overnight. The solution is then cooled to −10° C. and quenched with NH4Cl (10%, 100 mL). The THF is removed and the residue extracted with EtOAc (2×200 mL). The combined organic layers are washed with HCl (1 N, 3×50 mL), saturated aqueous NaHCO3 (3×50 mL), and brine, then dried over Na2SO4. The solution is filtered and concentrated to give a residue, which is purified on silica gel (EtOAc/hexane 1:4) to afford (2S,3R)-3-(2-butenyl)-2-hydroxysuccinic dimethyl ester B-2.

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