Hydrochloric Acid → di-tert-butyl (4S)-N-(tert-butoxycarbonyl)-4-prop-2-yn-1-yl-L-glutamate

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Reaction Conditions

Reaction Steps

Di-tert-butyl N-(tert-butoxycarbonyl)-L-glutamate (633 mg, 1.76 mmol) was dissolved in tetrahydrofuran (6 ml) and at −78° C., lithium bis(trimethylsilyl)amide (1M in tetrahydrofuran, 3.87 ml) were added dropwise. After 30 min, 3-bromo-1-(trimethylsilyl)-1-propyne (370 mg, 1.94 mmol) in tetrahydrofuran (2 ml) was added dropwise and the mixture was stirred at −78° C. for 3 h. The reaction was than warmed to 0° C. and 10 ml of 1 N hydrochloric acid were added. The mixture was extracted with dichloromethane, dried and concentrated in vacuo. The residue was purified by silica gel chromatography to give the intermediate TMS-protected alkyne. The intermediate was dissolved in 30 ml dichloromethane/methanol (1:1). Potassium carbonate (1 g) was added and the mixture was stirred for 1 h. Water (20 ml) was added and the mixture was extracted with dichloromethane, dried and concentrated in vacuo. The product (416 mg, 59%) was used in the following reaction without further purification.

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