Reaction #2003

Reaction equation

1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride

D-tryptophan benzyl ester

1-hydroxybenztriazole hydrate

t-butoxycarbonyl-α-methylalanine

→

(R)-α-[(2-t-Butoxycarbonylamino-2-methyl-1-oxopropyl)amino]-1H-indole-3-propanoic acid, benzyl ester

Solvents

water

chloroform

Conditions

Workup

1. 1
   OtherThe chloroform layer was separated
2. 2
   Washwashed with 5% aqueous citric acid solution (25 mL) and 5% aqueous sodium bicarbonate solution (25 mL)
3. 3
   DryingThe chloroform layer was dried over magnesium sulfate
4. 4
   Filtrationfiltered
5. 5
   Otherevaporated under vacuum
6. 6
   Otherto afford a thick oily foam
7. 7
   Otherafforded a yellow foam (0.822 g 50%)

Procedure

Crude D-tryptophan benzyl ester (1.0 g, 3.40 mmol), 1-hydroxybenztriazole hydrate (0.63 g, 4.1 mmol) and t-butoxycarbonyl-α-methylalanine (0.84 g, 4.11 mmol) were stirred together at room temperature in chloroform (20 mL). 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (980 mg, 5.11 mmol) was added to this mixture in a single portion. The reaction mixture was stirred at room temperature for 4 hours and worked up by pouring into water (50 mL). The chloroform layer was separated and washed with 5% aqueous citric acid solution (25 mL) and 5% aqueous sodium bicarbonate solution (25 mL). The chloroform layer was dried over magnesium sulfate, filtered and evaporated under vacuum to afford a thick oily foam. Chromatography on silica gel using ethyl acetate/hexanes (2:3 v/v) afforded a yellow foam (0.822 g 50%).

Source