Glutamic acid diethyl ester → Diethyl N-(4-ethynylbenzoyl)-L-glutamate

Participants

Reaction Steps

To a solution of 0.55 g of 4-ethynylbenzoic acid (obtained from tert.-butyl 4-ethynylbenzoate in 84% yield by hydrolysis with trifluoroacetic acid) in 50 ml of anhydrous ether and 25 ml of anhydrous tetrahydrofuran is added 1.58 ml of triethylamine. This is followed by 1.00 g of phenyl N-phenylphosphoramidochloridate. After stirring the reaction mixture at room temperature under nitrogen for 0.5 hour, 0.90 g of diethyl L-glutamate is added in one portion. The mixture is allowed to stir for another 8 hrs. After a workup, the residue is subjected to column chromatography using a 1% methanol:methylene chloride mixture as the eluent. The major fraction isolated from the column contained 0.68 g (54%) of diethyl N-(ethynylbenzoyl)-L-glutamate as an oil which slowly solidified: NMR (CDCl3, 300 MHz) delta 1.25 (t, 3H, J=6.9 Hz), 1.33 (t, 3H, J=6.9 Hz), 2.11-2.60 (m, 4H), 3.23 (s, 1H), 4.09 (q, 2H, J=6.9 Hz), 4.27 (l, 2H, J=6.9 Hz), 4.80 (m, 1H), 7.12 (d, 1H, J=7.2 Hz), 7.59 (d, 2H, J=8.4 Hz), 7.81 (d, 2H, J=8.4 Hz); IR (KBr) 3330, 3280, 2990, 1735, 1640, 1520, 1380, 1200, 1105, 1020, 855, and 770 cm- 1.

Provenance & Evidence