13574-13-5

1676-73-9

24424-99-5

13574-13-5

The general procedure for the synthesis of Boc-L-glutamic acid-O-benzyl from L-glutamic acid-5-benzyl ester and di-tert-butyl dicarbonate is as follows: Example 28 - Preparation of Formula 125-Compound 28a-Intermediate B: (S)-5-(benzyloxy)-2-(tert-butoxycarbonyl)-5-oxopentanoic acid 1. Compound A (5.0 g, 21.1 mmol) was dissolved in a solvent mixture of dioxane and water (1:1, 40 mL) and cooled at 0°C. 2. Boc2O (5.06 g, 23.1 mmol) was added to the above solution, followed by stirring the reaction mixture at room temperature overnight. 3. After completion of the reaction, the solvent was removed by distillation under reduced pressure. 4. The residue was diluted with water (30 mL) and alkalized with Na2CO3 (0.7 g). 5. The aqueous layer was washed with EtOAc (3 x 20 mL). 6. The pH of the aqueous layer was adjusted to 2-3 with 5 M aqueous HCl followed by extraction with EtOAc (4 x 50 mL). 7. The organic extracts were combined, washed with brine and dried with Na2SO4. 8. The solvent was removed under pressure to give (S)-5-(benzyloxy)-2-(tert-butoxycarbonyl)-5-oxovaleric acid (7.1 g, 100%) as a viscous colorless oil. Product characterization: LC-MS (Agilent): retention time (Rt) 3.40 min; m/z calculated value C17H23NO6 [M + Na]+ 360.15, measured value 360.1.