1-O-tert-butyl 5-O-methyl (2S)-2-[bis[(2-methylpropan-2-yl)oxycarbonyl]amino]pentanedioate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 13.4 g of Boc-Glu(OMe)-OtBu (˜39.6 mmol) are dissolved in 30 mL of acetonitrile and treated with 986 mg of DMAP (7.91 mmol, 0.2 eq). Under nitrogen atmosphere a solution of 17.6 g of di-tert-butylbicarbonate (77.1 mmol, 2 eq) in 100 mL of acetonitrile is added. After stirring overnight, the solvent is removed in vacuo and the obtained crude product is purified by chromatography on silica gel (column: 31*6.0 cm, petroleum ether/ethyl acetate 9:1) the solvent is removed in vacuo the obtained crude product is purified by chromatography on silica gel (column: 31*6.0 cm, petroleum ether/ethyl acetate 9:1)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 13.4 g of Boc-Glu(OMe)-OtBu (˜39.6 mmol) are dissolved in 30 mL of acetonitrile and treated with 986 mg of DMAP (7.91 mmol, 0.2 eq). Under nitrogen atmosphere a solution of 17.6 g of di-tert-butylbicarbonate (77.1 mmol, 2 eq) in 100 mL of acetonitrile is added. After stirring overnight, the solvent is removed in vacuo and the obtained crude product is purified by chromatography on silica gel (column: 31*6.0 cm, petroleum ether/ethyl acetate 9:1) the solvent is removed in vacuo the obtained crude product is purified by chromatography on silica gel (column: 31*6.0 cm, petroleum ether/ethyl acetate 9:1)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 1.3 g of N-tert.-butyloxycarbonyl-L-glutamic acid 5-methyl ester 1-tert.-butyl ester (1.2., 4.12 mmol) are dissolved in 15 ml of acetonitrile and mixed with 100 mg of N,N-dimethyl-4-aminopyridine (DMAP). A solution of 1.79 g of di-tert.-butyl-bicarbonate (8.2 mmol) in 7 ml of acetonitrile is added under nitrogen atmosphere. After stirring overnight, the solvent is removed under vacuum and the crude product obtained is purified by means of chromatography on silica gel. the solvent is removed under vacuum

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 13.4 g of Boc-Glu(OMe)-OtBu (˜39.6 mmol) are dissolved in 30 mL of acetonitrile and treated with 986 mg of DMAP (7.91 mmol, 0.2 eq). Under nitrogen atmosphere a solution of 17.6 g of di-tert-butylbicarbonate (77.1 mmol, 2 eq) in 100 mL of acetonitrile is added. After stirring overnight, the solvent is removed in vacuo and the obtained crude product is purified by chromatography on silica gel (column: 31*6.0 cm, petroleum ether/ethyl acetate 9:1) the solvent is removed in vacuo the obtained crude product is purified by chromatography on silica gel (column: 31*6.0 cm, petroleum ether/ethyl acetate 9:1)