Sodium hydride → N-(tert-Butoxycarbonyl)-O-(2-nitrophenyl)-L-threonine

Temperature

0 °C

A solution of N-[(1,1-dimethylethoxy)carbonyl]-L-threonine (5.02 g., 22.9 mmol.) in dry dimethylformamide (10 ml.) was added dropwise over a period of 30 minutes to a cooled (0° C.) suspension of 60% sodium hydride (1.93 g., 48.25 mmol., 2.11 eq.) in dry dimethylformamide (40 ml.). The reaction was stirred at 0° C. until the frothing subsided (about 3.5 hours). The reaction mixture was treated dropwise with 1-fluoro-2-nitrobenzene (2.67 ml., 25.2 mmol., 1.1 eq.) over a period of 20 minutes and stirred at 0° C. under argon for 2 hours. The reaction mixture was then placed in the cold room (5° C.) and stirred overnight. The reaction mixture was poured into ice-water (500 ml.) and extracted with ethyl ether (2×200 ml.). The aqueous phase was brought to DH 1.0 with 6N hydrochloric acid (200 ml.) and extracted with ethyl acetate (3×300 ml.). The combined ethyl acetate extracts were washed with water (2×300 ml.), and brine (300 ml.), dried (anhydrous sodium sulfate), filtered, evaporated to dryness and dried in vacuo. The crude residue was loaded onto celite and purified by chromatography on a 10×20 cm. silica gel column. Elution with methylene chloride (3 l.), 99:1 methylene chloride:methanol (2 l.), 95:5 methylene chloride:methanol, and 100:5:0.5 methylene chloride:methanol:acetic acid (5 l.) gave 6.07 g. of title compound. TLC (methylene chloride:methanol:acetic acid, 100:5;0.5) Rf =0.16.

1. temperaturea cooled
2. custom(about 3.5 hours)
3. stirringstirred at 0° C. under argon for 2 hours
4. customwas then placed in the cold room (5° C.)
5. stirringstirred overnight
6. extractionextracted with ethyl ether (2×200 ml.)
7. extractionextracted with ethyl acetate (3×300 ml.)
8. washThe combined ethyl acetate extracts were washed with water (2×300 ml.), and brine (300 ml.)
9. dry with materialdried (anhydrous sodium sulfate)
10. filtrationfiltered
11. customevaporated to dryness
12. customdried in vacuo
13. custompurified by chromatography on a 10×20 cm
14. washElution with methylene chloride (3 l.), 99:1 methylene chloride
15. custommethanol (2 l.), 95:5 methylene chloride:methanol, and 100:5:0.5 methylene chloride:methanol:acetic acid (5 l.) gave 6.07 g

ORD record

ord-71de4245449c4d6b882f5e5c1262b960

Source dataset

uspto-grants-1998_03

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05723602