Boc-L-aspartic acid 4-methyl ester

White solid

To a solution of 3.74 g (20.5 mmol) of (S-aspartate methyl monoester chlorhydrate in 85 mL of a mixture dioxane / HL-Aspartic acid 7 (5.03 g, 37.8 mmol) was added to methanol (25 mL) and cooled to -30 °C. Thionyl chloride (3.7 mL) was added dropwise to the mixture, the cooling bath was removed and the solution was slowly warmed to room temperature. After standing for 25 minutes, diethyl ether (25 mL) was added to the mixture and upon cooling and shaking, the product was precipitated as a white solid which was filtered immediately, washed with ice cold diethyl ether and collected. The L-aspartic acid methyl ester hydrochloride 8 was obtained as a colorless solid, and was used to the next reaction without further purification. To a stirred solution of L-aspartic acid methyl ester hydrochloride (5.93 g, 32.3 mmol) in dioxane (120 mL) was added at 0 °C aqueous solution of Na2CO3 (1 M, 105 mL) followed by Boc2O (8.25 mL, 35.9 mmol). The reaction mixture was stirred 18 h at 40 °C before being concentrated. The resulting solution was acidified pH 3.0 at 0 °C with 1M HCl and extracted with EtOAc. The combined organic layers were washed with water and dried over Na 2 SO 4 , and concentrated in vacuo. Purification on silica gel colum chromatography (MeOH/CH2Cl2 = 1/5) afforded 9 as a yellow oil (7.03 g, 28.4 mmol, 81percent (2 steps))In 100ml dry three-necked flask, at room temperature 4.73g (25.7mmol, 1.0eq) (S) -2-amino-4-methoxy-4-oxobutanoic acid hydrochloride dissolved 50ml 1:1 THF/ H2O system. Add 5.45g Na2CO3 (51mmol, 2.0eq). Stir at room temperature for 0.5h. Cooled to around 5 deg.C. Slowly added dropwise 6.17g(51.2mmol, 2.0eq) (Boc)2O in THF solution. At RT stir overnight. To spin of THF, treated three times the aqueous phase extracted with EA, the aqueous phasewas adjusted about PH = 4, spin dry the aqueous phase to give a white solid, the solid was washed several times with EA is not to have a product signal. EAspin to give the product 2.54g.

Molecular Weight:247.24
XLogP3:0.4
Hydrogen Bond Donor Count:2
Hydrogen Bond Acceptor Count:6
Rotatable Bond Count:7
Exact Mass:247.10558726
Monoisotopic Mass:247.10558726
Topological Polar Surface Area:102
Heavy Atom Count:17
Complexity:306
Defined Atom Stereocenter Count:1
Covalently-Bonded Unit Count:1
Compound Is Canonicalized:Yes