Patent Application
20140275624
The present invention relates to the preparation of 4-amino-2,4-dioxobutanoic acid.
The compound 4-amino-2,4-dioxobutanoic acid is a metabolite found in plants (see, for example: Ta et al., “Utilization of the Amide Groups of Asparagine and 2-Hydorxysuccinamic Acid by Young Pea Leaves,” Plant Physiology, July 1984, vol. 75, pp. 527-530, incorporated by reference). Meister reported in “Preparation and Enzymatic Reactions of the Keto Analogues of Asparagine and Glutamine,” J. Biol. Chem., vol. 200, (1953), pp. 571-589, which is incorporated by references, a process for synthesizing 4-amino-2,4-dioxobutanoic acid. This preparation was on a small scale and was expensive because it required crude snake venom.
The present invention provides a process for synthesizing 4-amino-2,4-dioxobutanoic acid involves reacting diethyl oxalate with sodium ethoxide in a suitable solvent to form a reaction mixture, and afterward adding 2-cyano-3-hydroxy-butenedioate to the reaction mixture and allowing a reaction to proceed under conditions suitable to form a first reaction product of the formula diethyl-2-cyano-3-hydroxy-butenedioate, and isolating said first reaction product of cyano-3-hydroxy-butenedioate, and then reacting said first reaction product of diethyl-2-cyano-3-hydroxy-butenedioate with aqueous sodium hydroxide under conditions suitable to form 4-amino-2,4-dioxobutanoic acid.
In an embodiment, a process for synthesizing 4-amino-2,4-dioxobutanoic acid includes the steps of reacting diethyl oxalate with sodium ethoxide in ethanol solvent to form a reaction mixture, then adding 2-cyano-3-hydroxy-butenedioate to the reaction mixture. After allowing the ingredients to react, the reaction mixture was extracted using dichloromethane and water. The aqueous layer was separated from the dichloromethane layer, acidified, and extracted with additional dichloromethane. The dichloromethane layers were combined. Removal of the dichloromethane left diethyl-2-cyano-3-hydroxy-butenedioate. The diethyl-2-cyano-3-hydroxy-butenedioate was combined with aqueous sodium hydroxide to form a reaction mixture that was subjected to conditions suitable for forming 4-amino-2,4-dioxobutanoic acid.
This invention is concerned with the synthesis of 4-amino-2,4-dioxobutanoic acid and derivatives thereof. The reaction sequence begins by reacting sodium metal with an alcohol to form a sodium alkoxide. The synthesis was demonstrated using ethanol as the alcohol, which reacted with sodium to form sodium ethoxide. However, it should be understood that other suitable alcohols may also be used (methanol, ethanol, and the like). After forming the sodium ethoxide in ethanol solution, diethyl oxalate was added, and afterward, ethyl cyanoacetate was added. An acidic workup resulted in 2-cyano-3-hydroxy-butenedioate which was isolated as a pale yellowish solid. Without further purification, the 2-cyano-3-hydroxybutenediorte was heated in the presence of aqueous sodium hydroxide. The chemical reactions summarized below.
The details of the synthesis now follow. The synthesis of diethyl 2-cyano-3-hydroxy-butenedioate began by fitting a dry 5-liter Morton flask with a reflux condenser. Absolute ethanol (1040 milliliters) was added to the flask under nitrogen, and sodium metal (35.2 g, 1.53 moles, 1.0 equivalent) was placed into the absolute ethanol also under nitrogen while an ice-water bath was used to cool the flask. After the mixture was stirred for about 6 hours, the ice water bath was removed and the reaction was brought to room temperature. The temperature rose briefly to about 30° C. After about 24 hours, the sodium metal had completely dissolved. Diethyl oxalate (219.2 grams, 1.5 moles, 1.0 equivalent) was added neat in a single portion to the flask. While the reaction mixture was stirring, a solution of ethyl cyanoacetate (169.7 grams, 1.5 moles, 1.0 equivalent) in absolute ethanol (1000 milliliters) was added dropwise at room temperature to the reaction mixture. The addition, which was made at a rate of 1 drop every 2 to 3 seconds, took about 2½ days to complete. Afterward, the reaction mixture was extracted with dichloromethane (1000 milliliters) and deionized water (1000 milliliters). The aqueous layer was extracted with an additional 100 milliliters dichloromethane. The resulting aqueous layer had a pH of about 8-9. The layers were separated. The aqueous layer was acidified to a pH of about 1 with 6 M HCl. The acidic aqueous layer was then extracted with dichloromethane (1000 milliliters) and the layers were separated. The organic layer was evaporated by rotary evaporator to yield diethyl 2-cyano-3-hydroxy-butenedioate as a pale yellowish solid (304 grams, 95%) that was used without any further purification.
The 4-amino-2,4-dioxobutanoic acid was synthesized using the 2-cyano-3-hydroxy-butenedioate prepared as described above. A 5-liter Morton flask was equipped with an air condenser. Diethyl 2-cyano3-hydroxy-butenedioate (214.2 .grams, 1.00 mole, 1.0 equivalent) was dissolved in aqueous sodium hydroxide (1.5 M, 2000 milliliters, 3.0 equivalents) at room temperature in the flask while stirring the contents of the flask. After about one minute, a heating mantle was placed underneath the flask. Using the heating mantle, the flask was heated sufficiently for reflux while the reaction mixture was stirred. After about 4½ hours at reflux, the heat was removed and the reaction mixture was allowed to cool to room temperature and was stirred overnight at room temperature. The reaction solution was placed into an ice-water bath and acidified using 6M HCl until the pH of was equal to about 1. Solids formed after about 5 minutes. The solids were filtered. The colorless solids (27 grams) were analyzed by NMR and were found to include carbonate (13C-NMR δ=162 ppm). The bulk of the water was evaporated using a rotary evaporator at about 40° C. The solids were stirred in acetone (1000 milliliters) and then filtered. The acetone was then removed under a vacuum using a rotary evaporator followed by a vacuum pump to yield the 4-amino-2,4-dioxobutanoic acid in good yield (how much?) as a viscous yellow oil.
Although the present invention has been described with reference to specific details, it is not intended that such details should be regarded as limitations upon the scope of the invention, except as and to the extent that they are included in the accompanying claims.
This invention was made with government support under Contract No. DE-AC52-06NA25396 awarded by the U.S. Department of Energy. The government has certain rights in the invention.
