methyl 2,5-dioxopyrrole-1-carboxylate

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Methylchloroformate (4.4 mL, 56.7 mmol, 1 eq) was added to a solution of maleimide (5.5 g, 56.7 mmol, 1 eq) and NMM (6.2 mL, 56.7 mmol, 1 eq) in 200 mL of EtOAc at 0° C. The suspension was stirred at 0° C. for 30 minutes, filtered and washed with EtOAc. Filtrate and washings were combined and washed with cold water and dried over anhydrous Na2SO4. After filtration and evaporation under vacuum a pink solid was obtained. Purification by column chromatography on silica gel (Hexane-EtOAc, 1:1, v/v) provided the product (4.8 g, 55%). filtered washed with EtOAc washed with cold water dried over anhydrous Na2SO4 After filtration and evaporation under vacuum a pink solid was obtained Purification by column chromatography on silica gel (Hexane-EtOAc, 1:1

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

Procedure: To a 1000 ml 3-neck round bottom flask was added 400 ml of ethyl acetate. The flask was placed in an ice bath and the temperature was allowed to drop to about 0° C. To the cooled flask was sequentially added with stirring 7.76 g of maleimide and 8.8 ml of N-methylmorpholine. Then, through an addition funnel was added to the stirring mixture 6.26 ml of methyl chloroformate at a rate so as not to raise the temperature above 3° C. Through the addition funnel was then added 5 ml of ethyl acetate as washing and the washing was added to the reaction mixture. The reaction mixture was stirred for 30 minutes at between 0°-3° C. Thereafter, the reaction mixture was filtered through a Buchner funnel. The flask was washed 2× with 10 ml of ethyl acetate and the washings were also filtered. The resulting precipitate was washed 2× with 10 ml of ethyl acetate. The combined filtrate and washings were extracted with 100 ml of ice cold water, dried (10 g Na2SO4), and evaporated to dryness under reduced pressure. The residue was redissolved in 50-100 ml of ethyl acetate:isopropyl ether (40:60 /v:v) using a water bath at 60° C. The resulting solution was filtered, cooled until crystals appeared. After 30 minutes in an ice bath, the cooled solution and crystals were filtered through a sintered glass funnel and the crystals washed 2× with 20 ml of isopropyl ether. The crystals were vacuum dried overnight, M.P. 61°-63° C. The flask was placed in an ice bath to drop to about 0° C To the cooled flask was sequentially added to raise the temperature above 3° C as washing the washing was added to the reaction mixture Thereafter, the reaction mixture was filtered through a Buchner funnel The flask was washed 2× with 10 ml of ethyl acetate the washings were also filtered The resulting precipitate was washed 2× with 10 ml of ethyl acetate The combined filtrate and washings were extracted with 100 ml of ice cold water dried (10 g Na2SO4) evaporated to dryness under reduced pressure The residue was redissolved in 50-100 ml of ethyl acetate:isopropyl ether (40:60 /v:v) at 60° C The resulting solution was filtered cooled until crystals After 30 minutes in an ice bath the cooled solution and crystals were filtered through a sintered glass funnel the crystals washed 2× with 20 ml of isopropyl ether dried overnight

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

Procedure: To a 1000 ml 3-neck round bottom flask was added 400 ml of ethyl acetate. The flask was placed in an ice bath and the temperature was allowed to drop to about 0° C. To the cooled flask was sequentially added with stirring 7.76 g of maleimide and 8.8 ml of N-methylmorpholine. Then, through an addition funnel was added to the stirring mixture 6.26 ml of methyl chloroformate at a rate so as not to raise the temperature above 3° C. Through the addition funnel was then added 5 ml of ethyl acetate as washing and the washing was added to the reaction mixture. The reaction mixture was stirred for 30 minutes at between 0°-3° C. Thereafter, the reaction mixture was filtered through a Buchner funnel. The flask was washed 2× with 10 ml of ethyl acetate and the washings were also filtered. The resulting precipitate was washed 2× with 10 ml of ethyl acetate. The combined filtrate and washings were extracted with 100 ml of ice cold water, dried (10 g Na2SO4), and evaporated to dryness under reduced pressure. The residue was redissolved in 50-100 ml of ethyl acetate:isopropyl ether (40:60 /v:v) using a water bath at 60° C. The resulting solution was filtered, cooled until crystals appeared. After 30 minutes in an ice bath, the cooled solution and crystals were filtered through a sintered glass funnel and the crystals washed 2× with 20 ml of isopropyl ether. The crystals were vacuum dried overnight, M.P. 61°-63° C. The flask was placed in an ice bath to drop to about 0° C To the cooled flask was sequentially added to raise the temperature above 3° C as washing the washing was added to the reaction mixture Thereafter, the reaction mixture was filtered through a Buchner funnel The flask was washed 2× with 10 ml of ethyl acetate the washings were also filtered The resulting precipitate was washed 2× with 10 ml of ethyl acetate The combined filtrate and washings were extracted with 100 ml of ice cold water dried (10 g Na2SO4) evaporated to dryness under reduced pressure The residue was redissolved in 50-100 ml of ethyl acetate:isopropyl ether (40:60 /v:v) at 60° C The resulting solution was filtered cooled until crystals After 30 minutes in an ice bath the cooled solution and crystals were filtered through a sintered glass funnel the crystals washed 2× with 20 ml of isopropyl ether dried overnight

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: (3-Aminophenyl)boronic acid (1.26 grams, 0.01 mole) is dissolved in saturated NaHCO3 (50 ml) by briefly heating the mixture on a hot plate. The solution is cooled in an ice bath to approximately 0° C., and N-methoxycarbonylmaleimide (1.55 grams, 0.01 mole) added with vigorous stirring. After 10 min. the solution is diluted with water (200 ml) and then stirred at room temperature for 30 to 40 min. The pH is adjusted to approximately 5.5 by addition of 1M H2SO4, and the precipitate collected by filtration. The precipitate is washed with 1M H2SO4 (2×50 ml), and then dried overnight in vacuo over NaOH pellets to afford 1.39 grams (64% yield) of (3-maleimidophenyl)boronic acid. The structure was confirmed by 300 MHz, 1H NMR spectrometry in d6 -DMSO. by briefly heating the mixture on a hot plate the precipitate collected by filtration The precipitate is washed with 1M H2SO4 (2×50 ml) dried overnight in vacuo over NaOH pellets

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

Procedure: A solution of 4.2 g (32.3 mmol) of 6-aminocaproic acid in 163 ml of saturated sodium bicarbonate solution is treated at 0° C., with vigorous stirring, with 5 g (32.3 mmol) of N-carbomethoxymaleimide. After 1 hour, the solution is diluted with 256 ml of water and stirred at room temperature for 1 hour. The pH of the solution (8.2) is then brought to 6.4 by adding concentrated sulfuric acid. The solution is then concentrated to 100 ml and acidified to pH 2 by adding 1 M sulfuric acid, and is extracted three times with ethyl acetate. The organic phases are combined, dried over anhydrous sodium sulfate and evaporated to dryness under vacuum. The residue is purified by chromatography on a silica column (elution: chloroform/acetic acid, 95:5). In this manner, 4.7 g of N-maleoyl-6-aminocaproic acid are obtained. The solution is then concentrated to 100 ml by adding 1 M sulfuric acid is extracted three times with ethyl acetate dried over anhydrous sodium sulfate evaporated to dryness under vacuum The residue is purified by chromatography on a silica column (elution: chloroform/acetic acid, 95:5)

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Maleimide (2.00 g, 20.6 mmol) and N-methyl morpholine (2.08 g, 20.6 mmol) in ethyl acetate were cooled to 0° C. Dropwise addition of methylchloroformate (1.4 mL, 20.7 mmol) produced white precipitate. The solution was stirred for 1 hour at 0° C., after which the solids were removed by filtration. Concentration of the filtrate yielded a pink oil, which was purified by column chromatography (eluant 3:1 hexanes:ethyl acetate) to yield pale yellow crystals. produced white precipitate after which the solids were removed by filtration Concentration of the filtrate yielded a pink oil, which was purified by column chromatography (eluant 3:1 hexanes:ethyl acetate) to yield pale yellow crystals

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

Procedure: As shown in FIG. 2, to a solution of 4-aminobutyraldehyde diethylacetal (5 g, 31 mmol) in 100 ml of saturated bicarbonate was added N-methoxycarbonylmaleimide (4.91 g, 31.6 mmol) at 0° C. (icebath). After 15 minutes, tetrahydrofuran (100 ml) was added at room temperature and the resultant mixture stirred for 1 hour. The resultant mixture was then acidified with 1N hydrochloric acid to pH 6-7 and extracted with ethyl acetate (3×200 ml). The combined organic extracts were dried (MgSO4) and evaporated in vacuo. The crude product was purified by chromatography on silica gel 60 eluting with ethyl acetate/petroleum ether 1:2 to yield 4-maleimidobutyraldehyde diethylacetal as a yellow oil (4.31 g; 58%), TLC Rf=0.65, ethyl acetate/hexane 1:1. extracted with ethyl acetate (3×200 ml) The combined organic extracts were dried (MgSO4) evaporated in vacuo The crude product was purified by chromatography on silica gel 60 eluting with ethyl acetate/petroleum ether 1:2

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: As shown in FIG. 1, to a solution of ethanolamine (1.8 g, 29.5 mmol) in saturated sodium bicarbonate solution (100 ml) was added N-methoxycarbonylmaleimide (95 g, 32.3 mmol) in portions with vigorous stirring at 0° C. The mixture was allowed to warm to room temperature and stirred for 1 hour. The pH of the mixture was adjusted to 6-7 by careful addition of concentrated sulfuric acid (5 ml). The resultant solution was freeze dried and the solid residue extracted with ethyl acetate (2×400 ml) by stirring for 30 min. with each extraction. The ethyl acetate extracts were collected by filtration and evaporated in vacuo to afford N-(2-hydroxyethyl)maleimide (formula I) as a white solid (4.0 g, 96% yield); thin layer chromatography (TLC), Rf=0.27, ethyl acetate/petroleum ether 1:1. to warm to room temperature stirred for 1 hour dried the solid residue extracted with ethyl acetate (2×400 ml) by stirring for 30 min. with each extraction The ethyl acetate extracts were collected by filtration evaporated in vacuo

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

Procedure: 11 mg (12 μmol) of N-(6-aminohexyl)-N-methyl-L-valyl-N-[(3R,4S,5S)-3-methoxy-1-{(2S)-2-[(1R,2R)-1-methoxy-2-methyl-3-oxo-3-{[(1S)-2-phenyl-1-(5-phenyl-1,3,4-oxadiazol-2-yl)ethyl]amino}propyl]pyrrolidin-1-yl}-5-methyl-1-oxoheptan-4-yl]-N-methyl-L-valinamide (Intermediate 235) were taken up in 500 μl of 1:1 dioxane/water and admixed with 253 μl of 1M aqueous sodium hydrogencarbonate solution and then with 2.8 mg (18 μmol) of methyl 2,5-dioxo-2,5-dihydro-1H-pyrrole-1-carboxylate. The reaction mixture was stirred at RT for 30 min and then acidified with trifluoroacetic acid. The reaction mixture was purified by means of preparative HPLC. After lyophilization, 0.8 mg (7% of theory) of the title compound was obtained. The reaction mixture was purified by means of preparative HPLC