4-(2,5-dioxopyrrol-1-yl)butanal

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

Procedure: 4-Maleimidobutyraldehyde diethylacetal (2 g, 8.29 mmol) in tetrahydrofuran (20 ml) and water (0.5 ml) was stirred under argon and DOWEX 50X8 ion exchange resin (H+, 2 g, ®Dow Chemical Co.) was added. After 12 hours stirring at room temperature, the solvent was decanted, dried (MgSO4) and evaporated in vacuo to afford 4-maleimidobutyraldehyde (formula III) as a yellow oil which rapidly solidified on standing (1.38 g, 99%); TLC Rf=0.4, ethyl acetate/hexane 1:1. The 4-maleimidobutyraldehyde turned out to be extremely unstable, so that it was necessary to do all work-up at low temperatures (0° C.) and under complete exclusion of oxygen (inert atmosphere). was added the solvent was decanted dried (MgSO4) evaporated in vacuo

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

Procedure: 4-Maleimidobutyraldehyde diethylacetal (2 g, 8.29 mmol) in tetrahydrofuran (20 ml) and water (0.5 ml) was stirred under argon and DOWEX 50X8 ion exchange resin (H+, 2 g, ®Dow Chemical Co.) was added. After 12 hours stirring at room temperature, the solvent was decanted, dried (MgSO4) and evaporated in vacuo to afford 4-maleimidobutyraldehyde (formula III) as a yellow oil which rapidly solidified on standing (1.38 g, 99%); TLC Rf=0.4, ethyl acetate/hexane 1:1. The 4-maleimidobutyraldehyde turned out to be extremely unstable, so that it was necessary to do all work-up at low temperatures (0° C.) and under complete exclusion of oxygen (inert atmosphere). was added the solvent was decanted dried (MgSO4) evaporated in vacuo

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

Procedure: 4-Maleimidobutyraldehyde diethylacetal (2 g, 8.29 mmol) in tetrahydrofuran (20 ml) and water (0.5 ml) was stirred under argon and DOWEX 50×8 ion exchange resin (H+, 2 g, ®Dow Chemical Co.) was added. After 12 hours stirring at room temperature, the solvent was decanted, dried (MgSO4) and evaporated in vacuo to afford 4-maleimidobutyraldehyde (formula III) as a yellow oil which rapidly solidified on standing (1.38 g, 99%); TLC Rf=0.4, ethyl acetate/hexane 1:1. The 4-maleimidobutyraldehyde turned out to be extremely unstable, so that it was necessary to do all work-up at low temperatures (0° C.) and under complete exclusion of oxygen (inert atmosphere). was added the solvent was decanted dried (MgSO4) evaporated in vacuo

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

Procedure: 4-Maleimidobutyraldehyde diethylacetal (2 g, 8.29 mmol) in tetrahydrofuran (20 ml) and water (0.5 ml) was stirred under argon and DOWEX 50X8 ion exchange resin (H+, 2 g, ® Dow Chemical Co.) was added. After 12 hours stirring at room temperature, the solvent was decanted, dried (MgSO4) and evaporated in vacuo to afford 4-maleimidobutyraldehyde (formula III) as a yellow oil which rapidly solidified on standing (1.38 g, 99%); TLC Rf=0.4, ethyl acetate/hexane 1:1. The 4-maleimidobutyraldehyde turned out to be extremely unstable, so that it was necessary to do all work-up at low temperatures (0° C.) and under complete exclusion of oxygen (inert atmosphere). was added the solvent was decanted dried (MgSO4) evaporated in vacuo

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

Procedure: 4-Maleimidobutyraldehyde diethylacetal (2 g, 8.29 mmol) in tetrahydrofuran (20 ml) and water (0.5 ml) was stirred under argon and DOWEX 50X8 ion exchange resin (H+, 2 g, ®Dow Chemical Co.) was added. After 12 hours stirring at room temperature, the solvent was decanted, dried (MgSO4) and evaporated in vacuo to afford 4-maleimidobutyraldehyde (formula III) as a yellow oil which rapidly solidified on standing (1.38 g, 99%); TLC Rf=0.4, ethyl acetate/hexane 1:1. The 4-maleimidobutyraldehyde turned out to be extremely unstable, so that it was necessary to do all work-up at low temperatures (0° C.) and under complete exclusion of oxygen (inert atmosphere). was added the solvent was decanted dried (MgSO4) evaporated in vacuo