Maleimide hydrolysis

Dissolve NHS-PEGg-maleimide (MW 601.6) into DMSO at a concentration of 20mM. Short, PEG-type crosslinkers often exist as a thick oily mass, and preparing the solution typically involves dissolving an entire vial of the compound into DMSO to determine accurately the required concentration. Use only dry DMSO to avoid hydrolysis of the NHS ester. 

The microspheres—synthesised via a two-step process (acid-catalysed hydrolysis and condensation of 3-mercaptopropyltrimethoxysilane (MPS) in aqueous solution, followed by condensation catalysed by triethanolamine)—have a narrow size distribution (Figure 5.16) and are considerably more stable than polystyrene divinylbenzene microspheres as shown in phosphoramidite oligonucleotide synthesis by the excellent retention of fluorescence intensity in each of the reagent steps involved in phosphoramidite DNA synthesis (Figure 5.17, in which the organo-silica microsphere free thiol groups are derivatized with ATTO 550 maleimide coupled to the entrapped dye). 

However, due to the aromatic ring adjacent to its maleimide functional group, MBS displays less stability toward maleimide ring opening than SMCC (see this chapter Section 1.3). Unlike SMCC, MBS is therefore not recommended for preparing freeze-dried, maleimide-activated proteins, since during the processing necessary to purify and stabilize the derivative much activity can be lost by hydrolysis. 

The maleimide group of MPBH is adjacent to an aromatic ring and thus may exhibit instability to hydrolysis in aqueous solutions, especially at alkaline pH. Hydrolysis... 

Recently, an antibody has been described which catalyzes not just a Diels-Alder reaction between an N-substituted maleimide and acetoxybutadiene (kcat = 0.055 s-1, Km = S3 mM, kcat/fCM = 6.6 (m s) but also the subsequent hydrolysis oftheacetoxy group (kcat = 9.2 x 1(T4 s 1, JCM = 1.1 rmvr, kcat/KM = 0.9 (m s) 1), which is about 1.5% as fast as the Diels-Alder reaction itself (Figure 18.9). 

The structures of these bisindole maleimides were confirmed by synthesis. The reaction of indolyl magnesium bromide (10) with 2,3-dibromo-A -methylmaleimide (11) in toluene led to bisindolylmaleimide (12), which was converted into arcyriarubin A (6) through alkaline hydrolysis followed by heating with ammonium acetate (Scheme 1). The reaction of 10 and 11 in THF yielded monosubstitution product (13) which after protection of the indole NH group with the Boc residue was used to prepare unsymmetrically substituted bisindolylmaleimide, arcyriarubin B (1) [8]. 

As electron-rich olefins are more reactive, vinyl-sulfones are the most reactive species and are capable of reacting with thiols, amines, and even with small nucleophilic alcohol groups. Less reactive are acrylamides and acrylates, which are reactive towards amines and thiols. Maleimides are the least reactive of the mentioned species and allow selective addition of thiols in the presence of amines in the pH range 6.5-7.5. However, hydrolysis of the imide, especially at elevated pH values [35], may be a concern for certain applications. The mentioned Michael addition reactions do not require organic solvents and can be carried out at physiological temperature and pH [36], In acidic conditions, the reaction is either very slow or does not proceed because protonation removes the nucleophilic form in the case of amines, and the thiolate anion is usually the active species in Michael additions involving thiols [25],... 

A15.1.1.9 Imides. Compounds that have two acyl groups bonded to a single nitrogen are known as imides (R—CO—NH—CO—R ). The most common imides are cyclic ones (maleimide). Maleimide will convert to maleic acid under water and acid/base. Another example of imide hydrolysis is pheno-barbital in which phenobarbital (a cyclic imide) is hydrolyzed to form urea and a-ethylbenzeneacetic acid. 

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