Anchoring maleimide

A special case is the binding of maleimides onto Tr resins (151) [260]. The latter were used efficiently in Diels-Alder and [2 -1- 3]-heterodipolar additions [261]. By anchoring maleimide to a trityl chloride resin through its silver salt [260], Barrett and co-workers [261] were able, after performing a one-pot synthesis by combining the preformed free base of the amino ester, the aldehyde, the dehydrating agent, the Lewis acid and the base in the presence of the solid-supported maleimide, to obtain the desired cycloadduct product (157). In this way, they were able to produce a 120-member library (Scheme 32). 

A frequently used strategy to couple peptides to the surface of liposomes consists in the use hydrophobic/amphipathic anchors that are functionalized with maleimide or bromoacetyl groups, i.e., thiol-reactive functions, which give by reaction with HS-peptides very stable thioether linkages. These functions are conveniently introduced into hydrophobic anchors such as phospholipids, e.g., PE (9,10), the adjuvant PamsCAG (11) or cholesterol... 

Figure 1 Conjugation reactions for coupling peptides to the surface of preformed liposomes. Functionalized lipophilic anchors were incorporated into liposomes and reacted with the peptides in aqueous media. Reactive endgroup functions (A) maleimide (B) bromo- or iodoacetyl (C) 2-pyridyldithio (D) carboxylic acid (E) />-nitrophenyl carbonate and (F) hydrazide. Abbreviations EDC, l-ethyl-3-(3-dimethylaminopropyl)carbodiimide NHS, 7V-hydroxysuccinimide.

A variety of these physisorbed molecules were used as anchor points for covalent immobilization in a so-called hybrid approach [16]. That is the case of bifunctional pyrenes (i.e. 1 -pyrenebutanoic acid sucdnimidyl ester, pyrene maleimide) or polymers with terminal amine/carboxylic groups that have been used to covalently immobilize proteins, functionalized oligonucleotides, and so on, (Figure 3.9) [43,44]. 

H. Deleuze, X. Schultze, D. C. Sherrington, Synthesis of porous supports containing N-(p-hydroxyphenyl)- or N-(3-4-dihydroxybenzyl) maleimide-anchored titanates and application as catalysts for transesterification and epoxidation reactions, /. Polym. Sci. Pol. Chem. 38 (2000) 2879. 

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