HMPB butyric

Coupling of 4-(4-hydroxymethyl-3-methoxyphenoxy)-butyric acid (HMPB, for synthesis of peptide acids) or p-[(R S)-a-[l- (9H- fluorenyl- methoxyform-amido]- 2,4- dimethoxybenzyl] - phenoxyacetic acid (modified Rink linker, for synthesis of carboxamide peptides) linkers to MBHA resin For Fmoc chemistry several types of solid supports are available, which include hydroxymethyl-based, aminomethyl-based, and trityl chloride resins. We describe the use of the MBHA resin. In this case the respective linker (to achieve peptide acid or amide) is coupled to the resin and first amino acid is then coupled to the linker. Attachment of the linker to the resin is a reaction between the carboxyl-group of the linker and amino-group of the MBHA resin. Commercially available resins with linkers already attached could also be used. 

A number of other useful highly acid-labile handles are also available. Most of these linkers are formed by introducing electron-donating substituents into the benzyl groups that serve as the peptide-resin anchor. The first handle of this type, 4-hydroxymethyl-3-methoxyphenoxyacetic acid (HMPA), 3, was introduced by Sheppard and Williams [22,23]. A closely related and more widely used alternative is 4-(4-hydroxymethyl-3-methoxyphenoxy) butyric acid [24-26] (HMPB), 4. 

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