Enzymatically cleavable anchors

This somewhat exotic class of anchors includes only a small number of examples. Although it also offers an orthogonal cleavage technique, few applications are found in the literature. 

4-Acetyloxybenzyloxy [332] Cleavage Lipase RB 001-05 pH 5.8, rt Product after cleavage Carboxylic acid Amide Alcohol 

Phenylalanine ester [10] Cleavage a-Chymotrypsin Product after cleavage Carboxylic acid 

Phosphoracid diester Cleavage Product after cleavage  

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Enzymatic and chemical cleavage sites of GPI anchors most commonly used for the identification and structural analysis of GPI anchors. In addition, all phosphoric esters are cleavable by aqueous hydrofluoric acid. GPI-PLC, GPI-specific phospholipase C GPI-PLD, GPI-spedfic phospholipase D PI-PLC, phosphatidyinositol-specific phospholipase C. Cleaves only if the inositol is unmodified... 

Depending on the chemical structure of the anchor and chemistry of its attachment to the resin, the product can be cleaved at the end of the synthesis either with acid, base or nucleophilic cleavage reagents, hydrogenolysis, enzymatic, palladium-catalyzed or photochemical, oxidative and reductive cleavage methods. In addition, the safety-catch anchors can be chemically modified at the end of the synthesis to provide a structure which is subsequently cleavable. 

The enzymatic deprotection principle has also been applied in solid phase synthesis to create an anchoring structure that contains two cleavable positions an allylic ester on the one hand and a hydrophilic ester on the other hand. The release of j ptide using a palladium(O) catalyst delivers the peptide that is still bound to the hydrophilic structure. The carboxylic function can be liberated [48] using lipase catalysts (Fig. 32). This strategy was successfully demonstrated in the solid phase synthesis of peptides as well as O- and iV-glycopeptides [48]. 

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