Synthesis and comparative properties of two amide‐generating resin linkers for use in solid phase peptide synthesis
Well‐characterized resins of high purity are critical for effective solid phase peptide synthesis (SPPS). The quality of commercial (4‐methyl)benzhydrylamine‐resin (MBHA‐resin), used for the synthesis of peptide amides, is not consistent and residual ketone functionalities are frequently present. Such ketone or aldehyde impurities lead to the formation of acylation‐resistant deletion peptides in SPPS. To avoid these undesirable side reactions, we have optimized the preparation of two amide‐generating linkers, which, in combination with aminomethyl‐resin prepared directly from polystyrene resin, serve as alternatives to MBHA‐resin for peptide amide synthesis. Then we have explored their comparative properties in SPPS. Use of sonication in reductive amination facilitated the synthesis of both benzhydrylamine (BHA) and MBHA linkers. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.
Resins with identical specifications are not identical. Identifying a useful solid-phase resin.
The quality of the most commonly used support for solid-phase syntheses, polystyrene resin cross-linked with 1% of divinylbenzene, differs considerably even among different lots of resin from the same source. Determination of the swelling capacity of resins before carrying out solid-phase syntheses represents a very simple means of nondestructive presynthetic resin characterization.
Effect of tertiary amine on the carbodiimide-mediated peptide synthesis.
The effect of tertiary amine (DIEA) on reaction rate and product purity of a carbodiimide/HOBt-mediated peptide synthesis was studied. It was found that very rapid activation can be achieved using carbodiimide/HOBt in non-polar solvents, such as DCM. Although the HOBt is poorly soluble in DCM, the activation proceeds within 2 min, probably forming the HOBt-ester. By such a preactivation followed by a coupling in the presence of DIEA the rate of coupling is comparable with other rapid methods using BOP or TBTU, and no racemization was found in a model coupling (less than 0.1%). For comparison, syntheses of neurotensin by means of different coupling reagents (BOP, TBTU, OPfp-esters) and the DIEA-catalyzed coupling after carbodiimide/HOBt-activation under comparable conditions have shown that these procedures are of the same value in view of coupling efficiency and product purity.