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New tools for superfast solid phase peptide synthesis

Calin Dan Sferdean, University of Massachusetts Amherst

Abstract

The work described here had as its goal the development of new techniques for very rapid synthesis of longer peptides. Current methods are often time-consuming and sometimes completely ineffective due to the incursion of peptide aggregation which may interfere with chain extension. Attention was directed to the three main problems in current methodologies: inefficient protecting groups, inefficient coupling reagents and problems due to peptide aggregation. ^ A new protecting group, more effective than the common Fmoc residue, was adopted for the present studies. An unforeseen by-product of these studies was the accidental observation that Bsmoc amino acids are more reactive than Fmoc amino acids as acylating agents as shown in competition experiments. This effect should increase the efficiency of the former for longer peptides. ^ As coupling reagent, O-HATU was adopted as the best of the currently available activators and in addition a new reagent, t-Bu-Dtp-OAt, was developed and shown to be equal in effectiveness to O-HATU. ^ The third problem, aggregation, was given the greatest amount of attention in these studies. While carrying out the first Bsmoc-based syntheses of longer peptides we identified the presence of some by-products of the same molecular weight as the target peptide. These were identified as depsipeptides which were formed at threonine positions during the final TFA treatment which removed the peptide from the resin during solid phase synthesis. The structures of these materials were proved by authentic syntheses and curiously these synthesis occurred very efficiently, showing no aggregation problems. Then the depsipeptide was converted to the desired peptide via a basic buffer. Fortunately this effect also led to greater solubility for the ester sequence thus making purification easier. Once this new technique or modifications involving the new N-dicyclopropylmethyl backbone protectant had been identified it was applied to the superfast synthesis of several difficult sequences, e.g. the JR 10-mer, the JR 26-mer, Crambin (16-46), Crambin (1-46) and the extremely difficult Aβ(1-43) amyloid peptide. ^

Subject Area

Organic chemistry

Recommended Citation

Sferdean, Calin Dan, "New tools for superfast solid phase peptide synthesis" (2008). Doctoral Dissertations Available from Proquest. AAI3340514.
https://scholarworks.umass.edu/dissertations/AAI3340514

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