Merrifield solid-phase technique

Kato and Anfinsen 245) have reported on the use of agarose-bound S-protein in the form of a column for the purification of synthetic S-peptide derivatives. This procedure has shown the presence of closely related products in material from the Merrifield solid phase techniques. Some of these products produced enzymically inactive complexes with S-protein. 

How To Synthesize a Peptide Using the Merrifield Solid Phase Technique 1097... 

Peptide synthesis is made possible by the use of selective protecting groups. An N-protected amino acid with a free carboxyl group is coupled to an 0-protected amino acid with a free amino group in the presence of dicyclo-hexylcarbodiimide (DCC). Amide formation occurs, the protecting groups are removed, and the sequence is repeated. Amines are usually protected as their tert-butoxycarbonyl (BOO derivatives, and acids are protected as esters. This synthetic sequence is often carried out by the Merrifield solid-phase technique, in which the peptide is esterified to an insoluble polymeric support. 

Automated Peptide Synthesis The Merrifield Solid-Phase Technique 1096... 

More recently, automated gene synthesizers have been developed that operate on principles similar to the Merrifield solid-phase technique for peptides. A protected nucleotide is covalently bonded to a polymer. Other protected nucleotides are then added sequentially to the chain, using a coupling reagent. Eventually, the protecting groups are removed, and the synthetic oligonucleotide is then detached from the solid support. 

Difficulties due to side reactions (cyclization) and a broad molecular weight distribution accompanying the polycondensation of active esters led to the application of methods wherein the polymers are built up stepwise. In 1968, Sakakibara et al.31) introduced the solid-phase technique using Merrifield s resin. By stepwise addition of tert-pentyloxycar-bonyl tripeptides, they have synthesized (Pro-Pro-Gly)n with n = 5, 10, 15 and 20. 

In preparing these various libraries, extensive use is made of solid phase synthetic methods. These methods are all derived from the solid phase peptide synthesis (SPPS) method developed by Merrifield in 1963. When performing a large number of syntheses, it is preferable to perform the synthetic steps on a solid bead rather than completing the entire synthesis in the solution phase. The solid-phase technique makes byproduct removal and final compound purification easier. The organic chemistry literature contains a wealth of different types of solid-phase supports and novel linkers for attaching the synthetic substrate to the bead. 

Merrifield s concept of a solid-phase method for peptide synthesis and his development of methods for carrying it out set the stage for an entirely new way to do chemical reactions. Solid-phase synthesis has been extended to include numerous other classes of compounds and has helped spawn a whole new field called combinatorial chemistry. Combinatorial synthesis allows a chemist, using solid-phase techniques, to prepare hundreds of related compounds (called libraries) at a time. It is one of the most active areas of organic synthesis, especially in the pharmaceutical industry. 

Development of the solid phase technique earned Merrifield the 1984 Nobel Prize in Chemistry and has made possible the synthesis of many polypeptides and proteins. 

The method described in Section 28.6 works well for the synthesis of small peptides. It is extremely time-consuming to synthesize larger proteins by this strategy, however, because each step requires isolation and purification of the product. The synthesis of larger polypeptides is usually accomplished by using the solid phase technique originally developed by R. Bruce Merrifield of Roekefeller University. 

Since the introduction of sohd-phase peptide synthesis (SPPS) on lightly crosslinked polystyrene (PSty) by Merrifield in 1962,this technique has been optimized in all its aspects and has subsequently found widespread application in many other fields of organic chemistry, e.g. for the synthesis of oligonucleotides, for catalysis, for the immobilization of enzymes in biotechnology, and for the preparation of polymeric reagents. A new but very rapidly growing field of application of this revolutionary method is the use of solid-phase techniques in combinatorial chemistry for the synthesis of hbraries of compounds whose constituents differ widely in their chemical nature. ... 

Although the solid-phase technique was first developed for the synthesis of peptide chains and has seen considerable use for this prupose, it has also been used to synthesize chains of polysaccharides and polynucleotides in the latter case, solid-phase synthesis has almost completely replaced synthesis in solution. The technique has been applied less often to reactions in which only two molecules are brought together (nonrepetitive syntheses), but many examples have been reported. Combinatorial chemistry had its beginning with the Merrifield synthesis, particularly when applied to peptide synthesis, and continues as an important part of modem organic chemistry. ... 

The peptide was then separated from the by-products and unreacted starting material and the process was repeated. Merrifield succeeded in assembling a peptide chain in a stepwise manner while it was attached at one end to a solid support that could easily be removed by the proper solvents. It soon became apparent to Merrifield that the solid phase technique should be applicable to units other than amino acids. He extended it to the synthesis of... 

Except for the synthesis of peptides and ohgonucleic acids, Uttle attention has been spent on the question of how synthesis can be carried out in an environment of sophisticated technologies which includes improved hardware. While peptides and oligonucleotides are conveniently prepared by Merrifield s solid phase technique, solution phase synthesis of most other synthetic targets have not been substantially replaced by this solid phase approach. Without discussing this aspect in detail it is obvious that today a renaissance of sophisticated solution phase synthesis can be noted. Immobilization of reagents and particularly catalysts, an old concept indeed, recently returned back onto the stage and this is addressed in this volume of Topics in Current Chemistry in a broader sense. 

Since Merrifield s first disclosure in 1963 [66] that his solid phase technique was useful for preparing peptides (Nobel Prize awarded to Merrifield in 1984), there has been an explosion of publications on the use of polymers as polymeric-supported catalysts for various reactions [67]. 

The solid phase technique of Merrifield (Chap. 5) proved very useful for obtaining a series of analogs of AA which were compared with respect to their antitoxic activities, ion binding capacities and molecular structures. 

In 1965, R. Bruce Merrifield developed a technique that revolutionized peptide synthesis. This solid-phase technique avoids many of the tedious aspects of previous methods and is now universally used. The principle is to assemble the peptide chain while one end of it is chemically anchored to an insoluble, inert solid. In this way, excess reagents and by-products can be removed simply by washing and filtering the solid. The growing peptide chain does not need to be purified at any intermediate stage. When the peptide is fully constructed, it is cleaved chemically from the solid support... 

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