Analysis of Support-Bound Amino Acid Derivatives

Analytical control forms an essential part of all organic chemical investigations. This is without any doubt not a simple task, however, in synthetic experiments on insoluble gel phases. 

As already discussed in the beginning, the chemical behavior of functional polymers is characterized by the heterogeneous and variable microenvironment of each reactive group on the macromolecular thread, which is randomly coiled and fixed in space by cross-linkages. Only with limitations does this situation allow one to apply the knowledge of analytical chemistry in solution to reactions in the gel state. A function on an insoluble 

To form a basis for the calculations of excess reagents to be used in a Merrifield synthesis and of reaction rates on the various stages, it is necessary to know the initial load of the gel phase with the starting amino acid or peptide attached onto it, as described in the preceding section. 

Difficulties or shortcomings, which will be discussed in the following are inherent in most of these tests. To gain more detailed insight to analytical problems of reactions on insoluble gelatinous phases, some aspects are given below according to 

With this method of analysis one takes the risk that not all bound molecules are liberated because some may be fixed in areas of the polymer scarcely solvated under the cleavage condition and therefore they are excluded from reaction. Since this effect depends on the polymeric properties of the macromolecular support, it will not be altered at the binding site by an elongated peptide built up under solvation conditions of a gel phase synthesis, which in most cases differ considerably from those for cleavage. Even at the end of a peptide synthesis those areas are poorly solvated during the detachment reaction and therefore are inaccessible. In other words, this method of load test does not always measure the total capacity of a support, but yields the amount which surely can be cleaved from the polymer at the end of a synthesis. 

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