Qualitative Analysis of Solid Phase Synthesis Reaction Products by X-ray Spectrometry

Abstract

Abstract: A novel method for the synthesis of polypeptides using polystyrene/divinylbenzene copolymers as solid supports has drawn the attention of medicinal, pharmaceutical, and agricultural chemists because of its utility in combinatorial chemistry and parallel synthesis. In this method, arrays of solid-phase organic synthesis experiments are conducted simultaneously thereby enabling the preparation of large numbers of novel compounds over a short time period. The analysis of organic compounds attached to polymer supports presents unique challenges to chemists. This study presents some results of the application of energy-dispersive X-ray spectrometry (EDS) in the environmental scanning electron microscope (ESEM) to this problem. EDS in the ESEM has the advantages of minimal sample size, speed, and simplicity because the analyses are performed without special specimen preparation. The progress of a two-step synthetic transformation was followed using EDS-ESEM by the presence of a sulfur peak in the first synthetic step and by a bromine peak in the second step. The synthetic products were also evaluated by infrared spectroscopy and by elemental analysis (ion chromatography). The agreement of the qualitative analysis among all three techniques was good. Analysis by EDS-ESEM not only complements current analytical techniques in solid phase synthesis; it also provides insight into the details of the synthetic transformation.