Maximizing efficiency in the production of compound libraries

Efficiency is one of the most important criteria in departments responsible for the production of compounds in a library format. Consequently, this was a key factor in the initial design of our automated medicinal chemistry department, established some years ago. Nonetheless, we were able to improve and optimize our workflows and processes constantly. Here, we outline our current setup, from design to submission of libraries, and discuss which procedures and techniques appear to be useful for us and which ones turned out to be less effective. The aim of the manuscript is not to present individualized and tailor-made solutions in our laboratory but rather to describe approaches (often executed with commercial equipment) which might be of relevance for a broader readership working in this field.

Parallel synthesis of peptide libraries using microwave irradiation

The application of microwave irradiation to solid-phase peptide synthesis increases product purity and reduces reaction time. Parallel synthesis in 96-well polypropylene filter plates with microwave irradiation is an efficient method for the rapid generation of combinatorial peptide libraries in sufficient purity to assay the products directly for biological activity without HPLC purification. In this protocol, the solid-phase support is arrayed into each well of a 96-well plate, reagents are delivered using a multichannel pipette and a microwave reactor is used to complete peptide coupling reactions in 6 min and Fmoc-removal reactions in 4 min under temperature-controlled conditions. The microwave-assisted parallel peptide synthesis protocol has been used to generate a library of difficult hexa-beta-peptides in 61% average initial purity (50% yield) and has been applied to the preparation of longer alpha- and beta-peptides. Using this protocol, a library of 96 different hexapeptides can be synthesized in 24 h (excluding characterization).

High-Throughput Microwave-Assisted Organic Synthesis: Moving from Automated Sequential to Parallel Library-Generation Formats in Silicon Carbide Microtiter Plates

A 48 deep-well microtiter plate system for sealed vessel parallel microwave synthesis is described. The plate consists of a standard 6 x 8 matrix of 48 wells with a maximum working volume of 300 microL and is made out of strongly microwave-absorbing sintered silicon carbide. In combination with an alumina sealing plate equipped with adequate conical bore holes for sample withdrawal, the setup can be used for microwave processing at temperatures up to approximately 200 degrees C and 20 bar of pressure. The microtiter plate setup displays excellent temperature and reaction homogeneity and was used for the generation of a 30-member library of 2-aminopyrimidines.