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Cholesterol-Modified Oligonucleotides as Internal Reaction Controls during DNA-Encoded Chemical Library Synthesis.

We report two cholesterol-modified oligonucleotides for use as internal controls for on-DNA reactions during the pooled stages of a DNA-encoded chemical library (DECL) synthesis. As these cholesterol-tagged oligonucleotides are chromatographically separable from normal DECL intermediates, they can be directly monitored by mass spectrometry to track reaction progression within a complex pool of DNA. We observed similar product conversions for reactions on substrates linked to a standard DECL DNA headpiece, to the cholesterol-modified oligonucleotides, and to the cholesterol-modified oligonucleotides while in the presence of pooled DECL synthetic intermediates-validating their use as a representative control. We also highlight an example from a DECL production in which the use of the cholesterol-modified oligonucleotides provided quality control information that guided synthetic decisions. We conclude that the use of cholesterol-modified oligonucleotides as a regular control will significantly improve the quality of DECL productions.