High-Throughput ¹H NMR and HPLC Characterization of a 96-Member Substituted Methylene Malonamic Acid Library

Abstract

A solid phase organic synthesis method has been developed for the preparation of substituted methylene malonamic acids and malonic ester mono acids 5. Two substituents are introduced into the core molecule 5 by preparation of unsymmetrical malonic acid derivatives 2, followed by Knoevenagel condensation with aromatic or aliphatic aldehydes, giving resin-bound 4. Evaluation of the scope of these reactions led to the preparation of a 96-member library from a set of eight amines/alcohols (seven amines and one alcohol) and 11 aldehydes leading to 88 substituted methylene malonamic/malonate mono acids 5 and eight unsymmetrical malonamic/malonate mono acids 3. Structural validation and quantitation for every member of the library was obtained by evaluation of 1H NMR and HPLC, respectively. The 1H NMR data were obtained using automated delivery of DMSO solutions of every library member from a 96-deep well microtiter plate to a flow probe-equipped NMR spectrometer. HPLC data were used for determination of the extent of conversion of malonamic/malonate esters 2 to the products 5 by an external standard method. Summary information from the 1H NMR and HPLC data is viewed as plate diagrams for analysis of the final library.