Abstract

1. A Focused Library of Tetrahydropyrimidinone Amides via a Tandem Biginelli-Ugi Multi-Component Reaction Process David M. Turner, Stefan Werner, Michael A. Lyon, Donna M. Huryn, Peter Wipf*Center for Chemical Methodologies and Library Development, University of Pittsburgh, Pittsburgh, PA 15260, USA Abstract A second generation focused library of 30 tetrahydropyrimidinone amides was prepared. The design was based on the structure of an Hsp70 modulator. This small library demonstrates the utility of tandem multi-component reactions in structure-activity relationship studies of biological lead molecules. The tandem Biginelli-Ugi multi-component reaction facilitated the effective variation of three different substituents and allowed the synthesis of the library members in a sequence of only two one-pot reactions. Introduction A multi-component reaction (MCR) is a sequence of bimolecular events whose product incorporates all or nearly all atoms of three or more starting materials, thus providing a large increase in structural complexity. Such reactions are increasingly popular in the synthesis of combinatorial libraries and in commercial drug discovery efforts.1 While MCRs have been combined with various other reactions to generate even higher degrees of complexity, few examples of tandem2 multi-component reactions (TMCRs) are known. In this context, the combination of the three-component Biginelli tetrahydropyrimidinone synthesis with the four component Ugi condensation is particularly attractive. This two-pot sequence yields products of increased structural diversity with seven possible points of variation, as well as the complementary combination of the Biginelli reaction’s heterocyclic scaffold and the Ugi reaction’s typical acyclic amide backbone. We previously reported results from an earlier library of Biginelli-Ugi TMCR products, and showed that these molecules have the ability to modulate endogenous and co-chaperone-stimulated Hsp70 ATPase activity.3 While Hsp70 molecular co-chaperones display an important function in several cellular processes, and have been linked to human diseases such as Parkinson’s and Huntington’s diseases and cancer, only a few small molecule inhibitors of Hsp70 are known to date.4 Fig. 1 Lead Compounds MAL3-1-1 and MAL3-39 and Negative Control MAL 3-51 Fig. 2 Library Member Building Blocks Conclusion We synthesized a second generation focused library of tetrahydropyrimidinone amides (1{1-12,1-10,1-8}) based on the structure of MAL3-101 that was previously found to block the ability of Hsp70 co-chaperones to enhance Hsp70 ATPase activity without affecting the Kcat for ATP hydrolysis. This library demonstrates the utility of TMCRs in SAR studies of biological lead molecules. The tandem Biginelli-Ugi MCR facilitated the effective variation of four different substituents and allowed the synthesis of the library members in a sequence of only two one-pot reactions. Detailed studies on the ability of the tetrahydropyrimidinone amides (1{1-12,1-10,1-8}) to modulate Hsp70 ATPase activity are ongoing and will be reported in due course. Library Design Based on the biological data acquired from the previous library, a second generation focused library was designed and synthesized around the structures of MAL3-101 (1{1,1,1}) and MAL3-39 (3).5 MAL3-101 (1{1,1,1}) and MAL3-39 (3) were able to block the abilities of Hsp70 co-chaperones to enhance Hsp70 ATPase activity, while having no effect on the Kcat for ATP hydrolysis. MAL3-51 showed no activity and was used as a negative control.3 In order to allow a detailed structure activity relationship (SAR) analysis, the library was synthesized in the indexed library format, with only a single change made to the substituents of MAL3-101 (1{1,1,1}) in any given sequence. Twelve Biginelli-type tetrahydropyrimidinones (7{1-12}) were synthesized with high purities (>96%), and yields ranging from modest for aliphatic aldehydes (15-20%) to high for aromatic derivatives (45-89%). These products were used as building blocks for the four-component Ugi reaction, along with ten aldehydes (8{1-10}), eight amines (9{1-8}), and n-butylisocyanide (10). After purification on an ISCO flash column chromatography system, final compounds were obtained with purities >85% (in some cases up to >99%) in an average yield of 25% and in amounts of 32-242 mg. Acknowledgment We gratefully acknowledge financial support provided by NIGMS (P50-GM067082). The authors also thank Dr. Claire M. Coleman and Ms. Leslie A. Twining for LC-MS/UV/ELSD analyses, and Prof. Jeff Brodsky for biological assays and stimulating discussions. References (1) Hulme, C.; Gore, C. Curr. Med. Chem.2003, 10, 51. (2) Nicolaou, K.C.; Montagnon, T.; Snyder, S.A. Chem. Commun.2003, 551. (3) Fewell, S.W.; Smith, C.M.; Lyon, M.A., Dumitrescu, T.P.; Wipf, P.; Day, B.W.; Brodsky, J.L.; J. Biol. Chem.2004, 279, 51131. (4) Fewell, S.W.; Day, B.W.; Brodsky, J.L. J. Biol. Chem.2001, 276, 910. (5) Werner, S.; Turner, D. M.; Lyon, M. A.; Huryn, D. M.; Wipf, P.; Synlett. (in press)