Preparation of kinase-biased compounds in the search for lead inhibitors of kinase targets

Abstract

This work describes the preparation of approximately 13,000 compounds for rapid identification of hits in high-throughput screening (HTS). These compounds were designed as potential serine/threonine or tyrosine kinase inhibitors. The library consists of various scaffolds, e.g., purines, oxindoles, and imidazoles, whereby each core scaffold generally includes the hydrogen bond acceptor/donor properties known to be important for kinase binding. Several of these are based upon literature kinase templates, or adaptations of them to provide novelty. The routes to their preparation are outlined. A variety of automation techniques were used to prepare >500 compounds per scaffold. Where applicable, scavenger resins were employed to remove excess reagents and when necessary, preparative high performance liquid chromatography (HPLC) was used for purification. These compounds were screened against an 'in-house' kinase panel. The success rate in HTS was significantly higher than the corporate compound collection.

Solid-Phase Synthetic Strategies for the Preparation of Purine Derivatives

“…It was demonstrated that depending on the type of the immobilization strategy, the target purines could be simply diversified at positions 2, 6, 8, and 9 using readily available starting materials. This fact led to the application of combinatorial solid-phase synthesis to produce and study collections of desired compounds, with CDK inhibitor libraries being the well-known examples. − …”

“…The method of immobilization is the key aspect of solid-phase synthesis because it typically limits the resulting diversification possibilities. Although positions C 6 and N 9 have been identified as the most suitable for this purpose, 10−13 a detailed literature survey revealed that the strategies for immobilization via any other position are available, except for the quaternary carbon atoms C 4 and C 5 .…”

“…Using 1,4-diazabicyclo[2.2.2]octane (DABCO), 6-chloro-2-halogen-9H-purine 67 was immobilized on Wang resin 66 via an ether linkage. 34 The subsequent N 9 regioselective alkylation was performed via the Mitsunobu procedure. In contrast, the alternative alkylation with 1-bromobutane and sodium hydride as a base afforded a mixture of 7-and 9-butyl isomers in a 1:1 ratio.…”

“…This method was tested for a variety of building blocks and afforded the target compounds 82 in high yields and crude purity. Note that the arylation was generally applicable only for N 9 -substituted intermediates, whereas 9H-purine analogues displayed a very low conversion. The incorporation of the new substituent at the purine C 8 position can be alternatively performed by the cyclization reaction of suitable pyrimidine intermediates.…”

Just-in-Time Purification: An Effective Solution for Cherry-Picking and Purifying Active Compounds from Large Legacy Libraries

“…Therefore, it is likely that pharmaceutical companies will continue to produce interesting data using legacy libraries of unpurified reaction mixtures. With reported library hit rates in the range of 0.1% to 1%, 6 it is less expensive to reserve purification initially for those reaction mixtures whose activities reconfirm and then for any focused libraries subsequently produced around the active series.…”