A modular approach to trim cellular targets in anticancer drug discovery

Three successive and regiocontroled palladium cross-coupling reactions to easily synthesize novel series of 2,4,6-tris(het)aryl pyrido[1',2':1,5]pyrazolo[3,4-d]pyrimidines

The first access to tris(het)arylated pyrido[1',2':1,5]pyrazolo[3,4-d]pyrimidine derivatives is reported. The series were generated from 4-chloroaminopyridinium, which afforded the key intermediate bearing three leaving groups, i.e. a C-2 methylsulfanyl, a lactame carbonyl group in C-4 and a chlorine atom in C-6. The regioselective reactions led to the tris(het)aryl derivatives with satisfying to high yields. The three successive cross-coupling reactions occurred first in C-6 by the displacement of chlorine, next in C-4 position by a sequential Pd-catalyzed phosphonium coupling and finally in C-2 under a Pd/Cu-catalyzed desulfitative cross-coupling reaction. The optimization and scope of each reaction are discussed and the original compounds characterized.

Synthesis and identification of unprecedented selective inhibitors of CK1ε

A small and structure-biased library of enantiopure anti-β-amino alcohols was prepared in a straightforward manner by a simplified version of the Reetz protocol. Antiproliferative activity testing against a panel of five human solid tumor cell lines gave GI50 values in the range 1-20 μM. The reverse screening by computational methods against 58 proteins involved in cancer pointed to kinases as possible therapeutic target candidates. The experimental determination of the interaction with 456 kinases indicated that the compounds behave as selective CK1ε inhibitors. Our results demonstrate that the lead compound represents the first selective CK1ε inhibitor with proven antiproliferative activity in cancer cell lines.

The first example of the Fischer-Hepp type rearrangement in pyrimidines

A N-nitroso moiety can be used for the activation of chloropyrimidines toward a nucleophilic substitution reaction with amines. The subsequent treatment of the obtained products with aq H₂SO₄ can lead to either N-denitrosation to obtain 4,6-pyrimidinediamines or to a Fischer–Hepp type rearrangement to obtain 5-nitroso-4,6-pyrimidinediamines. It was found that the outcome of the reaction strongly depends on the structure of the pyrimidines. Activation of the pyrimidine ring by three groups with a positive mesomeric effect is crucial for the intramolecular nitroso group migration.