Thiazolo[5,4-f]quinazolin-9-ones, inhibitors of glycogen synthase kinase-3 Alexandra Testard, a Ce ´dric Loge ´, b Benoı ˆt Le ´ger, b Jean-Michel Robert, b Olivier Lozach, c Me ´lina Blairvacq, c Laurent Meijer, c Vale ´rie Thie ´ry a and Thierry Besson a, * a Laboratoire de Biotechnologies et de Chimie Bio-organique, FRE CNRS 2766, UFR Sciences Fondamentales et Sciences pour l’Inge ´nieur, Universite ´ de La Rochelle, Ba ˆtiment Marie Curie, 17042 La Rochelle, France b Universite ´ de Nantes, Nantes Atlantique Universite ´s, Biomole ´cules et Cibles The ´rapeutiques, De ´ partement de Pharmacochimie, BioCiT-EA 1155, UFR Sciences Pharmaceutiques, 1 rue Gaston Veil, Nantes F-44000, France c Cell Cycle Group, UMR7150 and UPS2682, Station Biologique, B. P. 74, 29682 Roscoff Cedex, Bretagne, France Received 10 March 2006; revised 3 April 2006; accepted 3 April 2006 Available online 27 April 2006 Abstract—In an effort to identify new protein kinase inhibitors with increased potency and selectivity, we have developed the micro- wave-assisted synthesis of thiazolo[5,4-f]quinazolin-9-ones. The effects of eighteen derivatives on CDK1/cyclin B, CDK5/p25, and GSK-3 were investigated. Several turned out to inhibit GSK-3 in the micromolar range. Molecular modeling studies suggest that the most selective GSK-3 inhibitors 7a–d bind into the ATP-binding site through a key hydrogen bond interaction with Val135 and target the specific hydrophobic backpocket of the enzyme. Ó 2006 Elsevier Ltd. All rights reserved. Cyclin-dependent kinases (CDKs) constitute a family of highly conserved protein kinases involved in regulating the cell division cycle, apoptosis, numerous neuronal functions, insulin release, and transcription. Glycogen synthase kinase-3 (GSK-3) is a family of kinases in- volved in cell cycle control, insulin action, apoptosis, neuronal cell death, and developmental regulation. Both families of kinases are implicated in various human dis- eases such as cancers, Alzheimer’s disease, and diabetes, and therefore both have been extensively used as targets to identify small molecular weight pharmacological inhibitors of potential therapeutic interest. 1–4 More than 100 CDK inhibitors and 40 GSK-3 inhibitors have been identified; 2–4 most of which act by competing with ATP binding at the catalytic site of the kinase. Among the numerous inhibitors described, the most studied mem- bers contain a purine (e.g., olomoucine I and roscovitine II) or an oxindole ring (e.g., oxindole 91 III)(Fig. 1). While investigating the chemical interest of 4,5-dichloro- 1,2,3-dithiazolium chloride (Appel’s salt) 5–7 and its derivatives, we recently described the microwave- assisted multi-step synthesis of novel thiazoloquinazoli- nones 8–10 (IV and V, Fig. 1) which can be considered, at first glance, as hybrid molecules between the purines and the oxindoles mentioned above. After testing the effects of these molecules on CDKs and GSK-3, 10 it was ob- served that isomer (V) is completely inactive whatever substituent is present on the angular structure. Although most synthesized quinazolinones exhibited a moderate to potent GSK-3 inhibitory activity (IC 50 ranging from 1.3 to 60 lM), one derivative (molecule 7a, Scheme 1), analogue of IV, exerted a selective inhibition toward GSK-3 (IC 50 = 4.2 lM). This compound bears, at C-2 of the thiazoloquinazolinone, an amidine function incorporated into an imidazoline ring. Considering this product as a possible lead compound, we focused our efforts on the synthesis of various thiazoloquinazolinon- es, which possess an amidine function on C-2 of the thiazole moiety and various alkyl or aryl groups on N-8 of the quinazoline part of the molecule. In this article, we report the benefits associated with the microwave methodology 10,11 for the preparation of these new products and their effects on CDKs and GSK-3. Docking studies targeting the ATP-binding site 0960-894X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmcl.2006.04.006 Abbreviations: CDK, cyclin-dependent kinase; GSK-3, glycogen synthase kinase-3; ATP, adenosine triphosphate; MW, microwave; DMF, N,N-dimethylformamide; THF, tetrahydrofuran; AMP-PNP, 5 0 -adenylyl-imidodiphosphate; pdb code, RCSB Protein Data Bank. Keywords: Glycogen synthase kinase-3 inhibitors; Quinazolines; Microwave-assisted chemistry; Molecular modeling. * Corresponding author. Tel.: +33(0)546458255; fax: +33(0)546458247; e-mail: tbesson@univ-lr.fr Bioorganic & Medicinal Chemistry Letters 16 (2006) 3419–3423