Synthesis of Glutaminyl Adenylate Analogues that are Inhibitors of Glutaminyl-tRNA Synthetase SteÂphane Bernier, Daniel Y. Dubois, Manon Therrien, Jacques Lapointe and Robert CheÃnevert* De Âpartement de Chimie, De Âpartement de Biochimie et de Microbiologie, Centre de Recherche sur la Fonction, la Structure et l'Inge Ânierie des Prote Âines (CREFSIP), Faculte  des Sciences et de Ge Ânie, Universite  Laval, Que Âbec, Canada, G1K 7P4 Received 8 June 2000; accepted 17 August 2000 AbstractÐGlutaminol adenylate 5 is a competitive inhibitor of glutaminyl-tRNA synthetase with respect to glutamine (K i =280 nM) and to ATP (K i =860 nM). The corresponding methyl phosphate ester 4 is a weaker inhibitor (K i 10 mM) with respect to glutamine. # 2000 Elsevier Science Ltd. All rights reserved. Introduction Aminoacyl-tRNA synthetases (aaRSs) are essential enzymes involved in protein synthesis in all living organ- isms. They catalyze the esteri®cation of a particular tRNA with its corresponding amino acid. It has been established that this reaction is a two-step event (Scheme 1). 1,2 In the ®rst step, the appropriate amino acid (aa) is recog- nized by the enzyme and reacts with ATP to form an enzyme-bound mixed anhydride (aa-AMP, aminoacyl adenylate) with displacement of pyrophosphate (PP i ). In the second step, the activated amino acid is transferred to the CCA end of the cognate tRNA to form the amino- acyl-tRNA (aa-tRNA) and AMP. Glutaminyl-tRNA synthetase (GlnRS) has the charac- teristic, which is shared by glutamyl- and arginyl-tRNA synthetases, of requiring the presence of its cognate tRNA to catalyze the activation of its amino acid sub- strate. Selective inhibition of microbial aaRS has proved 0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0960-894X(00)00478-9 Bioorganic & Medicinal Chemistry Letters 10 (2000) 2441±2444 Scheme 1. *Corresponding author. Fax: +1-418-656-7916; e-mail: robert.chenevert@chm.ulaval.ca