Simplification of the tetracyclic SIRT1-selective inhibitor MC2141: Coumarin- and pyrimidine-based SIRT1/2 inhibitors with different selectivity profile Dante Rotili a , Vincenzo Carafa b , Domenico Tarantino a , Giorgia Botta a , Angela Nebbioso b , Lucia Altucci b,⇑ , Antonello Mai a,⇑ a Istituto Pasteur—Fondazione Cenci Bolognetti, Dipartimento di Chimica e Tecnologie del Farmaco, Università degli Studi di Roma ‘La Sapienza’, P.le A. Moro 5, 00185 Roma, Italy b Dipartimento di Patologia Generale, Seconda Università degli Studi di Napoli, vico L. De Crecchio 7, 80138 Napoli, Italy article info Article history: Received 15 November 2010 Revised 22 December 2010 Accepted 13 January 2011 Available online 19 January 2011 Keywords: Sirtuins Selective inhibition Apoptosis Cytodifferentiation abstract In this report we describe the synthesis and biological characterization of two series of sirtuins’ inhibitors (SIRTi), designed as simplification products of the previously reported SIRT1-selective inhibitor MC2141 (4). In the first series (5a–t) we report a number of 2-substituted-1,2-dihydrobenzo[f]chromen-3-ones with a marked selectivity for the inhibition of SIRT2 over SIRT1. Some of such derivatives showed also high pro-apoptotic (5i and 5l) and/or cytodifferentiating (5d, 5i, and 5o) properties in a human leukemia cell line (U937). The second group of SIRTi (6a–q) is characterized by some analogues of cambinol (3), a well known SIRTi active against the Burkitt lymphoma. Such compounds, differently from the unselective prototype, are endowed with a selective inhibition of SIRT1 over SIRT2, and, in some cases (6j, 6k, and 6q), are more efficient than 3 to induce apoptosis in U937 cells. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Class III histone deacetylases (HDACs), also called sirtuins (SIRTs) from their founding member, the Sir2 (silent information regulator 2) protein of Saccharomyces cerevisiae, are seven enzymes in humans (SIRT1-7) which have NAD + as a co-substrate for their catalytic activity, show no homology with the other classes of HDACs, and are sensible to specific inhibitors. 1 SIRTs catalyze the removal of the acetyl group from the lysine residues of their sub- strates, coupling this event with the hydrolysis of NAD + to generate nicotinamide, deacetylated protein, and O-acetyl-ADP-ribose. 1,2 The ADP-ribosyl transferase activity of sirtuins was long time con- sidered a low efficiency side-reaction due to the partial uncoupling of intrinsic deacetylation and acetate transfer to ADP-ribose. Recently, however, mono-ADP-ribosyl transferase (mART) activity has been found to be the main enzymatic activity of at least two human sirtuins, SIRT4 and SIRT6, whereas SIRT2 and SIRT3 display both deacetylase and mART activities. 3 Moreover, to date, no ro- bust enzymatic activity has been found for SIRT7 as yet. Like class I, II, IV HDACs, besides histones sirtuins deacetylate and/or ADP-ribosylate many other important proteins, including transcription factors (FOXO1, NF-jB, MEF2, HOXA10, PGC1-a, etc.), enzymes (AceCS1/2, GDH, p300), nuclear receptors (androgen receptor), and other regulatory (HIV Tat) and structural (a-tubulin) proteins, so modulating their own activities. 1–4 These evidences can explain the multiple biological functions of sirtuins, that range from repression of gene expression to regulation of cellular cytodifferentiating and/or apoptotic processes, from control of energetic metabolism to aging. 1–4 In yeast, Sir2 is critical for tran- scriptional silencing at three specific loci: the telomeres, ribosomal DNA, and the silent mating type loci. 5,6 Sir2 and its homologues have gained considerable attention for their ability to mimic the diet known as caloric restriction, which extends lifespan in a vari- ety of organisms, including yeast, 7 Caenorhabditis elegans, 8 ro- dents, 9 and probably primates. 10 Since their catalytic activity depends on the intracellular levels of the co-substrate NAD + and of the vitamin nicotinamide, that at physiological conditions exerts the classical non-competitive product inhibition, sirtuins have also been proposed as sensors of the cell metabolic state. 1–4 Moreover, since these enzymes in humans regulate cell survival under stress conditions as well as neuro/cardio protection, stimulate insulin secretion and lipolysis, and inhibit adipogenesis, sirtuins’ activa- tors (such as resveratrol) have been proposed for the treatment 0968-0896/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmc.2011.01.025 Abbreviations: BCL6, B-cell lymphoma 6; FACS, fluorescence activated cell sorting; FOXO, forkhead box class O; NAD + , nicotinamide adenine dinucleotide; NF-jB, nuclear factor-jB; PGC-1a, peroxisome proliferator-activated receptor c coactivator 1a; SIRT, silent information regulator 2 type enzyme. ⇑ Corresponding authors. Tel.: +39 081 5667569; fax: +39 081 450169 (L.A.); tel.: +39 06 49913392; fax: +39 06 49693268 (A.M.). E-mail addresses: lucia.altucci@unina2.it (L. Altucci), antonello.mai@uniroma1.it (A. Mai). Bioorganic & Medicinal Chemistry 19 (2011) 3659–3668 Contents lists available at ScienceDirect Bioorganic & Medicinal Chemistry journal homepage: www.elsevier.com/locate/bmc