N-Pyrrylarylsulfones with High Therapeutic Potential

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Review N-Pyrrylarylsulfones with High Therapeutic Potential

Valeria Famiglini 1, Sabrina Castellano 2 and Romano Silvestri 1,* 1 Department of Drug Chemistry and Technologies, Sapienza University of Rome, Laboratory afﬁliated to Istituto Pasteur Italia—Fondazione Cenci Bolognetti, Piazzale Aldo Moro 5, I-00185 Roma, Italy; [email protected] 2 Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, I-84084 Fiscano, Salerno, Italy; [email protected] * Correspondence: [email protected]; Tel.: +39-06-4991-3800

Academic Editor: Claudiu T. Supuran Received: 12 February 2017; Accepted: 3 March 2017; Published: 9 March 2017

Abstract: This review illustrates the various studies made to investigate the activity of N-pyrrylarylsulfone containing compounds as potential antiviral, anticancer and SNC drugs. A number of synthetic approaches to obtain tetracyclic, tricyclic and non-cyclic compounds, and their biological activity with regard to structure–activity relationships (SARs) have been reviewed. The literature reviewed here may provide useful information on the potential of N-pyrrylarylsulfone pharmacophore as well as suggest concepts for the design and synthesis of new N-pyrrylarylsulfone based agents.

Keywords: sulfonamide; heterocycle; polycyclic compound; therapeutic agent

1. Introduction Sulfonamide is the basis of several groups of drugs [1]. Intense interest focused on sulfonamide drugs after the discovery in 1935 that the activity of red dye Prontosil [2,3] was attributed to breakdown product sulfanilamide (1). The antibacterial sulfonamides work as competitive inhibitors of the dihydropteroate synthase, an enzyme involved in folate synthesis [4]. The simple 1 was cheaper than Prontosil, had fewer unwanted effects and did not impart the typical red color to the skin. Nowadays, sulfonamides have been replaced by other antibacterial drugs such as β-lactam antibiotics, with some important exception; for example, sulfamethoxazole (2) is used for treatment of urinary and respiratory-tracts infections [5]. Sulfa molecules have been chemically manipulated to obtain drug for the treatment of leprosy, fluid accumulation and diabetes. The modern era of drug treatment of leprosy began in 1937 when the sulfa drug dapsone (3)[6] proved to be highly effective. For more than six decades, 3 remained first line drug to treat leprosy. Since 1980s, 3 has been administered in combination with rifampicin and clofazimine for treatment of leprosy [7]. Chlorothiazide (4) is a carbonic anhydrase inhibitor which was introduced in 1958 as a diuretic drug and is used to treat hypertension and edema [8,9]. Before the discovery of 4, mercurial drugs associated with severe toxicity were the only available drugs to treat fluid retention. Few years later, in 1962, another sulfonamide, furosemide (5), was discovered as diuretic drug and is used to treat fluid retention and for the treatment of high blood pressure [10]. Tolbutamide (6), the first sulfonylurea anti-diabetic drug, was approved in the United States in 1957 for the treatment of type 2 diabetics [11]. Even though since 1964 there were concerns that sulfonylurea antidiabetic drugs may increase cardiovascular risk, the current literature does not confirm the detrimental risk profile of sulphonylureas compared with other anti-diabetic drugs [12]. Ethoxyzolamide (7) is a carbonic anhydrase inhibitor used in the treatment of glaucoma and duodenal ulcers, and as a diuretic [13]. Other sulfa drug examples include antivirals agents, such HIV-1 non-nucleoside reverse transcriptase and protease inhibitors [14–18], HCV NS3/4A protease [19] and NS5B polymerase inhibitors [20]; antibiotics, such mafenide, approved by the FDA in 1948 [21]; and nonsteroidal anti-inflammatory drug such celecoxib, a COX-2 selective inhibitor [22] (Chart1).

Molecules 2017, 22, 434; doi:10.3390/molecules22030434 www.mdpi.com/journal/molecules Molecules 2017, 22, 434 2 of 17

MoleculesNS5B2017 polymerase, 22, 434 inhibitors [20]; antibiotics, such mafenide, approved by the FDA in 1948 [21]; and2 of 18 nonsteroidal anti-inflammatory drug such celecoxib, a COX-2 selective inhibitor [22] (Chart 1).

ChartChart 1. 1.Examples Examples of of sulfa sulfa andand pyrrolepyrrole containing containing drugs. drugs.

Pyrrole ring is a well-known privileged scaffold that exhibits a wide variety of biological activities [23].Pyrrole Including ring isthe a pyrrole well-known into different privileged pharmacophores scaffold that has exhibitsresulted in a non-cyclic wide variety and polycyclic of biological activitiespyrrole-containing [23]. Including systems the pyrrole with potential into different therapeutic pharmacophores effects such as has anticancer resulted in(leukemia non-cyclic and and polycycliclymphoma), pyrrole-containing anti-microbic (bacteria, systems malaria, with potential protozoa, therapeutic and fungi) effectsand central such nervous as anticancer system (leukemiaagents and(antipsychotic lymphoma), anti-microbicand anxiolytic) (bacteria, (for example, malaria, pyrrolnitrin protozoa, (8 and) [24], fungi) tolmetin and central(9) [25], nervous isamoltane system agents(CGP-361A) (antipsychotic (10) [26], and porphobilinogen anxiolytic) (for (11 example,) [27], and pyrrolnitrin atorvastatin ( 128)[) [28]).24], tolmetin Recently, ( VU04101509)[25], isamoltane (13), (CGP-361A)a pyrrylarylsulfone (10)[26], porphobilinogencontaining compound, (11)[ 27has], andbeen atorvastatin discovered (as12 )[mGluR4-positive28]). Recently, allosteric VU0410150 (13),modulator a pyrrylarylsulfone and evaluated containing as potential compound, drug for treatment has been for discovered Parkinson’s as disease mGluR4-positive [29,30]. In the allosteric past modulatordecades, and numerous evaluated N-pyrrylarylsulfones as potential drug have for been treatment synthesized for Parkinson’s by our research disease group [29 in, several30]. In drug the past discovery projects. In this work, attempt has been made to review various N-pyrrylarylsulfone based decades, numerous N-pyrrylarylsulfones have been synthesized by our research group in several compounds to discuss the synthetic approaches and the biological activity with regard to structure– drug discovery projects. In this work, attempt has been made to review various N-pyrrylarylsulfone activity relationships (SARs). based compounds to discuss the synthetic approaches and the biological activity with regard to structure–activity2. Pyrrolo[1,2-b relationships]-s-triazolo[3,4- (SARs).d][1,2,5]benzothiadiazepine 5,5-dioxide

2. Pyrrolo[1,2-Tetracyclicb]-s-triazolo[3,4- systems, ford ][1,2,5]benzothiadiazepineexample mianserin, aptazepine 5,5-dioxide and bretazenil, have been widely investigated as psychotic drugs. The synthesis of pyrrolobenzothiadiazepine anellated with azole ringTetracyclic started as systems, a development for example of a previous mianserin, research aptazepine project on tetra-anellated and bretazenil, heterocycles have been [31–33]. widely investigatedPyrrolo[1,2- asb psychotic]-s-triazolo[3,4- drugs.d][1,2,5]benzothiadiazepine The synthesis of pyrrolobenzothiadiazepine 5,5-dioxide (14) was synthesized anellated by reaction with azole ringof started 2-nitrobenzensulfonyl as a development chloride of a previous with ethyl research pyrrole-2-carboxylate project on tetra-anellated in the presence heterocycles of potassium [31– 33 ]. Pyrrolo[1,2-tert-butoxideb]-s-triazolo[3,4- and 18-crown-6d][1,2,5]benzothiadiazepine to provide 2-ethoxycarbonyl-1-(2-nit 5,5-dioxiderobenzenesulfony)-1 (14) was synthesizedH-pyrrole by reaction(15). of 2-nitrobenzensulfonylAfter reduction of 15 to amino chloride derivative with ethyl 16, the pyrrole-2-carboxylate product was cyclized to in lactam the presence 17 in the presence of potassium of tert-butoxide2-hydroxypyridine and 18-crown-6 as a bifuncti to provideonal catalyst. 2-ethoxycarbonyl-1-(2-nitrobenzenesulfony)-1 Treatment of 17 with di-4-morpholinylphosphinicH-pyrrole chloride ( 15). After(18 reduction) in the presence of 15 to of amino sodium derivative hydride afforded16, the productphosphinyloxyimine was cyclized 19 towhich lactam was17 transformedin the presence into of 14 by reaction with formylhydrazine (Scheme 1) [34]. 2-hydroxypyridine as a bifunctional catalyst. Treatment of 17 with di-4-morpholinylphosphinic chloride (18) in the presence of sodium hydride afforded phosphinyloxyimine 19 which was transformed into 14 by reaction with formylhydrazine (Scheme1)[34]. Molecules 2017, 22, 434 3 of 18 Molecules 2017, 22, 434 3 of 17

Molecules 2017, 22, 434 3 of 17

Scheme 1. Synthesis of 14. Scheme 1. Synthesis of 14. 3. 2-Methyl-1,3,4,14b-tetrahydro-2H-pyrazino[2,1-Scheme 1. Synthesisd]pyrrolo[1,2- of 14. b][1,2,5]benzothiadia-zepine 3. 2-Methyl-1,3,4,14b-tetrahydro-210,10-dioxide H-pyrazino[2,1-d]pyrrolo[1,2-b][1,2,5]benzothiadia-zepine 10,10-dioxide3. 2-Methyl-1,3,4,14b-tetrahydro-2H-pyrazino[2,1-d]pyrrolo[1,2-b][1,2,5]benzothiadia-zepine Studies on tetracyclic analogs of mianserin as antidepressant drugs led to the development of 10,10-dioxide theStudies pyrrole on analog tetracyclic aptazepine analogs and ofthe mianserin strictly related as antidepressant isoaptazepine and drugs 10-methyl-10-azaaptazepine led to the development of the( pyrrole20). StudiesPursuing analog on this tetracyclic aptazepine research analogs andprojec the t,of 2-methyl-1,3,4,14b-tetrahydro-2 strictlymianserin related as antidepressant isoaptazepine drugsH and-pyrazino[2,1- led 10-methyl-10-azaaptazepine to the developmentd]pyrrolo[1,2- ofb] (20).[1,2,5]benzothiadiazepinethe Pursuing pyrrole analog this research aptazepine project,10,10-dioxide and the 2-methyl-1,3,4,14b-tetrahydro-2 strictly (21) (tiaaptazepine)related isoaptazepine was designed andH 10-methyl-10-azaaptazepine-pyrazino[2,1- as new putatived]pyrrolo[1,2- core for b] [1,2,5]benzothiadiazepinecentral(20). Pursuing nervous this system research (CNS) 10,10-dioxide projec activet, 2-methyl-1,3,4,14b-tetrahydro-2drugs. (21) The (tiaaptazepine) synthesis of 21 was is depicted designedH-pyrazino[2,1- in asScheme newd]pyrrolo[1,2- putative2. Reaction core bof] for central1-(2-aminobenzenesulfonyl)pyrrole[1,2,5]benzothiadiazepine nervous system (CNS) 10,10-dioxide active wi drugs.th ethyl(21) The (tiaaptazepine) glyoxylate synthesis via of awas Pictet-Spengler21 isdesigned depicted as type innew Scheme condensation putative2. Reactioncore gave for of 1-(2-aminobenzenesulfonyl)pyrrole11-ethoxycarbonyl-10,11-dihydropyrrolo[1,2-central nervous system (CNS) active with drugs. ethyl Theb glyoxylate][1,2,5]benzothiadiazepine synthesis via of a21 Pictet-Spengler is depicted 5,5-dioxide in Scheme type ( condensation22 2.). ReactionReaction ofof gave 11-ethoxycarbonyl-10,11-dihydropyrrolo[1,2-221-(2-aminobenzenesulfonyl)pyrrole with bromoacetyl bromide afforded with thethyle correspondingb ][1,2,5]benzothiadiazepineglyoxylate via bromoacetyl a Pictet-Spengler derivative 5,5-dioxide type condensation 23 which (22). Reaction reacted gave of 11-ethoxycarbonyl-10,11-dihydropyrrolo[1,2-b][1,2,5]benzothiadiazepine 5,5-dioxide (22). Reaction of 22 withwith bromoacetylbenzylamine ( bromide24) and subsequently afforded the thermally corresponding cycled to bromoacetyl 25. Compound derivative 25 was reduced23 which with reacted lithium with 22 with bromoacetyl bromide afforded the corresponding bromoacetyl derivative 23 which reacted benzylaminealuminum hydride (24) and (26 subsequently) and debenzylated thermally to 27 with cycled hydrogen to 25. Compoundover Pd/C. Finally,25 was 27 reducedwas converted with to lithium 21 viawith reductive benzylamine amination (24) and using subsequently formaldehyde thermally in the cycled presence to 25. Compoundof hydrogen 25 (Scheme was reduced 2) [35]. with lithium aluminumaluminum hydride hydride (26 (26)) and and debenzylateddebenzylated to to 2727 withwith hydrogen hydrogen overover Pd/C. Pd/C. Finally, Finally, 27 was converted27 was converted to 21 to 21viavia reductive reductive amination amination using using formaldehyde formaldehyde in the in presence the presence of hydrogen of hydrogen (Scheme (Scheme 2) [35]. 2)[35].

Scheme 2. Synthesis of 21, and structure of 10-methyl-10-azaaptazepine (20).

It is worthwhileSchemeScheme mentioning 2. 2.Synthesis Synthesis that of of21 21 direct,, andand structurestructurecyclization of of 10-methyl-10-azaaptazepineof 10-methyl-10-azaaptazepine 24 in the presence of excess (20). (20 of). methylamine via diketo intermediate 28, failed due the formation 11-carboxy-10,11-dihydropyrrolo[1,2-b][1,2,5] It is worthwhile mentioning that direct cyclization of 24 in the presence of excess of methylamine benzothiadiazepine-11-acetic acid bis methylamide 5,5-dioxide (29). Intramolecular cyclization of 29 viaIt isdiketo worthwhile intermediate mentioning 28, failed that due direct the cyclizationformation 11-carboxy-10,11-dihydropyrrolo[1,2- of 24 in the presence of excess of methylamineb][1,2,5] in the presence of 2-hydroxypyridine led exclusively to the spiro derivative 30. It should be noted that via diketobenzothiadiazepine-11-acetic intermediate 28, failed acid due bis methylamide the formation 5,5-dioxide 11-carboxy-10,11-dihydropyrrolo[1,2- (29). Intramolecular cyclization ofb][1,2,5] 29 benzothiadiazepine-11-aceticin the presence of 2-hydroxypyridine acid bis methylamideled exclusively 5,5-dioxideto the spiro derivative (29). Intramolecular 30. It should cyclizationbe noted that of 29

Molecules 2017, 22, 434 4 of 18 in theMolecules presence 2017, of 22, 2-hydroxypyridine 434 led exclusively to the spiro derivative 30. It should be noted4 of 17 that treatment of 24 with sodium hydrogen carbonate gave lactam 31, which might be the intermediate of treatment of 24 with sodium hydrogen carbonate gave lactam 31, which might be the intermediate of 24 29 the conversionthe conversion of of to24 to 29(Scheme (Scheme3)[ 3)36 [36].]. Molecules 2017, 22, 434 4 of 17

treatment of 24 with sodium hydrogen carbonate gave lactam 31, which might be the intermediate of the conversion of 24 to 29 (Scheme 3) [36].

Scheme 3. Chemical transformation of 24. Scheme 3. Chemical transformation of 24. Compounds 21 and 22 were enantioseparated by enantioselective HPLC, and the absolute Compoundsconfiguration of21 theand pure22 enantiomerswereScheme enantioseparated was3. Chemical established transformation byby circular enantioselective of dichroism24. (CD) HPLC, spectroscopy. and the absolute configurationThe in of vitro the binding pure enantiomers affinities for wasseveral established CNS receptors by circular (DA1, DA dichroism2, DA3, 5-HT (CD)1A, 5-HT spectroscopy.2A, 5-HT2C, 5-HT3, α1NA, α2NA and muscarinic receptors) showed that both enantiomers of derivative 21, (−)-(R)-21 The inCompounds vitro binding 21 and affinities 22 were for severalenantioseparated CNS receptors by enantioselective (DA1, DA2, DA HPLC,3, 5-HT and1A ,the 5-HT absolute2A, 5-HT 2C, and (+)-(S)-21, showed higher affinities than the (−)-(R)-22 and (+)-(S)-22 counterparts, with exception 5-HTconfiguration3, α1NA, α2NA ofand the muscarinicpure enantiomers receptors) was established showed that by bothcircular enantiomers dichroism (CD) of derivative spectroscopy.21,(− )-(R)-21 of α1NA for which (+)-(S)-22 was superior. Compound (+)-(S)-21 showed good affinities for 5-HT1A, 5-HT2A, and (+)-(SThe)-21 in, showedvitro binding higher affinities affinities for thanseveral the CNS (− )-(receptorsR)-22 and (DA (+)-(1, DAS2)-, 22DAcounterparts,3, 5-HT1A, 5-HT with2A, 5-HT exception2C, 5-HT2C3, ,α and1NA, αα1NA2NA receptorsand muscarinic but only receptors) moderate showed affinities th forat bothDA1, enantiomersDA2 and 5-HT3 of derivativereceptors. Compared21, (−)-(R)- 21to of α1NA for which (+)-(S)-22 was superior. Compound (+)-(S)-21 showed good affinities for 5-HT1A, 5-HT2A, andthe reference (+)-(S)-21 compounds, showed higher mirtazepine, affinities mianserinethan the (−)-( andR)- 5-methoxymianserin,22 and (+)-(S)-22 counterparts, this compound with exception showed 5-HT2C, and α1NA receptors but only moderate affinities for DA1, DA2 and 5-HT3 receptors. Compared ofhigher α1NA foraffinity which of (+)-( theS 5-HT)-22 was1A subtype, superior. and Compound different (+)-( generalS)-21 pharmacological showed good affinities profile for [37]. 5-HT 1A, 5-HT2A, to the reference compounds mirtazepine, mianserine and 5-methoxymianserin, this compound 5-HT2C, and α1NA receptors but only moderate affinities for DA1, DA2 and 5-HT3 receptors. Compared to showedthe4. Imidazo[5,1- reference higher affinity compoundsd]pyrrolo[1,2- of the mirtazepine, 5-HTb][1,2,5]benzothiadiazepine1A subtype, mianserine and and different 5-methoxymianserin, 9,9-dioxide general pharmacological this compound profile showed [37 ]. higherImidazo[5,1- affinity of dthe]pyrrolo[1,2- 5-HT1A subtype,b][1,2,5]benzothia-diazepine and different general 9,9-dioxide pharmacological (32) was profile synthesized [37]. as a new 4. Imidazo[5,1-d]pyrrolo[1,2-b][1,2,5]benzothiadiazepine 9,9-dioxide benzothiadiazepine tetracyclic ring of pharmaceutical interest. The synthesis of 32 was achieved by a Imidazo[5,1-simple4. Imidazo[5,1- procedured]pyrrolo[1,2-d]pyrrolo[1,2- involving thebb][1,2,5]benzothia-diazepine][1,2,5]benzothiadiazepine anellation of pyrrolo[1,2-b ][1,2,5]benzothiadiazepine9,9-dioxide 9,9-dioxide (32) was synthesized 5,5-dioxide ( as33) a new benzothiadiazepineat theImidazo[5,1- 10,11-azomethine tetracyclicd]pyrrolo[1,2- bond ring byb][1,2,5]benzothia-diazepine cycloaddition of pharmaceutical with tosylmethyl interest. 9,9-dioxide isocyanide The synthesis (32) was (TosMIC) synthesized of 32 inwas theachieved presenceas a new by a simplebenzothiadiazepineof buthyl procedure lithium. involving Alternatively, tetracyclic the anellationring 32 couldof ph armaceuticalbe of prepared pyrrolo[1,2- startinginterest.b][1,2,5]benzothiadiazepine from The synthesisaddition reactionof 32 was of achievednitromethane 5,5-dioxide by a (33) to the azomethine bond of 33 to provide 34 which was reduced to amino 35 with of hydrogen at high at thesimple 10,11-azomethine procedure involving bond bythe cycloaddition anellation of pyrrolo[1,2- with tosylmethylb][1,2,5]benzothiadiazepine isocyanide (TosMIC) 5,5-dioxide in the presence(33) pressure in the presence of nickel/Raney as a catalyst. Treatment of 35 with triethyl orthoformate of buthylat the lithium.10,11-azomethine Alternatively, bond by32 cycloadditioncould be prepared with tosylmethyl starting from isocyanide addition (TosMIC) reaction in the of nitromethanepresence furnishedof buthyl lithium. the dihydro Alternatively, derivative 3236 couldwhich be was prepared oxidized starting to 32 with from manganese addition reaction dioxide of (Scheme nitromethane 4) [38]. to the azomethine bond of 33 to provide 34 which was reduced to amino 35 with of hydrogen at high to the azomethine bond of 33 to provide 34 which was reduced to amino 35 with of hydrogen at high pressure in the presence of nickel/Raney as a catalyst. Treatment of 35 with triethyl orthoformate pressure in the presence of nickel/Raney as a catalyst. Treatment of 35 with triethyl orthoformate furnishedfurnished the dihydrothe dihydro derivative derivative36 36which which waswas oxidized to to 3232 withwith manganese manganese dioxide dioxide (Scheme (Scheme 4) [38].4)[ 38].

Scheme 4. Synthesis of 32.

SchemeScheme 4.4. Synthesis of of 3232. .

Molecules 2017, 22, 434 5 of 18 Molecules 2017, 22, 434 5 of 17

5.5. 5 5HH-pyrrolo[1,2--pyrrolo[1,2-bb][1,2,5]benzothiadiazepin-11(10][1,2,5]benzothiadiazepin-11(10HH)-one)-one 5,5-dioxide 5,5-dioxide 55HH-pyrrolo[1,2--pyrrolo[1,2-bb][1,2,5]benzothiadiazepin-11(10][1,2,5]benzothiadiazepin-11(10HH)-one)-one 5,5-dioxide 5,5-dioxide (PBTD) (PBTD) derivatives, derivatives, analogs analogs of of compoundcompound 1717 describeddescribed in in Scheme Scheme 1,1, were synthesized as a novel class of HIV-1-specific HIV-1-speciﬁc non-nucleoside reversereverse transcriptase transcriptase inhibitors inhibitors (NNRTIs). (NNRTIs). In In general, general, the the newly newly synthesized synthesized compounds compounds were were non non cytotoxiccytotoxic for MT-4MT-4 cellscells at at concentrations concentrations up up to to 300 300µM. μM. Maximum Maximum antiviral antiviral activity activity was was obtained obtained with withcompounds compounds37a– 37ah bearing–h bearing the chlorinethe chlorine atom atom at position at position 7 and 7 and the the alkyl/alkenyl alkyl/alkenyl group group at positionat position 10 10of of the the pyrrolo[1,2- pyrrolo[1,2-b][1,2,5]benzothiadiazepineb][1,2,5]benzothiadiazepine ring ring (Table (Table1). 1). Compounds Compounds37a 37aand and37b 37b(EC (EC5050 = 1.0 1.0 and and 0.50.5 μµM,M, respectively) respectively) showed showed the the highest highest potency potency and and se selectivitylectivity (SI (SI of of >300 >300 and and >600, >600, respectively) respectively) [39]. [39].

TableTable 1. Anti-HIV-1 activity of 7-Cl-PBTDs 37a–h a..

HIV-1 IIIB Compound R HIV-1 IIIB Compound R CC50 b (μM) EC50 c (μM) SI d CC b (µM) EC c (µM) SI d 37a H 50>300 501.0 >300 37a37b HMe >300>300 1.00.5 >600 >300 37b Me >300 0.5 >600 37c Et 283 2.4 118 37c Et 283 2.4 118 37d37d PropylPropyl 126126 14 9 9 37e37e IsopropylIsopropyl >300>300 Nd Nde e - - 37f37f AllylAllyl >300>300 3.7 >81 >81 37g37g CrotylCrotyl >300>300 4.1 >73 >73 37h Dimethylallyl >300 129 >2 37h a Dimethylallyl >300 129 b >2 Data are mean values of two to three independent experiments each one in triplicate. CC50: cytotoxic a b concentration Data are mean (µM) values to induce of two 50% to deaththree ofinde noninfectedpendent experiments cells, as evaluated each with one thein triplicate. MTT method CC in50 MT-4: cytotoxic cells. c concentrationEC50 (HIV-1, III (Bμ):M) effective to induce concentration 50% death (µ M)of no toninfected inhibit by 50%cells, HIV-1 as evaluated (IIIB strain) with induced the MTT cell death,method as evaluatedin MT-4 with the MTT method in MT-4 cells. d SI: selectivity index calculated as CC /EC ratio. e nd, no data. cells. c EC50 (HIV-1, IIIB): effective concentration (μM) to inhibit by 50%50 HIV-150 (IIIB strain) induced cell

death, as evaluated with the MTT method in MT-4 cells. d SI: selectivity index calculated as CC50/EC50 ◦ ratio.Crystal e nd, structure no data. [40] of 37a showed that the aromatic moieties adopted a dihedral angle of 114.4 , a value that was very near to the optimal value of the butterfly-like conformation reported by the Schaefer’sCrystal model structure [41]. [40] of 37a showed that the aromatic moieties adopted a dihedral angle of 114.4°, a value that was very near to the optimal value of the butterfly-like conformation reported by the6. Pyrrolo[1,2- Schaefer’s modelb][1,2,5]benzothiadiazepine [41]. Acetic Acid 5,5,-dioxide The PBTD scaffold has been exploited in several antiviral research programs. A series of 6.pyrrolo[1,2- Pyrrolo[1,2-b][1,2,5]benzothiadiazepineb][1,2,5]benzothiadiazepine acetic Acetic acid Acid derivatives 5,5,-dioxide was synthesized by reaction of 1-(2- aminobenzenesulfonyl)pyrroleThe PBTD scaffold has been with exploited ethyl 3,3-diethoxypropionate in several antiviral research in aqueous programs. acetic acid A toseries furnish of pyrrolo[1,2-ethyl 10,11-dihydro-pyrrolo[1,2-b][1,2,5]benzothiadiazepineb][1,2,5]benzothiadiazepine-11-acetic acetic acid derivatives was synthesized acetate 5,5-dioxide by reaction (38). Esterof 1-(2-38 aminobenzenesulfonyl)pyrrolewas N-acylated in the presence ofwith triisobutylamine ethyl 3,3-dietho toxypropionate afford ethyl 10,11-dihydro-10-(4-methylbenzoyl) in aqueous acetic acid to furnish ethylpyrrolo[1,2- 10,11-dihydro-pyrrolo[1,2-b][1,2,5]benzothiadiazepine-11-acetateb][1,2,5]benzothiadiazepine-11-acetic 5,5-dioxide (39 )acetate which 5,5-dioxide was hydrolyzed (38). Ester into the38 wascorresponding N-acylated in acetic the presence acid 40. Alternatively,of triisobutylamine alkaline to afford hydrolysis ethyl 10,11-dihydro-10-(4-methylbenzoyl) of 38 furnished acid 41 which was pyrrolo[1,2-transformedb][1,2,5]benzothiadiazepine-11-acetate into azetidone 42 by treatment with trifluoroacetic 5,5-dioxide ( anhydride39) which (Schemewas hydrolyzed5). Derivatives into the38 correspondingand 42 showed acetic significant acid 40 inhibition. Alternatively, of HIV-1 alkaline with EC hydrolysis50 = 19.5 and of 38 18 µfurnishedM, respectively) acid 41 [which42]. was transformedReplacement into azetidone of the pyrrole 42 by ring treatment of PBTD with with trifluoroaceti the indole (c43 anhydride) resulted (Scheme in weaker 5). antiretroviral Derivatives 38compounds and 42 showed [39]. On significant the other inhibition hand, the of 5H HIV-1-indolo[3,2- with ECb][1,5]benzothiazepine50 = 19.5 and 18 μM, respectively) isomers (e.g., [42].44), were endowed with anti-HIV-1 activity in the low micromolar range of concentrations [43]. In addition, 1H-pyrrolo[2,3-b][1,5]benzothiazepine (e.g., 45), 1H-pyrrolo[3,2-b][1,5]benzothiazepine (e.g., 46)[44] and 9H-pyrrolo[2,1-b][1,3,6]benzothiadiazocin-10(11H)-one 4,4-dioxide derivatives (47)[45] were

Molecules 2017, 22, 434 6 of 17

Molecules 2017, 22, 434 6 of 18 synthesized as new heterocyclic systems mimicking the structural features of the PBTDs scaffold

(ChartMolecules2). 2017, 22, 434 6 of 17

Scheme 5. Synthesis of 38 and 42.

Replacement of the pyrrole ring of PBTD with the indole (43) resulted in weaker antiretroviral compounds [39]. On the other hand, the 5H-indolo[3,2-b][1,5]benzothiazepine isomers (e.g., 44), were endowed with anti-HIV-1 activity in the low micromolar range of concentrations [43]. In addition, 1H-pyrrolo[2,3-b][1,5]benzothiazepine (e.g., 45), 1H-pyrrolo[3,2-b][1,5]benzothiazepine (e.g., 46) [44] and 9H-pyrrolo[2,1-b][1,3,6]benzothiadiazocin-10(11Scheme 5. SynthesisH)-one 4,4-dioxide of 38 and 42 derivatives. (47) [45] were synthesized Scheme 5. Synthesis of 38 and 42. as new heterocyclic systems mimicking the structural features of the PBTDs scaffold (Chart 2). Replacement of the pyrrole ring of PBTD with the indole (43) resulted in weaker antiretroviral compounds [39]. On the other hand, the 5H-indolo[3,2-b][1,5]benzothiazepine isomers (e.g., 44), were endowed with anti-HIV-1 activity in the low micromolar range of concentrations [43]. In addition, 1H-pyrrolo[2,3-b][1,5]benzothiazepine (e.g., 45), 1H-pyrrolo[3,2-b][1,5]benzothiazepine (e.g., 46) [44] and 9H-pyrrolo[2,1-b][1,3,6]benzothiadiazocin-10(11H)-one 4,4-dioxide derivatives (47) [45] were synthesized as new heterocyclic systems mimicking the structural features of the PBTDs scaffold (Chart 2).

Chart 2. Heterocyclic compounds structurally correlated to PBTD HIV-1 NNRTIs.NNRTIs.

7. PBTDs as Chronic Myelogenous Leukemia (CML) Agents The antitumorantitumor activityactivity ofof pyrrolo[2,1-pyrrolo[2,1-cc][1,4]benzodiazepines][1,4]benzodiazepines (PBDs,(PBDs, e.g.,e.g., 4848)) relatedrelated toto anthramycinanthramycin was extensively studied, as it was documented in Thurston’s review [46]. Given the high structural was extensively studied, as it was documented in Thurston’s review [46]. Given the high structural similarity between between PBTD PBTD and and PBD PBD compounds, compounds, two PBTDs, two PBTDs, 23 and its23 10-(4-methylbenzoyl)and its 10-(4-methylbenzoyl) derivative Chart 2. Heterocyclic compounds structurally correlated to PBTD HIV-1 NNRTIs. derivative49, were selected49, were for screening selected of for pro-apoptotic screening of and pro-apoptotic anti-leukemia and activity anti-leukemia (Chart 3, Tables activity 2 and (Chart 3) [47].3, PBTD 23 was prepared by an improved procedure using dimethoxyacetal of ethyl glyoxylate in Tables7. PBTDs2 and as3 Chronic)[ 47]. PBTDMyelogenous23 was preparedLeukemia by (CML) an improved Agents procedure using dimethoxyacetal of ethylabsolute glyoxylate ethanol in in the absolute presence ethanol of 4-toluenesulfonic in the presence acid of (PTSA). 4-toluenesulfonic Compound acid 23, prepared (PTSA). as Compound described 23in ,Scheme preparedThe antitumor 2, was as described N activity-acylated inof to Schemepyrrolo[2,1- 49 with2, was4-methylbenzoylc][1,4]benzodiazepinesN-acylated toby49 refluxinwith (PBDs, 4-methylbenzoylg in e.g., 1-bromo-3-chloropropane 48) related byto anthramycin refluxing in 1-bromo-3-chloropropanewasthe presence extensively of sodiumstudied, hydrogen as in it the was presence carbonate.documented of sodium PBTDs in Thurston’s hydrogen23 and 49 review carbonate.induced [46]. apoptosis PBTDsGiven the23 inand highK56249 structural cellsinduced and apoptosissimilaritycaused cell between in death K562 PBTD cellsin BCR-ABL-positive andand causedPBD compounds, cell deathleukemia two in BCR-ABL-positive PBTDs,cells obtained 23 and its from 10-(4-methylbenzoyl) leukemia chronic cells myeloid obtained derivativeleukemia from chronic49patients, were myeloidselectedwho were for leukemia at screening onset patientsor of were pro-apoptotic whoIM-resistant. were and at onsetApoptotic anti-leukemia or were mechanism IM-resistant.activity (Chartstudies Apoptotic 3, showed Tables 2 mechanism thatand PBTDs3) [47]. studiesPBTD23 and 23 49 showed wasactivated prepared that the PBTDs caspaseby 23anand improvedactivity49 activated through procedure the two caspase differentusing activitydimethoxyacetal pathways: through bothtwo of compounds ethyl different glyoxylate pathways: activated in bothabsolutecaspase-3; compounds ethanol 23 significantly in activatedthe presence reduced caspase-3; of 4-thetoluenesulfonic procaspase-8;23 significantly inacid contrast (PTSA). reduced 49 Compound evidenced the procaspase-8; a 23 decrease, prepared of in procaspase-9as contrast described49 evidencedinband. Scheme The 2, aapoptosis decreasewas N-acylated was of procaspase-9 observed to 49 with before band.4-methylbenzoyl the The ex apoptosispression by refluxin wasof BCR-ABL observedg in 1-bromo-3-chloropropane protein before theand expression the tyrosine ofin BCR-ABLthephosphorylation. presence protein of sodium PBTDs-mediated and thehydrogen tyrosine carbonate. suppression phosphorylation. PBTDs of K562 23 PBTDs-mediatedand cell 49 proliferation induced apoptosis suppressionwas characterized in K562 ofK562 cells by and cellthe proliferationcausedappearance cell ofdeath was DNAcharacterized in fragmentation BCR-ABL-positive by and the appearancewas leukemia associated ofcells DNAwith obtained the fragmentation poly(ADPribose) from chronic and was polymerasemyeloid associated leukemia (PARP) with thepatientscleavage. poly(ADPribose) who PBTDs were 23 atand polymeraseonset 49 treatment or were (PARP) IM-resistant.resulted cleavage. in caspase-3 Apoptotic PBTDs activa23 mechanismandtion49 throughtreatment studies down-regulation resulted showed inthat caspase-3 ofPBTDs Bcl-2 activation23and and up-regulation 49 throughactivated down-regulation ofthe Bax caspase [48]. activityPBTDs of Bcl-2 throughpossessed and up-regulation two inhibitory different of activitypathways: Bax [48 against]. PBTDsboth compoundsmTOR possessed and inhibitoryactivatedimpeded activitycaspase-3;hyper-phosphorylation against 23 significantly mTOR andof reduced Akt impeded as a the feedback procaspase-8; hyper-phosphorylation of inhibition in contrast of mTOR 49 of evidenced Akt by rapamycin as a feedbacka decrease [49]. of ofThese inhibitionprocaspase-9 findings of mTORband.highlighted The by rapamycin apoptosis PBTDs as [ was49potential]. Theseobserved agents findings before for highlightedthe the treatment expression PBTDs of CML of as BCR-ABL potential[50,51]. agentsprotein for and the treatmentthe tyrosine of CMLphosphorylation. [50,51]. PBTDs-mediated suppression of K562 cell proliferation was characterized by the appearance of DNA fragmentation and was associated with the poly(ADPribose) polymerase (PARP) cleavage. PBTDs 23 and 49 treatment resulted in caspase-3 activation through down-regulation of Bcl-2 and up-regulation of Bax [48]. PBTDs possessed inhibitory activity against mTOR and impeded hyper-phosphorylation of Akt as a feedback of inhibition of mTOR by rapamycin [49]. These findings highlighted PBTDs as potential agents for the treatment of CML [50,51].

Molecules 2017, 22, 434 7 of 18 Molecules 2017, 22, 434 7 of 17

Chart 3. PBTDs as CML agents.

Table 2. Apoptotic activity of 23 and 49 in cells from CML patients at onset at 10 μM [46]. Table 2. Apoptotic activity of 23 and 49 in cells from CML patients at onset at 10 µM[46]. % of Apoptosis Patient Sex Age Source a 23% of Apoptosis 49 Patient Sex Age Source a 24 h23 48 h 24 49 h 48 h 1 M 45 PB a 2464 h 48 h70 24 h77 48 h 85 2 1M M60 45 BM PB ab 6450 7070 7770 85 85 3 2 F M 73 60 BM PB b 50 65 7079 7066 85 82 4 3 M F 83 73 BM PB 6550 7970 6650 82 75 5 4 F M 46 83 PBBM 50 7070 5060 75 80 5 F 46 PB 50 70 60 80 6 6 F F 27 27 PB PB 50 7070 6060 80 80 7 7 F F 45 45 PB PB 60 8080 6464 80 80 8 8 M M 35 35 PB PB 60 8080 6565 85 85 9 9 M M 66 66 PB PB 60 8080 6060 80 80 10 F 38 PB 50 70 70 80 10 11F F38 65 PB PB 5250 7170 5570 78 80 11 12F F65 27 PB PB 52 7371 5555 78 78 12 F a PB: peripheral27 blood cells.PB b BM: bone52 marrow cells.73 55 78 a PB: peripheral blood cells. b BM: bone marrow cells.

Table 3.3. Apoptotic activity of 23 and 49 inin cells cells from from CML CML patients patients in in bl blastast crisis crisis and and Imatinib-resistant Imatinib-resistant at onset at 10 µμM.

PercentPercent Apoptosis Apoptosis Patient Sex AgeAge Source a 23 49 Patient Sex Source 23 49 24 h 48 h 24 h 48 h 24 h 48 h 24 h 48 h 13 M 38 PB a 60 80 40 60 a 1314 MF 3870 PB 5560 78 8050 4070 60 14 F 70 PB 55 78 50 70 a PB: peripheral blood cells. a PB: peripheral blood cells. 8. Pyrryl Aryl Sulfones 8. PyrrylDiarylsulfones Aryl Sulfones emerged as a chemical class of HIV-1 NNRTIs. The presence of the nitro group at position 2 of the phenyl ring and the sulfur bridging atom as sulfur dioxide are fundamental structural Diarylsulfones emerged as a chemical class of HIV-1 NNRTIs. The presence of the nitro group at characteristics for their activity. The antiviral activity of 2-nitrophenyl phenyl sulfone (50, NPPS) [52] position 2 of the phenyl ring and the sulfur bridging atom as sulfur dioxide are fundamental structural prompted the synthesis of a series of 41 pyrryl aryl sulfones (PAS) and some related derivatives [53]. characteristics for their activity. The antiviral activity of 2-nitrophenyl phenyl sulfone (50, NPPS) [52] Pyrryl 2-nitrophenyl sulfone (51) was straightforwardly prepared by nucleophilic substitution reaction prompted the synthesis of a series of 41 pyrryl aryl sulfones (PAS) and some related derivatives [53]. between 2-nitrobenzenesulfonyl chloride and pyrrole in the presence of n-tetrabutylammonium Pyrryl 2-nitrophenyl sulfone (51) was straightforwardly prepared by nucleophilic substitution reaction hydrogen sulfate (TBAS) as a phase transfer catalyst. On the other hand, alkaline hydrolysis of 2- between 2-nitrobenzenesulfonyl chloride and pyrrole in the presence of n-tetrabutylammonium ethoxycarbonylpyrrole (16) [34] afforded the acid 52 which was transformed into 53 by reaction with hydrogen sulfate (TBAS) as a phase transfer catalyst. On the other hand, alkaline hydrolysis of ethyl chloroformate in the presence of 4-methylmorpholine followed by treatment of the intermediate 2-ethoxycarbonylpyrrole (16)[34] afforded the acid 52 which was transformed into 53 by reaction with mixed anhydride with glycine ethyl ester (Scheme 6). ethyl chloroformate in the presence of 4-methylmorpholine followed by treatment of the intermediate Ester 55 was prepared by treating the corresponding acid 54 [54] with oxalyl chloride and then mixed anhydride with glycine ethyl ester (Scheme6). with anhydrous ethanol. Reaction of 1-(2-aminobenzenesulfonyl)pyrrole [35] with methyl malonyl chloride in the presence of triethylamine led to amide 56 which in turn was methylated to 57 or 58 with one or two equivalents of methyl chloride, respectively, in the presence of potassium carbonate

Molecules 2017, 22, 434 8 of 17

(SchemeMolecules 2017 6)., Compound22, 434 16, a 2-nitrophenyl 1-pyrryl sulfone bearing the 2-ethoxycarbonyl function,8 of 18 showed the highest anti HIV-1 activity (Table 4).

Scheme 6. Synthesis of PAS 51–58. Scheme 6. Synthesis of PAS 51–58.

Table 4. Anti-HIV-1 Activity of PASs 16 and 51–58 a. Ester 55 was prepared by treating the corresponding acid 54 [54] with oxalyl chloride and then HIV-1 IIIB with anhydrous ethanol.Compound Reaction of 1-(2-aminobenzenesulfonyl)pyrrole [35] with methyl malonyl chloride in the presence of triethylamineCC50 ledb (μ toM) amide 56 ECwhich50 c (μ inM) turn was SI methylated d to 57 or 58 with one or two equivalents16 of methyl chloride,>308 respectively,15.08 in the presence of>20 potassium carbonate (Scheme6). Compound 5116 , a 2-nitrophenyl36.55 1-pyrryl sulfone>36.55 bearing the 2-ethoxycarbonyl- function, showed the highest anti52 HIV-1 activity (Table>337.54). >337.5 - 53 >262.2 >262.2 - 54 Table 4. Anti-HIV-1>333 Activity of PASs 16>333and 51–58 a. - 55 255 >255 - HIV-1 III Compound56 >370 63 B >5.8 b c d 57 CC>27950 (µM) EC50>279(µM) SI - 5816 >285>308 15.08>285 >20- NPPS51 36.55- >36.551.4 - -

a Data are mean values of52 two to three independent>337.5 experiments >337.5 each one in triplicate; - b CC50: cytotoxic 53 >262.2 >262.2 - concentration (μM) to induce 50% death of non-infected cells, as evaluated with the MTT method in MT-4 54 >333 >333 - cells; c EC50 (HIV-1, IIIB): effective concentration (μM) to inhibit by 50% HIV-1 (IIIB strain) induced cell death, 55 255 >255 - as evaluated with the MTT56 method in MT-4 cells;>370 d SI: selectivity index 63 calculated as >5.8 CC50/EC50 ratio. 57 >279 >279 - The importance of the58 diaryl sulfone moiety>285 for the design >285 of new anti-HIV-1 - agents was further confirmed by the synthesisNPPS of new series of PAS- and indolyl 1.4 aryl sulfones [55,56]. - The amino-PAS a b derivativesData arewere mean synthesized values of two as follows. to three independentAlkylation experimentsof the 2-amino each onegroup intriplicate; was achievedCC50 :by cytotoxic reaction of concentration (µM) to induce 50% death of non-infected cells, as evaluated with the MTT method in MT-4 cells; 59a andc 59b with the appropriate aldehyde in the presence of sodium cyanoborohydride; carboxamides EC50 (HIV-1, IIIB): effective concentration (µM) to inhibit by 50% HIV-1 (IIIB strain) induced cell death, as evaluated d werewith obtained the MTT by method heating in MT-4 with cells; an acylSI: selectivity chloride index in pyridine calculated (Scheme as CC50/EC not50 ratio.shown). It was reported that the 4-chloroaniline moiety or the related 5-chloro-2-pyridylamine represented the key feature of highlyThe potent importance HIV-1 NNRTIs, of the diaryl for sulfoneexample moiety 8-Cl-TIBO for the [57], design 7-Cl-PBTD of new ( anti-HIV-137) [39] (Table agents 1), 3,3-dialkyl- was further 3,4-dihydroquinoxaline-2-(1conﬁrmed by the synthesisH of)thione new series [58], ofoxoquinoline PAS and indolyl [59], aryland sulfonesPETT [60]. [55 ,56In]. the The case amino-PAS of PAS

Molecules 2017, 22, 434 9 of 18 derivatives were synthesized as follows. Alkylation of the 2-amino group was achieved by reaction of 59a and 59b with the appropriate aldehyde in the presence of sodium cyanoborohydride; carboxamides were obtained by heating with an acyl chloride in pyridine (Scheme not shown). It was reported that the 4-chloroaniline moiety or the related 5-chloro-2-pyridylamine represented the key feature of Moleculeshighly potent2017, 22 HIV-1, 434 NNRTIs, for example 8-Cl-TIBO [57], 7-Cl-PBTD (37)[39] (Table1), 3,3-dialkyl-3,4-9 of 17 dihydroquinoxaline-2-(1H)thione [58], oxoquinoline [59], and PETT [60]. In the case of PAS derivatives, derivatives,the 4-chloroaniline the 4-chloroaniline moiety worked moiety as aworked pharmacophore as a pharmacophore only when theonly sulfonyl when the group sulfonyl was neargroup to wasthe aminonear to group. the amino The naturegroup. ofThe the nature pharmacophore of the pharmacophore could not be could modiﬁed not withoutbe modified affecting without the affectinganti-HIV-1 the activity. anti-HIV-1 The activity. highest The anti-HIV-1 highest activityanti-HIV-1 of compounds activity of compounds59a and 59b 59awas and also 59b associated was also associatedwith the presence with the of presence the alkoxycarbonyl of the alkoxycarbonyl group at position group at 2 position of the pyrrole 2 of th ring.e pyrrole Alkylation ring. Alkylation of aniline ofnitrogen aniline completelynitrogen completely abolished abo thelished activity the (dataactivity not (data shown), not shown) whereas, whereas acylation acylation led to weaklyled to weakly active activecompounds compounds (Table (Table5). The 5). ability The ability to inhibit to inhibit the recombinantthe recombinant reverse reverse transcriptase transcriptase (rRT) (rRT) of HIV-1of HIV-1 is isdepicted depicted in in Table Table6. 6. When When tested tested against against the the rRT rRT form form HIV-1 HIV-1 mutants mutants resistantresistant toto nevirapinenevirapine (Y181C) andand TIBO TIBO (L1001I), (L1001I), the compounds showed ac activitytivity at 10-fold higher concentrations.

TableTable 5. Anti-HIV-1 activity of amino-PAS 59a59a––hh againstagainst thethe WTWT strainstrain a..

HIV-1 IIIB 1 2 HIV-1 III Compound 1R 2 R B R R 50 b 50 c d CCb (μM) EC c (μM) SI d CC50 (µM) EC50 (µM) SI 59a 2-NH2-5-Cl 2-COOMe >300 0.18 >2140 59a 2-NH2-5-Cl 2-COOMe >300 0.18 >2140 59b 2-NH2-5-Cl 2-COOEt >300 0.14 >2140 59b 2-NH2-5-Cl 2-COOEt >300 0.14 >2140 59c59c 2-NO2-NO2 2 2-COOEt2-COOEt >300>300 15 >20 >20 59d59d 2-Cl2-Cl 2-COOEt2-COOEt 141141 25 5 5 59e 2-NH2-5-Cl 2-COOCH2CHC=CH2 100 0.40 250 59e 2-NH2-5-Cl 2-COOCH2CHC=CH2 100 0.40 250 59f 2-NHCHO-5-Cl 2-COOEt >300 1.0 >300 59g59f 2-NHCOMe-5-Cl2-NHCHO-5-Cl 2-COOEt2-COOEt ≥300 >300 1.0 >300≥300 59h59g 2-NHCOMe-5-Cl2-NHCOOEt 2-COOEt2-COOEt >300≥300 1.0 ≥300 >300 e NVP59h 2-NHCOOEt 2-COOEt >10000 >300 0.601.0 >300 >167 a b DataNVP are e mean values of two to three independent experiments each >10000 one in triplicate;0.60CC 50: cytotoxic>167 concentration (µM) to induce 50% death of non-infected cells, as evaluated with the MTT method in MT-4 cells; ac b DataEC50 (HIV-1,are mean IIIB values): effective of two concentration to three inde (µM)pendent to inhibit experiments by 50% HIV-1 (IIIeachB strain) one in induced triplicate; cell death, CC50 as: cytotoxic evaluated d e concentrationwith the MTT method (μM) to in MT-4induce cells; 50%SI: death selectivity of non-infected index calculated cells, as as CC evaluated50/EC50 ratio; with NVP:the MTT nevirapine. method in

MT-4 cells; c EC50 (HIV-1, IIIB): effective concentration (μM) to inhibit by 50% HIV-1 (IIIB strain) induced

cell death, as evaluatedTable with the 6. Anti-HIV-1 MTT method activity in MT-4 of cells; PAS 59a d SI:– hselectivityagainst the index rRT. calculated as CC50/EC50 ratio; e NVP: nevirapine. IC ± SD (µM) a Compound 50 Table 6. Anti-HIV-1WT IIIBactivity of PAS Y181C59a–h against the rRT. L100I 59a ± ± ± 0.45 0.09IC50 ± 6.9 SD (2.3μM) a 7.4 1.2 Compound59b 0.40 ± 0.05 7.5 ± 1.4 8.5 ± 1.0 59c 0.40WT± IIIB0.14 5.0 Y181C± 1.5 L100I10 ± 3.1 59d59a 0.270.45± ±0.10 0.09 8.0 6.9± ± 2.02.3 7.4 14 ±± 1.21.2 59e59b 0.900.40± ±0.12 0.05 147.5± ± 2.51.4 8.5 >20± 1.0 59f59c 0.40>20 ± 0.14 5.0 >20 ± 1.5 10 ± >20 3.1 59g >20 >20 >20 59d 0.27 ± 0.10 8.0 ± 2.0 14 ± 1.2 59h >20 >20 >20 NVP59e 0.600.90± ± 0.10.12 14 >20 ± 2.5 3.5 >20± 0.18 a Compound concentration59f required to>20 inhibit the HIV rRT>20 activity by 50%. SD:>20 standard deviation. 59g >20 >20 >20 Compound 59b was59h selected as lead>20 compound for>20 an antiviral project>20 based on molecular modeling studies. UsingNVP the three-dimensional 0.60 ± 0.1 structure >20 of HIV-1 RT 3.5 cocrystallized± 0.18 with α-APA a Compound concentration required to inhibit the HIV rRT activity by 50%. SD: standard deviation.

Compound 59b was selected as lead compound for an antiviral project based on molecular modeling studies. Using the three-dimensional structure of HIV-1 RT cocrystallized with α-APA (alpha-anilinophenyl acetamide) derivative R95845, a model of RT/59b complex was derived using previously developed SARs. The experimentally determined RT bound conformations of α-APA R90385 [61] served as basis to select conformations of 59b for docking studies. By scanning the rotatable bonds of the crystal structure of 59b, a low energy conformation was identified and this compound superimposable on α-APA R95845 about the aromatic rings and the COOEt/COMe and

Molecules 2017, 22, 434 10 of 18

(alpha-anilinophenyl acetamide) derivative R95845, a model of RT/59b complex was derived using previously developed SARs. The experimentally determined RT bound conformations of α-APA R90385 [61] served as basis to select conformations of 59b for docking studies. By scanning the rotatable Moleculesbonds of2017 the, 22 crystal, 434 structure of 59b, a low energy conformation was identiﬁed and this compound10 of 17 superimposable on α-APA R95845 about the aromatic rings and the COOEt/COMe and SO2/CONH2 SOgroups.2/CONH Inspection2 groups. ofInspection the RT/59b of thecomplex RT/59b revealed complex a revealed region of a theregion HIV-1 of the NNBS HIV-1 (non-nucleoside NNBS (non- nucleosidebinding site) binding delimited site) bydelimited Tyr181, Tyr188by Tyr181, and Tyr188 Trp229 and side Trp229 chains, side which chains, could which be ﬁled could by substituents be filed by Molecules 2017, 22, 434 10 of 17 substituentsat position 4 at of position the pyrrole 4 of ring. the pyrrole Among ring. the compounds Among the synthesized, compounds60 synthesized,(EC50 = 42 nM;60 (EC IC50 == 42 50 nM; nM) 50 ICwas = theSO 502 /CONH mostnM) was potent2 groups. the PAS most Inspection derivative potent of PAS the (Table RT/derivative759b). Comparedcomplex (Table revealed with7). Compared 59ba region, it showed of with the HIV-159b three-, it NNBS showed and (non- eight-fold three- andimprovement eight-foldnucleoside inimprovement binding cell-based site) delimited and in cell-based enzyme by Tyr181, assays, and Tyr188enzyme respectively and assays, Trp229 [62 respectively ].side chains, which[62]. could be filed by substituents at position 4 of the pyrrole ring. Among the compounds synthesized, 60 (EC50 = 42 nM; a IC50 = 50 nM) wasTableTable the 7. 7. mostAnti-HIV-1Anti-HIV-1 potent activityPAS activity derivative of of PAS PAS 60 60(Table inin MT-4 MT-4 7). Comparedcells and against with 59b rRT, it.. showed three- and eight-fold improvement in cell-based and enzyme assays, respectively [62].

Table 7. Anti-HIV-1 activity of PAS 60 in MT-4 cells and against rRT a.

HIV-1 IIIB b HIV-1 III e Compound CC50 b(μM) B IC50 (μe M)µ Compound CC50 (µM) 50 c d IC50 ( M) EC c (μM) SI d EC50 (µM) SI 60 240 0.042HIV-1 IIIB 5333 0.05 Compound CC50 b (μM) IC50 e (μM) 60 f 240EC 0.04250 c (μM) SI 5333d 0.05 NVP f >200 0.35 >571 0.64 NVP 60 >200240 0.042 0.35 5333 >571 0.05 0.64 a Data are mean values of two to three independent experiments each one in triplicate; b CC50: cytotoxic a Data are mean valuesf of two to three independent experiments each one in triplicate; b CC : cytotoxic concentration (μM)NVP to induce 50% >200death of non-infected 0.35 cells, as >571evaluated with0.64 the MTT50 method in concentrationa (µM) to induce 50% death of non-infected cells, as evaluated with the MTTb method in MT-4 cells; c Data care mean values of two to three independent experiments each one in triplicate; CC50: cytotoxic MT-4EC50 cells;(HIV-1, EC III50B): (HIV-1, effective III concentrationB): effective (concentrationµM) to inhibit by (μ 50%M) to HIV-1 inhibit (IIIB bystrain) 50% induced HIV-1 cell(IIIB death, strain) as induced evaluated concentration (μM) to induce d50% death of non-infected cells, as evaluated withe the MTT method in cellwith death, the MTT as evaluated method in MT-4with cells;the MTTSI: selectivitymethod in index MT-4 calculated cells; d SI: as selectivity CC50/EC50 indexratio; calculatedCompound as concentration CC50/EC50 MT-4 cells; c EC50 (HIV-1, IIIB): effective concentrationf (μM) to inhibit by 50% HIV-1 (IIIB strain) induced ratio;required e Compound to inhibit the concentration HIV rRT activity required by 50%; toNVP: inhibit nevirapine. the HIV rRT activity by 50%; f NVP: nevirapine. cell death, as evaluated with the MTT method in MT-4 cells; d SI: selectivity index calculated as CC50/EC50 ratio; e Compound concentration required to inhibit the HIV rRT activity by 50%; f NVP: nevirapine. FurtherFurther studies studies were were conducted conducted to to improve improve the the activity activity of of PAS PAS 59b59b [63].[63]. New New PAS PAS derivatives derivatives werewere synthesized synthesizedFurther studies by by introduction introduction were conducted of of different different to improve alkyl, alkyl, the alkenyl alkenylactivity ofor or PAScycloalkyl cycloalkyl 59b [63]. substituents substituents New PAS derivatives at at the the 2-ester 2-ester function,function,were along alongsynthesized with with aby a small smallintroduction series series ofof different2-carboxamid 2-carboxamide alkyl, ealkenyl derivatives, derivatives, or cycloalkyl in in order order substituents to to explore explore at the the the 2-ester effects effects of of substituentssubstituentsfunction, aa alongposition position with of of athe thesmall pyrrole pyrrole series ring. ring.of 2-carboxamid The The new new derivatives derivativese derivatives, were were in orderless less potent potentto explore and and thesometimes sometimes effects of more more toxictoxic thansubstituents than the the previously previously a position reported reported of the pyrrole 59a59a andand ring. 59b59b The. .This Thisnew study derivatives study confirmed conﬁrmed were less the the potentkey key role role and of of sometimes the the 4-chloroanilino 4-chloroanilino more toxic than the previously reported 59a and 59b. This study confirmed the key role of the 4-chloroanilino moietymoiety and and the the substituent substituent at at the the ester ester function. function. moiety and the substituent at the ester function. CompoundCompound 6060 waswas synthesized synthesized as depicted as depicted in Scheme in Scheme 7. 5-Chloro-2-nitrobenz7. 5-Chloro-2-nitrobenzenesulfonylenesulfonyl chloride chloride wasCompound reacted 60 with was 2-ethoxycarbonyl-1 synthesized as depictedH-pyrrole-4-carboxaldehyde in Scheme 7. 5-Chloro-2-nitrobenz in theenesulfonyl presence ofchloride potassium was reactedwas reacted with with 2-ethoxycarbonyl-1 2-ethoxycarbonyl-1HH-pyrrole-4-carboxaldehyde-pyrrole-4-carboxaldehyde in in the the presence presence of potassiumof potassium tert- tert- tert-butoxide and 18-crown-6 to give 61. Sodium borohydride reduction of aldehyde 61 afforded alcohol butoxidebutoxide and 18-crown-6and 18-crown-6 to giveto give 61 61. Sodium. Sodium borohydride borohydride reductionreduction of of aldehyde aldehyde 61 afforded61 afforded alcohol alcohol 6262,, and and62 ,the theand nitro nitrothe nitro group group group reduction reduction reduction with with with iron iron iron in inin glacial glacialglacial acetic acetic acidacid acid to to to provide provide provide the the the amino amino amino derivative derivative derivative 60 6060 (Scheme(Scheme(Scheme 77).). 7).

Scheme 7. Synthesis of PAS 60. Scheme 7. Synthesis of PAS 60. Scheme 7. Synthesis of PAS 60. Three pyrryl heteroaryl sulfones, ethyl 1-[(6-amino-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-5- yl)sulfonyl]-1H-pyrrole-2-carboxylate (63), ethyl 1-[(5-amino-1H-benzo[d]imidazol-6-yl)sulfonyl]-1H- Threepyrrole-2-carboxylate pyrryl heteroaryl (64), andsulfones, ethyl 1-[(6-amino-2 ethyl 1-[(6-amino-2-oxo-2,3-dihydro-1H-benzo[d][1,2,3]triazol-5-yl)sulfonyl]-1H-benzo[H-pyrrole-2-d]imidazol-5- yl)sulfonyl]-1carboxylateH-pyrrole-2-carboxylate (65), were designed as ( 63novel), ethyl HIV-1 1-[(5-amino-1 NNRTIs usingH-benzo[ structured]imidazol-6-yl)sulfonyl]-1 based computational H- pyrrole-2-carboxylate (64), and ethyl 1-[(6-amino-2H-benzo[d][1,2,3]triazol-5-yl)sulfonyl]-1H-pyrrole-2- carboxylate (65), were designed as novel HIV-1 NNRTIs using structure based computational

Molecules 2017, 22, 434 11 of 18

Three pyrryl heteroaryl sulfones, ethyl 1-[(6-amino-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-5-yl) sulfonyl]-1H-pyrrole-2-carboxylate (63), ethyl 1-[(5-amino-1H-benzo[d]imidazol-6-yl)sulfonyl]-1H- pyrrole-2-carboxylate (64), and ethyl 1-[(6-amino-2H-benzo[d][1,2,3]triazol-5-yl)sulfonyl]-1H-pyrrole- Molecules 2017, 22, 434 11 of 17 2-carboxylateMolecules 2017 (,65 22),, 434 were designed as novel HIV-1 NNRTIs using structure based computational11 of 17 methods (Chart4)[ 64]. These compounds inhibited the HIV-1 RT at micromolar concentrations, but methodsmethods (Chart (Chart 4) [64]. 4) [64]. These These co compoundsmpounds inhibited inhibited the HIV-1HIV-1 RT RT at at micromolar micromolar concentrations, concentrations, but but were found inactive in the MT-4 cells assay. were werefound found inactive inactive in thein the MT-4 MT-4 cells cells assay. assay.

Chart 4. Structure of pyrryl heteroaryl sulfones 63–65. Chart 4. StructureStructure of pyrryl heteroaryl sulfones 63–65. 9. Acylamino Pyrryl Aryl Sulfones 9. Acylamino Acylamino Pyrryl Aryl Sulfones A series of PAS related compounds bearing acylamino moieties at position 2 of the benzene ring Awere series synthesized of PAS related as truncated compounds analogs bearingof PBTDs acylaminoacylamin [39]. Furthermore,o moieties potent at position HIV-1 2NNRTIs, of the benzene such as ring were PETT synthesized (67) [65] asand truncated truncated-TIBO analogs (68 of ) [66]PBTDs compounds, [3 [399].]. Furthermore, were designed potent potent and synthesizedHIV-1 HIV-1 NNRTIs, based such on as PETTthe ( 67 structure))[ [65]65] and of truncated-TIBO8-Cl-TIBO (66) [67,68] ( 68))[ using[66]66] compounds, a ring-opening were strategy. designed Based and on these synthesized findings, based the on the structure same strategy of 8-Cl-TIBO was applied ( 66 to))[ 7-Cl-PBTD[67,68]67,68] using (37a ) a by ring-openingring-opening breaking the 11,11b strategy. bond. Based The drug on these design findings, ﬁndings, strategy the conceived a series of acylamino-PAS (APAS) derivatives, which were synthetized and characterized same strategy was applied to 7-Cl-PBTD ( 37a) by breaking breaking the 11,11b bond. The The drug drug design design strategy strategy for their antiviral properties [69] (Chart 5). conceived a series of acylamino-PAS (APAS) derivatives, which were synthetized and characterized for their antiviral properties [[69]69] (Chart5 5).).

Chart 5. Design of APAS derivatives.

Several APAS derivatives inhibited the HIV-1 replication in MT-4 cells in the 1–2 μM range. Two compounds, 69 and 70, showed activity at submicromolar concentrations with EC50 of 0.4 and 0.5 μM, Chart 5. DesignDesign of of APAS APAS derivatives. respectively. Both compounds failed to inhibit the HIV-1 K103N and Y181C mutant strains, similar to Severalthat observed APAS for derivatives structurally inhibited correlated the 2-amino-6-[(3,5-dimethyl)sulf HIV-1 replication in MT-4onylbenzonitrile cells in the 1–2 [70]. μ MAlthough range. Two Severalstructurally APAS related derivatives to the previously inhibited reported the HIV-1 PAS replication family, the inAPAS MT-4 derivatives cells in the were 1–2 investigatedµM range. Two compounds, 69 and 70, showed activity at submicromolar concentrations with EC50 of 0.4 and 0.5 μM, compounds,for binding69 andmode70 in, showed the non-nucleoside activity at submicromolarbinding site of the concentrations HIV-1 RT [71]. with Derivative EC of 69 0.4, the and most 0.5 µM, respectively. Both compounds failed to inhibit the HIV-1 K103N and Y181C mutant50 strains, similar to respectively.active among Both the compounds test APASs, failed was tomo inhibitdeled from the HIV-1the X-ray K103N coordinates and Y181C of 59b mutant and docked strains, into similar the to that observed for structurally correlated 2-amino-6-[(3,5-dimethyl)sulfonylbenzonitrile [70]. Although that observedHIV-1 NNBS for of structurally the RT using correlated the 2-amino-6-[(3,5- 2-amino-6-[(3,5-dimethyl)sulfonylbenzonitriledimethyl)sulfonylbenzonitrile/RT complex [70 [70].]. Although The structurally related to the previously reported PAS family, the APAS derivatives were investigated structurallybinding relatedmode of to 69 the shared previously similarities reported with previously PAS family, reported the APAS PASs derivatives[62,64]: the ethoxycarbonyl were investigated for bindingfilled the mode highly in hydrophobic the non-nucleoside region of NNBS,binding and site the of 4-chloro-2-methoxycarbonyl the HIV-1 RT [71]. Derivative moiety 69took, the up most for binding mode in the non-nucleoside binding site of the HIV-1 RT [71]. Derivative 69, the most activethe among H-bond the region. test APASs, was modeled from the X-ray coordinates of 59b and docked into the active among the test APASs, was modeled from the X-ray coordinates of 59b and docked into the HIV-1 NNBSAPAS of derivatives the RT using 69 and the 70 2-amino-6-[(3,5- were prepared bydimethyl)sulfonylbenzonitrile/RT reacting compound 59b with bromoacetyl complex bromide [70]. The HIV-1 NNBS of the RT using the 2-amino-6-[(3,5-dimethyl)sulfonylbenzonitrile/RT complex [70]. binding1-bromo-3-chloropropane mode of 69 shared insimilarities the presence with sodium previously hydrogen reported carbonate PASs to give[62,64]: 2-bromoacetylamino the ethoxycarbonyl The binding mode of 69 shared similarities with previously reported PASs [62,64]: the ethoxycarbonyl filledderivative the highly 71 hydrophobic. Treatment of regi71 withon of sodium NNBS, methoxide and the 4-chloro-2-methoxycarbonylor thiomethoxide afforded APASs moiety 69 or took70, up ﬁlled the highly hydrophobic region of NNBS, and the 4-chloro-2-methoxycarbonyl moiety took up the H-bondrespectively region. (Scheme 8). the H-bond region. APAS derivatives 69 and 70 were prepared by reacting compound 59b with bromoacetyl bromide APAS derivatives 69 and 70 were prepared by reacting compound 59b with bromoacetyl bromide 1-bromo-3-chloropropane in the presence sodium hydrogen carbonate to give 2-bromoacetylamino 1-bromo-3-chloropropane in the presence sodium hydrogen carbonate to give 2-bromoacetylamino derivative 71. Treatment of 71 with sodium methoxide or thiomethoxide afforded APASs 69 or 70, derivative 71. Treatment of 71 with sodium methoxide or thiomethoxide afforded APASs 69 or 70, respectively (Scheme 8). respectively (Scheme8).

Molecules 2017, 22, 434 12 of 18 Molecules 2017, 22, 434 12 of 17

Molecules 2017, 22, 434 12 of 17

Scheme 8. Synthesis of APASs 69 and 70. Scheme 8. Synthesis of APASs 69 and 70.

10. Smiles Rearrangement Scheme 8. Synthesis of APASs 69 and 70. 10. Smiles Rearrangement In the search for novel tetracyclic ring systems containing the benzothiadiazepine ring, a multistep10.In Smiles the search synthesis Rearrangement for novel was tetracyclicpla nned starting ring systems from 1-[(5-chl containingoro-2-nitrophenyl)sulfonyl]-1 the benzothiadiazepine ring,H-pyrrole-2- a multistep synthesiscarbohydrazideIn was the plannedsearch (72) for[72]. starting novel Reduction from tetracyclic 1-[(5-chloro-2-nitrophenyl)sulfonyl]-1 of 72 ringwith systironems powder containing in glacial the aceticbenzothiadiazepineH-pyrrole-2-carbohydrazide acid did not afford ring, thea (72expected)[multistep72]. Reduction 7-chloro-11-hydrazinopyrrolo[1,2- synthesis of was72 plawithnned iron starting powderb][1,2,5]benzothiadiazepine from in 1-[(5-chl glacialoro-2-nitrophenyl)sulfonyl]-1 acetic acid (73), did but only not a afford bicyclicH-pyrrole-2- the derivative expected 7-chloro-11-hydrazinopyrrolo[1,2-thatcarbohydrazide was identified ( 72as) 1-amino-6-chloro-(1 [72]. Reductionb][1,2,5]benzothiadiazepine of 72H-pyrrol-yl)benzimidazole with iron powder in (glacial73 ),(74 but). acetic Structure only acid a bicyclic of did 74 notwas derivative afford established the that wasbyexpected identified NMR spectroscopy 7-chloro-11-hydrazinopyrrolo[1,2- as 1-amino-6-chloro-(1 and elemental Hanalysis,-pyrrol-yl)benzimidazoleb][1,2,5]benzothiadiazepine and was confirmed by (74 (crystallographic73).), Structure but only a of bicyclic74 data.was derivative Formation established byof NMRthat 74 was spectroscopy identifiedhypothesized as and1-amino-6-chloro-(1 by elemental extrusion analysis, of Hthe-pyrrol-yl)benzimidazole sulfur and wasdioxide confirmed followed ( by74 by). crystallographic Structure Smiles rearrangement of 74 was data. established Formation [73] of of 7574by towas NMR 76. hypothesizedReduction spectroscopy of nitro byand extrusion group elemental to amino of analysis, the underwent sulfur and dioxidewas with confirmed followed concomitant by bycrystallographic Smilescyclization rearrangement of data. the intermediate Formation [73] of 75 to amino76of. Reduction74 wasderivative hypothesized of 77 nitro to form group by 74extrusion to(Scheme amino of 9). the underwent The sulfur structure dioxide with of concomitant followed74 was confirmed by Smiles cyclization by rearrangement direct of synthesis the intermediate [73] of of 75 75 to 76. Reduction of nitro group to amino underwent with concomitant cyclization of the intermediate aminoand subsequent derivative 77treatmentto form with74 (Scheme iron in 9acetic). The acid structure to provide of 7474.was It isconfirmed interesting byto directnote that synthesis any amino derivative 77 to form 74 (Scheme 9). The structure of 74 was confirmed by direct synthesis of 75 of attempt75 and subsequentto obtain 73 treatmentfrom 1-[(5-chloro-2-aminophenyl)sulfonyl]-1 with iron in acetic acid to provideH-pyrrole-2-carbohydrazide74. It is interesting to note (the that and subsequent treatment with iron in acetic acid to provide 74. It is interesting to note that any anycorresponding attempt to obtain amino 73derivativefrom 1-[(5-chloro-2-aminophenyl)sulfonyl]-1 of 72), by heating in the presence of 2-hydroxypyridine,H-pyrrole-2-carbohydrazide failed, 37a beingattempt the onlyto obtain product 73 from of reaction. 1-[(5-chloro-2-aminophenyl)sulfonyl]-1 H-pyrrole-2-carbohydrazide (the (thecorresponding corresponding amino amino derivative derivative of 72 of), 72by), heating by heating in the in presence the presence of 2-hydroxypyridine, of 2-hydroxypyridine, failed, 37a failed, 37a beingbeing the the only only product product of ofreaction. reaction.

Scheme 9. Smile rearrangement of 72 to 74. Scheme 9. Smile rearrangement of 72 to 74. 11. Structurally Related CompoundsScheme 9. Smile rearrangement of 72 to 74. 11. Structurally Related Compounds 11. StructurallyThe highly Related potent Compoundsanti-HIV-1 activity displayed by Merck carboxamide L-737,126 (78) [74–76] (HIV-1The WT highlyIIIB EC 50potent = 1 nM; anti-HIV-1 HIV-1 RT activity IC50 = displayed25 nM) prompted by Merck the carboxamide design of newL-737,126 indolylarylsulfone (78) [74–76] (IAS)(HIV-1The analogs. highly WTIIIB Due potentEC50 to= 1the anti-HIV-1 nM; lack HIV-1 of SAR activityRT ICinformation,50 = displayed 25 nM) theprompted by design Merck the of carboxamidefirstdesign IAS of derivatives new L-737,126indolylarylsulfone was (based78)[74 on –76 ] (HIV-1PASs’(IAS) WT structuralanalogs.IIIB EC Due50 features.= 1tonM; the In lack HIV-1 general, of SAR RT 2-ethoxycarbonyl-1-benzenesulfonyl-1 IC information,50 = 25 nM) the prompted design of the first design IAS derivatives ofH-indoles new indolylarylsulfone was showed based weak on (IAS)antiretroviralPASs’ analogs. structural Dueactivity, features. to the with lack In the general, of exception SAR 2-ethoxycarbonyl-1-benzenesulfonyl-1 information, of derivative the 79 design (HIV-1 of WT ﬁrstIIIB IAS ECH derivatives50-indoles = 8.3 μ showedM) wasbearing weak based the on PASs’4-chloroanilineantiretroviral structural activity, features.moiety with[77]. In general, theIndoles exception 2-ethoxycarbonyl-1-benzenesulfonyl-1bearing of derivativethe carbethoxy 79 (HIV-1 group WT atIIIB position EC50 =H 8.3-indoles3 of μ M)the bearingindole showed werethe weak 4-chloroaniline moiety [77]. Indoles bearing the carbethoxy group at position 3 of the indole were antiretroviralinactive. Moving activity, the with1-benzenesulfonyl the exception group of derivative of 79 to 79position(HIV-1 3 of WT theIIIB indoleEC50 =gave 8.3 µIASM) 80 bearing (HIV-1 the 4-chloroanilineWTinactive.IIIB EC50 Moving = 1.9 moiety μM) the that 1-benzenesulfonyl [77 showed]. Indoles 4.3-fold bearing group improvement the of carbethoxy79 to position of activity. group 3 of Replacement the at positionindole gave of 3 the of IAS the2-ester 80 indole (HIV-1 group were WTIIIB EC50 = 1.9 μM) that showed 4.3-fold improvement of activity. Replacement of the 2-ester group inactive.with a carboxyamide Moving the 1-benzenesulfonyl function, 81 (HIV-1 group WTIIIB of EC7950 to= 0.04 position μM) 3led of to the a indolenotably gave increase IAS of80 both(HIV-1 potencywith a andcarboxyamide selectivity. function, SAR studies 81 (HIV-1 led to partitionWTIIIB EC the50 = IAS0.04 scaffold μM) led in to three a notably regions: increase (A) the of activity both WTIIIB EC50 = 1.9 µM) that showed 4.3-fold improvement of activity. Replacement of the 2-ester group potency and selectivity. SAR studies led to partition the IAS scaffold in three regions: (A) the activity

Molecules 2017, 22, 434 13 of 18

with a carboxyamide function, 81 (HIV-1 WTIIIB EC50 = 0.04 µM) led to a notably increase of both Molecules 2017, 22, 434 13 of 17 potency and selectivity. SAR studies led to partition the IAS scaffold in three regions: (A) the activity 78 ofof 78against againstHIV-1 HIV-1mutant mutant strainsstrains significantlysignificantly improvedimproved by the presence presence of of two two methyl methyl groups groups at at positionspositions 3 3 and and 5 5 ofof thethe 3-phenylsulfonyl3-phenylsulfonyl moiety ( 82))[ [78];78]; (B) (B) coupling coupling the the indole-2-carboxamide indole-2-carboxamide with with eithereither natural natural oror unnaturalunnatural aminoamino acidsacids providedprovided potent HIV-1 i inhibitors,nhibitors, for for example example 8383––8585, ,against against thethe HIV-1 HIV-1 L100I, L100I, K103N,K103N, andand Y181CY181C strainsstrains inin CEMCEM cells, with potency potency comparable comparable to to the the fist fist line line HIV-1HIV-1 NNRTI NNRTI efavirenz efavirenz [[79,80];79,80]; andand (C)(C) thethe 5-chloro-4-fluoro5-chloro-4-fluoro substitution substitution patte patternrn at at the the indole indole ring, ring, compoundcompound86 86,, affordedafforded potentpotent inhibitorsinhibitors of HIV-1 RT WT and and RTs RTs carrying the the K103N, K103N, Y181I, Y181I, and and L100IL100I mutations mutations [ 81[81]] (Chart(Chart6 ).6).

Chart 6. Structure of indolylsulfones 78–86. Chart 6. Structure of indolylsulfones 78–86. 12. Conclusions 12. Conclusions N-pyrrylarylsulfones display a variety of biological activities. This review illustrates the various studiesN-pyrrylarylsulfones made to investigate display the N a variety-pyrrylarylsulfone of biological scaffold activities. as Thisprivileged review structure illustrates to the discover various studiesputative made antiviral, to investigate anticancer theand NSNC-pyrrylarylsulfone drugs. A number scaffold of synthetic as privileged approaches structure to obtain totetracyclic discover putativepyrrolo[1,2- antiviral,b]-s-triazolo[3,4- anticancerd and][1,2,5]benzothiadiazepine SNC drugs. A number of5,5-dioxide, synthetic approaches2-methyl-1,3,4,14b-tetrahydro- to obtain tetracyclic pyrrolo[1,2-2H-pyrazino[2,1-b]-s-triazolo[3,4-d]pyrrolo[1,2-d][1,2,5]benzothiadiazepineb][1,2,5]-benzothiadiazepine 5,5-dioxide, 10,10-dioxide, 2-methyl-1,3,4,14b-tetrahydro-2 imidazo[5,1-d]pyrrolo[1,2-bH] - pyrazino[2,1-[1,2,5]benzothia-diazepined]pyrrolo[1,2- b9,9-dioxide,][1,2,5]-benzothiadiazepine tricyclic 5H-pyrrolo[1,2- 10,10-dioxide,b][1,2,5]benzothiadiazepin-11(10 imidazo[5,1-d]pyrrolo[1,2-H)-b] [1,2,5]benzothia-diazepineone 5,5-dioxide (PBTD), and 9,9-dioxide, non-cyclic tricyclicpyrryl aryl 5H sulfone-pyrrolo[1,2- and acylamino-PASb][1,2,5]benzothiadiazepin-11(10 (APAS) compoundsH )-oneand 5,5-dioxidetheir biological (PBTD), activity and with non-cyclic regard to pyrryl structure–activity aryl sulfone relationships and acylamino-PAS (SARs) have (APAS) been compounds reviewed. The and theirliterature biological reviewed activity here with may regard provide to structure–activityuseful information relationships on the potential (SARs) of N have-pyrrylarylsulfone been reviewed. Thepharmacophore literature reviewed as well hereas suggest may provide concepts useful for the information design and on synthesis the potential of new of NN-pyrrylarylsulfone-pyrrylarylsulfone pharmacophorebased agents. as well as suggest concepts for the design and synthesis of new N-pyrrylarylsulfone based agents. Acknowledgments: This work was supported by Institute Pasteur Italy—Fondazione Cenci Bolognetti. Acknowledgments: This work was supported by Institute Pasteur Italy—Fondazione Cenci Bolognetti. Dedication: Dedicated with respect and gratitude to Giorgio Stefancich, medicinal chemistry teacher. Dedication: Dedicated with respect and gratitude to Giorgio Stefancich, medicinal chemistry teacher. Conflicts of Interest: The authors declare no conflict of interest. Conﬂicts of Interest: The authors declare no conﬂict of interest. References References 1. Gerald, M.C. The Drug Book; Sterling Education: New York, NY, USA, 2013. 1. Gerald, M.C. The Drug Book; Sterling Education: New York, NY, USA, 2013. 2. Dogmagk, G. Ein Beitrag zur Chemotherapie der bakteriellen Infektionen. Deutsch. Med. Wochenschr. 1935, 2. Dogmagk, G. Ein Beitrag zur Chemotherapie der bakteriellen Infektionen. Deutsch. Med. Wochenschr. 1935, 61, 250–253. 61, 250–253. [CrossRef] 3. Dogmagk, G. Eine neue Klasse von Desinfectionsmitteln. Deutsch. Med. Wochenschr. 1935, 61, 829–832. 3. Dogmagk, G. Eine neue Klasse von Desinfectionsmitteln. Deutsch. Med. Wochenschr. 1935, 61, 829–832. 4. Henry, R.J. The mode of action of sulfonamides. Bacteriol. Rev. 1943, 7, 175–262. [CrossRef] 5. Sulfamethoxazole. DrugBank. Available online: http://www.drugbank.ca (accessed on 17 August 2016). 6. Fromm, E.; Wittmann, J. Derivate des p-nitrophenols. Ber. Deutsch. Chem. Ges. 1908, 41, 2264–2273.

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