Alirio Palma

Inhibitors of the fungal cell wall. Synthesis of 4-aryl-4-N-arylamine-1-butenes and related compounds with inhibitory activities on β(1-3) glucan and chitin synthases

As part of our project devoted to the search for antifungal agents, which act via a selective mode of action, we synthesized a series of new 4-aryl- or 4-alkyl-N-arylamine-1-butenes and transformed some of them into 2-substituted 4-methyl-tetrahydroquinolines and quinolines by using a novel three-step synthesis. Results obtained in agar dilution assays have shown that 4-aryl homoallylamines not possessing halogen in their structures, tetrahydroquinolines and quinolines, display a range of antifungal properties in particular against Epidermophyton floccosum and Microsporum canis. Regarding the mode of action, all active compounds showed in vitro inhibitory activities against beta(1-3) glucan-synthase and mainly against chitin-synthase. These enzymes catalyze the synthesis of beta(1-3) glucan and chitin, respectively, major polymers of the fungal cell wall. Since fungal but not mammalian cells are encased in a cell wall, its inhibition may represent a useful mode of action for these antifungal compounds.

Synthesis and in vitro activity of new tetrahydronaphtho[1,2-b]azepine derivatives against Trypanosoma cruzi and Leishmania chagasi parasites

Series of 2-exo-aryl-1,4-epoxy-2,3,4,5-tetrahydronaphtho[1,2-b]azepines 3a-k and cis-2-aryl-4-hydroxy-2,3,4,5-tetrahydronaphtho[1,2-b]azepines 4a-j were synthesized and evaluated against free and intracellular live forms of Trypanosoma cruzi and Leishmania chagasi parasites using in vitro assays. Cell toxicity was also analyzed on Vero and THP-1 mammalian cell lines. The compounds 3c, 3f, and 4d were the most active against both live forms of T. cruzi parasites with low mammalian cell toxicity. Some compounds were active on free live forms of L. chagasi parasites but none was active on intracellular amastigotes of L. chagasi infecting THP-1 macrophages.

A simple synthesis of spiro-C6-annulated hydrocyclopenta[g]indole derivatives

Abstract A series of new spiro-C 6 -annulated hydrogenated cyclopenta[ g ]indoles ( 5 ) was prepared by applying Madelung method to the appropriate 4-( N -acetylamino)-1-spiroindanes ( 9 ), synthesised via acid-catalysed intramolecular rearrangement of 1-acetyl-3,4-dihydrospiro[quinoline-2,1′-cycloalkanes] ( 8 ).

Studies directed to the synthesis of new C-5 spiroannulated julolidines

Abstract Two series of new 7,9-disubstituted spirojulolidines 8a – d and 10a – e were synthesized by acid catalyzed intramolecular cyclization of N -(3-chloropropanoyl) spirodihydroquinolines 5a – d and N -carbethoxymethyl spirodihydroquinolines 7a – e using AlCl 3 and PPA, respectively. The spectroscopic analyses of intermediate compounds and the final spirojulolidines were discussed.

Three aryl-substituted tetrahydro-1,4-epoxy-1-benzazepines: hydrogen-bonded structures in two or three dimensions.

In (2SR,4RS)-7-chloro-2-exo-(4-chlorophenyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(16)H(13)Cl(2)NO, (I), the molecules are linked by a combination of C-H...O and C-H...N hydrogen bonds into a chain of edge-fused R(3)(3)(12) rings. The isomeric compound (2S,4R)-7-chloro-2-exo-(2-chlorophenyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, (II), crystallizes as a single 2S,4R enantiomer and the molecules are linked into a three-dimensional framework structure by two C-H...O hydrogen bonds and one C-H...pi(arene) hydrogen bond. The molecules of (2S,4R)-7-chloro-2-exo-(1-naphthyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(20)H(16)ClNO, (III), are also linked into a three-dimensional framework structure, here by one C-H...O hydrogen bond and two C-H...pi(arene) hydrogen bonds. The significance of this study lies in its observation of the variations in molecular configuration and conformation, and in the variation in the patterns of supramolecular aggregation, consequent upon modest changes in the peripheral substituents.

Four differently substituted 2-aryl-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepines: hydrogen-bonded structures in one, two and three dimensions.

In (2RS,4SR)-7-chloro-2-exo-(2-chloro-6-fluorophenyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(16)H(12)Cl(2)FNO, (I), molecules are linked into chains by a single C-H...pi(arene) hydrogen bond. (2RS,4SR)-2-exo-(2-Chloro-6-fluorophenyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(16)H(13)ClFNO, (II), is isomorphous with compound (I) but not strictly isostructural with it, as the hydrogen-bonded chains in (II) are linked into sheets by an aromatic pi-pi stacking interaction. The molecules of (2RS,4SR)-7-methyl-2-exo-(4-methylphenyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(18)H(19)NO, (III), are linked into sheets by a combination of C-H...N and C-H...pi(arene) hydrogen bonds. (2S,4R)-2-exo-(2-Chlorophenyl)-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(16)H(14)ClNO, (IV), crystallizes as a single enantiomer and the molecules are linked into a three-dimensional framework structure by a combination of one C-H...O hydrogen bond and three C-H...pi(arene) hydrogen bonds.

Three styryl-substituted tetrahydro-1,4-epoxy-1-benzazepines: configurations, conformations and hydrogen-bonded chains

(2SR,4RS)-7-Chloro-2-exo-[(E)-styryl]-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(18)H(16)ClNO, (I), crystallizes as a racemic twin in the space group P2(1) and the molecules are linked into a chain of edge-fused R(3)(3)(9) rings by a combination of C-H...O and C-H...N hydrogen bonds. The diastereoisomer (2RS,4RS)-7-chloro-2-endo-[(E)-styryl]-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, (II), also crystallizes as a racemic twin, but in the space group P2(1)2(1)2(1), and a two-centre C-H...N hydrogen bond and a three-centre C-H...(O,N) hydrogen bond combine to link the molecules into a complex chain of rings. In (2R,4R)-7-fluoro-2-endo-[(E)-styryl]-2,3,4,5-tetrahydro-1H-1,4-epoxy-1-benzazepine, C(18)H(16)FNO, (III), which is not isomorphous with (II), the molecules are linked by a single C-H...O hydrogen bond into simple chains, but the molecular arrangements in (II) and (III) are nonetheless very similar. The significance of this study lies in its observation of the variations in molecular configuration and conformation, and in the variation in the supramolecular aggregation, consequent upon modest changes in the peripheral substituents.

Unexpected and novel synthesis of spirojulolidines via intramolecular cyclization of N-carbethoxymethyl spirotetrahydroquinolines catalyzed by PPA

Abstract A series of N-carbethoxymethyl spirotetrahydroquinolines ( 6 ) were prepared and subjected to cyclization. We show that cyclization of ( 6 ) in the presence of excess PPA results in a 50–62% yield of unexpected spirojulolidines ( 7 ).

4-Hydroxy-2-vinyl-2,3,4,5-tetrahydro-1-benzazepine and its 7-fluoro and 7-chloro analogues are isomorphous but not strictly isostructural

4-Hydroxy-2-vinyl-2,3,4,5-tetrahydro-1-benzazepine, C(12)H(15)NO, (I), and its 7-fluoro and 7-chloro analogues, namely 7-fluoro-4-hydroxy-2-vinyl-2,3,4,5-tetrahydro-1-benzazepine, C(12)H(14)FNO, (II), and 7-chloro-4-hydroxy-2-vinyl-2,3,4,5-tetrahydro-1-benzazepine, C(12)H(14)ClNO, (III), are isomorphous, but with variations in the unit-cell dimensions which preclude in compound (III) one of the weaker intermolecular interactions found in compounds (I) and (II). Thus the compounds are not strictly isostructural in terms of the structurally significant intermolecular interactions, although the corresponding atomic coordinates are very similar. The azepine rings adopt chair conformations. The molecules are linked by a combination of N-H...O and O-H...N hydrogen bonds into chains of edge-fused R(3)(3)(10) rings, which in compounds (I) and (II) are further linked into sheets by a single C-H...pi(arene) hydrogen bond. The significance of this study lies in its observation of isomorphism in compounds (I)-(III), and its observation of a sufficient variation in one of the cell dimensions effectively to alter the range of significant hydrogen bonds present in the crystal structures.

Five closely related 4-chloro-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepines: similar molecular structures but different supramolecular assemblies.

Dibenz[b,f]azepine (DBA) is a privileged 6-7-6 tricyclic ring system of importance in both organic and medicinal chemistry. Benzo[b]pyrimido[5,4-f]azepines (BPAs), which also contain a privileged 6-7-6 ring system, are less well investigated, probably because of a lack of straightforward and versatile methods for their synthesis. A simple and versatile synthetic approach to BPAs based on intramolecular Friedel-Crafts alkylation has been developed. A group of closely-related benzo[b]pyrimido[5,4-f]azepine derivatives, namely (6RS)-4-chloro-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, C14H14ClN3, (I), (6RS)-4-chloro-8-hydroxy-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, C14H14ClN3O, (II), (6RS)-4-chloro-8-methoxy-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, C15H16ClN3O, (III), and (6RS)-4-chloro-8-methoxy-6,11-dimethyl-2-phenyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, C21H20ClN3O, (IV), has been prepared and their structures compared with the recently published structure [Acosta-Quintero et al. (2015). Eur. J. Org. Chem. pp. 5360-5369] of (6RS)-4-chloro-2,6,8,11-tetramethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, (V). All five compounds crystallize as racemic mixtures and they have very similar molecular conformations, with the azepine ring adopting a boat-type conformation in each case, although the orientation of the methoxy substituent in each of (III) and (IV) is different. The supramolecular assemblies in (II) and (IV) depend upon hydrogen bonds of the O-H...N and C-H...π(arene) types, respectively, those in (I) and (V) depend upon π-π stacking interactions involving pairs of pyrimidine rings, and that in (III) depends upon a π-π stacking interaction involving pairs of phenyl rings. Short C-Cl...π(pyrimidine) contacts are present in (I), (II) and (IV) but not in (III) or (V).