Search

Breast cancer is still considered a high-incidence disease, and numerous are the research efforts for the development of new useful and effective therapies. Among anticancer drugs, carbazole compounds are largely studied for their anticancer properties and their ability to interfere with specific targets, such as microtubule components. The latter are involved in vital cellular functions, and the perturbation of their dynamics leads to cell cycle arrest and subsequent apoptosis. In this context, we report the anticancer activity of a series of carbazole analogues 1–8. Among them, 2-nitrocarbazole 1 exhibited the best cytotoxic profile, showing good anticancer activity against two breast cancer cell lines, namely MCF-7 and MDA-MB-231, with IC50 values of 7 ± 1.0 and 11.6 ± 0.8 μM, respectively. Furthermore, compound 1 did not interfere with the growth of the normal cell line MCF-10A, contrarily to Ellipticine, a well-known carbazole derivative used as a reference molecule. Finally, in vitro immunofluorescence analysis and in silico studies allowed us to demonstrate the ability of compound 1 to interfere with tubulin organization, similarly to vinblastine: a feature that results in triggering MCF-7 cell death by apoptosis, as demonstrated using a TUNEL assay.

Our research groups have been involved for many years in studies aimed at identifying new active organic compounds endowed with pharmacological properties. In this work, we focused our attention on the evaluation of cardiovascular and molecular drug resistance (MDR) reverting activities of some nitrosubstituted sulphur-containing heterocycles. Firstly, we have examined the effects of 4-nitro-3-(4-methylphenyl)-3,6-dihydro-2H-thiopyran S,S-dioxide 5, and have observed no activity. Then we have extended our investigation to the 3-aryl-4-nitrobenzothiochromans S,S-dioxide 6 and 7, and have observed an interesting biological profile. Cardiovascular activities were assessed for all compounds using ex vivo studies, while the MDR reverting effect was evaluated only for selected compounds using tumor cell lines. All compounds were shown to affect cardiovascular parameters. Compound 7i exerted the most effect on negative inotropic activity, while 6d and 6f could be interesting molecules for the development of more active ABCB1 inhibitors. Both 6 and 7 represent structures of large possible biological interest, providing a scaffold for the identification of new ABCB1 inhibitors.

In this work triangular gold nanoplates (AuNTPs) are prepared by spontaneous conversion of spherical-like gold precursors induced by the shape-directing properties of the diacetylene N,N,N-trimethylpentacosa-10,12-diyn-1-ammonium bromide (PCD_ABr), employed as capping agent. In detail, thin AuNTPs with edge length below 200 nm are obtained by incubating premade isotropic gold nanoparticles protected with chitosan (Chit@AuNPs) in PCD_ABr solutions through a standard ligand-exchange reaction (LER) carried out in water at room temperature. Control of the AuNTPs size as well as the reaction shape-yield up to 65% is achieved by simply varying the reagents ratio in the incubation mixture. Because of the high anisotropy of the flat nanoparticles, the AuNTPs-containing hydrosols show intense, well-defined absorptions in the NIR spectral region, which make them excellent candidates as biosensors also for in vivo assays with biological tissues and fluids. When subjected to UV light, both triangular and nearly spherical PCD_ABr-coated gold nanoparticles exhibit fluorescent properties and Raman features typical of disordered, sp2-based carbon nanostructures. The photogeneration of graphite-like moieties within the diacetylene shell instead of expected polydiacetylene skeleton is most likely due to poor alignment of the monomer chains on the gold surfaces and seems to be favored on isotropic nanoparticles.

Novel, densely functionalized 2-methylideneazetidines can be obtained in high yields and mild conditions from the reaction of nitropentadienoates with primary amines, most likely through an aza-Michael addition followed by a 4-exo-trig cyclization. The initial, selective trans arrangement for the C3 and C4 ring hydrogens undergoes stereomutation due to the presence of an easily enolisable site at C3, eventually leading to mixtures where the cis isomer generally prevails.

Herein we report a significant, valuable extension of a recently implemented pyrrole benzannulation methodology that, employing versatile nitrodienes from our lab as useful C4 building blocks, led to indole derivatives characterized by unusual patterns of substitution. The 6-nitro-7-arylindoles resulting from suitably derivatized, non-symmetric dienes are of foreseeable synthetic interest in search for new polyheterocyclic systems. As an example, pyrrolocarbazoles with a rarely reported ring fusion were synthesized with the classical Cadogan protocol. Furthermore, the proven easy reducibility of the nitro group to amine will surely open the way to further interesting elaborations.

We report herein an original protocol to the indole nucleus, which could contribute to significantly expand the synthetic access to a heterocyclic moiety of undeniable paramount importance. The protocol consists in the construction of the benzene ring onto a pyrrole (benzannulation) starting from 2,3-dinitro-1,3-butadienes. This appealing, metal-free process characterized by high atom economy and mild reaction conditions allows to synthesize indoles possessing nitro group(s) on the benzene ring: a result which cannot be likewise easily obtained by exploiting most common pathways such as functionalization of a preformed indole or heteroannulation of a suitable benzene derivative. From a mechanistic point of view, a stepwise, ionic process is suggested by the identification of a pivot dihydroindole intermediate whose interception facilitates some selectivity in the preparation of different nitroindoles.

Stable hydrosols of gold and silver nanoparticles coated with the quaternary-ammonium group endowed diacetylene DAAMM (N,N,N-trimethyl-3-(pentacosa-10,12-diynamido)propan-1-ammonium) were obtained through a ligand-exchange reaction leaving the morphology of the pristine cores unmodified. Photopolymerization of the chemisorbed diacetylene shell occurred in both red and blue phases thanks to the presence of internal, H-bondable amide functions in the monomer chain, which are supposed to help the formation of a packed bilayer on the metal surfaces. Multidisciplinary characterization of the polymerized samples, including spectroscopic, morphological and thermal techniques, highlighted that differences occur in the polymerization process on gold and silver nanoparticles under different experimental conditions, suggesting a higher affinity of the trimethylammonium headgroup for gold substrates in acidic media. With respect to the extensively investigated PCDA (pentacosa-10,12-diynoic acid), DAAMM showed reduced capability of photogenerating thick polymer shells, especially in the more delocalized blue form, probably because of the inefficiency of the cationic monomer to form the multi-bilayered architecture typical of the highly-performing, carboxyl-terminated diacetylene. On the other end, the inner cross-linked structure gives to poly(DAAMM)-coated nanohybrids increased stability in water with respect to self-assembled counterparts deriving from saturated cationic surfactants, making them a promising sensing platform for rapid and cost effective assays of real samples.

The initial ring-opening of 3-nitrothiophene and further structural modifications lead to nitrobutadienic building-blocks whose synthetic usefulness in the field of heterocycles has been widely demonstrated. As a further example, the Michael addition of a hydrazone anion to the nitrovinyl moiety of nitrobutadienes generates 1,2-diazaheterocycles as the final result of an overall MIRC process. Depending on the nature of the substituents on the Michael-type acceptor and on the hydrazono nucleophile, an interesting dichotomy is observed that leads to either five-member or six-member N-heterocycles with complete selectivity. The results obtained appear to be both of mechanistic and synthetic interest e.g., in the field of heterocycles endowed with potential pharmacological/biological activity.

The ring opening of 3-nitro-4-(phenylsulfonyl)thiophene with amines and proper modification of the resulting 1,3-diene enables a simple and versatile approach to N-fused pyrroles of both synthetic and biological interest through 1,6-H shift followed by 6π 1,5-electrocyclization. This protocol is effectively driven to the isolated pyrroles by an easy aromatization.

The unusual migration of a nitro group from the - to the -position of a -aryl--nitroethenyl moiety, following a nitrocyclopropane to isoxazoline N-oxide isomerization, has been studied from a mechanistic and synthetic points of view. As a result, two series of isomeric isoxazoline N-oxides could be obtained under controlled conditions. When reacted with diazomethane, a model transposed isoxazoline cleanly furnished a new, interesting pyrazolylisoxazole.

The conjugated bis(sulfonyl)nitrobutadienes 1 undergo, with primary amines, competitive MeSO2 replacement [vinylic substitution at C(1)] versus aza-Michael addition to the nitroethenyl C(3)–C(4) double bond. The latter pathway eventually leads to the trisubstituted pyrroles 2 and conditions have been optimized in order to maximize the yield of such polyfunctionalized heterocycles. Interestingly, in trifluoroethanol tetrasubstituted pyrroles 7 are also formed, thanks to a final aromatization via oxidation by ‘endogenous’ nitrite.

The base-induced cyclization of ( E )-2-aryl-1-[2-(benzylsulfonyl)phenyl]-1-nitroethenes to polysubstituted thiochroman S , S -dioxides exhibits a diastereoselectivity that can be oriented towards a selected isomer by means of appropriate adjustments of the experimental conditions. The interest of such a result also rests on the promising pharmacological activity of the products, whose structure encompasses different well-acknowledged pharmacophores. A conformational 1 H NMR investigation, backed by molecular-mechanics calculations, has also been accomplished.

(1 E ,3 Z )-1-Aryl-4-methanesulfonyl-2-nitro-1,3-butadienes ( 8 ), derived from the initial ring-opening of 3-nitrothiophene ( 5 ), have been found to undergo a facile base-induced cyclization leading to thiopyran S , S -dioxides ( 9 ), thus furnishing a further example of effective ring-enlargement from 5- to 6-membered sulfur heterocycles. Compounds 9 are obtained as single racemic mixtures in satisfactory yields; they still contain a nitrovinylic moiety, which can be exploited for further modifications targeted to new derivatives endowed with either synthetic or pharmacological potentialities e.g., in the field of L-type Ca 2+ -channel blockers.

With the goal of their exploitation for the synthesis of heterocycles, sulfides 10 and sulfones 11, derived from the initial ring-opening of 2-nitrothiophene (5) with pyrrolidine/AgNO3 in EtOH, were reacted with diazomethane. Interesting dichotomic behavior was found to yield pyrazolines 17 from 10 and isoxazolines 18 (as the main products) from 11. Intriguingly enough, in the latter case, an unexpected apparent C-C methylene insertion was also observed, leading to the homologous cyclopropanes 19 as secondary products.

Reference EPFL-ARTICLE-150326doi:10.2174/157017807781024165 URL: http://www.bentham.org/loc/contabs/loc4-4.htm#13 Record created on 2010-08-06, modified on 2017-05-12

The reaction of nitrobutadienes (I) with indole leads to 1,3,4- and 1,2,4-nitrocarbazoles (III) and (IV).

As a continuation of our research on the synthetic exploitation of the nitrobutadienic building-blocks obtained from the ring-opening of nitrothiophenes, we herein report about their reaction with the π-nucleophilic indole. Thanks to their double Michael-acceptor nature, 2,3-dinitro and 2-nitro-3-phenylsulfonyl substituted 1,3-butadienes produce poly-functionalized carbazoles through a double (inter-+intra-molecular) conjugate addition, followed by aromatization of the newly built ring. Significance is attached to the results obtained in fluorinated solvents such as trifluoroethanol, whereby a mild process, with no need for catalysis, overcomes some practical difficulties otherwise limiting the scope of the reaction. Besides the mechanistic aspects, the reaction encompasses motifs for a synthetic interest, mainly in the field of further-tunable arylcarbazoles endowed with predictable applicative properties, e.g., as fluorescent devices.

In this paper, we report the synthesis of novel diacetylenes bearing trimethylammonium end groups, their photochemical polymerization and the spectroscopic characterization of the polymers by different techniques (UV–vis, fluorescence, FT-IR, Raman). The obtained results shed light on the role of the trimethylammonium head group (and its counterions) in the polymerization process. It is also demonstrated that the presence of an internal, H-bondable amide function in the diacetylene tail favors the photopolymerization process as well as the formation of the polydiacetylene in its blue, highly-conjugated form. Moreover, the corresponding polymer in the less-conjugated red phase, typical of polydiacetylenes in solution, shows significantly enhanced emission properties with respect to its counterparts carrying all-saturated lateral chains.

[reaction: see text] In prosecution of previous work on the thermal cyclization of 1-aryl-4-methanesulfonyl-2-nitro-3-phenylsulfonyl-1,3-butadienes (7), the 3-unsubstituted derivatives 8, deriving from the initial ring opening of 3-nitrothiophene (2), have been likewise found herein to undergo cyclization, followed by aromatization, in analogous mild experimental conditions, leading to the ring-fused homo- or heteroaromatic nitro derivatives 10. The concerted electrocyclic nature of the process is strongly supported by the outcome of tests based on the variation of the polarity of the solvent or of the electron density on the aryl of 8. Thus, the successful application of the process to the non-phenylsulfonyl-activated 8 significantly widens the scope of a synthetically valuable overall ring-opening/ring-closing procedure from nitrothiophenes. Support to the recently renewed interest in thermal 6pi electrocyclizations as a tool for the construction of the benzene ring is furthermore provided.

The treatment of 3,4-dinitrothiophene with an aryl Grignard reagent results in the reduction of one nitro group accompanied by the ipso-substitution of a hydrogen atom by an ortho-phenolic group on the ring carbon adjacent to the reduced nitro group. A Claisen-type intramolecular rearrangement is proposed as the pivotal step of a rather complex mechanism, followed by proton-transfer aromatizing steps. This work shows yet another facet of the variegated reactivity of 3,4-dinitrothiophene towards nucleophiles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Within an overall ring-opening/ring-forming protocol, the (E,E)-4-methylthio-2-nitro-3-phenylsulfonyl-1-pyrrolidino-1,3-butadiene (7) [derived from the initial opening of 3-nitro-4-(phenylsulfonyl)thiophene (6) with pyrrolidine and silver nitrate in EtOH] is revealed to be an excellent precursor of nitro(phenylsulfonyl) derivatives of ring-fused aromatic (naphthalene, phenanthrene) or heteroaromatic (benzothiophene) compounds whose substitution pattern cannot be easily achieved by conventional methods. The key step is represented by a thermal electrocyclic rearrangement of (E,E)-1-aryl-4-methylsulfonyl-2-nitro-3-phenylsulfonyl-1,3-butadienes (9), which, thanks to proper geometric and electronic factors, occurs in unprecedentedly mild conditions and is followed by an irreversible, concerted syn β-elimination of methanesulfinic acid to aromatize the newly formed cyclohexadienic ring.

The ring opening of 3-nitro-4-(phenylsulfonyl)thiophene with amines and proper modification of the resulting 1,3-diene enables a simple and versatile approach to N-fused pyrroles of both synthetic and biological interest through 1,6-H shift followed by 6π 1,5-electrocyclization. This protocol is effectively driven to the isolated pyrroles by an easy aromatization.

A new symmetrical disulfide containing a diacetylenic unit and bearing a fluorescent carbazolyl end-group forming polymerizable self-assembled monolayers on metallic nanostructures has been synthesized. Suitable modifications of the synthetic steps involved in the synthesis of such derivatives were made in order to assure better synthetic pathway. Conversion of the tosylated derivative into the final symmetrical disulfide is carried out using sodium hydrosulfide (NaSH).

Disulfide-functionalized fluorescent derivative of carbozole named 11-(9-carbazolyl)-1-undecyl disulfide (CBZDS) has been synthesized. Proton nuclear magnetic resonance spectroscopy was used to distinguish thiol from its corresponding symmetrical disulfide. Single step synthesis of gold nanoparticles coated with CBZDS was carried out which resulted in stable monolayers of CBZDS on gold nanoparticles.

Different approaches are investigated to the pharmaceutically interesting heterocyclic systems.

Nucleophilic addition of indole to nitroolefins gives the expected Michael-type adducts (III) and (VI) as well as the carbazoles (IX) and (X).

In prosecution of the synthetic exploitation of nitrobutadienes deriving from the initial ring-opening of nitrothiophenes, their multifaceted behavior finds a further clear-cut example in their Michael-type acceptor reactivity toward the anions of α-oxohydrazones. Thus, depending on the starting diene, new poly-functionalized pyrazoles are obtained. Furthermore, most interestingly, in one occasion a dichotomy has been observed, depending on the nature of the Michael-type donor, leading with complete selectivity to either 5-member or 6-member N-heterocycles. The outcome encompasses motifs for both mechanistic and synthetic interest, for example, in the field of heterocycles endowed with possible pharmacological/biological activity.

The multifaceted behavior of nitrobutadienes deriving from the initial ring-opening of nitrothiophenes finds a further clear-cut example in their Michael-type acceptor reactivity towards indole. Thus, depending on the starting diene, either newly-functionalized indoles or carbazoles are produced, the latter as the result of an appealing double (intermolecular + intramolecular) Michael-type addition to a nitrovinylic moiety. The outcome encompasses motifs for both mechanistic and synthetic interest in the field of heterocycles endowed with possible pharmacological activity.

The inhibition of cell proliferation by methyl (2Z,4E)-2-methylsulfanyl-5-(1-naphthyl)-4-nitro-2,4-pentadienoate (1-Naph-NMCB) and (1E,3E)-1,4-bis(2-naphthyl)-2,3-dinitro-1,3-butadiene (2-Naph-DNB) has been studied in vitro against four cell lines selected for their resistance to doxorubicin, cisplatin, taxol and 5-fluorouracil. In previous experiments both compounds showed good in vitro antiproliferative, cytotoxic and pro-apoptotic activities against cell lines of different histologic origin. The results of the experiments presented here suggest that 1-Naph-NMCB is able to overcome all of the different mechanisms of resistance showed by the resistant cell lines used for our experiments. On the contrary, when we used the taxol-resistant A549-T12 cell line, characterized by a mechanism of resistance due to a mutation of the target site of taxol on microtubules, it displayed a partial but significant cross-resistance to 2-Naph-DNB. Although the actual mechanism of this cross-resistance has not yet been definitively elucidated, our results from immunostaining of microtubules suggest that it may be linked to the presence of a shared target site for taxol and 2-Naph-DNB on microtubules.

On the grounds of previous encouraging results on the antitumor activity of (1 E ,3 E )-1,4-bis(1-naphthyl)-2,3-dinitro-1,3-butadiene ( 1 ), we have designed and synthesized two new molecules [(1 E ,3 E )-1,4-bis(4-carboxy-1-naphthyl)-2,3-dinitro-1,3-butadiene ( 2 ) and methyl (2 Z ,4 E )-2-methylsulfanyl-5-(1-naphthyl)-4-nitro-2,4-pentadienoate ( 3 )] characterized by a common naphthylnitrobutadiene array but with different structural properties, with the aim of approaching to some structure–activity correlation. When 2 and 3 were analyzed in vitro for their inhibition of cell proliferation and pro-apoptotic properties, the carboxyderivative 2 did not furnish appreciable results. In contrast, 3 (which contains only one of the two naphthylnitroethenyl moieties of the original compound 1 ) showed remarkable activities in the range of micromolar concentrations (in six over eight cell lines its IC 50 s are in the 1–3 μM range), with a significant improvement compared to 1 . In particular, 3 proved able to bind to DNA, to upregulate p53, to block cells in the G2/M phase of their cycle, and to induce apoptosis. Thus, very interestingly, the performance of 3 with respect to 1 shows that a single 1-(1-naphthyl)-2-nitroethene moiety is able to ensure better (on four out of eight of the cell lines tested) or comparable levels of activity. This result suggests that the ‘molecular-simplification strategy’ could furnish a useful instrument for future design in our antitumor research.

On the basis of our previous interesting results in vitro on the antiproliferative activity of (1E,3E)-1,4-bis(1-naphthyl)-2,3-dinitro-1,3-butadiene (1-Naph-DNB) we have designed and synthesized the new molecule methyl (2Z,4E)-2-methylsulphanyl-5-(1-naphthyl)-4-nitro-2,4-pentadienoate (1-Naph-NMCB) characterized by the same naphthylnitrobutadiene array but with a different functional group at one end of the diene system. This new molecule showed an in vitro antiproliferative activity more significant than that found for the original 1-Naph-DNB. In order to verify in vivo our in vitro results we have tested the antitumour activity of 1-Naph-DNB and 1-Naph-NMCB in several murine tumour models, namely the myelomonocytic P388 and the Lewis lung carcinoma 3LL in BDF1 mice, the melanoma B16 in C57Bl mice, the fibrosarcoma WEHI 164 in nude mice and, finally, the C51 colon cancer in Balb/c mice. In the case of 1-Naph-NMCB the analysis of the antitumour activity has been preceded by toxicological experiments on CD-1 mice, in order to determine the lethal (LD) and the maximal tolerated (MTD) doses together with the spectrum of histological alterations caused by its iv administration. The results obtained show that the modification of the original structure of 1-Naph-DNB according to the molecular-simplification strategy has led to an asymmetric nitrobutadiene array, i.e. that of 1-Naph-NMCB, endowed with an antitumour activity which is in some cases even better than that showed by the parental compound itself, together with differences in tumour selectivity and negligible histological toxic effects. A promising, versatile route to new, more active and/or safe nitrobutadiene derivatives has thus been positively tested.

Our interesting results on the antiproliferative (in vitro) and antitumour (in vivo) activities of (1E,3E)-1,4-bis(1-naphthyl)-2,3-dinitro-1,3-butadiene (1-Naph-DNB) have more recently induced us to design and synthesize some new 1,4-diaryl-2,3-dinitro-1,3-butadienes characterized by a common arylnitrobutadiene array but with different geometric and/or functional properties. This task was undertaken with the aim to obtain new compounds with an enhanced antiproliferative activity and, possibly, a different specificity with respect to the original (lead) compound. (1E,3E)-1,4-Bis(2-naphthyl)-2,3-dinitro-1,3-butadiene (2-Naph-DNB) is one of the molecules so obtained, a structural isomer of 1-Naph-DNB provided with a different spatial arrangement. When analyzed in vitro for its inhibition of cell proliferation 2-Naph-DNB showed a remarkable activity in the range of micromolar concentrations, with significant differences, with respect to 1-Naph-DNB, against some cell lines. Furthermore, it was able to significantly trigger apoptosis, to up-regulate p53, to block cells in the G2/M phase of the cell cycle and, finally, to slightly bind to DNA forming interstrand cross-links (ISCL). 2-Naph-DNB was then analyzed for its toxic activity in vivo in CD1 mice. This allowed the determination of toxicity parameters such as the lethal doses (LD) and the maximal tolerated dose (MTD) together with the definition of the spectrum of tissue alterations due to its administration i.v. Altogether our data suggest that the idea of modifying the geometry of the lead compound 1-Naph-DNB deserves further investigation aimed at synthesizing new molecules with similar chemical functionalities but with different spatial requirements, hopefully characterized by still enhanced activities in terms of inhibition of cell proliferation and apoptosis.

4-Alkyl-2-nitrothiophenes [10: R = CH3, CH(OH)CH3, CH(OCH3)CH3] react with secondary aliphatic amines, in the presence of AgNO3, to give 3-alkyl-2-amino-5-nitrothiophenes (12) through an oxidative nucleophilic substitution of hydrogen (ONSH) of synthetic interest. This behavior is in striking contrast with that of the parent 2-nitrothiophene (6), which was found to undergo ring-opening in analogous reaction conditions. A possible rationale for the crucial effect of alkyl groups is suggested, grounded also on a study of the corresponding Meisenheimer-like adducts.

[reaction: see text] In prosecution of previous work on the thermal cyclization of 1-aryl-4-methanesulfonyl-2-nitro-3-phenylsulfonyl-1,3-butadienes (7), the 3-unsubstituted derivatives 8, deriving from the initial ring opening of 3-nitrothiophene (2), have been likewise found herein to undergo cyclization, followed by aromatization, in analogous mild experimental conditions, leading to the ring-fused homo- or heteroaromatic nitro derivatives 10. The concerted electrocyclic nature of the process is strongly supported by the outcome of tests based on the variation of the polarity of the solvent or of the electron density on the aryl of 8. Thus, the successful application of the process to the non-phenylsulfonyl-activated 8 significantly widens the scope of a synthetically valuable overall ring-opening/ring-closing procedure from nitrothiophenes. Support to the recently renewed interest in thermal 6pi electrocyclizations as a tool for the construction of the benzene ring is furthermore provided.

The inhibition of cell proliferation by 1,4-bis (1-naphthyl)-2,3-dinitro-1,3-butadiene (Naph-DNB) was evaluated in vitro against 4 cell lines (L1210/DDP, A2780/DX3, HCT-8/FU7dR, A549-T12) selected for their resistance to cisplatin, doxorubicin, 5-fluorouracil and taxol, and their wild-type counterparts. Naph-DNB is a novel anti-cancer compound obtained years ago within a research project of Organic Chemistry aimed at synthesizing 2,3-dinitrobutadiene derivatives. Because of its chemical structure, Naph-DNB was suggested to interact with nucleic acids, in particular DNA, and the other cellular macromolecules. This hypothesis made us consider Naph-DNB as a candidate for studies concerning its antitumour activity. We used the MTT assay to test the inhibition of cell proliferation after incubation of the cell lines with Naph-DNB for 72 h. For comparison, resistant and wild-type cell lines were also tested against those anticancer drugs used in vitro for their selection. In these culture conditions Naph-DNB retained its inhibiting activity against all resistant cells with IC50 values similar to those obtained in corresponding wild-type cell lines. Moreover, Naph-DNB was twice as effective as 5-fluorouracil against wild-type HCT-8 cells. Our previous findings about the interaction of Naph-DNB with DNA through the formation of interstrand cross-links suggested a mechanism of action similar to that of platinum/alkylating agents or topoisomerase inhibitors (intercalating agents). Our present data obtained by the K-SDS precipitation assay in A2780 and A549 cells showed that Naph-DNB is not able to form a stable topoisomerase-DNA complex as is the case for topoisomerase inhibitors. In conclusion, our results indicate that Naph-DNB is able to overcome some of the classical mechanisms of resistance selected by some anticancer drugs mainly used in clinical setting.

1-(Methyl-p-tolyl-amino)-3-phenoxy-2-azetidinones 4-COX and 4-R substituted (COX: X=Me, Et, Ph, NMe2, NEt2, OBut; R=Me, Et, Ph) were smoothly prepared from the corresponding α-(methyl-p-tolyl)hydrazonylated ketones, amides and esters via [2+2] cycloaddition with phenoxyketene. The reaction was generally high-yielding and diastereoselective, leading to β-lactams with a cis relationship between the PhO and the COX moieties, except for R=Ph, where an opposite stereoselectivity was instead observed. The azetidinones represent interesting intermediates which couple protection at N(1) and functionalization at position 4 of the ring. Deprotection of N(1) can be easily attained by oxidative N–N cleavage with magnesium monoperoxyphthalate.

The (E)-2-aryl-1-[2-(methylthio)phenyl]-1-nitroethylenes 5 can easily be oxidized to the relevant sulfones 6 and effectively subjected to cyclization via an intramolecular Michael addition after metallation with lithium bis(trimethylsilyl)amide in THF. After quenching with ammonium chloride the 3-aryl-4-nitrothiochroman S,S-dioxides 2 are obtained as diastereomeric mixtures in good to excellent yields. Both yields and stereochemistry of the ring-closure step appear to be influenced by steric effects of the 3-aryl moiety. As sulfides 5 derive from an initial ring opening of 3-nitrobenzo[b]thiophene ( 1 ), the overall 1 to 2 process can be considered as an effective 5 to 6 ring enlargement of the sulfur heterocycle. A conformational 1H NMR and molecular-mechanics investigation on the isolated diastereomeric 2 has also been accomplished.

Within an overall ring-opening/ring-forming protocol, the (E,E)-4-methylthio-2-nitro-3-phenylsulfonyl-1-pyrrolidino-1,3-butadiene (7) [derived from the initial opening of 3-nitro-4-(phenylsulfonyl)thiophene (6) with pyrrolidine and silver nitrate in EtOH] is revealed to be an excellent precursor of nitro(phenylsulfonyl) derivatives of ring-fused aromatic (naphthalene, phenanthrene) or heteroaromatic (benzothiophene) compounds whose substitution pattern cannot be easily achieved by conventional methods. The key step is represented by a thermal electrocyclic rearrangement of (E,E)-1-aryl-4-methylsulfonyl-2-nitro-3-phenylsulfonyl-1,3-butadienes (9), which, thanks to proper geometric and electronic factors, occurs in unprecedentedly mild conditions and is followed by an irreversible, concerted syn beta-elimination of methanesulfinic acid to aromatize the newly formed cyclohexadienic ring.

Different nitronaphthylbutadienes have been previously proved to have antitumour activity. The main drawback of these derivatives is their low water solubility. With the aim of facilitating the administration of these new drugs we have synthesized the hexyl (2Z,4E)-2-methylsulfanyl-5-(1-naphthyl)-4-nitro-2,4-pentadienoate analogue (1-Naph-NHCB) which is demonstrated to be easily included into cyclodextrins and/or entrapped into liposomes. Its antitumour activity was revealed to be almost comparable with that of the previously studied methyl analogue ester (1-Naph-NMCB). On the other hand, in vitro studies with different cancer cell lines showed that the cytotoxic activity of both 1-Naph-NMCB and 1-Naph-NHCB were fully preserved and in some cases also enhanced when entrapped into liposomal carriers.