Synthesis, cytotoxic activity, and DNA binding properties of antitumor cis-1,2-dihydroxy-1,2-dihydrobenzo[b]acronycine cinnamoyl esters.

Monocinnamoyl esters at position 2 of (+/-)-cis-1,2-dihydroxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one and their acetyl derivatives at position 1 were prepared as stabilized analogues of the anticancer alkylating agent S23906-1. Monocinnamoyl esters at position 2 were slower DNA alkylators than the reference 2-monoacetate. Mixed esters bearing an acetyl ester group at position 1 and a cinnamoyl ester group at position 2 alkylated DNA slower than S23906-1. A strong correlation was observed between cytotoxicity and DNA alkylation kinetics, with slower alkylators displaying more potent antiproliferative activities. The most cytotoxic compounds proved to be significantly active in vivo against murine C-38 adenocarcinoma implanted in mice, but less potent than S23906-1.

2,2-dimethyl-2H-pyran-derived alkaloids I. Practical synthesis of acronycine and benzo[b]acronycine and their biological properties.

The 2,2-dimethyl-2H-pyran-derived alkaloids acronycine and its demethylated congeners were prepared in three steps from anthranilic acid and phloroglucinol. The phenylboronic acid-mediated interamolecular cyclization reaction of 1,3-dihydroxyacridone and 3-methylbut-2-enal was employed as a key step, which was also applied to the synthesis of related cytotoxic benzo[b]acronycine. Inhibitory activities of the compounds prepared on topoisomerase I and II as well as their cytotoxicities were evaluated. Cytotoxicity of 2 is closely related to the strong inhibitory activity against topo II at 20 microM level.

Synthesis, antitumor activity, and mechanism of action of benzo[a]pyrano[3,2-h]acridin-7-one analogues of acronycine.

Twenty-two derivatives belonging to the cis-1,2-diacyloxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[a]pyrano[3,2-h]acridin-7-one series were synthesized in nine steps starting from 3,5-dimethoxyacetanilide (5) and 2-methoxy-1-naphthalenecarboxylic acid (7). Most of them exhibited submicromolar cytotoxicity when tested against murine leukemia (L1210) and human epidermoid carcinoma (KB-3-1) cell lines. The cytotoxic activity correlated strongly with the ability of the compounds to form covalent adducts with purified DNA. Among the most active compounds, 25, with IC50 values of 0.7 and 0.15 microM against L1210 and KB-3-1, respectively, was selected for evaluation in vivo against Colon 38 adenocarcinoma implanted in mice. This compound was active at 3 mg/kg i.v. (day 12 and 24) with 3/7 tumor free mice by day 80.

Design, synthesis and antiproliferative activity of some new azapyranoxanthenone aminoderivatives.

Some novel aminosubstituted azapyranoxanthenones, bearing structural similarity to the acridone alkaloid acronycine, have been designed and synthesized. Their in vitro cytotoxicities against the murine L1210 leukemia and the human solid tumor HT-29 cell lines have been investigated. Their eventual selective effect on a phase of the cell cycle was evaluated, using HT-29 cells. A number of the new derivatives exhibited interesting cytotoxic activity against the human solid tumor cell line.

[Structure activity relationships and mechanism of action of antitumor benzo[b]acronycine antitumor agents]. / Relations structure, activité et mécanisme d'action des antitumoraux de série benzo[b]acronycine.

The acridone alkaloid acronycine, isolated from several Sarcomelicope species (Rutaceae) was shown to exhibit a promising activity against a broad spectrum of solid tumors. Nevertheless, subsequent clinical trials only gave poor results, probably due to the moderate potency of this drug. The isolation of the unstable acronycine epoxide from several New-Caledonian Sarcomelicope led to a hypothesis of bioactivation of acronycine by transformation of the 1.2-double bond into the corresponding oxirane in vivo. This hypothesis and the demonstration that acronycine should interact with DNA guided the development of a series of 1.2-dihydroxy-1.2-dihydrobenzo[b]acronycine esters and diesters as novel anticancer drug candidates. In vivo, cis-1.2-diacetoxy-1,2-dihydrobenzo[b]acronycine, selected for further development under the code S 23906-1, demonstated a marked antitumor activity in human orthotopic models of lung, ovarian and colon cancers xenografted in nude mice. The cytotoxic and antitumor activities of these compounds were strongly correlated with their ability to give covalent adducts with purified as well as genomic DNA. Such adducts involve reaction between the exocyclic N-2 amino group of guanines exposed in the minor groove of double helical DNA and the leaving ester group at the benzylic position 1 of the drug.

Synthesis and cytotoxic and antitumor activity of benzo[b]pyrano[3, 2-h]acridin-7-one analogues of acronycine.

Benzo¿bacronycine (6-methoxy-3,3,14-trimethyl-3, 14-dihydro-7H-benzo¿bpyrano¿3,2-hacridin-7-one, 4), an acronycine analogue with an additional aromatic ring linearly fused on the natural alkaloid basic skeleton, was synthesized in three steps, starting from 3-amino-2-naphthalenecarboxylic acid (5). Eight 1, 2-dihydroxy-1,2-dihydrobenzo¿bacronycine esters and diesters (17-24) were obtained by catalytic osmic oxidation, followed by acylation. All these compounds were significantly more cytotoxic than acronycine, when tested against L1210 leukemia cells in vitro. The potency of the cyclic carbonate 24 was in the range of the most active drugs currently used in cancer chemotherapy. Two selected diesters (17 and 24) were evaluated in vivo against P388 leukemia and colon 38 adenocarcinoma implanted in mice. Both compounds were markedly active at doses 16-fold lower than the dose of acronycine itself. Against colon 38 adenocarcinoma, compounds 17 and 24 were highly efficient, inhibiting tumor growth by more than 80%. Diacetate 17 was the most active, inhibiting tumor growth by 96% at 6.25 mg/kg, with two of seven mice being tumor-free on day 43.

Synthesis and cytotoxic and antitumor activity of esters in the 1,2-dihydroxy-1,2-dihydroacronycine series.

Seven 1,2-dihydroxy-1,2-dihydroacronycine and 1,2-dihydroxy-1,2-dihydro-6-demethoxyacronycine esters and diesters were synthesized via osmic oxidation of acronycine or 6-demethoxyacronycine followed by acylation. The 6-demethoxyacronycine derivatives were found to be inactive, whereas in contrast, all of the acronycine derivatives were more potent than acronycine itself when tested against L1210 cells in vitro. Four selected acronycine derivatives (17,19, 21, and 22) were evaluated in vivo against murine P388 leukemia and colon 38 adenocarcinoma implanted in mice. All compounds were markedly active against P388 at doses 4-16-fold lower than acronycine itself. Against the colon 38 adenocarcinoma, the three compounds 17, 21, and 22 were highly efficient. 1,2-Diacetoxy-1,2-dihydroacronycine (17) was the most active, all the treated mice being tumor-free on day 23.

Synthesis of 6-dialkylaminoalkylamino pyrano[2,3-c]acridones and benzo[b]pyrano[3,2-h]acridones: soluble acronycine analogues with increased cytotoxic activity.

The novel 6-dialkylaminoalkylamino-3,3,12-trimethyl-3,12-dihydro-7H-pyrano[2,3-c]acridine-7-ones 5-11 and their benzo [b]pyrano[2,3-h]acridine-7-one counterparts 12-18 were prepared by treatment of acronycine (1) or benzo[b]acronycine (4) with an excess of the appropriate dialkylaminoalkylamine. In both series, the introduction of a dialkylaminoalkylamino side chain at position 6 resulted in a significant increase of the cytotoxic activity against L1210 cells when compared with the parent compounds bearing a methoxy group, accompanied with an increased potency to arrest cells in the G2 + M phases of the cell cycle.

Evaluation of the cytotoxic mechanisms mediated by the broad-spectrum antitumor alkaloid acronycine and selected semisynthetic derivatives.

Acronycine (I) is a broad-spectrum antitumor agent whose development as a clinically useful agent has been hindered, in part, due to its poor solubility characteristics. With the goal of acquiring information that may prove of value in the development of structurally related compounds of greater clinical utility, mechanistic studies were performed with acronycine (I) and two semisynthetic derivatives, 2-nitroacronycine (II) and acronycine azine (III). These three substances demonstrated cytotoxic activity with several human tumor cell lines (breast, colon, lung, melanoma, KB-3, and drug-resistant KB-V1). Compounds II and III demonstrated greater activity than I, and more detailed studies were performed with cultured human breast cancer cells (UISO-BCA-1). Acronycine azine (III) induced the cells to accumulate in the G0/G1 phase of the cell cycle. It effectively inhibited the in vitro catalytic activities of partially purified DNA and RNA polymerases in a manner that was competitive with respect to DNA substrate. As judged by spectrophotometric titration, compound III interacted with calf thymus DNA, calf liver RNA, and a variety of single- and double-stranded (deoxy)ribonucleotides. Although no nucleic acid base specificity was discernable, this interaction appeared to be related to the cytotoxic mechanism of this dimeric substance. Monomeric compounds I and II did not interact with nucleic acids, but were effective inhibitors of DNA and RNA synthesis as judged by in vitro systems comprised of cultured UISO-BCA-1 cells or homogenates derived from these cells. The relative inhibitory activities of compounds I and II correlated with their cytotoxic activities suggesting a causal relationship. In addition, these two compounds induced cultured cells to accumulate in the phase of the cell cycle wherein the DNA content ranged from 2n-4n (S + G2/M), and inhibited in vitro DNA and RNA synthesis in a manner that was competitive with respect to nucleotide (TTP or UTP) substrate. Compounds I and II demonstrated greater cytotoxic activity with drug-resistant KB-V1 cells as compared with the parent (drug-sensitive) cell line, whereas this was not the case with compound III. Based on these results and previous literature reports, compounds I, II and III are likely to function by multiple mechanisms of action. However, it appears that alteration of nucleic acid metabolism is key to the activity of each of the substances.

Analysis of the prodrug 7-acetylacroninium perchlorate in presence of the parent compound acronine.

Analysis of acronine and the prodrug acetylacroninium perchlorate in parenteral solutions is described. The unstable prodrug reacts quantitatively with the nucleophilic agent aniline by an unusual mechanism to form a phenylimino derivative of acronine. This derivative and acronine itself were determined by a spectrophotometric two-component method.

Formation of a thio analog of noracronine.

Acronine was heated with tetraphosphorus decasulfide in benzene to give a mixture of products, the major component (A) being identified tentatively as an unstable product derived from four molecules of noracronine with one molecule of tetraphosphorus decasulfide. Treatment of Compound A with various solvents and heat converted it into a maroon solid (B), which was shown to be 7-thionoracronine.

Acetylacroninium salts as soluble prodrugs of the antineoplastic agent acronine.

The low aqueous solubility of acronine (approximately 2 mg/liter) has been overcome by identification of quaternary prodrug salts exhibiting apparent molar solubilities two to five orders of magnitude greater than acronine. The synthesis and kinetics of hydrolysis of the various prodrug acetylacroninium salts were studied, and the half-life for hydrolysis under conditions approximating the in vivo situation was estimated to be about 5 min. Such rapid reversion, together with the greatly increased solubility, appears to qualify the prodrug for intravenous use.

[New antitumor agents in the acronycine series]. / Conception de nouveaux agents antitumoraux en série acronycine.

The acridone alkaloid acronycine, isolated from several Sarcomelicope species (Rutaceae) was shown to exhibit a promising activity against a broad spectrum of solid tumors. Nevertheless, clinical trials only gave poor results, probably due to the moderate potency of this drug. The isolation of the unstable acronycine epoxide from several New-Caledonian Sarcomelicope led us to a hypothesis of bioactivation of acronycine by transformation of the 1,2-double bond into the corresponding oxirane in vivo. Consequently, we synthesized a series of cis-1,2-dihydroxy-1,2-dihydroacronycine diesters which exhibited interesting antitumor properties with a broadened spectrum of activity and an increased potency when compared with acronycine. The demonstration that acronycine should interact with DNA, by some noncovalent process prompted us to develop benzo[b] acronycine analogs possessing an additional aromatic ring linearly fused on the natural alkaloid basic skeleton. When tested against a panel of cancer cell lines in vitro, cis-1,2-dihydroxy-1,2-dihydrobenzo[b] acronycine diesters exhibited cytotoxic activities within the same range of potency as the most active drugs currently used in cancer chemotherapy. In vivo, cis-1,2-diacetoxy-1,2-dihydrobenzo[b] acronycine (S 23906-1), selected for further preclinical development, demonstrated a marked antitumor activity in human orthotopic models of lung, ovarian and colon cancers xenografted in nude mice.

Synthesis and cytotoxic activity of benzo[a]acronycine and benzo[b]acronycine substituted on the A ring.

The impact of substitutions at position 10 in the A ring of the cytotoxic benzo[a]acronycine and benzo[b]acronycine series has been explored. 10-Bromobenzo[a] and 10-bromobenzo[b]acronycine were prepared in 12% and 15% yield respectively from commercially available chemicals. Their 1,2-dihydro-1,2-dihydroxy diesters were synthesized. The different derivatives were tested against two cell lines KB-3-1 and L1210. Their cytotoxic activities were found in the same range of magnitude as their non-substituted counterparts. These structure-activity relationships permitted to conclude that the introduction of a substituent at position 10 maintains the activity in both the benzo[a] and [b]acronycine series and open the way to further pharmacomodulations.

Synthesis and cytotoxic activity of psorospermin and acronycine analogues in the 3-propyloxy-acridin-9(10H)-one and -benzo[b]acridin-125H-one series.

In order to explore the structure-activity relationships in the acronycine and psorospermin series, simplified analogues of the highly cytotoxic (+/-)-(2R*,1'R*)-5-methoxy-11-methyl-2-(2-methyloxiran-2-yl)-1,2-dihydro-11H-furo[2,3-c]acridin-6-one and (+/-)-(2R*,1'R*)-5-methoxy-13-methyl-2-(2-methyloxiran-2-yl)-1,2-dihydro-13H-benzo[b]furo[3,2-h]-acridin-6-one lacking the fused furan ring, including 3-allyloxy-1-methoxy-10-methyl-acridin-9(10H)-one, 3-allyloxy-1-methoxy-5-methyl-benzo[b]acridin-12(5H)-one, the corresponding epoxides, and related dihydrodiol esters and diesters were prepared. Only the simplified oxirane compounds displayed significant antiproliferative activity compared to the parent compounds. The oxirane alkylating unit appears indispensible to observe significant antiproliferative activity in both series, but the presence of the angularly fused furan ring does not appear as a crucial structural requirement to observe significant cytotoxic activity.

Synthesis, cytotoxic activity, and mechanism of action of furo[2,3-c]acridin-6-one and benzo[b]furo[3,2-h]acridin-6-one analogues of psorospermin and acronycine.

Compounds possessing the epoxyfuran system present in the natural cytotoxic dihydrofuroxanthone psorospermin (4) fused onto the acridone or benzo[b]acridone chromophores present in the antitumor acronycine (1) and S23906-1 (3) were prepared. The basic furoacridone and benzofuroacridone cores bearing an isopropenyl substituent at a convenient position were synthesized by condensation of 1,3-dihydroxyacridone (7) or 1,3-dihydroxybenz[b]acridin-12(5H)-one (9) with (E)-1,4-dibromo-2-methylbut-2-ene. In both series, the (2R*,1'S*) epoxides, with the same relative configuration as psorospermin, were the most active compounds, exhibiting cytotoxic properties with IC50 values in the 10-100 nM range. As in the acronycine and psorospermin series, the new compounds act through alkylation of the DNA guanine units. However, a strong difference was noted in the DNA alkylation site between the benzopyranoacridone S23906-1, which alkylates DNA guanine units at position N-2 in the minor groove, and the new 13H-benzo[b]furo[3,2-h]acridin-6-one derived epoxide 21, which alkylates DNA guanine units at position N-7 in the major groove.

Structure-activity relationships in the acronycine and benzo[b]acronycine series: role of the pyran ring.

In order to explore the structure-activity relationships in the acronycine series, simplified analogues of cis-1,2-diacetoxy-1,2-dihydroacronycine and cis-1,2-diacetoxy-1,2-dihydrobenzo[b]acronycine (S23906-1, under clinical trials) lacking the fused pyran ring, but possessing an acetoxymethyl leaving group at position 4 were prepared. These new analogues only displayed marginal antiproliferative activity compared to the parent compounds. The presence of the angularly fused dimethylpyran ring appears as an indispensable structural requirement to observe significant cytotoxic activity in this series.

Synthesis and cytotoxic activity of dimeric analogs of acronycine in the benzo[b]pyrano[3,2-h]acridin-7-one series.

Coupling of 6-hydroxy-3,3-14-trimethyl-3,14-dihydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one (6) with alpha,omega-diiodoalkanes of varying length under alkaline conditions gave dimers 7-10. Halogenated ethers 11-14, cyclization products 15-17, and compounds 18-22 were also isolated in small yield from the reaction mixtures. Compounds 7-10 were more potent than acronycine and benzo[b]acronycine in inhibiting L1210 cell proliferation. The length of the alkyl ether linkage between the two benzopyranoacridone units had a dramatic influence on the cytotoxic activity. Compound 9 (n=5) was the most active, with an IC(50) value against L1210 cells within the same range of magnitude as diacetate 5, currently under clinical development.

Synthesis and cytotoxic activity of benzo[a]pyrano[3,2-h] and [2,3-i]xanthone analogues of psorospermine, acronycine, and benzo[a]acronycine.

Condensation of 2-hydroxy-1-naphthalenecarboxylic acid with phloroglucinol afforded 9,11-dihydroxy-12H-benzo[a]xanthen-12-one (6). Construction of an additional dimethylpyran ring onto this skeleton, by alkylation with 3-chloro-3-methyl-1-butyne followed by Claisen rearrangement, gave access to 6-hydroxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (12) and 5-hydroxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (13), which were methylated into 6-methoxy-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (14) and 5-methoxy-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (15), respectively. Osmium tetroxide oxidation of 14 and 15 gave the corresponding (+/-)-cis-diols 16 and 17, which afforded the corresponding esters 18-21 upon acylation. Similarly, condensation of 2-hydroxy-1-naphthalenecarboxylic acid with 3,5-dimethoxyaniline gave 11-amino-9-methoxy-12H-benzo[a]xanthen-12-one (23) which was converted into 11-amino-9-hydroxy-12H-benzo[a]xanthen-12-one (24) upon treatment with hydrogen bromide in acetic acid. Alkylation with 3-chloro-3-methyl-1-butyne followed by Claisen rearrangement afforded 6-amino-3,3-dimethyl-3H,7H-benzo[a]pyrano[3,2-h]xanthen-7-one (25) and 5-amino-2,2-dimethyl-2H,6H-benzo[a]pyrano[2,3-i]xanthen-6-one (26). The new benzopyranoxanthone derivatives only displayed marginal antiproliferative activity when tested against L1210 and KB-3-1 cell lines. The only compounds found significantly active against L1210 cell line, 16 and 20, belong to the benzo[a]pyrano[3,2-h]xanthen-7-one series, which possess a pyran ring fused angularly onto the xanthone basic core.

Structure-activity relationship studies of new acronine analogues as suggested by molecular descriptors.

This work describes the results of an investigation on the structure-activity relationships of a series of acronine (CAS 7008-42-6) analogues which possess cytotoxic and antitumor activity. The results were obtained employing a commercially available software, which correlates structure and activity through calculations with different descriptors. The best results, obtained with electrostatic descriptors, led to propose new structures which present higher calculated activity than that of acronine.