Search

Lavendamycin methyl ester (LME) is a derivative of a highly functionalized aminoquinone alkaloid lavendamycin and could be used as a scaffold for novel anticancer agent development. This work demonstrated LME production by cultivation of an engineered strain of Streptomyces flocculus CGMCC4.1223 ΔstnB1, while the wild-type strain did not produce. To enhance its production, the effect of shear stress and oxygen supply on ΔstnB1 strain cultivation was investigated in detail. In flask culture, when the shaking speed increased from 150 to 220 rpm, the mycelium was altered from a large pellet to a filamentous hypha, and the LME production was almost doubled, while no significant differences were observed among varied filling volumes, which implied a crucial role of shear stress in the morphology and LME production. To confirm this suggestion, experiments with agitation speed ranging from 400 to 1,000 rpm at a fixed aeration rate of 1.0 vvm were conducted in a stirred tank bioreactor. It was found that the morphology became more hairy with reduced pellet size, and the LME production was enhanced threefolds when the agitation speed increased from 400 to 800 rpm. Further experiments by varying initial k L a value at the same agitation speed indicated that oxygen supply only slightly affected the physiological status of ΔstnB1 strain. Altogether, shear stress was identified as a major factor affecting the cell morphology and LME production. The work would be helpful to the production of LME and other secondary metabolites by filamentous microorganism cultivation.

Streptonigrin (STN, 1) is a highly functionalized aminoquinone alkaloid with broad and potent antitumor activity. Here, we reported the biosynthetic gene cluster of STN identified by genome scanning of a STN producer Streptomyces flocculus CGMCC4.1223. This cluster consists of 48 genes determined by a series of gene inactivations. On the basis of the structures of intermediates and shunt products accumulated from five specific gene inactivation mutants and feeding experiments, the biosynthetic pathway was proposed, and the sequence of tailoring steps was preliminarily determined. In this pathway, a cryptic methylation of lavendamycin was genetically and biochemically characterized to be catalyzed by a leucine carboxyl methyltransferase StnF2. A [2Fe-2S](2+) cluster-containing aromatic ring dioxygenase StnB1/B2 system was biochemically characterized to catalyze a regiospecific cleavage of the N-C8' bond of the indole ring of the methyl ester of lavendamycin. This work provides opportunities to illuminate the enzymology of novel reactions involved in this pathway and to create, using genetic and chemo-enzymatic methods, new streptonigrinoid analogues as potential therapeutic agents.

The total synthesis of the bacterial-derived, pentacyclic, antitumor antibiotic lavendamycin has been achieved through a highly convergent strategy. The key step of this synthesis is a ruthenium-catalyzed [2+2+2] cycloaddition of an electron-deficient nitrile to an alkynyl-ynamide to prepare the carboline scaffold. The elaborate cycloaddition substrate is obtained in few steps by an N-ethynylation using alkynyliodonium salt chemistry and two palladium-catalyzed cross-coupling reactions. An efficient synthesis of a halogenated quinoline-5,8-dione building block starting from hydroquinone is presented.

A series of lavendamycin analogues with two, three or four substituents at the C-6, C-7 N, C-2′, C-3′ and C-11′ positions were synthesized via short and efficient methods and evaluated as potential NAD(P)H:quinone oxidoreductase (NQO1)-directed antitumor agents. The compounds were prepared through Pictet-Spengler condensation of the desired 2-formylquinoline-5,8-diones with the required tryptophans followed by further needed transformations. Metabolism and toxicity studies demonstrated that the best substrates for NQO1 were also the most selectively toxic to NQO1-rich tumor cells compared to NQO1-deficient tumor cells.

Indole-substituted N-propargylamides undergo a gold(III)-catalyzed cyclization to give oxazoles or β-carbolinones, depending on the substitution pattern at the amide nitrogen. Secondary amides furnished oxazoles via a 5-exo-dig cyclization, while tertiary indole-2-carboxamides cycloisomerized to give 2,9-dihydro-β-carbolin-1-ones upon treatment with catalytic amounts of gold(III) chloride. An optimized procedure was developed to prepare several new N-benzyl-β-carbolinones as well as the corresponding β-carbolines, which are of interest as core structures found in various natural products such as the harman, ervolanine, and lavendamycin class of alkaloids.

A 1H69 crystal structure-based in silico model of the NAD(P)H:quinone oxidoreductase 1 (NQO1) active site has been developed to facilitate NQO1-directed lavendamycin antitumor agent development. Lavendamycin analogues were designed as NQO1 substrates utilizing structure-based design criteria. Computational docking studies were performed using the model to predict NQO1 substrate specificity. Designed N-acyllavendamycin esters and amides were synthesized by Pictet-Spengler condensation. Metabolism and cytotoxicity studies were performed on the analogues with recombinant human NQO1 and human colon adenocarcinoma cells (NQO1-deficient BE and NQO1-rich BE-NQ). Docking and biological data were found to be correlated where analogues 12, 13, 14, 15, and 16 were categorized as good, poor, poor, poor, and good NQO1 substrates, respectively. Our results demonstrated that the ligand design criteria were valid, resulting in the discovery of two good NQO1 substrates. The observed consistency between the docking and biological data suggests that the model possesses practical predictive power.

Novel lavendamycins including two water soluble derivatives were synthesized via short and efficient methods. Pictet-Spengler condensation of 7-N-acylamino-2-formylquinoline-5,8-diones with tryptophans produced lavendamycin esters or amides 11-17. Lavendamycins 18-21 were obtained, respectively, by further transformations of 13-15 and 17. Several lavendamycins were found to be potent HIV reverse transcriptase inhibitors with very low toxicity in vitro and in vivo. Several compounds also acted either additively or synergistically to inhibit enzyme activity together with AZT-triphosphate.

Highly functionalized 4-bromopyridines were prepared and found to undergo fluoride-promoted, Pd-catalyzed cross-coupling with aryltrialkoxysilanes to give sterically demanding biaryls. The 3-nitro-4-bromopyridine derivative coupled in good yield with TBAT (tetrabutylammonium triphenyldifluorosilicate) to provide a biaryl adduct that serves as a model system for the total synthesis of the antitumor antibiotics streptonigrin and lavendamycin. [reaction: see text]

International audience

A convergent synthesis of lavendamycin analogues has been accomplished by using A3 coupling reaction between carboline aldehydes, anilines, and phenylacetylenes. Our approach features the use of the ionic liquids as an environmentally benign solvent medium and synthesis of lavendamycin analogues with diverse substitution pattern. Additionally, the formation of α-dihydropyrido-β-carboline was observed during the reaction of α-formyl-β-carboline, aniline, and ethylpropiolate.

A series of 7-amino- and 7-acetamidoquinoline-5,8-diones with aryl substituents at the 2-position were synthesized, characterized, and evaluated as potential NAD(P)H:quinone oxidoreductase (NQO1) -directed antitumor agents. The synthesis of lavendamycin analogues is illustrated. Metabolism studies demonstrated that 7-amino analogues were generally better substrates for NQO1 than 7-amido analogues, as were compounds with smaller heteroaromatic substituents at the C-2 position. Surprisingly, only two compounds, 7-acetamido-2-(8'-quinolinyl)quinoline-5,8-dione (11) and 7-amino-2-(2-pyridinyl)quinoline-5,8-dione (23), showed selective cytotoxicity toward the NQO1-expressing MDA468-NQ16 breast cancer cells versus the NQO1-null MDA468-WT cells. For all other compounds, NQO1 protected against quinoline-5,8-dione cytotoxicity. Compound 22 showed potent activity against human breast cancer cells expressing or not expressing NQO1, with respective IC50 values of 190 nM and 140 nM and a low NQO1-mediated reduction rate, which suggests that the mode of action of 22 differs from that of lavendamycin and involves an unidentified target(s).

The synthesis of the CD ring system of Streptonigrin and Lavendamycin alkaloid analogues by cross-coupling under Suzuki's conditions has been studied. Steric hindrance is the main problem. It has been solved either by using strong bases or working in a sealed tube under pressure.

The novel 7-(N-formyl-, 7-(N-acetyl-, and 7-(N-isobutyrylamino)-2-methylquinoline-5,8-diones were synthesized in excellent overall yields in three steps via the nitration of the commercially available 8-hydroxy-2-methylquinoline followed by a reduction-acylation step and then oxidation. Acid hydrolysis of 7-(N-acetylamino)-2-methylquinoline-5,8-dione (14a) afforded the novel 7-aminoquinoline-5,8-dione 7 in excellent yields. Due to our efficient preparation of dione 14a, we now report a short and practical method for the total synthesis of the potent antitumor agent lavendamycin methyl ester (1b) with an excellent overall yield.

A convergent formal synthesis of lavendamycin methyl ester and synthesis of its analogues have been delineated through the Povarov approach. This protocol is also applied to the formal synthesis of nitramarine (3) in good yield.

Aza Wittig reaction of iminophosphorane derived from ethyl α-azido-β-(3-indolyl)butyrate and 8-benzyloxy-7-bromo-2-formylquinoline is the key step in a new synthesis of lavendamycin ethyl ester.

A range of pyridine and quinoline carboxaldehydes have been prepared by palladium catalysed carbonylation from the corresponding bromides and triflates.

An efficient route to a key intermediate in the synthesis of lavendamycin from a suitably substituted 2-chloroquino-line derivative via aminocarbonylation with tryptophan methyl ester as nucleophile, is reported.

A convergent synthesis of streptonigrin and lavendamycin analogues incorporating a quinoline-5,8-dione structure is reported. The approach is based on our synthetic methodology which involves such reactions as metalation, heteroring cross-coupling and oxidative demethylation.

A three-steps approach to the lavendamycin skeleton from benzene, pyridine and quinoline blocks is described. It is based on a new synthetic methodology for the preparation of α-substituted β-carbolines which involves such reactions as Directed Ortho Metalation and Heteroring Cross-Coupling.

Novel cytocidal compounds designated oxopropalines A, B, D, E and G were isolated from the fermentation of an actinomycete named Streptomyces sp. G324, a strain that also produced an antitumor antibiotic, lavendamycin. All these compounds possessed a beta-carboline chromophore. The structures of the oxopropalines were elucidated by several NMR spectral analyses and other spectroscopic experiments.

Aza-Wittig reaction of iminophosphorane 3, derived from ethyl a-azido-β-(3-indolyl) propenoate and tri-phenylphosphine, with 2-formylpyrrole and 2-formylquinolines leads to Eudistomins A and M and Lavendamycin derivatives respectively.

A three-steps approach to the lavendamycin skeleton from benzene, pyridine and quinoline blocks is described. It is based on a new synthetic methodology for the preparation of α-substituted β-carbolines which involves such reactions as Directed Ortho Metalation and Heteroring Cross-Coupling.

A convergent synthesis of streptonigrin and lavendamycin analogues incorporating a quinoline-5,8-dione structure is reported. The approach is based on our synthetic methodology which involves such reactions as metalation, heteroring cross-coupling and oxidative demethylation.

Lavendamycin methyl ester (2), an antitumor antibiotic, was synthesized by a practical and short route in an excellent overallyield of 33% from known starting materials. Pictet-Spengler condensation of 7-acetamido-2-formylquinoline-5,8-dione (4) with the methyl ester of (2RS,3SR)-β-methyltryptophan (5) followed by hydrolysis afforded 2. Aldehyde 4 was prepared by the oxidation of 7-acetamido-2-methylquinoline-5,8-dione (9). Dione 9 was obtained via the Diels-Alder condensation of the novel 1-[(tert-butyldimethylsilyl)oxy]-2-methyl-1-aza-1,3-butadiene (7) with 2-acetamido-6-bromobenzene-1,4-dione (8)

The novel 7-(N-formyl-, 7-(N-acetyl-, and 7-(N-isobutyrylamino)-2-methylquinoline-5,8-diones were synthesized in excellent overall yields in three steps via the nitration of the commercially available 8-hydroxy-2-methylquinoline followed by a reduction−acylation step and then oxidation. Acid hydrolysis of 7-(N-acetylamino)-2-methylquinoline-5,8-dione (14a) afforded the novel 7-aminoquinoline-5,8-dione 7 in excellent yields. Due to our efficient preparation of dione 14a, we now report a short and practical method for the total synthesis of the potent antitumor agent lavendamycin methyl ester (1b) with an excellent overall yield.

Indole-substituted N-propargylamides undergo a gold(III)-catalyzed cyclization to give oxazoles or β-carbolinones, depending on the substitution pattern at the amide nitrogen. Secondary amides furnished oxazoles via a 5-exo-dig cyclization, while tertiary indole-2-carboxamides cycloisomerized to give 2,9-dihydro-β-carbolin-1-ones upon treatment with catalytic amounts of gold(III) chloride. An optimized procedure was developed to prepare several new N-benzyl-β-carbolinones as well as the corresponding β-carbolines, which are of interest as core structures found in various natural products such as the harman, ervolanine, and lavendamycin class of alkaloids.

An efficient route to a key intermediate in the synthesis of lavendamycin from a suitably substituted 2-chloroquinoline derivative via aminocarbonylation with tryptophan methyl ester as nucleophile, is reported.

Aza-Wittig reaction of iminophosphorane 3, derived from ethyl a-azido-β-(3-indolyl) propenoate and tri-phenylphosphine, with 2-formylpyrrole and 2-formylquinolines leads to Eudistomins A and M and Lavendamycin derivatives respectively.

ABC analogues of the antitumor antibiotic lavendamycin, which contain the key metal chelation site and redox-active quinone unit essential for biological activity, were prepared via the palladium(0)-catalyzed cross-coupling reaction of various 2-haloheteroaromatics with 2-stannylated pyridines and quinolines. Using the Stille reaction, 2-bromo substituted quinolines and 1-bromoisoquinolines were found to undergo efficient coupling with 2-pyridinylstannanes to provide unsymmetrical heterobiaryl derivatives. While the Stille reaction using the reverse coupling partners (i.e., 2-quinolinylstannanes and haloheteroaromatics) had not received much attention in the literature, we found that this alternative coupling reaction efficiently provided several new heterobiaryl derivatives. The gold-catalyzed intramolecular cycloisomerization of N-(prop-2-ynyl)-1H-indole-2-carboxamide smoothly afforded a beta-carbolinone derivative that was subsequently used for a Pd(0)-catalyzed cross-coupling directed toward the synthesis of lavendamycin analogues.

A series of N-propargylindole-2-carboxamides were found to undergo a AuCl 3-catalyzed cycloisomerization to give beta-carbolinones in high yield. The corresponding beta-chlorocarboline derivative was prepared and used for Pd(0)-catalyzed cross-coupling chemistry directed toward the synthesis of lavendamycin analogues.

We review some reactions devised in our laboratory for the rapid assembly of pyridines and pyridones. Applications of the new methods in the total synthesis of lavendamycin, pyridoacridine and phenanthroizidine alkaloids (pyridine chemistry), and of camptothecin, nothapodytine B and streptonigrone (pyridone-forming reactions) are described.

Friedlander reaction between methyl acetoacetate and 2,4-diaminobenzaldehyde provided quinoline 11. Subsequent tosylation, reduction, silylation, and then oxidation led to aldehyde 15. The latter was subjected to a Pictet–Spengler reaction with tryptophan methyl ester that yielded product 16, and then desilylation gave the lavendamycin analogue 17. This compound was oxidized by Dess–Martin periodinane, and the cyclized derivative 18 was obtained via a hemiaminal intermediate. The same sequence from 2,4-diamino-5-methoxybenzaldehyde or from (2,4-diaminophenyl)propan-3-one led to compounds 30 and 31, or 40 and 41, respectively.

A series of 7-N-acyllavendamycins with zero, one or two substituents at the C-2', C-3', and C-11' were synthesized through short and efficient methods. Pictet-Spengler condensation of 7-N-acylamino-2-formylquinoline-5,8-diones with tryptamine or tryptophans produced the desired lavendamycins. Screening data on a panel of three ras oncogene-transformed cell lines and the non-transformed parent cell line showed that a significant number of these analogues are potent antitumor agents and appear to be particularly active against K-ras transformed cells. Compared with the corresponding quinolinediones, these novel lavendamycins are much more inhibitory toward the transformed cells indicating that the beta-carboline moiety of the lavendamycin analogues plays an important role in its potency and selective toxicity.

The naphthoquinone skeleton is found in many natural products and has been employed as a synthetic intermediate for the preparation of numerous heterocyclic compounds with interesting biological properties such as antitumor, antibacterial, antifungal and antiinflammatory agents. The quinone core of streptonigrin and lavendamycin has been proposed to be a determining factor in their antitumor activity. Recently, the linearly substituted quinolinediones have revealed the importance of the quinone framework for potent antitumor activity against the cell lines. Furthermore, Cheng et al. designed the fused benzofuroquinone that possesses a characteristic “2-phenylnaphthalene-type” structural framework in which the two rings are coplanar. They found that the designed benzo[b]naphtho[2,3-d]furan6,11-dione derivatives exhibited strong inhibitory activity throughout the entire series of cancer cell lines. A decade ago, dinaphtho[1,2-b;2',3'-d]furan-7,12-dione 3 was isolated from stems of Paulownia tomentos, a perennial tree widely distributed in China, Japan, and Korea. The naphthofuroquinone 3 significantly reduced viral cytopathic effect in a standard in vitro antiviral assay with HeLa cells. It is also interesting that this structural pattern is commonly observed in other biologically active compounds including camptothecin, ellipticine, and mappicine, a class of DNA Topoisomerase-I (Topo-I) inhibitors that exhibit efficious antitumor activity. Here, we would like to report the synthesis of naphthofuroquinone derivatives, and their DNA TopoI inhibition and cytotoxicity against various cancer cell lines.

Novel lavendamycin analogues with various substituents were synthesized and evaluated as potential NAD(P)H:quinone oxidoreductase (NQO1)-directed antitumor agents. Pictet-Spengler condensation of quinoline- or quninoline-5,8-dione aldehydes with tryptamine or tryptophans yielded the lavendamycins. Metabolism studies with recombinant human NQO1 revealed that addition of NH2 and CH2OH groups at the quinolinedione-7-position and indolopyridine-2'-position had the greatest positive impact on substrate specificity. The best and poorest substrates were 37 (2'-CH2OH-7-NH2 derivative) and 31 (2'-CONH2-7-NHCOC3H7-n derivative) with reduction rates of 263 +/- 30 and 0.1 +/- 0.1 micromol/min/mg NQO1, respectively. Cytotoxicity toward human colon adenocarcinoma cells was determined for the lavendamycins. The best substrates for NQO1 were also the most selectively toxic to the NQO1-rich BE-NQ cells compared to NQO1-deficient BE-WT cells with 37 as the most selective. Molecular docking supported a model in which the best substrates were capable of efficient hydrogen-bonding interactions with key residues of the active site along with hydride ion reception.

Lavendamycin methyl ester (2), an antitumor antibiotic, was synthesized by a practical and short route in an excellent overallyield of 33% from known starting materials. Pictet-Spengler condensation of 7-acetamido-2-formylquinoline-5,8-dione (4) with the methyl ester of (2RS,3SR)-β-methyltryptophan (5) followed by hydrolysis afforded 2. Aldehyde 4 was prepared by the oxidation of 7-acetamido-2-methylquinoline-5,8-dione (9). Dione 9 was obtained via the Diels-Alder condensation of the novel 1-[(tert-butyldimethylsilyl)oxy]-2-methyl-1-aza-1,3-butadiene (7) with 2-acetamido-6-bromobenzene-1,4-dione (8)

In the course of our investigation aimed at the discovery of novel antitumor antibiotics from microorganisms, Streptomyces sp. G324 was found to produce the antitumor antibiotic, lavendamycin, and also, to yield the novel beta-carboline compounds, oxopropalines. We isolated five compounds as oxopropalines A, B, D, E and G. Oxopropalines B, D and G showed cytocidal activities against human or murine tumor cell lines in vitro.

The isolation of streptonigrin and its structural elucidation by Rao, Bieman and Woodward in 1960 attracted the attention of many synthetic chemists. However, it took two decades for the first synthesis to be accomplished. Subsequent isolation of lavendamycin, fredericamycin and recently cervinomycin belonging to the same class, with pronounced anti-tumor activity, were reported during this decade. All these molecules, except cervinomycin, have been synthesised by more than two groups.

We review some reactions devised in our laboratory for the rapid assembly of pyridines and pyridones. Applications of the new methods in the total synthesis of lavendamycin, pyridoacridine and phenanthroizidine alkaloids (pyridine chemistry), and of camptothecin, nothapodytine B and streptonigrone (pyridone-forming reactions) are described.

A modified Knoevenagel–Stobbe pyridine formation and a thermolytic nitrene insertion are the key steps in a practical new synthesis of lavendamycin methyl ester.

A five-step approach to the preparation of the β-carboline CDE ring system of lavendamycin is detailed and is based on: (1) thermal cycloaddition of 3,5,6-tricarbomethoxy-1,2,4-triazine with the pyrrolidine enamine of o-bromopropiophenone followed by (2) implementation of a newly developed palladium (O) mediated β-carboline synthesis.

Cycloaddition de Diels Alder de triazine-1,2,4 tricarboxylate de triethyle avec des enamines conduit aux aryl-4 pyridinetricarboxylates-2,3,6 de triethyle; le methyl-4 β-carbolinedicarboxylate-1,3 de dimethyle est ensuite obtenu par cyclisation en presence d'un complexe de Pd(0) de l'amino-3 bromo-2' phenyl-4 methyl-5 pyridinedicarboxylate-2,6. Preparation des amino-7 et amino-7 [pyridyl-2]-2 quinoleinequinones-5,8

A regiospecific and convergent synthesis of Lavendamycin (1) starting from 8-hydroxyquinoline and indole via Bischler-Napieralski cyclisation is described.