Diazo Group Electrophilicity in Kinamycins and Lomaiviticin A:  Potential Insights into the Molecular Mechanism of Antibacterial and Antitumor Activity

Laufer, Radoslaw; Dmitrienko, Gary I.

doi:10.1021/ja0167809

Cited by 87 publications

(44 citation statements)

References 17 publications

(20 reference statements)

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“…In the presence of a cupric acetate oxidant the kinamycin F analog 9-diazofluorene was able to nick DNA [11] which suggests possible oxidative activation. In other prior chemical studies we showed that the diazo group of isoprekinamycin, an analog of kinamycin A, reacted with the nucleophile 2-naphthol, which is known to have good reactivity towards aryldiazonium salts, to yield the azo-coupled product [12]. Collectively these observations led us to the hypothesis that the kinamycins represent variants of the same pharmacophore in which the diazo group, with its diazonium-like character, has unusual biological reactivity and plays a key role in their action as cytotoxic agents.…”

Section: Introductionmentioning

confidence: 97%

Mechanism of the cytotoxicity of the diazoparaquinone antitumor antibiotic kinamycin F

O’Hara

Patel

et al. 2007

Free Radical Biology and Medicine

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The bacterial metabolite kinamycin F, which is being investigated as a potent antitumor agent, contains an unusual and potentially reactive diazo group as well as a paraquinone and a phenol functional group. Kinamycin F reacted with glutathione (GSH) in a complex series of reactions which suggested that kinamycin F may have its cytotoxicity modulated by GSH. Consistent with this idea 2-oxo-4-thiazolidinecarboxylic acid treatment to increase cellular GSH levels and buthionine sulfoximine treatment to decrease GSH levels resulted in decreased and increased kinamycin F cytotoxicity, respectively, in K562 leukemia cells. Kinamycin F weakly bound to DNA and induced DNA damage in K562 cells that was independent of GSH levels. The GSH-promoted DNA nicking induced by kinamycin F in vitro was attenuated by deferoxamine, dimethyl sulfoxide, and by catalase, which indicated that DNA damage initiated by this agent occurred in an iron-, hydrogen peroxideand hydroxyl radical-dependent manner. Electron paramagnetic resonance spectroscopy experiments showed that the GSH/kinamycin F system produced a semiquinone free radical and that the hydrogen peroxide/peroxidase/kinamycin F system generated a phenoxyl free radical. In conclusion, the results indicated that kinamycin F cytotoxicity may be due to reductive and/or peroxidative activation to produce DNA-and protein-damaging species.

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Section: Introductionmentioning

confidence: 97%

Mechanism of the cytotoxicity of the diazoparaquinone antitumor antibiotic kinamycin F

O’Hara

Patel

et al. 2007

Free Radical Biology and Medicine

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“…The couplings of arenediazonium ions with thiolates to generate diazosulfides and their decomposition to form aryl radicals are well-known. 35 Although the diazofluorene is formally not an arenediazonium ion, Dmitrienko 30 had shown that this functional group displays enhanced (diazonium-like) electrophilicity. Hydrogen atom abstraction from the deoxy-ribose backbone initiates SSB formation with production of (–)-lomaiviticin C ( 6 ).…”

Section: The Dimeric Diazofluorene Is Required For Potent Cytotoxicitymentioning

confidence: 99%

The Mechanism of Action of (−)-Lomaiviticin A

Herzon

2017

Acc. Chem. Res.

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CONSPECTUS (–)-Lomaiviticin A (4) is a complex C2-symmetric bacterial metabolite that contains two diazofluorene functional groups. The diazofluorene consists of naphthoquinone, cyclo-pentadiene, and diazo substituents fused through a σ- and π-bonding network. Additionally, (–)-lomaiviticin A (4) is a potent cytotoxin, with half-maximal inhibitory potency (IC50) values in the low nanomolar range against many cancer cell lines. Because of limitations in supply, its mechanism of action had remained a “black box” since its isolation in the early 2000s. In this Account, I describe how studies directed toward the total synthesis of (–)-lomaiviticin A (4) provided a platform to elucidate the emergent properties of this metabolite and thereby connect chemical reactivity with cellular phenotype. We first developed a convergent strategy to prepare the diazofluorene (9 + 10 → 13). We then adapted this chemistry to the synthesis of lomaiviticin aglycon (21/22) and the natural monomeric diazofluorene (–)-kinamycin F (3). The key step in the lomaiviticin aglycon (21/22) synthesis involved the stereoselective oxidative coupling of two monomeric diazofluorenes (2 × 18→ 20) to establish the cojoining carbon–carbon bond of the target. As the absolute stereochemistry of the aglycon and carbohydrate residues of (–)-lomaiviticin A (4) were unknown, we developed a semisynthetic route to the metabolite that proceeds in one step and 42% yield by diazo transfer to the more abundant isolate (–)-lomaiviticin C (6). This allowed us to complete the stereochemical assignment of (–)-lomaiviticin A (4) and provided a renewable source of material. Using this material, we established that the remarkable cytotoxic effects of (–)-lomaiviticin A (4) derive from the induction of highly toxic double-strand breaks (DSBs) in DNA. At the molecular level, 1,7-nucleophilic additions to each electrophilic diazofluorene trigger homolytic decomposition pathways that produce sp2 radicals at the carbon atoms of each diazo group. These radicals abstract hydrogen atoms from the deoxyribose of DNA, a process known to initiate strand cleavage. NMR spectroscopy and molecular mechanics simulations were used to elucidate the mode of DNA binding. These studies showed that both diazofluorenes of (–)-lomaiviticin A (4) penetrate into the duplex. This mode of non-covalent binding places each diazo carbon atom in close proximity to each DNA strand. Throughout these studies, isolates containing one diazofluorene, such as (–)-lomaiviticin C (6) and (–)-kinamycin C (2), were used as controls. Consistent with our mechanistic model, these compounds do not induce DSBs in DNA and are several orders of magnitude less potent. Reactivity studies suggest that (–)-lomaiviticin A (4) is more electrophilic than simple monomeric diazofluorenes. We attribute this to through-space delocalization of the developing negative charge in the transition state for 1,7-addition. Consistent with this mechanism of action, (–)-lomaiviticin A (4) displays selective low-picomolar potencies toward DNA ...

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“…In order to study the molecular mechanism of the antitumor activity of kinamycins [73], Dmitrienko synthesized a structurally simplified analogue of kinamycin involving a Pd-catalyzed C-N bond-forming process. Utilizing the Pd/1 catalyst system, benzylamine was coupled with an aryl bromide to give the secondary amine VIII and debenzylated product IX in a combined 95 % yield.…”

Section: Primary Aliphatic Aminesmentioning

confidence: 99%