Sequence analysis of porothramycin biosynthetic gene cluster.

The biosynthetic gene cluster of porothramycin, a sequence-selective DNA alkylating compound, was identified in the genome of producing strain Streptomyces albus subsp. albus (ATCC 39897) and sequentially characterized. A 39.7 kb long DNA region contains 27 putative genes, 18 of them revealing high similarity with homologous genes from biosynthetic gene cluster of closely related pyrrolobenzodiazepine (PBD) compound anthramycin. However, considering the structures of both compounds, the number of differences in the gene composition of compared biosynthetic gene clusters was unexpectedly high, indicating participation of alternative enzymes in biosynthesis of both porothramycin precursors, anthranilate, and branched L-proline derivative. Based on the sequence analysis of putative NRPS modules Por20 and Por21, we suppose that in porothramycin biosynthesis, the methylation of anthranilate unit occurs prior to the condensation reaction, while modifications of branched proline derivative, oxidation, and dimethylation of the side chain occur on already condensed PBD core. Corresponding two specific methyltransferase encoding genes por26 and por25 were identified in the porothramycin gene cluster. Surprisingly, also methyltransferase gene por18 homologous to orf19 from anthramycin biosynthesis was detected in porothramycin gene cluster even though the appropriate biosynthetic step is missing, as suggested by ultra high-performance liquid chromatography-diode array detection-mass spectrometry (UHPLC-DAD-MS) analysis of the product in the S. albus culture broth.

Usabamycins A-C: new anthramycin-type analogues from a marine-derived actinomycete.

New anthramycin-type analogues, designated usabamycin A-C (1, 2 and 3), have been isolated from cultures of Streptomyces sp. NPS853, a bacterium found in marine sediments. The structures of the new compounds were established on the basis of extensive spectroscopic analyses including 1D- and 2D-NMR ((1)H-(1)H COSY, HSQC, and HMBC) experiments. The usabamycins show weak inhibition of HeLa cell growth and selective inhibition of serotonin (5-hydroxytrypamine) 5-HT(2B) uptake.

Concise formal synthesis of porothramycins A and B via Zincke pyridinium ring-opening/ring-closing cascade.

Short formal syntheses of the antitumor antibiotics porothramycins A and B from a commercially available ester of the unnatural amino acid 3-(3-pyridyl)alanine are presented. A rearrangement cascade that presumably involves a Zincke-type pyridinium ring-opening followed by cyclization of a pendant nucleophilic amide generates the salient pyrroline ring of the alkaloids.

Synthesis and cytotoxicity on sensitive and doxorubicin-resistant cell lines of new pyrrolo[2,1-c][1,4]benzodiazepines related to anthramycin.

A new 7,8-methylenedioxy analogue (4) of (+)-porothramycin B (2) and its water-soluble sodium bisulfite derivative (15) have been synthesized in high yields and have been shown to exhibit high cytotoxic activities against several tumor cell lines. The new pyrrolo[2,1-c][1,4]benzodiazepine 4 was as effective against the resistant cell lines as against the doxorubicin-sensitive cell lines tested.

Heterocyclic analogs of DNA minor groove alkylating agents.

It is generally accepted that neoplastic transformation is related to genes alteration or oncogene activation. In particular, DNA minor groove binding drugs have been extensively studied through the years in order to influence the regulation of gene expression by means of specific interactions with DNA bases moieties. Pyrrolo[2,1-c],[1,4].benzodiazepines (PBDs), CC-1065 and distamycins are three classes of minor groove binders which showed interesting cytotoxicity profiles, refined through already reviewed processes of SAR studies. Among the modifications to the three families of antitumor compounds, heterocyclic substitutions have been extensively applied by many groups in order to either modify the reactivity profile or introduce extra interactions within the minor groove, thus changing the binding site or modulating the binding sequence. The updated material related to these modifications has been rationalised and ordered to offer an overview of the argument.

Cellular pharmacology of novel C8-linked anthramycin-based sequence-selective DNA minor groove cross-linking agents.

The cellular pharmacology of a series of C8-linked pyrrolobenzodiazepine dimers with polymethylene linkers of n = 3-6 (compounds 1-4) has been studied in a range of human tumour cell lines. The four compounds showed the same pattern of relative activity in five ovarian carcinoma cell lines and one cervical carcinoma cell line with the order of IC50 values of 1 < or = 3 < 4 < 2, which correlated with the previously demonstrated DNA interstrand cross-linking ability of the compounds in plasmid DNA. In human leukaemic K562 cells the agents produced a block in the G2/M phase of the cell cycle characteristic of cross-linking drugs, and extensive interstrand cross-linking was observed in cells by alkaline elution with no evidence of single-strand breaks. Cross-links continued to increase up to 24 h following a 1 h exposure to drug, and no repair was evident by 48 h. In a series of ovarian and cervical carcinoma cell lines with acquired resistance to cisplatin no cross-resistance to the most potent compound 1 was observed in two lines whose major mechanism of resistance to cisplatin was reduced platinum transport. Cross-resistance to 1 was observed in a cell line (A2780cisR) possessing elevated glutathione, and depletion of intracellular glutathione using D,L-buthionine-S,R-sulphoximine (BSO) from 10.25 nmol to 2.8 nmol 10(-6) cells reduced the level of resistance from 11-fold to 2-fold compared with sensitive cells. Cross-linking in the resistant cells was restored to 80% of the level in the parent line by BSO pretreatment. There was also a correlation between glutathione levels and sensitivity to 1 measured in several other ovarian cell lines. Compound 1 also showed cross-resistance in the doxorubicin-resistant cell line 41MdoxR and partial cross-resistance in CH1doxR cells. Both these lines possess elevated levels of p170 glycoprotein. Following treatment with 6 microM verapamil, the resistance in these lines decreased almost 2-fold and 8-fold respectively.

DNA binding properties of a new class of linked anthramycin analogs.

We have investigated the DNA binding properties of the anthramycin analogues 4, 5, and 6 using fluorescence spectroscopy. A considerable fluorescence enhancement occurs when pyrrolo [1,4] benzodiazepines (P[1,4]Bs) are covalently attached to duplex DNA, which was used to show that neither the presence of RNA, single-stranded DNA, or protein had any effect on the degree of fluorescence enhancement resulting from the incubation of 5 and 6 with DNA. The enhancement was found to be dependent on the presence of the imine functionality in each of the compounds. A wavelength of 320 nm was used to excite the chromophore and its emission wavelength maximum was 420 nm. Additionally, we have discovered that the P[1,4]B ring system exhibits exceptionally favorable fluorescence polarization anisotropy (FPA) decay characteristics. For these more detailed fluorescence measurements, we used the structurally simpler analogue 4,. The time resolved maximum FPA for 4 in glycerol at 25 degrees C is 0.28. This result indicates that the P[1,4]B family of antibiotics could serve as sensitive probes of DNA dynamics in the 0.1 to 35 ns time scale.

Two-dimensional NMR studies on the anthramycin-d(ATGCAT)2 adduct.

Two-dimensional NMR experiments were performed on the adduct of anthramycin with d(ATGCAT)2 to obtain the assignments of the nucleotide base and sugar protons as well as the anthramycin protons. Anthramycin is covalently attached to a guanine 2-amino group, forming the d(ATamGCAT).d(ATGCAT) modified duplex. The anthramycin protons in the minor groove exhibit NOEs to several nucleotide protons. The network of anthramycin-nucleotide NOEs and the measurement of the 10-Hz coupling constant between the anthramycin H11 and H11a protons shows that anthramycin is covalently attached as the S stereoisomer at the anthramycin C11 position with the side chain of anthramycin oriented toward the 5' end of the modified strand. The NOE data show that the anthramycin-modified duplex is in a right-handed conformation with all bases in an anti conformation. Analysis of the J1'-2' coupling constants for the resolved H1' resonances shows that the S-type conformation of the sugars is highly preferred.

Porothramycin, a new antibiotic of the anthramycin group: production, isolation, structure and biological activity.

A new antitumor antibiotic porothramycin was produced by a new strain of Streptomyces albus. The antibiotic was isolated in two active forms, the natural free hydroxyl form (porothramycin A) or the crystalline methyl ether form (porothramycin B) depending upon the isolation process used. Structural studies established that porothramycin is a new member of the pyrrolo[1,4]benzodiazepine group antibiotics having only one substituent on the benzene ring. The antibiotic exhibited antimicrobial activity against Gram-positive bacteria and anaerobes and significantly prolonged the survival times of mice implanted with experimental tumors.

Abbeymycin, a new anthramycin-type antibiotic produced by a streptomycete.

A new antibiotic, abbeymycin, has been isolated from Streptomyces sp. AB-999F-52. The structure of abbeymycin was assigned on the basis of NMR, mass spectrometric and UV spectral data. Abbeymycin has weak activity against a limited number of anaerobic bacteria.

[Immunomodulation by antitumor antibiotics].

Antibiotics exhibiting immunomodulatory activities were found among antitumor antibiotics. These antibiotics had antileukemic activity. Neothramycin and mazethramycin, which are classified as anthramycin-group antibiotics, activated macrophages so that they became antitumor effector cells. Aclacinomycin and oxanosine inhibited generation of suppressor cells in tumor-bearing mice and oxanosine enhanced antitumor effector cells. Therapy using spergualin produced specific antitumor immunity in cured mice. The immunomodulatory activities of auromomycin and bactobolin were also reported.

Bicyclic and tricyclic analogues of anthramycin.

As analogues of pyrrolo[2,1-c][1,4]benzodiazepine antitumor antibiotics, such as anthramycin and tomaymycin, several benzo[1,4]diazepine imines and carbinolamine ethers were prepared and tested in vivo against P388 leukemia. Two different synthetic approaches, namely, a reduction of an aromatic nitro group with a concomitant cyclization and a reduction of a lactam, were employed to generate an imine or a carbinolamine moiety. Bicyclic analogues 6a', 6f, and 6g were found to be active, indicating that the pyrroline ring of anthramycin is not an absolute necessity for the antitumor activity. Compound 6g, 3,4-dihydro-9-hydroxy-4-propargyl-5H-1,4-benzodiazepin-5-one, was at least as active as neothramycin although it was 5 times less potent. Among the tricyclic analogues, compounds 5, 7a, and 8b were active against P388 leukemia, and they generally appear to be more potent than bicyclic analogues.

Chemical conversion of anthramycin 11-methyl ether to didehydroanhydroanthramycin and its utilization in studies of the biosynthesis and mechanism of action of anthramycin.

Reaction of anthramycin 11-methyl ether (AME) with trifluoroacetic acid results in formation of (1,11a)-didehydroanhydroanthramycin (DAA). Anthramycin biosynthetically labelled from DL-[3'RS(3'-3H)]; DL-[3'S(3'-3H)] and DL-[3'R(3'-3H)] tyrosine each lose approximately 50% of their tritium during this conversion to DAA confirming the labelling pattern of 3'-tritiated species of tyrosine in AME. As expected negligible losses of tritium occurred from AME biosynthetically labelled fron L-[2- or 6-3H] or L-[3- or 5-3H]tyrosine. DAA did not form a stable adduct with DNA in accord with the postulated mechanism of action of anthramycin.

[Research on agents with antineoplastic activity. LXIII. Anthramycin and analogous compounds. X. Synthesis of 11-phenyl-5H-pyrrolo[2,1-c] [1,4] benzodiazepine derivatives]. / Ricerche su sostanze ad attività antiblastica. Nota LXIII - Antramicina e composti analoghi. Parte X: Sintesi di derivati della 11-fenil-5H-pirrolo[2,1-c] [1,4] benzodiazepina.

Reaction between arolychlorides and 1-(2-aminobenzyl)-2-cyanopyrrole afforded the corresponding aroylamides, which were transformed by intramolecular cyclization into 11-aryl-3-cyano-5H-pyrrolo[2,1-c] [1,4] benzodiazepines. Hydrolysis of cyanoderivatives furnished the corresponding amides or acids depending on the reaction conditions. Decarboxylation and reduction of some derivatives to afford 11-aryl-5H-pyrrolo[2,1-c] [1,4] benzodiazepines and 11-aryl-3-cyano-10,11-dihydro-5H-pyrrolo[2,1-c] [1,4] benzodiazepines are described.

[Studies on substances with antiblastic activity. IX. Anthramycin and analogs. IX. Synthesis of 7-methoxy-8-hydroxy-10,11-dihydro-5H-pyrrolo[2,1-c] [1,4] benzodiazepine and other compounds related to oxotomaymycin]. / Richerche su sotanze ad attivtià antiblastica. Nota LX - Antramicina e composti analoghi. Parte IX: Sintesi della 7-metossi-8-idrossi-10,11-diidro-5H-pirrolo[2,4-c] [1,4]benzodiazepina e di altri composti correlati con la oxotomaimicina.

The synthesis of some pyrrolobenzodiazepine derivatives related to oxotomaymycin, an antibiotic recovered together with tomaymycin from fermentation broths of Streptomyces achromogenes var. tomaymycetics, is described. Reaction between 2-nitro-4-benzyloxy-5-methoxybenzylbromide and pyrrole-2-carboxyaldehyde afforded 1-(2-nitro-4-benzyloxy-5-methoxybenzyl)pyrrole-2-carboxyaldehyde. Catalytic reduction of this compound with hydrogen in the presence of Pd/C gave 10,11-dihydro-8-hydroxy-7-methoxy-5H-pyrrolo[2.1-c] [1,4]benzodiazepine. Amides obtained from condensation between 2-nitro-4-benzyloxy-5-methoxybenzoic acid chloride and proline or hydroxyproline were reduced catalytically to 2,3-dihydro-8-hydroxy-7-methoxy-1H-pyrrolo [2,1-c] [1,4]benzodiazepine-5,11 (10H, 11aH)-dione and its 2-hydroxyderivative respectively. The synthesis of 10,11-dihydro-8-hydroxy-9-methoxy-5-pyrrolo [2,1-c] [1,4]benzodiazepine is also reported.

[Study on substances with antiblastic activity. LIX - Anthramycin and analogs. VIII : synthesis of derivatives of 4H-pyrrolo/1,2-a/[1,5]benzodiazepine]. / Ricerche su sostanze ad attività antiblastica Nota LIX - Antramicina e composti analoghi. Parte VIII: Sintesi di derivati della 4H-pirrolo [1,2-a] [1,5]benzodiazepina

Preparation of 4H-pyrrolo[1,2-a][1,5]benzodiazepine derivatives related to the antitumoral antibiotic anthramycin, a derivative of 5H-pyrrolo[2,1-c] [1,4]benzodiazepine, is reported. Reaction between 1-(o-acetamidophenyl)-2-dimethylaminomethylpyrrole iodomethylate and potassium cyanide afforded 4,6-dihydro-5H-pyrrolo[1,2-a][1,5]benzodiazepine-5-one, which was then reduced to 5,6-dihydro-4H-pyrrolo[1,2-a][1,5]benzodiazepine by the action of lithium aluminum hydride. Some 6-acylderivatives of the latter compound are also described. The Vilsmeier-Haack reaction on 6-acetyl-5,6-dihydro-4H-pyrrolo[1,2-a][1,5]benzodiazepine furnished the corresponding 1-formyl derivative which was then condensed with ethyl cyanoacetate to give the related compound with the acrylic moiety.