Microwave Assisted Synthesis of Pyridophenoxazinones, a Class of Powerful Antiproliferative Compounds

In order to obtain new antiproliferative compounds good for acting through the forementioned mechanisms, including DNA intercalation and topoisomerase inhibition, our attention was focused on the derivatives of pyridophenoxazinone (PPH, 1 R=H) system, an iminoquinone containing a planar tetracyclic system suitable for intercalating DNA G-C base pairs in a site specific mode(2). Namely, we designed, after molecular modeling calculations, PPH carboxyamide derivatives holding at C-9 and C-10 positions an amino acidic chain or a sugar. Unfortunately, the real obstacle to the availability of such molecule was represented by their synthesis. Therefore, in our opinion it seems to be worthwhile to report a new microwave (μW) assisted synthetic procedure to prepare PPH carboxyamides. In order to assess the validity of our method, we applied the procedure to the synthesis of variously substituted PPHs 1 and received evidence that microwave irradiation enables the preparation of those compounds in high yields and short reaction times

Thiazolidin-4-one formation. Mechanistic and synthetic aspects of the reaction of imines and mercaptoacetic acid under microwave and conventional heating

Microwave irradiation of a mixture of benzylidene-anilines and mercaptoacetic acid in benzene gives 1,3-thiazolidin-4- ones in very high yield (65–90%), whereas the same reaction performed through using the conventional method, at refluxtemperature, requires a much longer time and gives a much lower yield (25–69%). This difference seems to be due to someintermediates and by-products formed during the conventional reaction. On the basis of 1H NMR studies, two differentmechanisms, acting in benzene and in DMF, respectively, have been hypothesized for the thiazolidin-4-one system formation

Antitumor Agents. 5. Synthesis, Structure-Activity Relationships, and Biological Evaluation of Dimethyl-5H-pyridophenoxazin-5-ones, Tetrahydro-5H-benzopyridophenoxazin-5-ones, and 5H-Benzopyridophenoxazin-5-ones with Potent Antiproliferative Activity

New antiproliferative compounds, dimethyl-5H-pyrido[3,2-a]phenoxazin-5-ones (1-6), tetrahydro-5Hbenzopyrido[ 2,3-j]phenoxazin-5-ones (7-9), and 5H-benzopyrido[3,2-a]phenoxazin-5-ones (10-12) were synthesized and evaluated against representative human neoplastic cell lines. Dimethyl derivatives 1-6 were more active against carcinoma than leukemia cell lines. The tetrahydrobenzo derivatives 7-9 were scarcely active, whereas the corresponding benzo derivatives 10-12 showed notable cytotoxicity against a majority of the tested cell lines. Molecular modeling studies indicated that the high potency of 10 and 11, the most cytotoxic compounds of the whole series, could be due to the position of the condensed benzene ring, which favors ð-ð stacking interactions with purine and pyrimidine bases in the DNA active site. Biological studies suggested that 10-12 have no effect on human topoisomerases I and II and that they induce arrest at the G2/M phase

Antitumor Agents 6. Synthesis, Structure-Activity Relationships, and Biological Evaluation of Spiro[imidazolidine-4,3′-thieno[2,3-g]quinoline]-tetraones and Spiro[thieno[2,3-g]quinoline-3,5′- [1,2,4]triazinane]-tetraones with Potent Antiproliferative Activity†

Two series of quinolinquinone derivatives, 2′H-spiro[imidazolidine-4,3′-thieno[2,3-g]quinoline]-2,4′,5,9′- tetraones (2a-n) and 2H-spiro[thieno[2,3-g]quinoline-3,5′-[1,2,4]triazinane]-3′,4,6′,9-tetraones (3a-e), were designed and synthesized using the previously described ethyl 3-amino-4,9-dioxo-2,3,4,9-tetrahydrothieno[2,3- g]quinoline-3-carboxylate (1) as a starting material. All compounds were evaluated for their antiproliferative activity against a panel of representative liquid and solid human tumor cell lines and exhibit IC50 values in the micromolar/submicromolar range. Series 2 displayed higher cytotoxicity than did series 3. The nature of the substituents on both imidazoline and triazinane N1 nitrogen markedly affected the activity profile of these series. Spectrophotometric and fluorescence measurements as well as unwinding assays performed on the most cytotoxic compounds, 2c, 2g, and 2k, showed that they are nonintercalative DNA agents and inhibit the catalytic activity of Topo II in a concentration-dependent mode. 2g was the most active Topo II inhibitor with activity levels comparable to those of VP-16

Antitumor Agents. 2. Synthesis, Structure-Activity Relationships, and Biological Evaluation of Substituted 5H-Pyridophenoxazin-5-ones with Potent Antiproliferative Activity

New antiproliferative compounds, 5H-pyrido[3,2-a]phenoxazin-5-ones (1-10), 5H-benzophenoxazin- 5-one (11), 5H-pyrido[2,3-a]phenoxazin-5-one (12), 5H-pyrido[3,4-a]phenoxazin-5-one (13), and 5H-pyrido[4,3-a]phenoxazin-5-one (14), were synthesized and evaluated against representative human neoplastic cell lines. The excellent cytotoxic activity of these polycyclic phenoxazinones, structurally related to the actinomycin chromophore, is discussed in terms of structural changes made to rings A and D (Chart 1). Electron-withdrawing or electron-donating substituents were introduced at different positions of ring A to probe the electronic and positional effects of the substitution. A nitro group in R2 or in R1 increases the cytotoxic activity, whereas electron-donating methyl groups in any position lead to 10- to 100-fold decreasing of the activity. The low antiproliferative activity of benzophenoxazinone 11 and pyridophenoxazinones 13 and 14 confirms the crucial role of pyridine nitrogen in the W position of ring D in DNA binding. The unexpected high activity exhibited by 12, which has the nitrogen in the X position, could be ascribed to a different mechanism of action, which needs further investigation

An NMR Study of the Bortezomib Degradation under Clinical Use Conditions

The (R)-3-methyl-1-((S)-3-phenyl-2-(pyrazine-2-carboxamido)propanamido)butyl-boronic acid, bortezomib (BTZ), which binds the 20S proteasome subunit and causes a large inhibition of its activity, is a peptidomimetic boronic drug mainly used for the treatment of multiple myeloma. Commercial BTZ, stabilized as mannitol derivative, has been investigated under the common conditions of the clinical use because it is suspected to be easily degradable in the region of its boronic moiety. Commercial BTZ samples, reconstituted according to the reported commercial instructions and stored at 4°C, were analyzed by high-field nuclear magnetic resonance spectroscopy in comparison with identical samples bubbled with air and argon, respectively. All the samples remained unchanged for a week. After a month, the air filled samples showed the presence of two main degradation products (6% of starting material), the N-(1-(1-hydroxy-3-methylbutylamino)-1-oxo-3-phenylpropan-2-yl) pyrazine-2-carboxamide (BTZ1; 5%, determined from NMR integration) and the (S)-N-(1-(3-methylbutanamido)-1-oxo-3-phenylpropan-2-yl)pyrazine-2-carboxamide (BTZ2; 1%, determined from NMR integration), identified on the basis of their chemical and spectroscopic properties. The BTZ1 and BTZ2 finding suggests that, under the common condition of use and at 4°C, commercial BTZ-mannitol is stable for a week, and that, in time, it undergoes slow oxidative deboronation which partially inactivates the product. Low temperature and scarce contact with air decrease the degradation process

Antitumor Agents. 1. Synthesis, Biological Evaluation, and Molecular Modeling of 5H-Pyrido[3,2-a]phenoxazin-5-one, a Compound with Potent Antiproliferative Activity

The iminoquinone is an important moiety of a large number of antineoplastic drugs and plays a significant role in the nucleus of actinomycins, powerful, highly toxic, natural antibiotics that target DNA as intercalating agents. A series of polycyclic iminoquinonic compounds, 2-amino-3H-phenoxazin-3-one (1), 2-amino-1,9-diacetyl-3H-phenoxazin-3-one (2), 2-acetylamino- 3H-phenoxazin-3-one (3), 3H-phenoxazin-3-one (4), 5H-pyrido[3,2-a]phenoxazin-5-one (5), and 5H-pyrido[3,2-a]phenothiazin-5-one (6), strictly related to the actinomycin chromophore, were synthesized for developing new anticancer intercalating drugs. The antiproliferative activity of these compounds, evaluated against representative human liquid and solid neoplastic cell lines, showed that 5 and its isoster 6 were the most active compounds inhibiting cell proliferation in a submicromolar range. Compound 5 was also evaluated against KB subclones (KBMDR, KB7D, and KBV20C), which overexpress the MDR1/P-glycoprotein drug efflux pump responsible for drug resistance. All the above KB subclones did not show altered sensitivity to the antiproliferative activity of 5. UV-vis and 1H NMR spectroscopy experiments support the phenoxazinone 5/DNA binding. Molecular mechanics methods were used to build a three-dimensional model of the 5/[d(GAAGCTTC)]2 complex. Electrostatic interactions between the hydrogen of the positively charged pyridine nitrogen of 5 and the negatively charged oxygen atoms (O4¢ and O5¢) of the cytosine C5 residue together with stacking forces contribute to the high antiproliferative activity. The metal(II)-assisted synthesis procedure of 5 is described, and the formation mechanism is proposed

An 1H NMR study of the cytarabine degradation in clinical conditions to avoid drug waste, decrease therapy costs and improve patient compliance in acute leukemia

Cytarabine, the 4-amino-1-(β-D-arabinofuranosyl)-2(1H)-pyrimidinone, (ARA-C) is an antimetabolite cytidine analogue used worldwide as key drug in the management of leukaemia. As specified in the manufacturers' instructions, once the components-sterile water and cytarabine powder-are unpackaged and mixed, the solution begins to degrade after 6 hours at room temperature and 12 hours at 4°C. To evaluate how to avoid wasting the drug in short-term, low-dose treatment regimens, the reconstituted samples, stored at 25°C and 4°C, were analyzed every day of the test week by reversed-phase HPLC and high-field NMR spectroscopy. All the samples remained unchanged for the entire week, which corresponds to the time required to administer the entire commercial drug package during low-dose therapeutic regimens. The drug solution was stored in a glass container at 4°C in an ordinary freezer and drawn with sterile plastic syringes; during this period, no bacterial or fungal contamination was observed. Our findings show that an cytarabine solution prepared and stored in the original vials retains its efficacy and safety and can, therefore, be divided into small doses to be administered over more days, thus avoiding unnecessary expensive and harmful waste of the drug preparation. Moreover, patients who require daily administration of the drug could undergo the infusion at home without need to go to hospital. The stability of the aliquots would help decrease hospitalization costs