Synthesis and anticancer activity studies of novel 1-(2,3-dihydro-5H-1,4-benzodioxepin-3-yl)uracil and (6′-substituted)-7- or 9-(2,3-dihydro-5H-1,4-benzodioxepin-3-yl)-7H- or 9H-purines

Study of Direct N7 Regioselective tert-Alkylation of 6-Substituted Purines and Their Modification at Position C6 through O, S, N, and C Substituents

A new N7 direct regioselective method allowing the introduction of tert-alkyl groups into appropriate 6-substituted purine derivatives is developed. This method is based on a reaction of N-trimethylsilylated purines with a tert-alkyl halide using SnCl4 as a catalyst. In this work, we study the structure and optimal reaction conditions leading to the N7 isomer and in some cases also to the N9 isomer. The main goal is devoted to preparing 7-(tert-butyl)-6-chloropurine as a suitable compound for other purine transformations. The stability of the tert-butyl group at the N7 position is tested for classic model reactions, leading to the preparation of new 6,7-disubstituted purine derivatives, which is also interesting from the point of view of possible biological activity.

Design, synthesis, HER2 inhibition and anticancer evaluation of new substituted 1,5-dihydro-4,1-benzoxazepines

A series of 11 new substituted 1,5-dihydro-4,1-benzoxazepine derivatives was synthesised to study the influence of the methyl group in the 1-(benzenesulphonyl) moiety, the replacement of the purine by the benzotriazole bioisosteric analogue, and the introduction of a bulky substituent at position 6 of the purine, on the biological effects. Their inhibition against isolated HER2 was studied and the structure–activity relationships have been confirmed by molecular modelling studies. The most potent compound against isolated HER2 is 9a with an IC₅₀ of 7.31 µM. We have investigated the effects of the target compounds on cell proliferation. The most active compound (7c) against all the tumour cell lines studied (IC₅₀ 0.42–0.86 µM) does not produce any modification in the expression of pro-caspase 3, but increases the caspase 1 expression, and promotes pyroptosis.

Azouracil and Its Cu(II)-Catalyzed Cyclization to an Anticancer Active Triazole Derivative: Symmetrical and Asymmetrical Reductive Cleavage, DNA Interaction, and Molecular Docking Studies

The 6-amino-1,3-dimethyl uracil-based azo derivative (p-carboxy phenylazouracil, L11) undergoes Cu(II)-catalyzed cyclization to a triazole derivative, namely, 1,3-dimethyl-8-(p-carboxy phenyl) azapurine (L11P). Interestingly, the azo functionality of L11 undergoes both symmetrical and asymmetrical reductive cleavage at two different reaction conditions. The chloride salts of Mn(II), Ni(II), and Pd(II) catalyze reductive cleavage of an azo moiety in an asymmetric manner, producing a new uracil hydrazine derivative (A3). On the other hand, hydrazine catalyzes symmetrical reductive cleavage of the azo moiety of L11, resulting in 5,6-diamino-1,3-dimethyl uracil (A2) along with the starting p-aminobenzoic acid (A1). Time-dependent density functional theoretical (TD-DFT) studies provide optimized geometries of L11, L11P, and A3 along with their orbital energies. The L11 and L11P bind firmly to genomic DNA of E. coli with a site size n ∼ 9 and n ∼ 8. The L11P shows anticancer activity on selected murine lymphoma cancer cell lines (DL, YAC1, and 2PK3). In addition, its antiproliferative activity is measured with several cancer cell lines and found hemocompatible toward blood cells. Corresponding molecular docking studies of L11P with caspase-3 (cysteine-aspartic proteases) unlock their mode of interaction.

Synthesis and crystal structure of new heterocyles derived from saccharin and uracil carrying 1,2,4-oxadiazolylmethyl group

Saccharin, uracil, and 1,2,4-oxadiazole heterocyles are important in terms of exhibiting various biological acitivities. In this work, four series of 1,2,4-oxadiazolylmethyl-substituted saccharin, and uracil derivatives are synthesized and their structures are identified by means of spectral/physical characteristics. The first series are oxadiazolylmethyl-substituted saccharins. The second one is oxadiazole-substituted uracils which are obtained as a separable mixture of both mono- and bis-substituted end products. Third series is obtained from 5-amino uracil and chloromethyl oxadiazoles. The fourth group is oxadiazolyl methyl-substituted imino uracils. The structures of some title compounds are also confirmed by X-ray diffraction data.

Stereospecific alkylation of substituted adenines by the Mitsunobu coupling reaction under microwave-assisted conditions

The Mitsunobu reaction under microwave-assisted conditions reveals a complete inversion of the stereogenic centre of the secondary alcohol giving an alkylated purine linked to a homochiral six-membered ring.

1H and 13C NMR spectral assignments of pyridinium salts linked to a N-9 or N-3 adenine moiety

(1)H and (13)C NMR spectral data of 13 new compounds containing a 4-(dimethylamino)- or 4-(pyrrolidin-1-yl)pyridinium moiety linked to the N-9 or N-3 nitrogen atom of an adenine moiety were assigned. 1D and 2D NMR experiments (DEPT, HSQC and HMBC) allowed the unequivocal identification of N-9 and N-3 isomers.

Synthesis and anticancer activity of the (R,S)-benzofused 1,5-oxathiepine moiety tethered to purines through alkylidenoxy linkers

Herein we report the design, synthesis, and anticancer activity of a series of substituted (R,S)-9-[2- or 3-(3,4-dihydro-2H-1,5-benzoxathiepine-3-yloxy)alkyl]-9H-purines. Derivatives with propylenoxy-linked 2',6'-dichloro- and 6'-bromopurines are more active than their respective ethylenoxy-linked purine conjugates. On the other hand, the compound with a propylenoxy-linked 6'-chloropurine is nearly equipotent to the corresponding ethylenoxy-linked conjugate. Our results show that bromo- and chloropurine-conjugated benzoxathiepines containing a propylenoxy linker are able to inhibit PI3 kinase (PI3K) phosphorylation in MCF-7 breast cancer cells, indicating that the activation of eIF2α, together with inhibition of the PI3K pathway, is the mechanism of action by which these compounds effect their antitumor activity in the MCF-7 cell line; apoptosis was induced in a p53-independent manner.

Highly efficient Suzuki-Miyaura coupling of heterocyclic substrates through rational reaction design

A dicyclohexyl(2-sulfo-9-(3-(4-sulfophenyl)propyl)-9H-fluoren-9-yl)phosphonium salt was synthesized in 64% overall yield in three steps from simple commercially available starting materials. The highly water-soluble catalyst obtained from the corresponding phosphine and [Na(2)PdCl(4)] enabled the Suzuki coupling of a broad variety of N- and S-heterocyclic substrates. Chloropyridines (-quinolines) and aryl chlorides were coupled with aryl-, pyridine- or indoleboronic acids in quantitative yields in water/n-butanol solvent mixtures in the presence of 0.005-0.05 mol % of Pd catalyst at 100 degrees C, chloropurines were quantitatively Suzuki coupled in the presence of 0.5 mol % of catalyst, and S-heterocyclic aryl chlorides and aryl- or 3-pyridylboronic acids required 0.01-0.05 mol % Pd catalyst for full conversion. The key to the high activity of the Pd-phosphine catalyst is the rational design of the reaction parameters (i.e., the presence of water in the reaction mixture, good solubility of reactants and catalyst in n-butanol/water (3:1), and the electron-rich and sterically demanding nature of the phosphine ligand).

Anticancer activity of (1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl)-pyrimidines and -purines against the MCF-7 cell line: Preliminary cDNA microarray studies

Completing a SAR study, a series of (RS)-1- or 3-(1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl)-pyrimidines and (RS)-6-substituted-7- or 9-(1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl)-7H- or 9H-purines have been prepared. Their antiproliferative activities on MCF-7 cells are here presented and discussed. (RS)-6-Chloro-9-[1-(9H-9-fluorenylmethoxycarbonyl)-1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl]-9H-purine (28) is the most active (IC(50)=0.67+/-0.18 microM) of the series so far described. cDNA microarray technology reveals potential drug targets, which are mainly centred on apoptosis regulatory pathway genes.

Regiospecific Solid-Phase Strategy to N7-Substituted Purines and Its Application to 8-Azapurines and [i]-Condensed Purines

A highly regioselective and traceless solid-phase route to 1,7,8-trisubstituted purines has been developed. This methodology could be extended to the preparation of 8-azapurines and [i]-condensed purines. A representative set of 17 purines, azapurines, and [i]-condensed purines was synthesized. This paper also describes a mild method to prepare the p-benzyloxybenzylamine (BOBA) resin.