Synthetic Studies on Tricyclic Diterpenoids: Direct Allylic Amination Reaction of Isopimaric Acid Derivatives.

A selective synthesis of 7- or 14-nitrogen containing tricyclic diterpenoids was completed according to a strategy in which the key step was the catalyzed direct allylic amination of methyl 14α-hydroxy-15,16-dihydroisopimarate with a wide variety of nitrogenated nucleophiles. It was revealed that the selectivity of the reaction depends on the nature of nucleophile. The catalyzed reaction of the mentioned diterpenoid allylic alcohol with 3-nitroaniline, 3-(trifluoromethyl)aniline, and 4-(trifluoromethyl)aniline yield the subsequent 7α-, 7β- and 14αnitrogen-containing diterpenoids.

Phenolic compounds from Glycyrrhiza pallidiflora Maxim. and their cytotoxic activity.

Twenty-one phenolic compounds (1-21) including dihydrocinnamic acid, isoflavonoids, flavonoids, coumestans, pterocarpans, chalcones, isoflavan and isoflaven, were isolated from the roots of Glycyrrhiza pallidiflora Maxim. Phloretinic acid (1), chrysin (6), 9-methoxycoumestan (8), isoglycyrol (9), 6″-O-acetylanonin (19) and 6″-O-acetylwistin (21) were isolated from G. pallidiflora for the first time.

Synthesis, in vivo Anticoagulant Evaluation and Molecular Docking Studies of Bicoumarins Obtained from Furocoumarin Peucedanin.

Background: Synthesis of 7,7.-linked bicoumarins, 3,3.-linked bi(2-isopropyl)psoralens as well as 1H-1,2,3-triazole linked coumarin-2,3-dihydrofurocoumarin and furocoumarin-2,3-dihydrofurocoumarin hybrids was performed by two alternative pathways, either involving a catalyzed transformations of the ethynyl derivatives of plant coumarins - peucedanin or peuruthenicin.

Synthesis of 1H-1,2,3-triazole linked aryl(arylamidomethyl) - dihydrofurocoumarin hybrids and analysis of their cytotoxicity.

A series of 2-(4-R-triazolyl)substituted 3-oxo-2,3-dihydrofurocoumarins have been synthesized by a regioselective cycloaddition of 2-azidooreoselone 1 or 2-azido-9-[(4-methylpiperazin-1-yl)methyl]oreoselone 2 with various alkynes in the presence of Cu(II)/ascorbate in water/methylene chloride reaction medium. The structure of 2-azidooreoselone was established by X-ray structure analysis. The cytotoxicity of 2-substituted dihydrofurocoumarins was determined against three cancer cell lines (CEM-13, MT-4, U-937) using the conventional MTT assays.

Synthesis and cytotoxic activity of a new group of heterocyclic analogues of the combretastatins.

A series of new analogs of combretastatin A-4 (CA-4, 1) with the A or B-ring replaced by a 3-oxo-2,3-dihydrofurocoumarin or a furocoumarin residue have been designed and synthesized by employing a cross-coupling approach. All the compounds were evaluated for their cytotoxic activity with respect to model cancer cell lines (CEM-13, MT-4, U-937) using conventional MTT assays. Structure-activity relationship analysis reveals that compounds 2, 3, 6-8 in which the (Z)-styryl substituent was connected to the 2-position of the 3-oxo-2,3-dihydrofurocoumarin core, demonstrated increased potency compared to 3-(Z)-styrylfurocoumarins 4, 5, 9-11.

Experimental and computational study on the structure and properties of Herz cations and radicals: 1,2,3-benzodithiazolium, 1,2,3-benzodithiazolyl, and their Se congeners.

Salts of 1,2,3-benzodithiazolium (1), 2,1,3-benzothiaselenazolium (3), and 1,2,3-benzodiselenazolium (4) (Herz cations), namely, [1][BF4], [1][SbCl6], [3][BF4], [3][GaCl4], [3][SbCl6], and [4][GaCl4], were prepared from the corresponding chlorides and NaBF4, GaCl3, or SbCl5. It was found that [1][SbCl6] and [3][SbCl6] spontaneously transform in MeCN solution to [1]3[SbCl6]2[Cl] and [3]3[SbCl6]2[Cl], respectively. [1][BF4], [1]3[SbCl6]2[Cl], [3][BF4], [3]3[SbCl6]2[Cl], and [4][GaCl4] were structurally characterized by X-ray diffraction (XRD).

Synthesis and characterization of fluorinated homocysteine derivatives as potential molecular probes for ¹⁹F magnetic resonance spectroscopy and imaging.

A N-trifluoroacetyl-protected amino acid containing a thioester function, 2,2,2-trifluoro-N-(2-oxo-tetrahydrothiophen-3-yl)acetamide (TFA-tHcy), has been synthesized and characterized. It was then used to prepare a fluorine-labeled N-homocysteinylated protein, (19)F-Hcy-εN-Lys-albumin, that was characterized by SDS-PAGE, MALDI-TOF-MS, UV-vis and (19)F NMR spectroscopy. On average, four N-trifluoroacetylhomocysteine residues were covalently conjugated to human serum albumin through the N-substituted homocysteine thiolactone.

Interaction of 1,3,2,4-benzodithiadiazines and their 1-Se congeners with Ph3P and some properties of the iminophosphorane products.

Interaction between Ph(3)P and 1,3,2,4-benzodithiadiazine (1); its 6,7-difluoro (2), 5,6,8-trifluoro (3) and 5,6,7,8-tetrafluoro (4) derivatives; and 5,6,8-trifluoro-3,1,2,4-benzothiaselenadiazine (5) proceeded via a 1:1 condensation to give Ph(3)P═N-R iminophosphoranes (1a-5a, R = corresponding 1,2,3-benzodichalcogenazol-2-yls), which are inaccessible by general approaches based on the Staudinger and Kirsanov reactions. In contrast, neither Ph(3)As nor Ph(3)Sb reacted with 1 and 4. Molecular structures of 1a-5a and 5 were confirmed by X-ray diffraction (XRD).

Why do p-nitro-substituted aryl azides provide unintended dark reactions with proteins?

Aryl azide-mediated photo cross-linking has been widely used to obtain structural features in biological systems, even though the reactive species generated upon photolysis in aqueous solution have not been well characterized. We have established a mechanistic framework for the formation of adducts between photoactivated 5-azido-2-nitrobenzoyl reagents and protein functional groups. Photolysis of the aryl azide tethered to biotin via an amide linkage yields a cross-link with streptavidin.

RNA-hydrolyzing activity of human serum albumin and its recombinant analogue.

The comparative analysis of RNA-hydrolyzing activity of albumin from human serum and albumin expressed in methylotrophic yeast Pichia pastoris has been carried out. The rate of polyribonucleotide phosphodiester bond cleavage in the presence of recombinant albumin has been found to be similar to that of the reaction mediated by the native protein. According to 31P NMR data, RNA hydrolysis follows the mechanism of intermolecular trans-esterification to yield 2',3'-cyclophosphodiester reaction products that are further slowly hydrolyzed to form nucleoside-3'- and nucleoside-2'-phosphates.

Efficient synthesis of the first betulonic acid-acetylene hybrids and their hepatoprotective and anti-inflammatory activity.

The Sonogashira reaction can be applied for the preparation of acetylenic derivatives of betulonic acid where the triterpenoid moiety can serve as either the halo- or the acetylenic component. This reaction opened access to the first derivatives of betulonic acid containing either the arylethynyl (C[triple bond]C-Ar(Het) or the ethynyl (C[triple bond]CH) moieties. From the fundamental perspective, this work illustrates the possibility of selective Pd-catalyzed cross-coupling at terminal acetylenes in the presence of a terminal alkene.

Human serum albumin as a catalyst of RNA cleavage: N-homocysteinylation and N-phosphorylation by oligonucleotide affinity reagent alter the reactivity of the protein.

Kinetic parameters for the cleavage of UpA site in an oligonucleotide in the presence of human serum albumin (HSA) or one of its clinically relevant modification were measured. The RNA-hydrolyzing activity of HSA was decreased by its nonenzymatic N-homocysteinylation. According to (31)P NMR data, Lys and Tyr residues were the labeling targets when a phosphorylating analog of oligoribonucleotide substrate was employed.

Interaction of human serum albumin and its clinically relevant modification with oligoribonucleotides.

Human serum albumin (HSA) was shown to mediate oligoribonucleotide cleavage. Nonenzymatic glycation of HSA decreased the ribonuclease-like activity of the protein. According to (31)P NMR data, both native and glycated albumins induced hydrolysis of RNA molecule through 2',3'-cyclophosphate intermediates.

5,6,7,8-Tetrafluoro-3lambda4delta2,1,2,4-benzothiaselenadiazine, 5,6,7,8-tetrafluoro-1,3lambda4delta2,2,4-benzodithiadiazine, and their hydrocarbon analogues: molecular and crystal structures.

5,6,7,8-Tetrafluoro-3lambda4delta2,1,2,4-benzothiaselenadiazine (1) is prepared by the intramolecular nucleophilic cyclization of C6F5SeN=S=NSiMe3 (2) mediated by CsF. According to an X-ray diffraction analysis, the heterocycle of 1 is bent along the Se(1)..

Does a stabilising interaction favouring the Z,Z configuration of -S-N=S=N-S- systems exist?

The existence of the orbital interaction presented in the literature as being the cause for the stabilisation of the Z,Z configuration of Ph-S-N=S=N-S-Ph (1) and its derivatives in the crystal phase, has been investigated. The results of theoretical calculations at the DFT/B3LYP/6-311+G* level of theory suggest that such a stabilising interaction might not exist or be extremely weak and that packing forces must be the main cause of the observed Z,Z configuration in the solid. To reach this conclusion structural and energetic parameters were combined to study the bonding in these -S-N=S=N-S- systems.