Jubaraj B. Baruah

Polyphenolic compounds: an overview

A comprehensive review on the polyphenolic compounds is presented. The emphasis is placed on the structural and functional implications on the regiochemistry as well as on the stereochemistry of oligomeric polyphenols. A correlation between the natural polyphenolic compounds and the synthetic ones is highlighted by making a general classification of polyphenolic compounds. The uses and applications of polyphenolic compounds are discussed in detail.

Structure-Activity Studies on Therapeutic Potential of Thymoquinone Analogs in Pancreatic Cancer

ABSTRACTPurposePancreatic cancer (PC) is one of the deadliest of all tumors. Previously, we were the first to show that Thymoquinone (TQ) derived from black seed (Nigella sativa) oil has anti-tumor activity against PC. However, the concentration of TQ required was considered to be high to show this efficacy. Therefore, novel analogs of TQ with lower IC50 are highly desirable.MethodsWe have synthesized a series of 27 new analogs of TQ by modifications at the carbonyl sites or the benzenoid sites using single pot synthesis and tested their biological activity in PC cells.ResultsAmong these compounds, TQ-2G, TQ-4A1 and TQ-5A1 (patent pending) were found to be more potent than TQ in terms of inhibition of cell growth, induction of apoptosis and modulation of transcription factor-NF-κB. We also found that our novel analogs were able to sensitize gemcitabine and oxaliplatin-induced apoptosis in MiaPaCa-2 (gemcitabine resistant) PC cells, which was associated with down-regulation of Bcl-2, Bcl-xL, survivin, XIAP, COX-2 and the associated Prostaglandin E2.ConclusionFrom our results, we conclude that three of our novel TQ analogs warrant further investigation against PC, especially in combination with conventional chemotherapeutic agents.

Perspectives on Medicinal Properties of Benzoquinone Compounds

Benzoquinones are class of natural quinones found chiefly in higher plants, fungi, bacteria and animal kingdom. They are involved in important biological functions such as bioenergetic transport, oxidative phosphorylation and electron transport processes. In recent years it has become increasingly clear that some of them possess potent antioxidant, anti-inflammatory and anticancer activities. There is clearly a common thread running through these activities and there have been a large number of studies carried out to unravel the mechanisms of these activities. In the present review we have provided a brief account of these studies especially covering these aspects. Although antioxidant potentials of these compounds constitute the basis of their biological activities its nature and scope is dictated by many microscopic biological environments. One of the important advantages offered by these compounds is the ease with which they can be synthesized and chemically manipulated. This can easily provide impetus for further research in developing some potentially useful drug molecules.

Organic oxidative reactions mediated by copper

Copper containing enzymes are indispensable for their ability to act as oxygen carrier and oxidation reactions of different substrates. The recent developments on various copper catalysed as well as stoichiometric organic oxidative reactions involving copper complexes are discussed. The emphasis is put on the state of art on the role of copper complexes to delineate structure reactivity correlation to perform selective oxidative transformations.

RhCl(PPh3)3 catalyzed hydrosilylation of styrene and phenylacetylene with phenylsilanes

Abstract Reaction of styrene with Ph 2 SiH 2 catalyzed by RhCl(PPh 3 ) 3 ( 2 SiH(CH 2 CH 2 Ph) in 77–89% yields although the reaction is accompanied by formation of Ph 2 SiH(CH-CHPh), ethylbenzene, and Ph 3 SiH in small amounts. Similar reaction in toluene also gives a mixture of Ph 2 SiH(Ch 2 CH 2 Ph), Ph 2 SiH(CH-CHPh), ethylbenzene, and Ph 3 SiH with lower yield of the hydrosilylation product than the reaction in THF. Reaction of styrene with Ph 2 SiD 2 catalyzed by RhCl(PPh 3 ) 3 in toluene gives a mixture of these products which are partly deuterated on the non-aromatic hydrogens. The 1 H NMR spectrum of the products indicates complete deuterium scrambling on the hydrogen atoms of styrene and the phenylsilanes prior to or during the reaction. Further reaction of Ph 2 SiH(CH 2 CH 2 Ph) with HSPh catalyzed by RhCl(PPh 3 ) 3 gives Ph 2 Si(SPh)(Ch 2 CH 2 Ph). Hydrosilylation of styrene with PhSiH 3 catalyzed by RhCl(PPh 3 ) 3 is much slower than the reaction with Ph 2 SiH 2 . Hydrosilylation of phenylacetylene with PhSiH 3 catalyzed by 0.1 mol% of RhCl(PPh 3 ) 3 gives PhSiH 2 (CH-CHPh) in 67% as the sole reaction product. Similar reaction of 1-octyne gives PhSiH 2 [CH-CH(CH 2 ) 5 Me]. These hydrosilylation products are converted into thiolato substituted organosilane through RhCl(PPh 3 ) 3 catalyzed dehydrogenative condensation with HSAr (Ar-C 6 H 5 , C 6 H 4 - p -Me, C 6 H 4 - o -Me).

Solid-state hydrogen bonded assembly of N,N′-bis(glycinyl)-pyromellitic diimide with aromatic guests

The compound N,N′-bis(glycinyl)pyromellitic diimide (L) forms inclusion compounds with aromatic hydrocarbons such as anthracene (D1), phenanthrene (D2) and perylene (D3) as well as tetrathiafulvalene (D4). The aromatic guest molecules are held in the spaces between the aromatic units of extended self-assembly of L derived from the hydrogen bonding between the carboxylic acid end groups of L. The crystal structures of each of these inclusion compounds are determined along with the parent compound L. A R44(12) hydrogen bond pattern involving the carboxylic groups and two bridging methanol molecules is observed in the anthracene inclusion compound of L, whereas in the case of other inclusion compounds conventional R22(8) type hydrogen bonding is observed. While forming inclusion compounds of L with tetrathiafulvalene, the carboxylic acid of L has R22(8) and C11(3) types of hydrogen bonding patterns in the lattice. Preferential inclusion compound formation of L with anthracene over isomeric phenanthrene is observed.

Aromatic N-oxide bridged copper(II) coordination polymers: Synthesis, characterization and magnetic properties

Abstract The complexes [Cu2(o-NO2–C6H4COO)4(PNO)2] (1), [Cu2(C6H5COO)4(2,2′-BPNO)] n (2), [Cu2(C6H5COO)4(4,4′-BPNO)] n (3), [Cu(p-OH–C6H4COO)2(4,4′-BPNO)2·H2O] n (4), (where PNO=pyridine N-oxide, 2,2′-BPNO=2,2′-bipyridyl-N,N′-dioxide, 4,4′-BPNO=4,4′-bipyridyl-N,N′-dioxide) are prepared and characterized and their magnetic properties are studied as a function of temperature. Complex 1 is a discrete dinuclear complex while complexes 2–4 are polymeric of which 2 and 3 have paddle wheel repeating units. Magnetic susceptibility measurements from polycrystalline samples of 1–4 revealed strong antiferromagnetic interactions within the {Cu2}4+ paddle wheel units and no discernible interactions between the units. The complex 5, [Cu(NicoNO)2·2H2O] n ·4nH2O, in which the bridging ligand to the adjacent copper(II) ions is nicotinate N-oxide (NicoNO) the transmitted interaction is very weakly antiferromagnetic.

Allylic amination promoted by copper

A mild method for the synthesis of allylic amines by using a mixture of copper(II)perchlorate and copper metal is described.

Zinc(II) and cobalt(II) complexes of (3-carboxymethoxy-naphthalen-2-yloxy)-acetic acid: a structural study

Different types of cyclic polynuclear complexes and one-dimensional coordination polymers of zinc(II) derived from (3-carboxymethoxy-naphthalen-2-yloxy)-acetic acid (LH2) are synthesised and characterised. The macrocyclic effect of ligand L leads to the formation of a coordination polymer having composition {[Na2Zn2(L)2(OH)2]}n and a binuclear zinc complex having composition [Zn2Na2(L)2(CH3COO)2(Pyz)2(MeOH)2] (where Pyz = pyrazole). A tetranuclear cyclic zinc(II) metallacycle with two dimethylformamide molecules in two different environments is synthesized and it has two symmetry non-equivalent cyclic molecules in its unit cell. The mononuclear complexes of zinc with L and the bidentate ligands such as 2,2′-bipyridine or 1,10-phenanthroline ancillary ligands are structurally characterised.

Variations in product in reactions of naphthoquinone with primary amines.

Reaction of 1,2-naphthoquinone with primary amines gives a 2-amino-1,4-naphthoquinone derivative which is equivalent to 1,2 to 1,4 carbonyl transposition. For example the reaction of 1,2-naphthoquinone with 4-methoxyaniline gives 2-(4-methoxyanilino)-naphthoquinone-1,4-(4-methoxyanil) (1) and with n-butylamine gives 2-(butylamino)-naphthoquinone-1,4-butylimine (2) respectively. The compounds 1 and 2 are characterized by X-ray crystallography; they have hydrogen-bonded dimeric structures. Similar reaction of 1,4-naphthoquinone with 3-picolylamine and 4-picolylamine gives the corresponding 2-amino 1,4-naphthoquinones; two products are characterized by X-ray crystallography. The reaction of 1,4-naphthoquinone with 4-aminothiophenol and 1,4-naphthoquinone with 4-aminophenol are compared. The former leads to C-S and the latter to C-N bond formation. The reaction of 1,4-naphthoquinone with 4-aminothiophenol in an NMR tube is studied to explain that 2-(4-anilinothiolato) 1,4-naphthoquinone derivative to be the sole product in the reaction.