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  • 61 Reads

1,2-Aminoalcohols have been demonstrated to be excellent chiral auxiliaries and chiral catalysts , including aldol reaction , addition of organozincs to aldehydes , reduction of ketones to alcohols in asymmetric syntheses.

In this work, a library of neoisopulegol-based octahydrobenzofuran core 1,2-aminoalcohol derivatives was developed and applied as chiral catalysts in the enantioselective addition of diethylzinc to benzaldehyde.

Allylic chlorination of (+)-neoisopulegol, derived from natural (-)-isopulegol , followed by cyclisation was accomplished to provide the key intermediate exo-methylene-substituted perhydrobenzofurane. Stereoselective epoxidation of the double bond followed by aminolysis with primary amines produced 1,2-aminoalcohols. The treatment of aminoalcohols with formaldehyde resulted in the formation of spiro-oxazolidines. The syn -selective dihydroxylation with OsO4/NMO of the key-intermediate produced bicyclic, terpenoid –type diol in highly stereoselective reaction.

The antimicrobial activity of the prepared compounds was evaluated on multiple bacterial and fungal strains.

The stereochemistry of the resulting compounds was determined by 2D-NMR techniques (COSY, NOESY, HSQC and HMBC).

  • Open access
  • 88 Reads
s-Triazine: A Multidisciplinary and International Journey

2,4,6-Trichloro-1,3,5-triazine (TCT) offers unique ability to undergo sequential nucleophilic substitution reaction using regular nucleophiles (first Cl replacement at 0 ºC, second at rt and third at > 90 ºC) making s-triazine a privileged scaffold finding application in drug development with an extension towards development of new materials.

This selective chemical property of TCT fulfills the goal of the chemists to control the organic structures and make it react in the required condition for achieving each objective. In this regard, orthogonality and chemoselectivity are two modern organic chemistry concepts which have been exploited in various areas of research ranging from supramolecular chemistry to organic/bioconjugation chemistry. We have demonstrated the fusion of these two concepts using TCT as “Orthogonal Chemoselectivity” and defined it as discrimination between reactive sites in any order. The usage of azide as one of the nucleophiles modulated the reactivity of s-triazine core for the last Cl replacement. This allowed us to overcome the barrier of higher temperature (> 90 ºC) for the last Cl replacement which happened at rt taking advantage of side chain of Cys, Tyr and Lys in biological context.

In this presentation, we revise the chemistry developed in our laboratories to manipulate the TCT core for application in our medicinal chemistry programs and in bioconjugation.

  • Open access
  • 130 Reads
Synthesis of Amidines and its application to heterocycles synthesis

Amidines are the important classes of nitrogenous compounds, which have been widely used as antibiotics, diuretics, antiphogistic drugs, anthelmintics, and acaricides. They represent an important pharmacophore in modern drug discovery, and can be found in DNA and RNA binding diamidine diminazene, ASIC inhibitor, muscarinic agonists for the treatment of Alzheimer’s disease, platelet aggregation inhibitors, and recently, serine protease inhibitors, to give some examples. In fact, many of the top-selling pharmaceuticals of the fast few years feature an amidine as a key structural components. In addition, they also serve as ligands for transition metals due to their unique structure. These enormous significant applications have attracted the research community towards the development of simple and economically viable methods for the synthesis of amidines. Several synthetic methods have been developed, in which the nucleophilic addition of amine to nitrile is the most convenient and atom-economic method. In synthetic chemistry, amidines have been used as valuable precursors for the preparation of azaheterocycles of biological interest such as- imidazoles, benzimidazoles, quinazolines, triazine, triazoles, oxazole, pyrimidines, pyrimidopyrimidines etc. Recently, we have demonstrated a synthetic protocol for the preparation of substituted pyrimido[4,5-d]pyrimidines via TBHP-mediated direct oxidative coupling of N-uracil amidines and methylarenes under metal-free conditions. Very recently, we also reported the synthesis of functionalized pyrimidouracils by ruthenium catalyzed oxidative insertion of (hetero)aryl methanols into N-uracil amidines. A dehydrogenative coupling of N-uracil amidines with (hetero)aryl methanols has been developed, allowing for the facile synthesis of a broad range of structurally diverse pyrimidouracils. In this paper, recent advances in the synthesis of amidines and their application towards the preparation of biologically important heterocycles has been discussed.

  • Open access
  • 65 Reads
Microwave-assisted multicomponent syntheses of heterocyclic phosphonates

Organophosphorus compounds play an important role in several fields of life; they have widespread use in organic and medicinal chemistry, as well as in agriculture and plastic industry. Over the last years, the chemistry of heterocyclic phosphonates has received an intensively growing interest. One of the most efficient tools for the preparation of these compounds is the synthesis via multicomponent reactions, which transformations meet several criteria of an “ideal synthesis”, such as high atom economy, fast and simple accomplishment, ability to save time and energy and being environment-friendly.

The synthesis of isoindolin-1-one-3-phosphonate derivatives was studied by the microwave(MW)-assisted three-component reaction of 2‑formylbenzoic acid, aliphatic primary amines and various dialkyl phosphites. A suitable method was also developed for the preparation of the isoindolin-1-one-3-phosphonates at a “few g” scale by using a continuous flow MW reactor.

(2-Amino-4H-chromen-4-yl)phosphonates were also synthesized by the three-component condensation of salicylaldehydes, malononitrile and dialkyl phosphites under MW conditions.

Furthermore, 3,4-dihydropyrimidin-2(1H)-one phosphonates were prepared by the MW-assisted Biginelli reaction of β-ketophosphonates.