Narshinha P. Argade

Copper-Catalyzed Intramolecular N-Arylation of Quinazolinones: Facile Convergent Approach to (−)-Circumdatins H and J

A copper-catalyzed intramolecular N-arylation of a quinazolinone nucleus that furnished the central benzodiazepine core unit has been demonstrated to accomplish an efficient convergent total synthesis of (-)-circumdatins H and J.

Aryne Insertion Reactions Leading to Bioactive Fused Quinazolinones: Diastereoselective Total Synthesis of Cruciferane

Insertion reactions of an in situ generated arynes to a variety of suitably substituted 1,3-quinazolin-4-ones have been demonstrated for a new efficient one-step approach to a diverse range of fused quinazolinone architectures. The present protocol has been effectively utilized to accomplish the concise total synthesis of recently isolated bioactive natural products tryptanthrin, phaitanthrins A-C, and cruciferane.

Palladium-Promoted [2 + 2 + 2] Cocyclization of Arynes and Unsymmetrical Conjugated Dienes: Synthesis of Justicidin B and Retrojusticidin B

A facile synthesis of natural and unnatural arylnaphthalenes has been demonstrated via the unprecedented palladium-promoted [2 + 2 + 2] cocyclization of arynes and unsymmetrical conjugated dienes using the N-heterocyclic carbene as a ligand. The unsymmetrical dienes used herein are actually α-coupled acrylate-cinnamate combinations bearing two β-positive carbons and follow the key [2 + 2 + 2] cocyclization pathway.

N-Bromosuccinimide-dibenzoyl peroxide/azabisisobutyronitrile: a reagent for Z- to E-alkene isomerization

Abstract N -Bromosuccinimide-dibenzoyl peroxide/azobisisobutyronitrile is used to carry out several types of Z - to E -alkene isomerizations. The NBS-bromination conditions are sufficient for both allylic bromination and alkene isomerization. When the allylic hydrogens are not available in substrates, only the isomerization of the alkene takes place. The present conditions for isomerization of carbon–carbon double bonds are mild and efficient.

Enantioselective total synthesis of desbromoarborescidines A-C and the formal synthesis of (S)-deplancheine.

Starting from Boc-protected tryptamine and (S)-tetrahydro-5-oxo-2-furancarboxylic acid, facile enantioselective total synthesis of desbromoarborescidines A-C and the formal synthesis of (S)-deplancheine have been accomplished via a common intermediate (S)-indolo[2,3-a]quinolizine. Synthesis of enantiomerically pure (S)-acetoxyglutarimide, stereoselective reductive intramolecular cyclization, hydroxyl group-assisted in situ N-Boc-deprotection, selective deoxygenation of the xanthate ester, and lactam hydrolysis followed by an appropriate exchange of nitrogen regioselectivity in intramolecular cyclization were the decisive steps.

Regio- and stereoselective selenium dioxide allylic oxidation of (E)-dialkyl alkylidenesuccinates to (Z)-allylic alcohols: Synthesis of natural and unnatural butenolides

The first SeO(2) induced (Z)-selective allylic alcohol formation of dialkyl alkylidenesuccinates has been demonstrated to accomplish one-step syntheses of several essential butenolides and fused butenolides via an unusual E- to Z- carbon-carbon double bond isomerisation followed by the lactonization pathway. The observed regio- and stereoselective SeO(2) allylic oxidation protocol has also been extended to the diastereoselective total synthesis of bioactive natural product isomintlactone, its direct conversion to mintlactone and an example of the base-catalyzed intramolecular rearrangement of γ-lactone to δ-lactone.

Total Synthesis of Proposed Auranthine

Starting from CBz-protected glutamic anhydride and Boc-protected o-aminobenzyl amine, the first total synthesis of proposed structure of auranthine has been reported. An intramolecular aza-Wittig reaction involving a lactam carbonyl group that delivered the diazepine core unit was the key step in the synthesis.

Diversity Oriented Convergent Access for Collective Total Synthesis of Bioactive Multifunctional Carbazole Alkaloids: Synthesis of Carbazomycin A, Carbazomycin B, Hyellazole, Chlorohyellazole, and Clausenaline D

Facile syntheses of imperative carbazole alkaloids carbazomycin A, carbazomycin B, hyellazole, chlorohyellazole, and clausenaline D have been demonstrated starting from readily available Boc-protected 3-formylindole and dimethyl maleate. The suitably substituted aromatic rings have been designed comprising three/four significant C-C bond forming reactions. The competent Wittig reaction, selective monoalkylations, one-pot regioselective Weinreb amide formation and Boc-deprotection, well designed Grignard reactions, dehydrative intramolecular cyclizations, and Baeyer-Villiger rearrangement of aromatic aldehydes were the main features.

Synthesis and screening of a combinatorial library of naphthalene substituted chalcones: inhibitors of leukotriene B4.

A combinatorial mini library of naphthalene substituted chalcones has been prepared by solution phase chemistry. Screening of these mixtures for leukotriene B4 inhibitory activity using human whole blood assay (HWBL) afforded a lead compound, 1-(6-butoxy-2-naphthyl)-3-(4-nitrophenyl)-prop-2-en-1-one (K4A3) with an IC50 value of 18.5 microM.

Enantioselective enzymatic approach to (+)- and (−)-2-acetoxy/hydroxycyclopentanones

Abstract A new practical enzymatic approach to (+)- and (−)-2-acetoxy/hydroxycyclopentanones with 96–98% ee has been described via enzymatic hydrolysis of the meso-diacetate 2, Swern oxidation of the thus formed (±)-hydroxy acetates 3 and 4, followed by re-enzymatic resolution. Enantiomerically pure (+)- and (−)-2-hydroxycyclopentanones are in equilibrium with enediol 9 and slowly undergo racemisation, a process which could be arrested by protecting the hydroxyl group as the acetate.