First total synthesis of Macrotricolorin A and its enantiomer.

Herein, we demonstrate the first total synthesis of Macrotricolorin A and its enantiomer from the key intermediate which is accessible from two precursors phenol and resorcinol, by two different sequences. Macrotricolorin A possesses anti-inflammatory properties and is a novel diarylpropanoid. The first total synthesis of Macrotricolorin A was accomplished using simple reactions such as Williamson's etherification, Claisen-Schmidt condensation, reduction, and chiral resolution.

Prins cyclization: new strategy for the stereoselective total synthesis of Polyrhacitide A.

A highly stereoselective total synthesis of polyrhacitide A, a polyketide natural product, has been accomplished by means of Prins cyclisation. The key precursor i.e.

Stereoselective total synthesis of arachnid harvestmen natural product: (4,5)‑4-hydroxy-γ-decalactone.

Herein, we described the novel synthetic strategy for the total synthesis of harvestmen natural product (4,5)‑4-hydroxy-γ-decalactone (minor) from an inexpensive precursor (()-2,2-dimethyl-1,3-dioxolane-4-carbaldehyde) with 31% overall yield. Hydroxy-γ-lactones represent a special class of harvestmen exocrine defense compounds. The present convergent synthesis utilizes classical reactions like the Barbier reaction, the Grignard reaction, and the employment of an olefin as a masked carboxylic acid functionality followed by lactone formation as key steps.

Zinc Chloride-Catalyzed Synthesis of Carbamates: An Application for the Synthesis of the Anti-Alzheimer's Drug Rivastigmine.

Herein, we report a synthetic protocol for the synthesis of carbamates by employing zinc chloride as a catalyst from carbamoyl chlorides and aromatic/aliphatic alcohols. The developed protocol successfully utilizes the gram-scale synthesis of the FDA-approved rivastigmine drug and its derivative. The utility of zinc chloride over other catalysts such as zinc dust and zinc acetate exhibits a 49-87% yield of carbamates.

Synthetic Approaches toward the Synthesis of Brivaracetam: An Antiepileptic Drug.

Epilepsy is a chronic neurological disorder in the brain, affecting individuals of all age groups. Nearly 1% of the world population is affected by seizure disorder, of which 80% of the patients are observed in underdeveloped and developing countries. The predominant treatment option for epilepsy includes an antiepileptic drug named brivaracetam.

Total synthesis of (-)-cephalosporolide D.

In this communication, a concise and efficient synthetic route for the synthesis of -Cephalosporolide D in enantioselective way has been described. In this synthesis, Mitsunobu esterification and Ring Closing Metathesis (RCM) for macrocyclic ring formation have been applied as key steps.

Total Synthesis and Structural Revision of Greensporone F and Dechlorogreensporone F.

The first asymmetric total syntheses of the real isolation product (2,5,8)-greensporone F and (2,5,8)-dechlorogreensporone F, 14-membered resorcylic acid lactones with a -2,5-disubstituted tetrahydrofuran ring system, was accomplished. The synthesis features a late-stage Lewis acid-catalyzed stereoselective intramolecular oxa-Michael reaction, -selective ring-closing metathesis, De Brabander's esterification, and Jacobsen's hydrolytic kinetic resolution as the key steps. Synthesis of both real isolation and erroneously proposed structure necessitated the revision of the absolute configuration of greensporone F and dechlorogreensporone F.

Stereoselective Synthesis of the C1-C16 Fragment of the Purported Structure of Formosalide B.

The first stereoselective synthesis of the C1-C16 fragment possessing stereo-enriched fully substituted tetrahydropyran (THP) along with tetrahydrofuran (THF) rings of the proposed structure of formosalide B is described in 12 longest linear steps with 22% overall yield, starting from two cheap and commercially available 1,5-pentanediol and l-glutamic acid, following a convergent approach. The key steps involve in this synthesis are Horner-Wadsworth-Emmons reaction, Sharpless asymmetric dihydroxylation, and acid-mediated ketalization to assemble the substituted THP ring, one-pot Sharpless dihydroxylation-S2-type cyclization, and Wittig homologation to construct the THF derivative.

Total synthesis and stereochemical revision of relgro and 10'-oxorelgro.

The first asymmetric total synthesis and stereochemical assignments of 10-membered macrolactones relgro and 10'-oxorelgro are disclosed. To this end, palladium-catalyzed Stille coupling, the Mitsunobu reaction, ring-closing metathesis, EDCI promoted coupling and the Jacobsen hydrolytic kinetic resolution are used as key steps. The total synthesis followed by thorough evaluation of the optical rotation and CD spectral data led to the revision of the absolute configuration at C-6' for both relgro and 10'-oxorelgro.

Stereoselective Total Syntheses of Acutifolone A, Bisacutifolone A and B, Pinguisenol, and Isonaviculol.

Stereoselective total syntheses of pinguisane type of sesquiterpenoids are described following a unified approach using a chiral building block derived from ()-pulegone. The functionality embodied in the key intermediate enables their facile elaboration into more complex structures of biological relevance such as acutifolone A (9 steps, 22% overall yield) and bisacutifolone A and B (6 and 8%, respectively) following Furukawa's modified Simmons-Smith cyclopropanation, Luche reduction, Saegusa-Ito oxidation, pyridinium chlorochromate-mediated 1,3-oxidative transposition, and Diels-Alder dimerization as key steps.

Asymmetric Total Synthesis of the Putative Structure of Diplopyrone.

The first asymmetric total synthesis of the putative structure of diplopyrone was achieved in 17 linear steps starting from cis-1,4-butene-diol. The synthetic route features iodine-catalyzed tandem isomerization followed by C-O and C-C bond formation reaction strategy developed by our own group to construct the trans-2,6-disubstituted dihydropyran ring, asymmetric α-aminoxylation reaction, and Still-Gennari (Z)-selective olefination reactions. Careful comparison of H and C NMR spectroscopic data as well as investigation of the UV and circular dichroism spectrum in trifluoroethanol for compound 2 suggest that the putative structure for diplopyrone {6-[(1S)-1-hydroxyethyl]-2,4a(S),6(R),8a(S)-tetrahydropyran[3,2-b]pyran-2-one} requires revision.

A Convergent Total Synthesis of Balticolid.

A convergent total synthesis of the 12 membered macrolide, Balticolid (1) is described, starting from readily available homoallylic alcohol and 1,3 propane diol The synthetic strategy involves the construction of the 12-membered lactone.

Asymmetric Total Syntheses of Two Possible Diastereomers of Gliomasolide E and Its Structural Elucidation.

The first total syntheses of two possible diastereomers of gliomasolide E, a 14-membered macrolides isolated from the marine sponge Phakellia fusca Thiele, which was collected from the South China Sea, is reported. Highlights of the synthesis include macrolactonization through intramolecular Horner-Wadsworth-Emmons olefination, Yamaguchi-Hirao alkynylation, and base-induced elimination reactions for propargyl alcohol synthesis as the key reactions. Detailed comparison of their H and C NMR (1D and 2D NMR data) and specific rotation with those of the natural product revealed that the absolute stereochemistry of gliomasolide E should be (2E,5R,7R,9R,13R).

Total Synthesis of Anticancer Agent EBC-23.

Total synthesis of spiroketal EBC-23 has been described by two divergent approaches from three simple building blocks. Gold-catalyzed cycloisomerization of alkynol and acid-mediated spirocyclization of diketalketone were successfully utilized to effect spiroketal formation. A Cu(I)-P(Cy)3-catalyzed protocol for the highly regio- and stereocontrolled hydroboration of internal propargylic alcohol was effectively applied toward the β-hydroxy ketone via vinylboronates.

Total Synthesis of a Diacetonide Derivative of Thuggacin A.

A highly stereoselective total synthesis of the diacetonide derivative of the antibiotic thuggacin A has been described. The synthesis features the stereoselective Stille cross-coupling reaction to set up the whole carbon framework, aldol condensation to construct the highly substituted conjugated diene, non-Evans syn aldol, CBS reduction, Hantzsch's thiazole synthesis, Horner-Wadsworth-Emmons reaction, and Shiina's macrolactonization.

Total synthesis of Ivorenolide A following a base-induced elimination protocol.

A concise and stereocontrolled first total synthesis of Ivorenolide A (1) is reported in 16 longest linear steps with a 13.4% overall yield starting from (+)-diethyl tartrate (DET). Key features are base-induced elimination protocol for the construction of chiral propargyl alcohols in both fragments, Pd-catalyzed cross-coupling of terminal acetylenes, and Shiina's 2-methyl-6-nitrobezoic anhydride (MNBA) mediated macrolactonization.

Rugulactone derivatives act as inhibitors of NF-κB activation and modulates the transcription of NF-κB dependent genes in MDA-MB-231cells.

Rugulactone and its analogues were synthesized following Horners-Wadsworth-Emmons and ring-closing metathesis as the key reactions. A library of new rugulactone analogues were designed, synthesized and evaluated for their anticancer activity in breast cancer cells. All analogues have shown anti-proliferative activity, while some of them exhibited significant cytotoxicity.

Total synthesis of nhatrangin A.

A concise and stereoselective approach for the synthesis of key intermediates for aplysiatoxins, oscillatoxins, and nhatrangins and their utility for the total synthesis of nhatrangin A has been demonstrated. The advanced intermediates aromatic aldehyde 11 and dihydroxy acid 12 were synthesized in eight steps (44% overall yield) and three steps (55% overall yield), respectively. An asymmetric Michael addition, CBS reduction, and proline-catalyzed crossed-aldol reactions were utilized as key steps for the generation of all the chirality of main chain hydroxyaldehyde, while the appended side-chain-protected 3,4-dihydroxypentanoic acid was achieved in a shortest route, using Sharpless dihydroxylation, diol protection, and RuO4-catalyzed aromatic over-oxidation reactions.

Synthesis of acylsilanes via nickel-catalyzed reactions of α-hydroxyallylsilanes.

The redox isomerization processes and tandem isomerization-aldolization reactions, mediated by nickel catalysts, offer new versatile entries to acylsilanes. For the second reaction, high diastereoselectivities, up to 98:2, have been obtained with bulky substituents on silicon.

Facile total synthesis of (-)-(5R,6S)-6-acetoxy-5-hexadecanolide from carbohydrate, a mosquito oviposition attractant pheromone.

Total synthesis of (-)-(5R,6S)-6-acetoxy-5-hexadecanolide, a major component of mosquito oviposition attractant pheromones is reported. The key synthetic steps involve epoxide opening by lithiated salt of ethylpropionate and acid catalysed lactonization. The total synthesis was achieved in 11 linear steps staring from a readily available carbohydrate δ-gluconolactone in 18% overall yield making it simple, practical and elegant.

Plant HDAC inhibitor chrysin arrest cell growth and induce p21WAF1 by altering chromatin of STAT response element in A375 cells.

Background: Chrysin and its analogues, belongs to flavonoid family and possess potential anti-tumour activity. The aim of this study is to determine the molecular mechanism by which chrysin controls cell growth and induce apoptosis in A375 cells.

Methods: Effect of chrysin and its analogues on cell viability and cell cycle analysis was determined by MTT assay and flowcytometry.

1,3-Dipolar cycloaddition of sugar azides with benzyne: a novel synthesis of 1,2,3-benzotriazolyl glycoconjugates.

Glycosyl azides undergo smooth 1,3-dipolar cycloaddition with benzyne generated in situ from 2-(trimethylsilyl)phenyltrifluoromethanesulfonate and cesium fluoride under mild conditions to furnish 1,2,3-benzotriazole-linked glycoconjugates in excellent yields and with high stereoselectivity. This method provides a novel class of benzotriazole linked glycoconjugates in a single-step reaction. This is the first example of a fluoride- triggered 1,3-dipolar cycloaddition of benzyne with glycosyl azides.

Sub-cellular internalization and organ specific oral delivery of PABA nanoparticles by side chain variation.

Background: Organic nanomaterials having specific biological properties play important roles in in vivo delivery and clearance from the live cells. To develop orally deliverable nanomaterials for different biological applications, we have synthesized several fluorescently labelled, self-assembled PABA nanoparticles using possible acid side chain combinations and tested against insect and human cell lines and in vivo animal model. Flurophores attached to nanostructures help in rapid in vivo screening and tracking through complex tissues.

Stereoselective synthesis of four possible isomers of streptopyrrolidine.

The synthesis of (4R,5R)-streptopyrrolidine (1), (4S,5R)-streptopyrrolidine (2) (4R,5S)-streptopyrrolidine (3) and (4S,5S)-streptopyrrolidine (4) have been achieved in a concise and highly efficient manner via a highly stereoselective aldol type reaction with the trimethylsilyl enolate of ethyl acetate and Lewis acid mediated lactamization as the key reactions in ≈42% yield over six steps starting from D-phenylalanine and L-phenylalanine, respectively. The absolute configuration of the natural product was shown to be (4S,5S) by comparing its spectral and analytical data with the reported values.