Asymmetric synthesis of 3(S),17-dihydroxytanshinone

The first synthesis of 3(S),17-dihydroxytanshinone was achieved by ultrasound promoted Diels-Alder reaction of the protected 3-hydroxymethyl-4,5-benzofurandione with a vinylcyclohexene derivative. Bioassay showed that the synthetic 3(S),17-dihydroxytanshinone was active in vitro against HL-60 tumor cell line by MTT method.     

Synthesis and determination of the relative structure of akaterpin, a potent inhibitor of PI-PLC

We describe the first total synthesis and structural determination of akaterpin, an inhibitor of phosphatidylinositol-specific phospholipase C (PI-PLC). The key features of the synthetic strategy include a regio- and stereoselective C-alkylation at the angular C1′ position and an exo-selective intermolecular Diels-Alder reaction. The relative stereochemistry was determined by a comparison of the NMR spectra of synthetic akaterpin with those of natural akaterpin.     

Total synthesis of cannabisin F

A practical eight-step synthesis of lignanamide cannabisin F starting from vanillin is reported for the first time. This synthetic strategy applies the aldol reaction followed by the Wittig reaction to afford the key 8-O-4′-neolignan intermediate diacid. The diacid was condensed with N,O-protected tyramine giving, after deprotection, cannabisin F.     

Domino Michael/aza-Wittig reaction in the diastereoselective construction of spiro[azepane-4,3′-oxindoles]

A convenient synthetic strategy for the diastereoselective assembly of spiro[azepane-4,3′-oxindoles] was developed via a Staudinger/Michael/aza-Wittig/reduction/N-deprotection reaction sequence starting from PMB-protected oxindole-substituted ethylazides. The key step of the method is a domino self-catalytic Michael/aza-Wittig reaction wherein the phosphazene moiety acts first as the catalyst and then as the reactant, resulting in the formation of a seven-membered N-heterocycle.     

Synthetic approach to seco-tetracenomycin natural products saccharothrixone A–C

Design and development of first synthetic approach to the functionalized tetracyclic framework of structurally novel seco-tetracenomycin natural products saccharothrixones A–C has been reported. A thermal dehydro Diels-Alder reaction of an arenyne-alkyne unit has been utilized as the key synthetic step. This strategy has been extended for the generation of a small library of diversely functionalized tetracyclic systems of seco-tetracenomycins. An approach for the synthesis of poly-hydroxyl tetracyclic system has also been described. This report represents the first synthetic approach to the tetracenomycin natural products saccharothrixones A–C.     

Highly Z/E stereoselective approach to β-iodo aza Morita-Baylis-Hillman adducts

A multicomponent reaction between sulfonyl-protected imines, magnesium iodide, and acetylenic esters or ketones is described. The resulting β-iodo aza Morita-Baylis-Hillman adducts were obtained in good yields and excellent Z/E stereoselectivities. The reaction showed good tolerance for sulfonyl protecting groups, as well as for acetylenic ketones and esters. This work presents the first synthetic approach to β-iodo aza Morita-Baylis-Hillman adducts.     

The first catalytic asymmetric total synthesis of ent-hyperforin

The first catalytic asymmetric total synthesis of ent-hyperforin was described here in detail. Keys to the success were a catalytic asymmetric Diels-Alder reaction, a stereoselective Clasien rearrangement, an intramolecular aldol cyclization, and a vinylogous Pummerer rearrangement. Along with the successful synthetic route, several attempted approaches toward the construction of bicyclo[3.3.1] core and the C2 oxidation were discussed.     

Total synthesis of motualevic acids A-E

The first total synthesis of motualevic acids A-E, isolated from Siliquariaspongia sp., starting from commercially available 1,10-decanediol, is described. The key steps in the synthetic sequence involve stereoselective olefination, Corey-Fuchs reaction, and amide coupling.     

Stereoselective synthesis of (-)-4-epiaxinyssamine

The synthetic studies towards axinyssamine, a cytotoxic and coral-lethal compound isolated from the Caribbean sponge Axinyssa ambrosia were performed. The Ritter reaction on the key intermediate with chloroacetonitrile, resulted in the introduction of the amino group at C-4 generating the configuration of this stereocentre opposite to that of the natural product. As a result, the first total synthesis of the unnatural (-)-4-epiaxinyssamine was achieved.     

Electrochemistry of 6-methyl-5,6,7,8-tetrahydropterin

The electrochemical oxidation of 6-methyl-5,6,7,8-tetrahydropterin (6-MTHP), the most effective of the synthetic aromatic amino acid hydroxylase pseudo cofactors, has been studied in aqueous solution over a wide pH range at a pyrolytic graphite electrode. The first electrooxidation of 6-WTHP occurs by a quasi-reversible 2e-2H⁺ reaction giving an unstable quinonoid-dihydropterin. The latter undergoes a first order chemical follow-up reaction yielding 6-methyl-7,8-dihydropterin (6-MDHP). At pH values ?5.6 6-MDHP forms an equilibrium mixture of a covalently hydrated species and non-hydrated species. The covalently hydrated form of 6-MDHP is electrooxidized in a 2e-2H⁺ quasi-reversible reaction to another unstable quinonoid that appears to undergo a two-step rearrangement to 6-methylpterin. Non-hydrated 6-MDHP is electrooxidized at the most positive potential in an irreversible 2e-2H⁺ reaction giving 6-methylpterin.     

Synthesis of functionalized tetrahydroisoquinolines via palladium-catalyzed 6-exo-dig carbocyclization of 2-bromo-N-propargylbenzylamines

An efficient twostep synthetic strategy for tetrahydroisoquinolines has been described. The first step involves CuI catalyzed three-component coupling reaction of terminal alkyne, aldehyde and amine that provides the requisite propargyl amine. Regio- and stereoselective palladium-catalyzed 6-exo-dig carbocyclization of propargyl amine, which provides a concise access to functionalized tetrahydroisoquinolines in good yields has been developed.     

<Subscript>N</Subscript>-alkyl-2-halo- and 2,2-dihaloaldimines in the Pudovik reaction

The use of N-alkyl-2-haloaldimines in the imine version of the Pudovik reaction, namely, in the reaction of imines with acid esters of phosphorus acids, much extended the synthetic potential of this reaction due to the fact that the primary addition and protonation product, having quite a mobile single hylogen atom, can undergo both spontaneous transformations and transformations involving other reagents. The reduction of the С–Hlg bond in N-alkyl-2-halo- and -2,2-dihaloaldiminium salts with О,О-dialkyl phosphorodithioic acids was observed for the first time.     

Six-membered nitrogen ring formation by radical cyclization of trichloroacetamides with enones. A synthetic entry to cis-perhydroisoquinoline-3,6-diones

Intramolecular reactions between 1-(carbamoyl)dichloromethyl radicals and enones acting as radical acceptors are reported for the first time. The Bu₃SnH promoted 6-exo reaction of trichloroacetamides with enones, avoiding the 1,5-hydrogen transfer, constitutes a new synthetic entry to cis-perhydoisoquinoline-3,6-diones.     

Biodegradation of Bisphenol A and Decolorization of Synthetic Dyes by Laccase from White-Rot Fungus, Trametes polyzona

Purified laccase from Trametes polyzona WR710-1 was used as biocatalyst for bisphenol A biodegradation and decolorization of synthetic dyes. Degradation of bisphenol A by laccase with or without redox mediator, 1-hydroxybenzotriazole (HBT) was studied. The quantitative analysis by HPLC showed that bisphenol A rapidly oxidized by laccase with HBT. Bisphenol A was completely removed within 3 h and 4-isopropenylphenol was found as the oxidative degradation product from bisphenol A when identified by GC-MS. All synthetic dyes used in this experiment, Bromophenol Blue, Remazol Brilliant Blue R, Methyl Orange, Relative Black 5, Congo Red, and Acridine Orange were decolorized by Trametes laccase and the percentage of decolorization increased when 2 mM HBT was added in the reaction mixture. This is the first report showing that laccase from T. polyzona is an affective enzyme having high potential for environmental detoxification, bisphenol A degradation and synthetic dye decolorization.     

A new method for pyrrole peri-annulation: synthesis of 1H-1,5,7-triazacyclopenta[c,d]phenalenes from 1H-perimidines

New methods for the synthesis of 1H-1,5,7-triazacyclopenta[c,d]phenalenes have been developed based on a sequence involving Schmidt reaction of keto-perimidines and acylation of the intermediate amides with 1,3,5-triazines or carboxylic acids. The same synthetic sequence starting from the corresponding alkylperimidine includes acylation with acetic acid as the first step.     

The syntheses of rac-inthomycin A, (+)-inthomycin B and (+)-inthomycin C using a unified synthetic approach

The Stille coupling between a common oxazole vinyl iodide and stereodefined stannyl-diene units is described as the cornerstone of a unified synthetic route to the inthomycin family of bioactive Streptomyces metabolites. This procedure has been utilised to prepare (+)-inthomycin B and (+)-inthomycin C for the first time; in these examples the stereogenic centre was introduced using the Kiyooka ketene acetal/amino acid-derived oxazaborolidinone variant of the Mukaiyama aldol reaction. In addition, a convenient preparation of rac-inthomycin A is described based on the same strategy.     

The use of selenium(IV) chloride for the preparation of diarylselenium dichlorides

Two new synthetic routes for the preparation of diarylselenium dichlorides are reported both of which use selenium(IV) chloride as a starting meterial. In the first method, bis(p-methóxyphenyl) and bis(p-ethoxyphenyl)-selenium dichlorides are prepared by the reaction of SeCl₄ with anisole and phenetole respectively. In the second, diphenylselenium dichloride is prepared by the reaction of SeCl₄ with tetraphenyllead, a reaction in which the lead—carbon bond is cleaved.The far infrared and Raman spectra of the diarylselenium dichlorides are reported.     

A convenient synthesis of olefins via deacylation reaction

A convenient and environmentally-friendly synthetic method of olefins via deacylation reaction is described. The reaction gives olefins by condensation of aldehydes with a variety of 1,3-dicarbonyl compounds in the presence of anhydrous potassium carbonate at room temperature in high yields (70-90%) in one step. The synthetic potential of this strategy can be used as an alternative procedure to the Wittig, Wittig-Horner reactions. The stereochemistry of the resulted olefins was determined by NOE experiment with correct radio frequency and X-ray analysis. The E/Z selectivity of the deacylation reaction depends on the α-substituents of the 1,3-dicarbonyl compounds.     

Heteroligand and heteronuclear clamshell-type phthalocyanines: selective preparation, spectral properties, and synthetic application

A direct synthetic method to produce heteronuclear and heteroligand clamshell-type binuclear phthalocyanines via a nucleophilic coupling reaction between A₃B-type monophthalocyanines is developed with the target compounds demonstrating the possibility to form sandwich-type heterocomplexes for the first time.     

Copper-catalyzed asymmetric silylative cyclization of cyclohexadienone-containing 1,6-enynes

The first copper-catalyzed asymmetric silylative cyclization of cyclohexadienone-containing 1,6-enynes has been accomplished through a tandem process: regioselective silylcupration of terminal unactivated alkynes and subsequently enantioselective conjugate addition to cyclohexadienones. This reaction proceeded smoothly to afford the cis-hydrobenzofuran and cis-hydroindole frameworks bearing two consecutive chiral carbon centers in high to excellent yields and moderate enantioselectivities. Additionally, the cyclization products could be readily subjected to several transformations for elaborating synthetic utilities.