An asymmetric organo- and gold-catalyzed one-pot sequential Mannich/hydroamination reaction has been developed. Using this protocol, spiro[pyrrolidin-3,2′-oxindole] derivatives were synthesized in good yields (up to 91%) excellent enantioselectivities 97% ee).

Qinghaosu and derivatives were easily reduced by ferrous sulfate in aqueous acetonitrile to give results different from those reported for other reducing systems. The unstable epoxide 7, a compound that was postulated earlier as species responsible the antimalarial activity, now has been isolated characterized. speculative secondary C-4 radical also trapped with 2-methyl-2-nitrosopropane thus provides very first direct evidence involvement of radicals vitro cleavage QHS-type compounds. A...

The first total synthesis of ent-(−)-azonazine has been accomplished using a hypervalent iodine-mediated biomimetic oxidative cyclization to construct the highly strained core. Based on results from completed synthesis, both relative and absolute configurations natural (+)-azonazine were revised.

(3R,4R,5S)-4-Acetylamino-5-amino-3-hydroxy-cyclohex-1-ene-carboxylic acid ethyl ester, a functionalized cyclohexene skeleton of GS4104, was diastereoselectively synthesized. A major advantage this synthesis is the use readily available l-serine to replace frequently used (−)-shikimic or (−)-quinic as starting material. Ring-closing metathesis and diastereoselective Grignard reactions successfully served key steps. Absolute configurations intermediates were confirmed by corresponding...

Total syntheses of 22-hydroxyacuminatine and luotonin A were achieved in direct fashion high overall yields (16% eight steps 47% five steps, respectively). mild cascade methodology was successfully applied both as a common strategy. The new approach presents the advantages short routes, yields, use stable intermediates, ease operations.

Transformation of reactive isochromenylium intermediates to the corresponding storable and stable reagents has been achieved, a number tetrafluoroborates (ICTBs, 1) have conveniently prepared characterized. Direct metal-free treatment tetrafluoroborate 1a with olefins afforded variety polycyclic frameworks 4 via mild cascade reactions. Starting from prefunctionalized o-alkynylbenzaldehydes, one-pot procedure intramolecular annulation 2,3-dihydrophenanthren-4(1H)-one derivatives was also developed.

A tandem reaction initiated by Au(I)-catalyzed C1-C5 cyclization of enediynes bearing an internal carboxy nucleophile has been developed, providing a distinctive methodology for the assembly fused indenes including indeno[1,2-c]isochromen-5(11H)-ones and indeno[1,2-b]pyran-2(5H)-ones. mechanism involving concerted formation five- six-membered rings was proposed.

Chloroazaphilone is a common structure found in number of natural products. Reported herein practical synthesis model chloroazaphilone that utilizes Pb(OAc)4 oxidation HClO4/HOAc pyrinium salt key one-pot operation. Reaction this with various primary amines to afford the corresponding vinylogous γ-pyridones was also fully investigated. The isolation stable enamine intermediates provided direct evidence reaction mechanisms.

Abstract A highly efficient organocatalyzed Michael addition of 2‐oxindole‐3‐carboxylate esters to nitroolefins using a Cinchona alkaloid‐thiourea and an achiral Brønsted acid as cooperative organocatalysts is reproted that affords significantly improved enantioselectivity diastereoselectivity. It also provides approach the synthesis spirooxindole derivatives with high enantioselectivity.

Annonaceous acetogenins, a large family of naturally occurring polyketides isolated from various species the plant genus Annonaceae, have been found to exhibit significant cytotoxicity against variety cancer cells. Previous studies showed that these compounds could act on mitochondria complex-I and block corresponding electron transport chain terminate ATP production. However, more details mechanisms action remain ambiguous. In this study we tested effects set mimetics annonaceous acetogenin...

This paper presents a formal total synthesis of 3-deoxy-D-manno-2-octulosonic acid (KDO) based on highly double-stereoselective hetero Diels-Alder reaction between an electron-rich diene and ethyl glyoxylate catalyzed by (Salen)Co(II) complex, new catalyst for reactions. A facial specific hydroboration followed oxidative workup leads to diol system with the trans-diequatorial arrangement hydroxyl groups at C-4 C-5. Inversion configuration C-5 group in 12 then ketal formation afford desired...

New expeditious total syntheses of (S)-camptothecin (16% overall yield, 95% ee) and (S)-10-hydroxycamptothecin (14% 99% have been accomplished, respectively, starting from readily available inexpensive materials. Development, optimization, successful application the cascade reaction consisting a pyrrolidine-catalyzed Michael addition, an intramolecular aldol condensation, oxidative aromatization, oxa Diels−Alder cycloaddition, Sharpless asymmetric dihydroxylation make these two new more...

The first total synthesis of chlorofusin was accomplished in a convergent fashion. With all four unambiguous diastereomeric model chromophores as references, the absolute stereochemistry chromophore determined and revised to be (4S,8R,9S) by 1H NMR studies asymmetric synthesis. This allows complete structure natural assigned for time. Enantioselective copper-mediated oxidation 4, mild coupling azaphilone 2 with free amine-bearing cyclopeptide 3, one-pot three-step protocol final spiro-aminal...

An efficient methodology taking advantage of the excellent nucleophilicity aminoquinone to assemble azaanthraquinone framework was developed via an iodine-induced 6-endo-dig electrophilic cyclization. Therefore, starting from N-propargylaminoquinones, various 3-iodo-1-azaanthraquinones were obtained in yields ranging 45% 90%. The metal-free protocol features facile installation iodine atom on ring and benign functional group compatibility.

Cyclic N,O-aminals can be chemoselectively and efficiently deprotected using a catalytic amount of bismuth(III) bromide in acetonitrile at room temperature. This selectivity was also achieved the presence terminal O,O-acetal functionality. The susceptibility various other groups to cleavage investigated. method has advantages ease operation use nontoxic inexpensive reagents amounts.

Total syntheses of cassiarins A and B have been efficiently accomplished using a common strategy with biomimetic considerations. Key reactions involved in this synthesis include Negishi-type coupling, Ag(I)-promoted formation the tricyclic 8H-pyrano[2,3,4-de]chromen-8-one core, sequential amine-condensation cyclization. Three new analogues cassiarin bearing different substituents at C-11 position were synthesized parallel from same intermediate. In addition, two other transformations to key...

Efficient methodologies for constructing several multiring frameworks have been developed utilizing the cascade reactions of air-stable isochromenylium tetrafluoroborates with olefins. Successive additions two equivalents styrene-type olefins to tetrafluoroborate (ICTB) 1 observed and their mechanisms were proposed discussed. Intramolecular capture early stage cationic intermediates by predevised heteroatoms or Friedel−Crafts donors provided different types bridged-ring systems.

Abstract Small, organic, fluorescent molecules with large Stokes shifts and long emission wavelengths are ideal dyes for various modern imaging technologies such as FRET. In this study, we designed synthesized a number of new on the basic structures two pyrrolocoumarin skeletons where Fischer's indole synthesis Suzuki coupling successfully served efficient molecular editing protocols. The examination properties further structural optimization these compounds afforded three notably...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDiastereoselective Propargylation of .alpha.-Alkoxy Aldehydes with Propargyl Bromide and Zinc. A Versatile Efficient Method for the Synthesis Chiral Oxygenated Acyclic Natural ProductsWen-Lian Wu, Zhu-Jun Yao, Yun-Long Li, Jin-Cui Yi Xia, Yu-Lin WuCite this: J. Org. Chem. 1995, 60, 10, 3257–3259Publication Date (Print):May 1, 1995Publication History Published online1 May 2002Published inissue 1...

Abstract A class of structurally simplified analogues the naturally occurring annonaceous acetogenins were developed, amongst which some non‐THF showed remarkable cytotoxicities against tumor cell lines, as well good selectivity between human cells and normal cells. The synthetic routes significantly shortened because removal chiral centers bearing THF rings on natural templates. This simplification also provides access to parallel synthesis these mimics by a combinatorial strategy....

The potent anticancer agent AA005 has been successfully biolabeled with fluorescein. Of the two compounds synthesized, only AA005-flu retained selectivity of for cancerous (e.g., BEL-7404) over normal LO2) cells. Fluorescent-imaging studies revealed that AA005-flu's distribution in human cells was significantly difference from cancer cells, where accumulates mitochondria. This direct and visible evidence suggests membrane recognition is involved its selective action. Supporting information...

An efficient synthesis of the tricyclo[4,3,1,01, 5]decane core (B/C/D rings) plumisclerin A, a unique cytotoxic marine diterpenoid, is described. A Pauson–Khand reaction and SmI2-mediated radical 1,4-conjugate addition successfully served as key reactions for construction fully functionalized 5,6-fused rings highly strained cyclobutanol moiety with correct relative stereochemistries, respectively.

On the basis of ionophore model, polyether analogues 4 and 6 were designed synthesized to mimic naturally occurring annonaceous acetogenins corossolin (2) bullatin (5), which discovered as members a large family novel polyketides with cytotoxicity, antitumoral, other biological activities since 1982. The preliminary screening shows that they have compatible cytotoxicity corresponding natural acetogenins. These results open potential way find more active antitumor agents simplified structures based on