Rapid Assembly of 1,3-Dicarbonyl Fused 5-phenyl-1-Azabicyclo[3.1.0]hexanes and Their Cytotoxic Activities.

Synthesis of complex, multiring, spirocyclic, 1,3-dicarbonyl fused, and highly functionalized 5-phenyl-1-azabicyclo[3.1.0]hexanes (ABCH) has been achieved by an intermolecular reaction of 2-(2'-ketoalkyl)-1,3-indandiones or α,γ-diketo esters with (1-azidovinyl)benzenes under transition metal-free conditions.

Synthesis of Spirocyclic-1,3-Indandione Containing-Cyclopentenones and -Benzotropones.

Synthesis of functionalized 1,3-indandiones containing-cyclopentenones and -benzotropones has been achieved by the reaction of 1,5-diphenylpenta-1,4-diyn-3-ones with 1,3-indandiones, bindone respectively. The developed method involves Michael-anti-Michael addition cascade reactions under transition-metal-free conditions. This is the first report to synthesise diverse benzotropone fused with 1,3-indandiones under transition metal-free conditions from bindone.

A Three-Component Synthesis of Spiropyrrolines.

A rapid synthesis of medicinally important spiropyrrolines has been achieved by the reaction of 1,3-indanediones, benzaldehyde, and (1-azidovinyl)benzene under catalyst- and reagent-free conditions. This is the first report to synthesize diverse spiropyrroline compounds from readily available feedstock materials under metal-free conditions.

Total Synthesis and Determination of the Absolute Configuration of Berkeleylactone I.

Herein, we report the first total synthesis of berkeleylactone I and its 12 diastereomer. Consequently, this chemical synthesis allowed us to establish the unknown absolute stereochemistry at the C-12 center as 12, which was unidentified by the isolation group. This synthetic approach includes several critical reactions, such as the Sharpless asymmetric dihydroxylation, Baran's Ni-catalyzed alkyl-alkyl cross-coupling reaction, Brown allylation, Mitsunobu reaction, and ring-closing metathesis, as key steps.

Total Synthesis, Revised Structure, and Biological Evaluation of Elgonene B and Analogues.

Herein, we report the first total synthesis of elgonene B and its congeners, thus resulting in a revision of the configuration at the C-6 carbon of the originally proposed structure of elgonene B. This synthetic approach demonstrates the utility of several important reactions such as the chiral oxazaborolidinium ion-catalyzed Diels-Alder reaction, Ando's Horner-Wadsworth-Emmons olefination, and the intermolecular Nozaki-Hiyama-Kishi reaction as key steps. Additionally, the study explores the cytotoxic and antibacterial activities of elgonene B and its congeners (-).

Synthesis of Highly Functionalized Spirocycles and Pentafulvene-Containing Dyes Involving 2-(2'-ketoalkyl)-1,3-indandiones.

Synthesis of highly functionalized spiro[4.4]nonane and spiro[4.5]decane motifs by the reaction of dimethylacetylenedicarboxylate (DMAD) with 2-(2'-ketoalkyl)-1,3-indandiones and 2-(3'-ketoalkyl)-1,3-indandiones, respectively, has been developed by utilizing a catalytic amount of DABCO.

Cascade Nucleophilic Addition-Cyclic Michael Addition of Arynes and Indoles Bearing Michael Acceptor: A Strategy to Construct Pyrroloacridines and Study of Their Physicochemical Properties.

A facile synthetic approach to 6-pyrrolo[3,2,1-]acridines has been developed by using cascade -nucleophilic addition-cyclic Michael addition process of arynes and indoles substituted with Michael acceptors under metal-free conditions. Additionally, photophysical studies of a few of the newly synthesized pyrroloacridine compounds indicated good fluorescence emission properties.

A Method to Access Highly Functionalized Dibenzobicyclo[3.2.1]octadienones: Application to the Construction of the 6/6/5/6/6 Carbon Skeleton of Rubialatin A.

The dibenzobicyclo[3.2.1]octadienone scaffold, which has been found in naphthocyclinones, engelharquinones, rubialatin A, etc.

Total synthesis of proposed elgonene C and its (4,5)-diastereomer.

The total synthesis of the proposed elgonene C (1) and its (4,5)-diastereomer (1a) has been achieved using a second-generation oxazaborolidinium ion-catalysed Diels-Alder reaction, Sharpless asymmetric dihydroxylation, and a Ni-catalysed cross-carboxyl coupling reaction redox-active ester (RAE) formation as key reactions. The spectral and analytical data for our synthetic compounds 1 and 1a do not match the isolation data provided by Stadler . which indicates that structural revision is required for the proposed elgonene C.

Strategies for the construction of γ-spirocyclic butenolides in natural product synthesis.

Over the last four decades, a number of γ-spirocyclic butenolide containing natural products, drugs, and medicinally useful synthetic compounds have been reported. In this review, we discuss diverse chemical approaches to synthesize γ-spiro butenolides and their application towards natural product synthesis. The collective perception of various methods may allow superior approaches capable of delivering efficient synthetic approaches to obtain γ-spiro butenolide comprising natural products and their hybrid analogues for further drug discovery and development.

Useful Applications of Enantioselective (4 + 2)-Cycloaddition Reactions to the Synthesis of Chiral 1,2-Amino Alcohols, 1,2-Diamines, and β-Amino Acids.

The scope of enantioselective (4 + 2)-cycloaddition reactions has been expanded to include reactive olefinic components that are equivalents of three inoperable and unstable ethylene derivatives: 1-hydroxy-2-aminoethylene, 1,2-diaminoethylene, and β-aminoacrylic acid. In this way, a variety of otherwise unavailable functionalized (4 + 2)-cycloadducts have been synthesized from 1,3-dienes with high enantioselectivity (92-98%) and in good yields. The research leading up to this synthetic advance has also produced some surprising insights on reactivity and positional selectivity in catalytic enantioselective (4 + 2)-cycloaddition.

Acceleration of Enantioselective Cycloadditions Catalyzed by Second-Generation Chiral Oxazaborolidinium Triflimidates by Biscoordinating Lewis Acids.

The activation of second-generation fluorinated oxazaborolidines by the strong acid triflimide (Tf2NH) in CH2Cl2 solution leads to highly active chiral Lewis acids that are very effective catalysts for (4 + 2) cycloaddition. We report herein that this catalytic activity can be further enhanced by the use of Tf2NH in combination with the biscoordinating Lewis acid TiCl4 or SnCl4 as a coactivator. The effective increase in acidity of an exceedingly strong protic acid is greater for biscoordinating TiCl4 and SnCl4 than for monocoordinating salts, even the strong Lewis acids AlBr3 and BBr3 in CH2Cl2 or CH2Cl2/toluene.

Gold-catalyzed Hosomi-Sakurai type reaction for the total synthesis of herboxidiene.

Total synthesis of herboxidiene/GEX1A/TAN-1609 has been accomplished in the 22 longest linear sequences starting from 2-butyne-1,4-diol following our recently developed gold-catalyzed Hosomi-Sakurai type of reaction on lactols with allyltrimethyl silane and Stille cross coupling to assemble the advanced fragment. The synthesis of the C10-C19 fragment was accomplished by means of Sharpless epoxidation and asymmetric alkylation reactions starting from (R)-methyl lactate.

Cationic Chiral Fluorinated Oxazaborolidines. More Potent, Second-Generation Catalysts for Highly Enantioselective Cycloaddition Reactions.

The coordination of chiral ligands to Lewis acid metal derivatives, a useful strategy for enantioselective, electrophilic catalysis, generally leads to a lower level of catalytic activity than that of the original uncomplexed compound. Activation by further attachment of a proton or strong Lewis acid to the complex provides a way to overcome the deactivating effect of a chiral ligand. The research described herein has demonstrated that further enhancement of catalytic activity is possible by the judicious placement of fluorine substituents in the chiral ligand.

A carbohydrate-based total syntheses of (+)-pyrenolide D and (-)-4-epi-pyrenolide D.

Efficient total syntheses of (+)-pyrenolide D (5) and (-)-4-epi-pyrenolide D (6) have been achieved from a known 5-deoxy-d-xylose derivative 9 in ten steps with 19% overall yield either exclusively as 5 or as pure 5 and 6 in a 3:2 ratio. Key steps involved are one-pot epoxidation-cyclization by Corey-Chaykvosky reagent, reductive Barton-McCombie deoxygenation, and per-acid mediated oxidative spiroketalization.

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.