Concise, asymmetric total synthesis of spirotryprostatin A

Enantioselective formal total synthesis of dihydrospirotryprostatin B

Spirotryprostatins are representative members of medicinally interesting bioactive molecules of the spirooxindole natural products. In this communication, we present a novel enantioselective total synthesis of the spirooxindole alkaloid dihydrospirotryprostatin B. The synthesis takes advantage of copper-catalyzed tandem reaction of o-iodoanilide chiral sulfinamide derivatives with alkynone to rapidly construct the key quaternary carbon stereocenter of the natural product dihydrospirotryprostatin B.

Recent Advances in the Total Synthesis of Spirotryprostatin Alkaloids

Spirotryprostatin alkaloids, a class of alkaloids with a unique spirocyclic indoledionepiperazine structure, were first extracted from the fermentation broth of Aspergillus fumigatus and have garnered significant attention in the fields of biology and pharmacology. The investigation into the pharmacological potential of this class of alkaloids has unveiled promising applications in drug discovery and development. Notably, certain spirotryprostatin alkaloids have demonstrated remarkable anti-cancer activity, positioning them as potential candidates for anti-tumor drug development. In recent years, organic synthetic chemists have dedicated efforts to devise efficient and viable strategies for the total synthesis of spirotryprostatin alkaloids, aiming to meet the demands within the pharmaceutical domain. The construction of the spiro-C atom within the spirotryprostatin scaffold and the chirality control at the spiro atomic center emerge as pivotal aspects in the synthesis of these compounds. This review categorically delineates the synthesis of spirotryprostatin alkaloids based on the formation mechanism of the spiro-C atom.

Design, Synthesis, Antifungal Evaluation, Structure-Activity Relationship (SAR) Study, and Molecular Docking of Novel Spirotryprostatin A Derivatives

Phytopathogenic fungi cause plant diseases and economic losses in agriculture. To efficiently control plant pathogen infections, a total of 19 spirotryprostatin A derivatives and 26 spirooxindole derivatives were designed, synthesized, and tested for their antifungal activity against ten plant pathogens. Additionally, the intermediates of spirooxindole derivatives were investigated, including proposing a mechanism for diastereoselectivity and performing amplification experiments. The bioassay results demonstrated that spirotryprostatin A derivatives possess good and broad-spectrum antifungal activities. Compound 4d exhibited excellent antifungal activity in vitro, equal to or higher than the positive control ketoconazole, against Helminthosporium maydis, Trichothecium roseum, Botrytis cinerea, Colletotrichum gloeosporioides, Fusarium graminearum, Alternaria brassicae, Alternaria alternate, and Fusarium solan (MICs: 8-32 µg/mL). Compound 4k also displayed remarkable antifungal activity against eight other phytopathogenic fungi, including Fusarium oxysporium f. sp. niveum and Mycosphaerella melonis (MICs: 8-32 µg/mL). The preliminary structure-activity relationships (SARs) were further discussed. Moreover, molecular docking studies revealed that spirotryprostatin A derivatives anchored in the binding site of succinate dehydrogenase (SDH). Therefore, these compounds showed potential as natural compound-based chiral fungicides and hold promise as candidates for further enhancements in terms of structure and properties.

Highly Stereodivergent Synthesis of Chiral C4-Ester-Quaternary Pyrrolidines: A Strategy for the Total Synthesis of Spirotryprostatin A

In this work, we disclose two sets of highly diastereo- and enantioselective [3 + 2] cycloadditions of iminoesters with various α-substituted acrylates, especially for sterically hindered and weakly activated α-aryl or alkyl-substituted acrylates and alkenal, alkynal, or unstable aliphatic aldehyde-derived iminoesters, catalyzed by the AgHMDS/DTBM-Segphos or Ag₂O/CA-AA-Amidphos catalytic system, achieving the stereodivergent synthesis of chiral C4-ester-quaternary exo- or endo-pyrrolidines with high yields and excellent diastereo- and enantioselectivities (up to >99:1 dr and >99% ee). More importantly, the gram-scale synthetic exo-adduct displays significant applications in the aspect of realizing the total synthesis of the spirotryprostatin A alkaloid via nine steps in a 36% overall yield.

Enantioselective Total Synthesis of Spirotryprostatin A

In this paper, we disclosed a novel enantioselective total synthesis of spirotryprostatin A (1) in 15 steps with a 7.4% total yield from commercially available 2-iodo-5-methoxyaniline and γ-butyrolactone. The key step features of this synthesis include the copper-catalyzed cascade reaction of o-iodoaniline derivatives with alkynone to introduce the quaternary carbon stereocenter and an aza-Michael tandem reaction to construct the spiro[pyrrolidine-3,3'-oxindole] moiety.

Asymmetric Synthesis of Spiro[3,2'-morpholine-oxindoles] Derivatives via the [5 + 1] Annulation Reaction

An efficacious method in which BINOL-type chiral imidodiphosphoric acid catalyzed the asymmetric [5 + 1] annulation reaction of 2-pyrrolylphenol with 1-methylindoline-2,3-dione was established. The strategy tolerated a broad substrate scope, and 30 examples were obtained. A range of enantioenriched spiro[3,2'-morpholine-oxindole] derivatives which incorporate a tertiary stereocenter, with moderate to excellent yields (up to 96%) and enantioselectivities (up to 99%) under mild conditions, was delivered.

Nine-step total synthesis of (−)-strychnofoline

The asymmetric synthesis of an anti-cancer spirooxindole alkaloid, (−)-strychnofoline, has, for the first time, been accomplished in only nine steps.

Synthesis of Functionalized 6-Hydroxy-2-oxindole Derivatives by Phenoxide Cyclization

An apparent intramolecular cross-dehydrogenative coupling of N-(3-hydroxy)monoanilide of maleic esters comprising base promoted phenoxide cyclization and subsequent base-mediated aerobic oxidation was developed to synthesize a variety of 2-(6-hydroxy-2-oxoindolin-3-ylidene)acetate derivatives. The isolation of intermediate cyclized products during the large scale reactions and their ready dehydrogenation with 1 equiv of base support this proposed two-step path.

2-Indolinone a versatile scaffold for treatment of cancer: a patent review (2008-2014)

INTRODUCTION

2-Indolinone is a well-known aromatic heterocyclic organic compound. A lot of work has been done on this bicyclic structure by academic and company researchers to synthesize compounds directed to a plethora of molecular targets in order to discover new drug leads. This review presents up-to-date information in the field of cancer therapy research based on this small building block.

AREAS COVERED

The present review gives an account of the recent patent literature (2008-2014) describing the discovery of 2-indolinone derivatives with selected therapeutic activities. In this period, a large amount of patents were published on this topic. We have limited the analysis to 37 patents on 2-indolinone derivatives having potential clinical application as chemotherapeutic agents. In this review, the therapeutic applications of 2-indolinone derivatives for the treatment of cancer reported in international patents have been discussed.

EXPERT OPINION

2-Indolinone is the scaffold of the compounds considered from a medicinal chemistry perspective. Many of them have been developed and marketed for therapeutic use. In cancer chemotherapy, progress has been made in designing selective 2-indolinone derivatives. Some of them show preclinical efficacy. However, 2-indolinone has not exhausted all of its potential in the development of new compounds for clinical applications and remains a great tool for future research.

Molecular diversity of spirooxindoles. Synthesis and biological activity

Spirooxindoles are important synthetic targets possessing extended biological activity and drug discovery applications. This review focuses on the various strategies for the enantioselective synthesis of spirocyclic oxindoles relying on reports over the past decade and from earlier work. The spirooxindoles in this review are separated into three structural classes, and then further categorized into the method type from which the spirocycle is generated.

Rapid and Efficient Synthesis of Spiro-Oxindoles using Fe3+-Montmorillonite under Ultrasonic Irradiation

A simple and efficient one-pot three-component approach was devised for the synthesis of spiro-oxindoles through the reaction of isatin derivatives, malononitrile and 1,3-dicarbonyl compounds in the presence of modified montmorillonite (Fe3+-mont.) under ultrasonic irradiation. The reaction furnished the desired products in excellent yields (85–95%) and short reaction times (2–7 min).

Organocatalytic Highly Enantioselective Substitution of 3-(1-Tosylalkyl)indoles with Oxindoles Enables the First Total Synthesis of (+)-Trigolutes B

A highly enantioselective organocatalytic substitution of 3-(1-tosylalkyl)indoles with oxindoles has been established by using chiral bifunctional organocatalysts, providing an efficient entry to multiply functionalized 3,3'-disubstituted oxindoles, and was exploited as the key step to enable the first asymmetric total synthesis of optically pure (+)-trigolutes B to be accomplished in a concise manner, within seven steps with an 18% overall yield.

Tuneable radical cyclisations: a tin-free approach towards tricyclic and spirocyclic heterocycles via a common precursor

A novel common precursor approach towards both tricyclic and spirocyclic heterocycles is described. Cyclisations are based on thiyl radical/isocyanide methodology and avoid the use of tin.

Secondary metabolites from the endophytic fungi Penicillium polonicum and Aspergillus fumigatus

Two new compounds, rhodostegone (1) from endophytic fungus Penicillium polonicum and cyclo-(l-Val-l-Leu) (2) from Aspergillus fumigatus, together with six known diketopiperazines (3-8), were isolated. The structures of these compounds were characterized through a combination of extensive IR, MS, NMR, and CD analysis.

Expanding the chemical diversity of spirooxindoles via alkylative pyridine dearomatization

A mild and practical synthesis of spirooxindole [1,3]oxazino derivatives from N-substituted isatins and 1,3-dicarbonyl compounds with pyridine derivatives is reported. The reactions provided good to excellent yields. Further exploration of the molecular diversity of these compounds is demonstrated through Diels–Alder reactions.

SYNTHETIC STUDIES ON MPC1001: A DIPOLAR CYCLOADDITION APPROACH TO THE PYRROLIDINE RING SYSTEM

A novel [1,3]-dipolar azomethine ylide cycloaddition has been developed in an approach to the synthesis of the MPC1001 family of natural products.

Natural products synthesis: enabling tools to penetrate Nature's secrets of biogenesis and biomechanism

Selected examples from our laboratory of how synthetic technology platforms developed for the total synthesis of several disparate families of natural products was harnessed to penetrate biomechanistic and/or biosynthetic queries is discussed. Unexpected discoveries of biomechanistic reactivity and/or penetrating the biogenesis of naturally occurring substances were made possible through access to substances available only through chemical synthesis. Hypothesis-driven total synthesis programs are emerging as very useful conceptual templates for penetrating and exploiting the inherent reactivity of biologically active natural substances. In many instances, new enabling synthetic technologies were required to be developed. The examples demonstrate the often untapped richness of complex molecule synthesis to provide powerful tools to understand, manipulate and exploit Nature's vast and creative palette of secondary metabolites.

Cycloaddition of homochiral dihydroimidazoles: a 1,3-dipolar cycloaddition route to optically active pyrrolo[1,2-a]imidazoles

N-Alkylation of optically active 1-benzyl-4-phenyl-4,5-dihydroimidazole with active alkyl halides and treatment of the so-formed 4,5-dihydroimidazolium ions with DBU in the presence of a range of electron-deficient alkene dipolarophiles, constitutes a 'one-pot' cascade terminating in a 1,3-dipolar cycloaddition reaction that affords optically active pyrrolo[1,2-a]imidazoles. Three bonds of the so-formed pyrrolidine moiety are constructed in this cascade. The cycloaddition follows an endo approach of dipole and dipolarophile with anti geometry of the dipole and facial selectivity derived from the phenyl substituent. Inter- and intramolecular cycloaddition modes are observed.

A rapid three-component MgI(2)-mediated synthesis of 3,3-pyrollidinyl spirooxindoles

The rapid synthesis of 3,3-pyrollidinyl-spirooxindole cores from readily available cyclopropyl spirooxindoles and commercially available aldehydes, amines, and sulfonamides is reported. This general procedure utilizes microwave heating to access a biologically privileged scaffold in an efficient route amenable to library population.

Indole prenylation in alkaloid synthesis

Important biologically active indole alkaloids are decorated with prenyl (3,3-dimethylallyl) and tert-prenyl (1,1-dimethylallyl) groups. Covering the literature until the end of 2010, this review article comprehensively summarises and discusses the currently available technologies of prenylation and tert-prenylation of indoles, which have been applied in natural products total syntheses or could be applied there in the near future. We focus on those procedures which introduce the C(5) units in one step, organised according to the indole position to be functionalised. Key strategies include electrophilic and nucleophilic prenylation and tert-prenylation, prenyl and tert-prenyl rearrangements, transition metal-mediated reactions and enzymatic methods.

Synthetic Studies on Palau'amine. Construction of the Cyclopentane Core via an Asymmetric 1,3-Dipolar Cycloaddition

The cyclopentane core of palau'amine has been constructed in optically pure form through the use of an asymmetric azomethine ylid [1,3]-dipolar cycloaddition reaction.

Multicomponent reaction discovery: three-component synthesis of spirooxindoles

The Lewis acid-catalyzed, three-component reaction of isatin and two 1,3-dicarbonyl compounds is reported. Reactions proceed with high efficiency under mild reaction conditions and with good functional group tolerance to afford spirooxindole pyranochromenedione derivatives.

Asymmetric 1,3-dipolar cycloadditions of acrylamides

This critical review, which is relevant to researchers in synthetic organic chemistry, focuses on asymmetric 1,3-dipolar cycloadditions with acrylamides. The use of chiral acrylamides as dipolarophiles leads to high levels of stereocontrol, due to conformational constraint in the acrylamides. Employment of chiral tertiary acrylamides containing nitrogen heterocycles is particularly effective in controlling the stereoselectivity. Following a general overview of 1,3-dipolar cycloadditions, the main body of the review focuses on asymmetric 1,3-dipolar cycloadditions of acrylamides with nitrile oxides, nitrones, diazoalkanes and azomethine ylides, with particular emphasis on the rationale for the observed stereocontrol (215 references).

Pyrrolidinyl-spirooxindole natural products as inspirations for the development of potential therapeutic agents

The 3,3'-pyrrolidinyl-spirooxindole unit is a privileged heterocyclic motif that forms the core of a large family of alkaloid natural products with strong bioactivity profiles and interesting structural properties. Significant recent advances in the synthesis of this fused heterocyclic system have led to intense interest in the development of related compounds as potential medicinal agents or biological probes.