Multi-Component Reactions in Protein Modification and Immobilization

Protein modification/immobilization has been introduced as a large toolbox for creating a myriad of engineered proteins with profound implications for various scientific and industrial applications. Proteins immobilization techniques are generally performed through protein fixation in/to heterogeneous materials or via inter cross-linking of protein molecules, enabling the development of biocatalysts, biosensors, and drug delivery systems. On the other hand, chemical modification of proteins offers tailored changes in their functionality, enhances protein performance, extends their shelf life, and enables their specific binding interactions. The choice of immobilization or modification technique depends on the significance of various factors for the final product. Chemical coupling methods that create covalent bonds are commonly used for both proposes. Multi-component reactions are particularly effective because they operate under mild conditions to maintain protein functionality while simultaneously introducing multiple functional groups. This review provides an overview of multi-component reactions employed for the immobilization and modification of proteins.

One-pot three-component synthesis of azaspirononatriene derivatives

The present investigation has introduced a new class of isocyanide/acetylene-based multicomponent reactions (IAMCRs). These are a robust technique for efficiently synthesizing intricate spiro architectures through a zwitterionic adduct. The coupling reaction between the "in situ" generated dipoles of the isocyanide-acetylenic ester adducts and 3-alkyl-4-arylidene-isoxazol-5(4H)-one derivative presents a highly effective synthetic pathway for obtaining novel 1-oxo-2-oxa-3-azaspiro[4.4]nona-3,6,8-triene heterocycles. The broad range of substrates, standard experimental conditions, straightforward procedure, and impressive yields make our catalyst-free three-component approach highly practical and green, as it remarkably offers step-, time- and cost-effectiveness based on the green metrics.

Efficacy of radical reactions of isocyanides with heteroatom radicals in organic synthesis

Isocyanide is a promising synthetic reagent not only as a one-carbon homologation reagent but also as a nitrogen source for nitrogen-containing molecules. Because of their isoelectronic structure with carbon monoxide, isocyanides also react with nucleophiles, electrophiles, carbon radicals, and transition metal reagents, and are widely used in organic synthesis. On the other hand, the use of isocyanides in reactions with heteroatom radicals is limited. However, the reaction of isocyanides with heteroatom radicals is a promising synthetic tool for the construction of nitrogen-containing organic molecules modified with a variety of heteroatoms. In this Perspective, we review the addition and cyclization reactions of heteroatom radicals with isocyanides and discuss the synthetic prospects of the reaction of isocyanides with heteroatom radicals.

Construction of Diverse Fused Chromene Frameworks via Isocyanide-Based Three-Component Reaction

A convenient synthetic protocol for diverse fused chromenes was successfully developed by a three-component reaction of alkyl isocyanides, dialkyl but-2-ynedioates, and various cyclic 1,3-dipolarophiles containing o-hydroxyphenyl group. In the absence of any catalyst, the three-component reaction of alkyl isocyanides, dialkyl but-2-ynedioates, and 3-(o-hydroxyarylidene)indolin-2-ones in tetrahydrofuran at 60 °C resulted in unique functionalized spiro[cyclobuta[c]chromene-1,3'-indolines] in good yields and with high diastereoselectivity. However, the similar three-component reaction with 2-(5-halo-2-hydroxyarylidene)indolin-2-ones afforded unexpected chain products in satisfactory yields. In addition, the three-component reaction of alkyl isocyanides, dialkyl but-2-ynedioates, and 2-(o-hydroxyarylidene)-1,3-indanediones in tetrahydrofuran at 60 °C resulted in complex indeno[2',1':5,6]pyrano[3,4-c]chromene derivatives in high yields and with high diastereoselectivity.

Rapid construction of tricyclic tetrahydrocyclopenta[4,5]pyrrolo[2,3-b]pyridine via isocyanide-based multicomponent reaction

An efficient protocol for the synthesis of polyfunctionalized tetrahydrocyclopenta[4,5]pyrrolo[2,3-b]pyridine-3,4b,5,6,7(1H)-pentacarboxylates was developed by a three-component reaction. In the absence of any catalyst, the three-component reaction of alkyl isocyanides, dialkyl but-2-ynedioates and 5,6-unsubstituted 1,4-dihydropyridines in refluxing acetonitrile afforded polyfunctionalized tetrahydrocyclopenta[4,5]pyrrolo[2,3-b]pyridine-3,4b,5,6,7(1H)-pentacarboxylates in high yields and with high diastereoselectivity. The reaction was finished by in situ generation of activated 5-(alkylimino)cyclopenta-1,3-dienes from addition of alkyl isocyanide to two molecules of but-2-ynedioates and sequential formal [3 + 2] cycloaddition reaction with 5,6-unsubstituted 1,4-dihydropyridine.

Photocatalytic cyclization of 3-(2-isocyanophenyl)quinazolin-4(3H)-ones for the construction of quinoxalino[2,1-b]quinazolinones

A new kind of building unit, 3-(2-isocyanophenyl)quinazolin-4(3H)-ones, was designed and synthesized for the construction of novel quinoxalino[2,1-b]quinazolinones. The radical cyclization of 3-(2-isocyanophenyl)quinazolin-4(3H)-ones with ethers afforded ether-substituted tetracyclic quinoxalino[2,1-b]quinazolinones under photocatalytic and metal-free conditions. In the process, the isocyano accepts a carbon radical to give an imidoyl radical, which adds to the electron-deficient CN bond in quinazolin-4(3H)-one.

Isocyanide-based multicomponent reactions for the synthesis of benzopyran derivatives with biological scaffolds

Benzopyrans (BZPs) are among the most privileged and influential small O-heterocycles that form the core of many natural compounds, commercial drugs, biological compositions, agrochemicals, and functional materials. BZPs are divided into six general categories including coumarins, chromans, 2H-chromenes, 4H-chromenes, chromones, and 4-chromanones, each of which is abundant in many plants and foods. These oxygenated heterocyclic compounds are fascinating motifs and have extensive applications in biology and materials science. Hence, numerous efforts have been made to develop innovative approaches for their extraction and synthesis. However, most of them are step-by-step or multi-step strategies that suffer from waste material generation and a tedious extraction process. Isocyanide-based multicomponent reactions (I-MCRs) offer a highly efficient method for overcoming these problems. The I-MCR is a simple and environmentally friendly one-pot domino procedure that does not require intermediate isolation or workup and is generally more efficient in material usage. This review covers all research articles related to I-MCRs for synthesizing BZP derivatives from the beginning to the middle of the year 2023. This strategy will be useful for organic and pharmaceutical chemists to design new drugs and optimize the synthesis steps of biological compounds and commercial drugs with benzopyran cores.

Cyanation with isocyanides: recent advances and perspectives

Cyanation has attracted considerable attention in organic synthesis because nitriles are key structural motifs in numerous important dyes, agrochemicals, natural products and drug molecules. As the fourth generation of cyanating reagents, isocyanides occupy a prominent place in the synthesis of nitriles due to their favorable stability, easy operability and high reactivity. In recent years, three types of cyanation with isocyanides have been established: the cleavage of the C-NC bond of tertiary alkyl isocyanides (Type I), the rearrangement of aryl isocyanides with azides (Type II), and the reductive cyanation of ketones with α-acidic isocyanides (Type III). This review focuses on advances in cyanation with isocyanides with an emphasis on reaction scope, limitations and mechanisms, which could reveal their remarkable value and superiority for accessing various nitriles. In addition, the future development prospects of this specific field are also introduced. We believe that this feature article will serve as a comprehensive tool to navigate cyanation with isocyanides across the vast area of synthetic chemistry.

Isocyanide-based synthesis of spirorhodanine-cyclopentadiene and spirorhodanine-iminobutenolide conjugates from Winterfeldt's zwitterions and 5-ylidene rhodanines

An ultrasonic-assisted isocyanide-based protocol to access a series of functionalized spirorhodanine-cyclopentadiene and spirorhodanine-iminobutenolide conjugates from alkyl isocyanides and dialkyl acetylenedicarboxylates in the presence of 5-ylidene rhodanines in MeCN, is described. The reaction proceeds via interception of the reactive Winterfeldt's zwitterions by 5-ylidene rhodanine derivatives. The structures of the target compounds were confirmed by X-ray diffraction studies.

First-row transition metal for isocyanide-involving multicomponent reactions (IMCR)

First-row transition metal catalyzed transformations that are able to construct complex molecules from simple, readily obtainable feedstocks have become a keystone of modern synthetic organic chemistry. Particularly, the multicomponent reaction (MCR) involving carbon-carbon (C-C) as well as carbon-heteroatom (C-X) bond formation plays an essential role in many chemical conversions, and insurgencies in these reactions powerfully improve the overall synthetic efficiency. Recently, MCRs emerges rapidly because of its greener sides like eco-friendly nature, swift and straightforward execution, high atom/step economy, and construction of aimed product with lowest or no by-product, usually in quantitative yield. Curiously, the exceptional divalent carbon atoms of isocyanides make them predominantly useful components in multicomponent reactions. As a result of widespread research over the past few decades, numerous well-designed and effective procedures for the first-row TM-catalyzed MCR to afford the various entities have been reported. These aspects are summarized in this review article. A particular focus on comparative discussion of various first-row transition-metal catalyzed isocyanide-based multicomponent reactions through mechanistic details included in the review article.

Multicomponent cyclization with azides to synthesize N-heterocycles

Heterocyclic compounds, both naturally derived and synthetically produced, constitute a wide variety of biologically active and industrially important compounds. The synthesis and application of heterocyclic compounds have garnered significant attention and experienced rapid growth in recent decades. Organic azides, due to their unique properties and distinctive reactivity, have become a convenient chemical tool for achieving a wide range of heterocycles such as triazoles and tetrazoles. Importantly, the field of multicomponent reaction (MCR) chemistry provides a convergent approach to access various N-heterocyclic scaffolds, offering novelty, diversity, and complexity. However, the exploration of MCR pathways to N-heterocyclic compounds remains incomplete. Here, we review the use of multicomponent reactions for the preparation of N-heterocycles. A wide range of reactions based on azides for the synthesis of various types of N-heterocyclic systems have been developed.

Ethyl 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylate in the smiles rearrangement reaction: straightforward synthesis of amino acid derived quinolin-2(1H)-one enamines

This paper describes the development of 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylate compound as a heterocyclic enols containing a Michael acceptor so that it participates in an Ugi-type multicomponent condensation through a Smiles rearrangement in replacement of acid components. The new four-component containing 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylate, aldehyde derivatives, amine derivatives and isocyanides process leads readily and efficiently to heterocyclic enamines. This report is an outstanding strategy for the preparation of new biologically structures containing peptidic or pseudo-peptidic with quinolin-2(1H)-one scaffolds.

Multicomponent Reactions between Heteroatom Compounds and Unsaturated Compounds in Radical Reactions

In this mini-review, we present our concepts for designing multicomponent reactions with reference to a series of sequential radical reactions that we have developed. Radical reactions are well suited for the design of multicomponent reactions due to their high functional group tolerance and low solvent sensitivity. We have focused on the photolysis of interelement compounds with a heteroatom-heteroatom single bond, which readily generates heteroatom-centered radicals, and have studied the photoinduced radical addition of interelement compounds to unsaturated compounds. First, the background of multicomponent radical reactions is described, and basic concepts and methodology for the construction of multicomponent reactions are explained. Next, examples of multicomponent reactions involving two interelement compounds and one unsaturated compound are presented, as well as examples of multicomponent reactions involving one interelement compound and two unsaturated compounds. Furthermore, multicomponent reactions involving intramolecular cyclization processes are described.

Bronsted Acid-Catalyzed Regioselective Carboxamidation of 2-Indolylmethanols with Isonitriles

A regioselective direct carboxamidation reaction of 2-indolylmethanols with readily available isocyanoesters/isocyanides has been reported in this work. The reaction was catalyzed by Bronsted acid such as p-TsOH to deliver the benzylic regioselective amides in 67-86% yield under mild conditions. The developed methodology provides alternative access to traditional metal-free carboxamidation via C-C and C-O bond formation with high atom economy. Furthermore, the developed approach was diversified to synthesize chiral indole-2-carboxamide derivatives with a moderate enantiomeric excess (61-73% ee) using an (R)-chiral phosphoric acid.

Ni-Catalyzed Mild Synthesis of Sulfonylurea via Tandem Coupling of Sulfonyl Azide, Isocyanide, and Water

An efficient, mild, and novel route is developed to synthesize sulfonylurea via the nickel-catalyzed tandem coupling of sulfonyl azide, isocyanide, and water in aqueous media. The sulfonyl azide is expected to act as a nitrene precursor, which upon reaction with isocyanide generates carbodiimide. Herein, water acts as a nucleophile and reacts with carbodiimide to deliver the product. The protocol uses an inexpensive nickel catalyst, environmentally friendly water (as the nucleophile), and room temperature and provides products in moderate to good yields.

Multicomponent Reaction-Assisted Drug Discovery: A Time- and Cost-Effective Green Approach Speeding Up Identification and Optimization of Anticancer Drugs

Multicomponent reactions (MCRs) have emerged as a powerful strategy in synthetic organic chemistry due to their widespread applications in drug discovery and development. MCRs are flexible transformations in which three or more substrates react to form structurally complex products with high atomic efficiency. They are being increasingly appreciated as a highly exploratory and evolutionary tool by the medicinal chemistry community, opening the door to more sustainable, cost-effective and rapid synthesis of biologically active molecules. In recent years, MCR-based synthetic strategies have found extensive application in the field of drug discovery, and several anticancer drugs have been synthesized through MCRs. In this review, we present an overview of representative and recent literature examples documenting different approaches and applications of MCRs in the development of new anticancer drugs.

Multicomponent Reaction of Isocyanide, Ditelluride, and Mn(III) Carboxylate: Synthesis of N-Acyl Tellurocarbamate

A multicomponent reaction of isocyanides, ditellurides and manganese(III) carboxylates under mild reaction conditions leads to the synthesis of various N-acyl tellurocarbamates. This method demonstrates good functional tolerance and broad substrate scope and, as a result, is especially suitable for the postfunctionalization of complicated molecules such as drugs. The given method can be further extended to the synthesis of selenocarbamates.

Design and Synthesis of Dipeptidomimetic Isocyanonaphthalene as Enhanced-Fluorescent Chemodosimeter for Sensing Mercury Ion and Living Cells

A novel valine-based isocyanonaphthalene (NpI) was designed and synthesized by using an easy method and enabled the selective fluorescence detection of Hg2+. The chemodosimeter can display an immediate turn-on fluorescence response (500-fold) towards target metal ions upon the Hg2+-mediated conversion of isocyano to amino within NpI. Based on this specific reaction, the fluorescence-enhancement probe revealed a high sensitivity toward Hg2+ over other common metal ions and exhibited excellent aqueous solubility, good antijamming capability, high sensitivity (detection limit: 14.2 nM), and real-time detection. The response mechanism of NpI was supported by NMR spectroscopy, MS analysis and DFT theoretical calculation using various techniques. Moreover, a dipeptidomimetic NpI probe was successfully applied to visualize intracellular Hg2+ in living cells and monitor Hg2+ in real water samples with good recoveries and small relative standard deviations.

Enantioselective Synthesis of Azetidines through [3 + 1]-Cycloaddition of Donor-Acceptor Aziridines with Isocyanides

The enantioselective [3 + 1]-cycloaddition of racemic donor-acceptor (D-A) aziridines with isocyanides was first realized under mild reaction conditions using a chiral N,N'-dioxide/Mg^II complex as catalyst, providing a facile route to enantioenriched exo-imido azetidines with good to excellent yield (up to 99%) and enantioselectivity (up to 94% ee). An obvious chiral amplification effect was observed in this system, and an explanation was elucidated based on the experimental investigation and X-ray crystal structure of the enantiomerically pure catalyst.

Asymmetric synthesis of polycyclic spiroindolines via the Dy-catalyzed cascade reaction of 3-(2-isocyanoethyl)indoles with aziridines

An asymmetric cascade reaction catalyzed by a chiral N,N′-dioxide–Dy(iii) complex was realized to construct the valuable [6,5,5,6] tetracyclic spiroindolines with good yields and enantioselectivities by a concise and one-step protocol.

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

Chemoselective sulfonylation and isonitrilation reactions for the divergent synthesis of valuable diarylmethyl sulfones and isonitrile diarylmethanes starting from easy-to-synthesize para-quinone methides (p-QMs) and commercially abundant p-toluenesulfonylmethyl isocyanide (TosMIC) by using respectively zinc iodide and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as catalysts were developed. The distinguishing feature of this method is that TosMIC plays a dual role from the same substrates in the reaction: as a sulfonyl source or as an isonitrile source. The synthetic utility of this protocol was also demonstrated in the synthesis of difluoroalkylated diarylmethane 5 and diarylmethane ketone derivatives 6 and 7, which are important core structures in natural products and medicines.

Unexpected Formation of Metallofulleroids from Multicomponent Reactions, with Crystallographic and Computational Studies of the Cluster Motion

New multicomponent reactions involving an isocyanide, terminal or internal alkynes, and endohedral metallofullerene (EMF) Lu₃ N@C₈₀ yield metallofulleroids which are characterized by mass-spectrometry, HPLC, and multiple 1D and 2D NMR techniques. Single crystal studies revealed one ketenimine metallofulleroid has ordered Lu₃ N cluster which is unusual for EMF monoadducts. Computational analysis, based on crystallographic data, confirm that the endohedral cluster motion is controlled by the position of the exohedral organic appendants. Our findings provide a new functionalization reaction for EMFs, and a potential facile approach to freeze the endohedral cluster motion at relatively high temperatures.

Isocyanide-Induced Annulation Leading to Cyclopento-, Methano-, and Cyclopentano-[60]Fullerene Derivatives

The three-component annulation reactions of C₆₀, alkyl isocyanide, and dimethyl acetylenedicarboxylate (DMAD) or unsymmetric alkynes are investigated to afford cyclopent-2-en-1-imino- and ketenimine methano-[60]fullerene derivatives, which, upon hydration in the presence of acid, yield the corresponding fullerene amides. Dimethyl 2,3-pentadienedioate, the allene counterpart of DMAD, and ethyl buta-2,3-dienoate undergo four-component annulation with C₆₀, alkyl isocyanide, and water under similar conditions to yield cyclopentano-[60]fullerene derivatives with similar amide groups.

Recent advances in the transition-metal-free synthesis of quinoxalines

Quinoxalines, also known as benzo[a]pyrazines, constitute an important class of nitrogen-containing heterocyclic compounds as a result of their widespread prevalence in natural products, biologically active synthetic drug candidates, and optoelectronic materials. Owing to their importance and chemists' ever-increasing imagination of new transformations of these products, tremendous efforts have been dedicated to finding more efficient approaches toward the synthesis of quinoxaline rings. The last decades have witnessed a marvellous outburst in modifying organic synthetic methods to create them sustainable for the betterment of our environment. The exploitation of transition-metal-free catalysis in organic synthesis leads to a new frontier to access biologically active heterocycles and provides an alternative method from the perspective of green and sustainable chemistry. Despite notable developments achieved in transition-metal catalyzed synthesis, the high cost involved in the preparation of the catalyst, toxicity, and difficulty in removing it from the final products constitute disadvantageous effects on the atom economy and eco-friendly nature of the transformation. In this review article, we have summarized the recent progress achieved in the synthesis of quinoxalines under transition-metal-free conditions and cover the reports from 2015 to date. This aspect is presented alongside the mechanistic rationalization and limitations of the reaction methodologies. The scopes of future developments are also highlighted.

Carbamoylation of Azomethine Imines via Visible-Light Photoredox Catalysis

A versatile and robust photocatalytic methodology to install the amide functional group into azomethine imine ions is described. This protocol is distinguished by its broad scope and mild reaction conditions, which are well suited for the preparation of structurally complex compounds in the form of amino acids, peptides, and small drug-like molecules. Moreover, the generated pyrazolidinone core could be easily converted into β-alanine analogues.

Catalytic asymmetric multicomponent reactions of isocyanide, isothiocyanate and alkylidene malonates

Several unique chiral 3,4-dihydro-2H-pyrrole-2-thiones were made readily available by carrying out, in each case, a chiral-Mg(OTf)₂/N,N'-dioxide-complex-promoted formal [2+1+2] cycloaddition in the presence of tetraethylenediamine. Control experiments revealed that in situ-generated ammonium thiocyanate was crucial for maintaining high enantioselectivity through its inhibition of the HNCS-induced racemization of the products.

Enantioselective Isocyanide-based Multicomponent Reaction with Alkylidene Malonates and Phenols

A highly enantioselective isocyanide-based multicomponent reaction catalyzed by a chiral N,N'-dioxide/Mg^II complex was reported. A wide range of substrates were tolerated in this reaction, including alkyl- and aryl-substituted isocyanides with alkylidene malonates and various phenols, affording the corresponding phenoxyimidate products in good to excellent yields (up to 94% yield) with good to excellent enantioselectivities (up to 95.5:4.5 er). A catalytic cycle and transition state were proposed to rationalize the reaction process and enantiocontrol.

Electrochemical TEMPO-Catalyzed Oxidative Ugi-Type Reaction

Oxidative isocyanide-based multicomponent reactions (oxidative IMCRs) are very useful tools for the rapid construction of molecular diversity starting from readily available and stable substrates. Despite all their benefits, such multicomponent reactions are underdeveloped and strictly limited to 3-component processes. Indeed, in the presence of several reaction partners, the oxidation event needs to be rigorously chemoselective, which becomes incredibly more intricate as the number of reactive components increases. Nonetheless, we could overcome this significant pitfall and reach the first oxidative Ugi-type 4-IMCR by capitalizing on a very mild and green TEMPO-catalyzed electro-oxidation process. Employing alcohols as aldehyde surrogates and in the notable absence of any supporting electrolyte, this transformation proved to be extremely chemoselective in the presence of an amine and was compatible with a wide range of alcohols, amines, isocyanides, and carboxylic acids.

Three-Component Reactions of 3-Arylidene-3H-Indolium Salts, Isocyanides and Amines

A multicomponent reaction of isocyanides with aryl(indol-3-yl)methylium salts and amines has been found. A series of aryl(indol-3-yl)acetimidamides was obtained in up to 96% yields. In the case of ethyl isocyanoacetate, the reaction is followed by cyclization to form 3,5-dihydro-4H-imidazol-4-one derivatives.

Cascade synthesis of 2,4-disulfonylpyrroles by the sulfonylation/[2 + 3]-cycloaddition reactions of gem-dibromoalkenes with arylsulfonyl methyl isocyanides

An efficient cascade reaction involving sulfonylation and [2 + 3]-cycloaddition reactions of gem-dibromoalkenes with arylsulfonyl methyl isocyanides was described for the synthesis of 3-aryl-2,4-disulfonyl-1H-pyrroles. The main highlight of this study is the introduction of a new dual-functional reactivity of arylsulfonyl methyl isocyanides as the sulfonyl source as well as a 1,3-dipolar reagent in the same reaction. This system is facilitated by Cs2CO3 mediation in DMSO and 100 °C conditions.

Brønsted Acid Organocatalyzed Three-Component Hydroamidation Reactions of Vinyl Ethers

Hydroamidation of carbon-carbon double bonds is an attractive strategy for installing nitrogen functionality into molecular scaffolds and, with it, increasing molecular complexity. To date, metal-based approaches have dominated this area of chemical synthesis, despite the drawbacks of air and moisture sensitivity, limited functional group tolerance, toxicity, and/or high cost often associated with using metals. Here, in offering an alternative solution, we disclose an operationally simple, metal-free, one-pot, regioselective, multicomponent synthetic procedure for the hydroamidation of carbon-carbon double bonds. This method features mild reaction conditions and utilizes isocyanides and vinyl ethers for the rapid and modular synthesis of privileged α-oxygenated amide scaffolds. In unraveling the mechanistic underpinning of this non-metal-based reactivity, we present kinetic solvent isotope effect studies, variable time normalization analysis, and density functional theory computations offering insight into the mechanism of this multistep catalytic hydroamidation process.

Synthesis of Nβ-Protected Amino Sulfenyl Methyl Formamides and Sulfonyl Methyl Formamides: A Simple Protocol

Chiral amino acid-derived formamides represent one of the most versatile components in multicomponent reactions. Herein, we describe a facile synthesis of N^β-protected amino sulfenyl methyl formamides and sulfonyl methyl formamides via the Mannich reaction of N^α-protected amino alkyl thiols followed by oxidation using 3-chloroperbenzoic acid (m-CPBA). This protocol is applicable to a wide range of Fmoc- and Cbz-protected amino acids. Notably, the reaction provides high yield and retains the stereochemistry of the chiral center of the starting component.

Oxazole Synthesis by Sequential Asmic-Ester Condensations and Sulfanyl-Lithium Exchange-Trapping

Oxazoles are rapidly assembled through a sequential deprotonation-condensation of Asmic, anisylsulfanylmethylisocyanide, with esters followed by sulfanyl-lithium exchange-trapping. Deprotonating Asmic affords a metalated isocyanide that efficiently traps esters to afford oxazoles bearing a versatile C-4 anisylsulfanyl substituent. Interchange of the anisylsulfanyl substituent is readily achieved through a first-in-class sulfur-lithium exchange-electrophilic trapping sequence whose versatility is illustrated in the three-step synthesis of the bioactive natural product streptochlorin.

Synthesis of d-glycopyranosyl depsipeptides using Passerini reaction

A protocol based on Passerini multi-component reaction has been developed for facile, efficient and atom economical synthesis of a small library of twenty potential bioactive (2R)-2-(d-glycopyranosyl)-2-acyloxyacetamides using perbenzylated d-glycopyranosyl aldehydes, substituted isocyanides and different aliphatic/aromatic carboxylic acids. All twenty synthesized d-glycopyranosyl α-acyloxy amides, commonly known as depsipeptides were unambiguously identified on the basis of their spectral (IR, ¹H, ¹³C NMR, COSY, HSQC, NOESY and HRMS) data analysis.