A modular approach to prepare enantioenriched cyclobutanes: synthesis of (+)-rumphellaone A

Enantioselective Hydrofunctionalization of Cyclobutenones: Total Synthesis of gem-Dimethylcyclobutane Natural Products

Cyclobutanes with a gem-dimethyl group are common motifs in natural products. However, strategies for constructing enantioenriched gem-dimethyl cyclobutanes are still underdeveloped. Herein, we report an enantioselective approach to synthesize a broad group of chiral 2,3-disubstituted cyclobutanones through sequential 1,4-conjugate addition/trapping/cross-coupling of readily available cyclobutenones. The intermediate 2-bromocyclobutanone provides a valuable synthetic handle for further coupling transformations. In addition, this strategy was successfully utilized to synthesize gem-dimethyl cyclobutane-containing natural products, including (+)-β-caryophyllene, (-)-raikovenal, (-)-1β,9αH-5-linoleoyloxy-4,5-secocaryophyllen-4-one, and (-)-rumphellanones A-C.

Transition-metal catalyzed C-H activation as a means of synthesizing complex natural products

Over the past few decades, the advent of C-H activation has led to a rethink among chemists about the synthetic strategies employed for multi-step transformations. Indeed, deploying innovative and masterful tricks against the numerous classical organic transformations has been the need of the hour. Despite this, the immense importance of C-H activation remains unfulfilled unless the methodology can be deployed for large-scale industrial processes and towards the concise, step-economic synthesis of prodigious natural products and pharmaceutical drugs. Lately, the growing potential of C-H activation methodology has indeed driven the pioneers of synthetic organic chemists into finding more efficient methods to accelerate the synthesis of such complex molecular scaffolds. This review aims to draw a general overview of the various C-H activation procedures that have been adopted for synthesizing these vast majority of structurally complicated natural products. Our objective lies in drawing a complete picture and taking the readers through the synthesis of a series of such complex organic compounds by simplified techniques, making it step-economic on a larger scale and thus instigating the readers to trigger the use of such methodology and uncover new, unique patterns for future synthesis of such natural products.

A General Strategy for the Synthesis of Truxinate Natural Products Enabled by Enantioselective [2+2] Photocycloadditions

Pseudodimeric cyclobutanes constitute a large class of natural products that could, in principle, be efficiently synthesized via [2+2] photocycloadditions. However, the difficulty in developing chemo-, regio-, diastereo-, and enantioselective cycloadditions has limited their use in asymmetric syntheses. Herein, we show that chiral acid catalysts promote highly selective visible-light photocycloadditions, the products of which can be quickly transformed into truxinate natural products. This general approach has enabled the synthesis of both dimeric and pseudodimeric cyclobutane natural products with excellent enantioselectivity.

Site- and Stereoselective C(sp3 )-H Borylation of Strained (Hetero)Cycloalkanols Enabled by Iridium Catalysis

Transition metal-catalyzed site- and stereoselective C-H activation of strained (hetero)cycloalkanes remains a formidable challenge. We herein report a carbamate-directed iridium-catalyzed asymmetric β-C(sp³ )-H borylation of cyclopropanol derivatives. A variety of densely functionalized cyclopropanols were obtained in good enantioselectivities via desymmetrization and kinetic resolution. In addition, site-selective C(sp³ )-H borylation of methine groups furnished α-borylated (hetero)cycloalkanols in moderate to good yields. The synthetic utility of the method was further shown in a gram-scale synthesis and diverse downstream transformations of borylated products.

Palladium-Catalyzed Cyclization Coupling with Cyclobutanone-Derived N-Tosylhydrazones: Synthesis of Benzofuran-3-Cyclobutylidenes and Spirocyclobutanes

A palladium-catalyzed cyclization coupling of iodoarene-tethered alkynes with cyclobutanone-derived N-tosylhydrazones is reported, providing a convenient and efficient approach to benzofuran-3-cyclobutylidenes. On this basis, spirocyclobutanes can be generated smoothly in an efficient cascade manner by the addition of dienophiles. Good yields and scalability are demonstrated. Sequential intramolecular carbopalladation, palladium-carbene migratory insertion, δ-hydride elimination, and cycloaddition processes are involved.

Synthesis of 3-borylated cyclobutanols from epihalohydrins or epoxy alcohol derivatives

There is an increasing interest in cyclobutanes within the medicinal chemistry community. Therefore, methods to prepare cyclobutanes that contain synthetic handles for further elaboration are of interest. Herein, we report a new approach for the synthesis of 3-borylated cyclobutanols via a formal [3 + 1]-cycloaddition using readily accessible 1,1-diborylalkanes and epihalohydrins or epoxy alcohol derivatives. 1-Substituted epibromohydrin starting materials provide access to borylated cyclobutanols containing substituents at three of the four positions on the cyclobutane core, and enantioenriched epibromohydrins lead to enantioenriched cyclobutanols with high levels of enantiospecificity (>98%). Finally, derivatization studies demonstrate the synthetic utility of both the OH and Bpin handles.

Ligand-Enabled Pd(II)-Catalyzed β-Methylene C(sp3)-H Arylation of Free Aliphatic Acids

Ligand development has enabled rapid advances in Pd(II)-catalyzed β-methyl C(sp3)-H activation of free carboxylic acids. However, there are only a handful of reports of free-acid-directed β-methylene C(sp3)-H activation, all of which are limited to intramolecular reactions. Herein, we report the first Pd(II)-catalyzed intermolecular β-methylene C(sp3)-H arylation of free aliphatic acids, which is enabled by bidentate pyridine-pyridone ligands. The bite angle of this ligand has been discovered to play a key role in promoting β-methylene C-H activation of free carboxylic acid. This new transformation provides a disconnection for alkylation of arenes with simple aliphatic acids. A variety of free aliphatic acids, including the antiasthmatic drug seratrodast, were compatible with the reported protocol.

Gram-Scale Enantioselective Synthesis of (+)-Lucidumone

The first enantioselective total synthesis of (+)-lucidumone is described through a 13-step synthetic pathway (longest linear sequence). The key steps involve the formation of a bridged bicyclic lactone by an enantioselective inverse-electron-demand Diels-Alder cycloaddition, C-O bond formation to assemble two fragments, and a one-pot retro-[4 + 2]/[4 + 2] cycloaddition cascade. The synthesis is scalable, and more than one gram of natural product was synthesized in one batch.

Bioinspired Palladium-Catalyzed Intramolecular C(sp3 )-H Activation for the Collective Synthesis of Proline Natural Products

Bioinspired palladium-catalyzed intramolecular cyclization of amino acid derivatives containing a vinyl iodide moiety by C-H activation enabled rapid access to a wide range of functionalized proline derivatives with an exocyclic olefin. To demonstrate the practicality of this methodology, the functionalized prolines were used as intermediates for the synthesis of several natural products: lucentamycin A, oxotomaymycin, oxoprothracarcin, and barmumycin.

Carboxylic Acid-Directed Manganese(I)-Catalyzed Regioselective Hydroarylation of Unactivated Alkenes

A carboxylic acid-directed regioselective hydroarylation reaction of unactivated alkenes with aryl boronic acids was reported. This transformation was enabled by homogeneous manganese catalyst MnBr(CO)₅ in the presence of KOH and H₂O in the m-xylene reaction medium. Both internal and terminal alkenes worked well in this transformation, and a series of functional groups were tolerated. This reaction not only provided an expeditious method to prepare γ-aryl carboxylic acids from simple starting materials but also would inspire further studies in employing homogeneous manganese catalysis in organic synthesis.

Concise synthesis of piperarborenine B

A concise synthesis of piperarborenine B is reported. Organocatalytic electrophilic amination of pyrrolidines, stereospecific oxidative ring contraction and an original diastereoselective Krapcho dealkoxycarbonylation/transmethylation contribute to a novel synthetic strategy to the preparation of a non-symmetrical cyclobutane core. Being transition-metal-free, directing-group-free and protecting-group-free, a five-step synthesis of piperarborenine B was accomplished.

Dimerizing cascades of enallenamides reveal the visible-light-promoted activation of cumulated C-C double bonds

The visible-light-promoted activation of conjugated C-C double bonds is well developed, while that of cumulated systems is underexplored. We present the feasibility of this challenging approach. The localization of a triplet on an allenamide arm can be favored over that on a conjugated alkene. Allenamides with an arylacryloyl arm dimerize at room temperature in the presence of visible light and an iridium(iii) photocatalyst. Two orthogonal polycyclizations took place and their outcome is entirely dictated by the substitution of the alkene partner. Both cascades afford complex molecular architectures with high selectivity. Products form through the ordered rearrangement of twelve π electrons, providing a [3.2.0] bicyclic unit tethered to a fused tricycle, whose formation included an aryl C-H functionalization step, using disubstituted alkenes. The outcome was reverted with trisubstituted ones, which gave rise to taxane-like bridged tricycles that had two six-membered lactams flanking a cyclooctane ring, which was established through the creation of four alternate C-C bonds.

Pd(II)-Catalyzed Enantioselective C(sp3)-H Arylation of Cyclopropanes and Cyclobutanes Guided by Tertiary Alkylamines

Strained aminomethyl-cycloalkanes are a recurrent scaffold in medicinal chemistry due to their unique structural features that give rise to a range of biological properties. Here, we report a palladium-catalyzed enantioselective C(sp³)-H arylation of aminomethyl-cyclopropanes and -cyclobutanes with aryl boronic acids. A range of native tertiary alkylamine groups are able to direct C-H cleavage and forge carbon-aryl bonds on the strained cycloalkanes framework as single diastereomers and with excellent enantiomeric ratios. Central to the success of this strategy is the use of a simple N-acetyl amino acid ligand, which not only controls the enantioselectivity but also promotes γ-C-H activation of over other pathways. Computational analysis of the cyclopalladation step provides an understanding of how enantioselective C-H cleavage occurs and revealed distinct transition structures to our previous work on enantioselective desymmetrization of N-isobutyl tertiary alkylamines. This straightforward and operationally simple method simplifies the construction of functionalized aminomethyl-strained cycloalkanes, which we believe will find widespread use in academic and industrial settings relating to the synthesis of biologically active small molecules.

Nickel-Catalyzed Chemo- and Regioselective Benzylarylation of Unactivated Alkenes with o-Bromobenzyl Chlorides

Chemo- and regioselectively nickel-catalyzed reductive benzylarylation of unactivated alkenes with o-bromobenzyl chlorides is disclosed herein, in which electrophiles participate through a single-component double-site approach. Moreover, its utility is underscored by the concise synthesis of bioactive Indane compounds and postreaction functionalizations leading to structurally diverse scaffolds. Preliminary mechanistic investigations suggest a radical chain reaction mechanism.

Transition-Metal-Catalyzed, Coordination-Assisted Functionalization of Nonactivated C(sp3)-H Bonds

Transition-metal-catalyzed, coordination-assisted C(sp³)-H functionalization has revolutionized synthetic planning over the past few decades as the use of these directing groups has allowed for increased access to many strategic positions in organic molecules. Nonetheless, several challenges remain preeminent, such as the requirement for high temperatures, the difficulty in removing or converting directing groups, and, although many metals provide some reactivity, the difficulty in employing metals outside of palladium. This review aims to give a comprehensive overview of coordination-assisted, transition-metal-catalyzed, direct functionalization of nonactivated C(sp³)-H bonds by covering the literature since 2004 in order to demonstrate the current state-of-the-art methods as well as the current limitations. For clarity, this review has been divided into nine sections by the transition metal catalyst with subdivisions by the type of bond formation. Synthetic applications and reaction mechanism are discussed where appropriate.

Sequential Photocatalytic Reactions for the Diastereoselective Synthesis of Cyclobutane Scaffolds

The synthesis of densely functionalized cyclobutanes containing all-carbon quaternary stereocenters in high regio- and diastereoselectivity remains synthetically challenging. Herein, we show that this can be achieved by using a sequential photocatalysis strategy, wherein 3-chloromaleimides undergo triplet sensitized [2 + 2] photocycloadditions with alkynes or alkenes followed by photoredox-catalyzed dechlorinative C-C bond forming reactions to install quaternary stereocenters. This allows the rapid assembly of structurally complex and sterically congested 3-azabicyclo[3.2.0]heptane scaffolds from readily available starting materials.

Palladium-Catalyzed Carbene Coupling Reactions of Cyclobutanone N-Sulfonylhydrazones

Described herein are the palladium-catalyzed cross-coupling reactions of cyclobutanone-derived N-sulfonylhydrazones with aryl or benzyl halides, suggesting that the metal carbene process and β-hydride elimination can smoothly occur in strained ring systems. Structurally diversified products including cyclobutenes, methylenecyclobutanes, and conjugated dienes are selectively afforded in good to excellent yields. Preliminary success in asymmetric carbene coupling reactions in strained ring systems has been achieved, providing a promising route for the synthesis of enantioenriched four-membered-ring molecules.

Advancing the Logic of Chemical Synthesis: C-H Activation as Strategic and Tactical Disconnections for C-C Bond Construction

The design of synthetic routes by retrosynthetic logic is decisively influenced by the transformations available. Transition-metal-catalyzed C-H activation has emerged as a powerful strategy for C-C bond formation, with myriad methods developed for diverse substrates and coupling partners. However, its uptake in total synthesis has been tepid, partially due to their apparent synthetic intractability, as well as a lack of comprehensive guidelines for implementation. This Review addresses these issues and offers a guide to identify retrosynthetic opportunities to generate C-C bonds by C-H activation processes. By comparing total syntheses accomplished using traditional approaches and recent C-H activation methods, this Review demonstrates how C-H activation enabled C-C bond construction has led to more efficient retrosynthetic strategies, as well as the execution of previously unattainable tactical maneuvers. Finally, shortcomings of existing processes are highlighted; this Review illustrates how some highlighted total syntheses can be further economized by adopting next-generation ligand-enabled approaches.

A Study of an 8-Aminoquinoline-Directed C(sp2)-H Arylation Reaction on the Route to Chiral Cyclobutane Keto Acids from Myrtenal

This work outlines a synthetic route that can be used to access chiral cyclobutane keto acids with two stereocenters in five steps from the inexpensive terpene myrtenal. Furthermore, the developed route includes an 8-aminoquinoline-directed C(sp²)–H arylation as one of its key steps, which allows a wide range of aryl and heteroaryl groups to be incorporated into the bicyclic myrtenal scaffold prior to the ozonolysis-based ring-opening step that furnishes the target cyclobutane keto acids. This synthetic route is expected to find many applications connected to the synthesis of natural product-like compounds and small molecule libraries.

Construction of Complex Cyclobutane Building Blocks by Photosensitized [2 + 2] Cycloaddition of Vinyl Boronate Esters

Cyclobutyl moieties in drug molecules are rare, and in general, they are minimally substituted and stereochemically simple. Methods to assemble structurally complex cyclobutane building blocks suitable for rapid diversification are thus highly desirable. We report herein a photosensitized [2 + 2] cycloaddition with vinyl boronate esters affording straightforward access to complex, densely functionalized cyclobutane scaffolds. Mechanistic studies suggest an activation mode involving energy transfer to the styrenyl alkene rather than the vinyl boronate ester.

Biomimetic Total Syntheses of Ergot Alkaloids via Decarboxylative Giese Coupling

Biomimetic total syntheses of Festuclavine and Pyroclavine were achieved by a sequential radical coupling. The key steps include intramolecular decarboxylative Giese reaction to form the central C ring and 4-nitrobenzenesulfonyl (Ns)-directed indole C4-H olefination to introduce the indole C4 component. In addition, D-ring formation was completed by decarboxylative alkenylation and intramolecular S_N2 reaction.

Novel Caryophyllane-Related Sesquiterpenoids with Anti-Inflammatory Activity from Rumphella antipathes (Linnaeus, 1758)

Two previously undescribed caryophyllane-related sesquiterpenoids, antipacids A (1) and B (2), with a novel bicyclo[5.2.0] core skeleton, and known compound clovane-2β,9α-diol (3), along with rumphellolide L (4), an esterified product of 1 and 3, were isolated from the organic extract of octocoral Rumphella antipathes. Their structures, including the absolute configurations were elucidated by spectroscopic and chemical experiments. In vivo anti-inflammatory activity analysis indicated that antipacid B (2) inhibited the generation of superoxide anions and the release of elastase by human neutrophils, with IC₅₀ values of 11.22 and 23.53 μM, respectively, while rumphellolide L (4) suppressed the release of elastase with an IC₅₀ value of 7.63 μM.

Orthogonal Syntheses of 3.2.0 Bicycles from Enallenes Promoted by Visible Light

Enallenes can be readily converted into two families of 3.2.0 (hetero)bicycles with high diastereoselectivities through the combination of visible light with a suitable Ir(III) complex (1 mol %). Two complementary pathways, namely, a photocycloaddition versus a radical chain, can then take place. Both manifolds grant complete regiocontrol of the allene difunctionalization. This is accompanied by an original 1,3-group shift using sulfonyl allenamides that deliver a congested tetrasubstituted headbridging carbon in the corresponding product.

A Concise Bioinspired Semisynthesis of Rumphellaones A-C and Their C-8 Epimers from β-Caryophyllene

The first semisynthetic route toward rumphellaones B (2) and C (3) and their C-8 epimers as well as the shortest synthesis of rumphellaone A (1) and its C-8 epimer from the most accessible sesquiterpene, β-caryophyllene (4), is presented. Synthetic routes involved caryophyllonic acid as a key intermediate, which was converted to rumphellaone A (and epimer) via acid-catalyzed lactonization and rumphellaone C (and epimer) using one-pot epoxidation-lactonization. Rumphellaone B (2) and its epimer were obtained from rumphellaone A (1) and its epimer, respectively, using Saegusa-Ito oxidation. The absolute configuration at C-8 was confirmed by single-crystal X-ray analysis of rumphellaone B (2) and an acylated derivative of rumphellaone C.

Evolution of a Strategy for the Enantioselective Synthesis of (-)-Cajanusine

The first enantioselective synthesis of (-)-cajanusine is presented. Key features of the route include a rapid synthesis of the [4.2.0]bicyclooctane core by an enantioselective isomerization/stereoselective [2+2]-cycloaddition strategy as well as prominent use of catalytic methods for bond construction. The evolution of the approach is also presented that highlights unexpected roadblocks and how novel solutions were developed.

Synthesis of Elaborate Benzofuran-2-carboxamide Derivatives through a Combination of 8-Aminoquinoline Directed C-H Arylation and Transamidation Chemistry

Herein, we present a short and highly modular synthetic route that involves 8-aminoquinoline directed C-H arylation and transamidation chemistry, and which enables access to a wide range of elaborate benzofuran-2-carboxamides. For the directed C-H arylation reactions, Pd catalysis was used to install a wide range of aryl and heteroaryl substituents at the C3 position of the benzofuran scaffold in high efficiency. Directing group cleavage and further diversification of the C3-arylated benzofuran products were then achieved in a single synthetic operation through the utilization of a one-pot, two-step transamidation procedure, which proceeded via the intermediate N-acyl-Boc-carbamates. Given the high efficiency and modularity of this synthetic strategy, it constitutes a very attractive method for generating structurally diverse collections of benzofuran derivatives for small molecule screening campaigns.

Regio- and Stereoselective Rhodium(II)-Catalyzed C-H Functionalization of Cyclobutanes

Recent developments in controlled C-H functionalization transformations continue to inspire new retrosynthetic disconnections. One tactic in C-H functionalization is the intermolecular C-H insertion reaction of rhodium bound carbenes. These intermediates can undergo highly selective transformations through the modulation of the ligand framework of the rhodium catalyst. This work describes our continued efforts towards differentiating C-H bonds in the same molecule by judicious catalyst choice. Substituted cyclobutanes which exist as a mixture of interconverting conformers and possess neighboring C-H bonds within a highly strained framework are the targets herein for challenging the current suite of catalysts. While most C-H functionalization tactics focus on generating 1,2-disubstituted cyclobutanes via substrate-controlled directing group methods, the regiodivergent methods in this paper provide access to chiral 1,1-disubstituted and cis-1,3-disubstituted cyclobutanes simply by changing the catalyst identity, thus permitting entry to novel chemical space.

A chiral porous organic polymer as a heterogeneous ligand for enantioselective Pd-catalyzed C(sp3)–H functionalization

Catalytic enantioselective C(sp³)–H functionalization remains a difficult task, even more so using heterogeneous catalysts.

A macrocycle directed total synthesis of di-O-methylendiandrin A

The synthesis of di-O-methylendiandrin A has been achieved using diastereoselective, vicinal alkylation and transannular McMurry reactions of a macrocyclic 1,4-diketone, to establish stereochemistry and the strained ring of the natural product.

Catalytic Enantioselective Synthesis of Cyclobutenes from Alkynes and Alkenyl Derivatives

Discovery of enantioselective catalytic reactions for the preparation of chiral compounds from readily available precursors, using scalable and environmentally benign chemistry, can greatly impact their design, synthesis, and eventually manufacture on scale. Functionalized cyclobutanes and cyclobutenes are important structural motifs seen in many bioactive natural products and pharmaceutically relevant small molecules. They are also useful precursors for other classes of organic compounds such as other cycloalkane derivatives, heterocyclic compounds, stereodefined 1,3-dienes, and ligands for catalytic asymmetric synthesis. The simplest approach to make cyclobutenes is through an enantioselective [2 + 2]-cycloaddition between an alkyne and an alkenyl derivative, a reaction which has a long history. Yet known reactions of this class that give acceptable enantioselectivities are of very narrow scope and are strictly limited to activated alkynes and highly reactive alkenes. Here, we disclose a broadly applicable enantioselective [2 + 2]-cycloaddition between wide variety of alkynes and alkenyl derivatives, two of the most abundant classes of organic precursors. The key cycloaddition reaction employs catalysts derived from readily synthesized ligands and an earth-abundant metal, cobalt. Over 50 different cyclobutenes with enantioselectivities in the range of 86-97% ee are documented. With the diverse functional groups present in these compounds, further diastereoselective transformations are easily envisaged for synthesis of highly functionalized cyclobutanes and cyclobutenes. Some of the novel observations made during these studies including a key role of a cationic Co(I)-intermediate, ligand and counterion effects on the reactions, can be expected to have broad implications in homogeneous catalysis beyond the highly valuable synthetic intermediates that are accessible by this route.

1-Aminopyridinium Ylides as Monodentate Directing Groups for sp3 C-H Bond Functionalization

1-Aminopyridinium ylides are efficient directing groups for palladium-catalyzed β-arylation and alkylation of sp³ C-H bonds in carboxylic acid derivatives. The efficiency of these directing groups depends on the substitution at the pyridine moiety. The unsubstituted pyridine-derived ylides allow functionalization of primary C-H bonds, while methylene groups are unreactive in the absence of external ligands. 4-Pyrrolidinopyridine-containing ylides are capable of C-H functionalization in acyclic methylene groups in the absence of external ligands, thus rivaling the efficiency of the aminoquinoline directing group. Preliminary mechanistic studies have been performed. A cyclopalladated intermediate has been isolated and characterized by X-ray crystallography, and its reactivity was studied.

Recent Advances in Enantioselective Photochemical Reactions of Stabilized Diazo Compounds

Diazo compounds have proven to be a useful class of carbenes or metal carbenoids sources under thermal, photochemical, or metal-catalyzed conditions, which can subsequently undergo a wide range of synthetically important transformations. Recently, asymmetric photocatalysis has provoked increasing research interests, and great advances have been made in this discipline towards the synthesis of optically enriched compounds. In this context, the past two decades have been the most productive period in the developments of enantioselective photochemical reactions of diazo compounds due to a better understanding of the reactivities of diazo compounds and the emergence of new catalytic modes, as well as easier access to and treatment of stabilized diazo compounds. This review highlights these impressive achievements according to the reaction type, and the general mechanisms and stereochemical inductions are briefly discussed as well.

Directed C(sp3)-H arylation of tryptophan: transformation of the directing group into an activated amide

The aminoquinoline-directed C–H activation was used to synthezise unnatural tryptophans for solid phase peptide synthesis for the first time.

The 8-aminoquinoline (8AQ) directed C(sp³)–H functionalization was applied in the synthesis of β-arylated tryptophan derivatives. The laborious protecting group reorganization towards α-amino acids compatible for solid phase peptide synthesis (SPPS) was cut short by the transformation of the directing group into an activated amide, which was either used directly in peptide coupling or in the gram scale synthesis of storable Fmoc-protected amino acids for SPPS. In this work, directed C–H activation and nonplanar amide chemistry complement each other for the synthesis of hybrids between phenylalanine and tryptophan with restricted side chain mobility.

Modular, stereocontrolled Cβ-H/Cα-C activation of alkyl carboxylic acids

The combination of two newly emerging methods for chemical synthesis enables access to molecular space that was previously challenging or impossible to access. Thus, a C–H activation of ubiquitous carboxylic acids followed by their decarboxylative functionalization provides modular access to difunctionalized carbon frameworks with distinctly controlled stereochemistry. Application of this strategy to simplify the synthesis of medicinally important entities and to discover potent antimalarial compounds is described.

The union of two powerful transformations, directed C–H activation and decarboxylative cross-coupling, for the enantioselective synthesis of vicinally functionalized alkyl, carbocyclic, and heterocyclic compounds is described. Starting from simple carboxylic acid building blocks, this modular sequence exploits the residual directing group to access more than 50 scaffolds that would be otherwise extremely difficult to prepare. The tactical use of these two transformations accomplishes a formal vicinal difunctionalization of carbon centers in a way that is modular and thus, amenable to rapid diversity incorporation. A simplification of routes to known preclinical drug candidates is presented along with the rapid diversification of an antimalarial compound series.