Showing papers on "Intramolecular force published in 2019"
TL;DR: The concept of high-performance excited-state intramolecular proton transfer (ESIPT)-based fluorescent metal-organic framework (MOF) probes for Al3+ probes, established by regulating the hydroxyl groups on the organic linker step by step, strongly supports the concept of ESIPT-based fluorescent MOF Al3+, and makes Mg-TPP-DHBDC one of the most powerful Al 3+ fluorescent sensors.
Abstract: The concept of high-performance excited-state intramolecular proton transfer (ESIPT)-based fluorescent metal–organic framework (MOF) probes for Al3+ is proposed in this work. By regulating the hydroxyl groups on the organic linker step by step, new fluorescent magnesium–organic framework (Mg–MOF) probes for Al3+ ions were established based on the ESIPT fluorescence mechanism. It is observed for the first time that the number of intramolecular hydrogen bonds between adjacent hydroxyl and carboxyl groups can effectively adjust the ESIPT process and lead to tunable fluorescence sensing performance. Together with the well-designed porous and anionic framework, the Mg–TPP–DHBDC probe decorating with a pair of intramolecular hydrogen bonds exhibits extra-high quantitative fluorescence response to Al3+ through an unusual turn-off (0–1.2 μM) and turn-on (4.2–15 μM) luminescence sensing mechanism. Notably, the 28 nM limit of detection value represents the lowest record among all reported MOF-based Al3+ fluorescent...
152 citations
TL;DR: An intramolecular dearomatization of indole derivatives based on visible-light-promoted [2+2] cycloaddition was achieved via energy transfer mechanism and constituted a rare example of indoles functionalization by exploiting visible- light-induced reactivity at the excited states.
Abstract: An intramolecular dearomatization of indole derivatives based on visible-light-promoted [2+2] cycloaddition was achieved via energy transfer mechanism. The highly strained cyclobutane-fused angular tetracyclic spiroindolines, which were typically unattainable under thermal conditions, could be directly accessed in high yields (up to 99%) with excellent diastereoselectivity (>20:1 dr) under mild conditions. The method was also compatible with diverse functional groups and amenable to flexible transformations. In addition, DFT calculations provided guidance on the rational design of substrates and deep understanding of the reaction pathways. This process constituted a rare example of indole functionalization by exploiting visible-light-induced reactivity at the excited states.
148 citations
TL;DR: The two systems described here show that the HBeXB concept extends the range of interaction energies and geometries to be significantly greater than that of the XB alone.
Abstract: The halogen bond (XB) has become an important tool for molecular design in all areas of chemistry, including crystal and materials engineering and medicinal chemistry. Its similarity to the hydrogen bond (HB) makes the relationship between these interactions complex, at times competing against and other times orthogonal to each other. Recently, our two laboratories have independently reported and characterized a synergistic relationship, in which the XB is enhanced through direct intramolecular HBing to the electron-rich belt of the halogen. In one study, intramolecular HBing from an amine polarizes the iodopyridinium XB donors of a bidentate anion receptor. The resulting HB enhanced XB (or HBeXB) preorganizes and further augments the XB donors. Consequently, the affinity of the receptor for halogen anions was significantly increased. In a parallel study, a meta-chlorotyrosine was engineered into T4 lysozyme, resulting in a HBeXB that increased the thermal stability and activity of the enzyme at elevated temperatures. The crystal structure showed that the chlorine of the noncanonical amino acid formed a XB to the protein backbone, which augmented the HB of the wild-type enzyme. Calorimetric analysis resulted in an enthalpic contribution of this Cl-XB to the stability of the protein that was an order of magnitude greater than previously determined in biomolecules. Quantum mechanical (QM) calculations showed that rotating the hydroxyl group of the tyrosine to point toward rather than away from the halogen greatly increased its potential to serve as a XB donor, equivalent to what was observed experimentally. In sum, the two systems described here show that the HBeXB concept extends the range of interaction energies and geometries to be significantly greater than that of the XB alone. Additionally, surveys of structural databases indicate that the components for this interaction are already present in many existing molecular systems. The confluence of the independent studies from our two laboratories demonstrates the reach of the HBeXB across both chemistry and biochemistry and that intentional engineering of this enhanced interaction will extend the applications of XBs beyond these two initial examples.
94 citations
TL;DR: The Ru-catalyzed enantioselective annulation of 1,4,2-dioxazol-5-ones to furnish γ-lactams in up to 97% yield and 98% ee via intramolecular carbonylnitrene C-H insertion is reported.
Abstract: We report the Ru-catalyzed enantioselective annulation of 1,4,2-dioxazol-5-ones to furnish γ-lactams in up to 97% yield and 98% ee via intramolecular carbonylnitrene C—H insertion. By employing chiral diphenylethylene diamine (dpen) as ligands bearing electron-withdrawing arylsulfonyl substituents, the reactions occur with remarkable chemo- and enantioselectivities; the competing Curtius-type rearrangement was largely suppressed. Enantioselective nitrene insertion to allylic/propargylic C—H bonds was also achieved with remarkable tolerance to the C═C and C≡C bonds.
93 citations
TL;DR: The introduction of hydroxyl groups and n-butyl groups into COF-4-OH for the construction of COFs with strong dual emission was demonstrated.
Abstract: Here we reveal the effects of hydrogen bonds and alkyl groups on the structure and emission of covalent organic frameworks (COFs). Hydrogen bonds improve molecular rigidity leading to high crystallinity and restrict intramolecular rotation to enhance the emission of COFs. An excited-state intramolecular proton transfer (ESIPT) effect for dual emission is achieved via the intramolecular hydrogen bonds between hydroxyl groups and imine bonds. Alkyl groups increase interlayer spacing as a natural "scaffold" and achieve a staggered AB stacking mode to decrease aggregation-caused quenching. Based on the above guidance, COF-4-OH with strong emission is prepared with 2,4,6-triformylphloroglucinol (TFP) and 9,9-dibutyl-2,7-diaminofluorene (DDAF). Strong dual emission is observed and used to differentiate organic solvents with different polarities, to determine the water content in organic solvents, and to detect different pH levels. Our work serves as a guide for the rational design of functional monomers for the preparation of emissive COFs.
93 citations
TL;DR: Dinickel complexes catalyze [4 + 1]-cycloaddition reactions of 1,3-dienes, and high levels of asymmetric induction are achieved in the intramolecular cycloadditions using a C2-symmetric chiral ligand that stabilizes a metal-metal bond.
Abstract: Cycloaddition reactions provide direct and convergent routes to cycloalkanes, making them valuable targets for the development of synthetic methods. Whereas six-membered rings are readily accessible from Diels-Alder reactions, cycloadditions that generate five-membered rings are comparatively limited in scope. Here, we report that dinickel complexes catalyze [4 + 1]-cycloaddition reactions of 1,3-dienes. The C 1 partner is a vinylidene equivalent generated from the reductive activation of a 1,1-dichloroalkene in the presence of stoichiometric zinc. Intermolecular and intramolecular variants of the reaction are described, and high levels of asymmetric induction are achieved in the intramolecular cycloadditions using a C 2 -symmetric chiral ligand that stabilizes a metal-metal bond.
91 citations
TL;DR: Interestingly, a divergence between intermolecular hydrogen-atom transfer (HAT) catalysis and intramolecular [1,5] HAT was observed through precise manipulation of the protecting group, which was leveraged to achieve excellent α/δ site-selectivity.
Abstract: The synthetic utility of tertiary amines to oxidatively generate α-amino radicals is well established, however, primary amines remain challenging because of competitive side reactions. This report describes the site-selective α-functionalization of primary amine derivatives through the generation of α-amino radical intermediates. Employing visible-light photoredox catalysis, primary sulfonamides are coupled with electron-deficient alkenes to efficiently and mildly construct C-C bonds. Interestingly, a divergence between intermolecular hydrogen-atom transfer (HAT) catalysis and intramolecular [1,5] HAT was observed through precise manipulation of the protecting group. This dichotomy was leveraged to achieve excellent α/δ site-selectivity.
90 citations
TL;DR: One mononuclear Ni(II) complex [Ni(L1)(MeOH)2]·MeOH (1) and two novel trinuclear Ni (II) complexes [Ni3(L2)3(EtOH)6] (2) and [Ni 3(L 2) 3(H2O)6], constructed from symmetric N2O2-donors chelating ligands (H2L1 and H2L2), were synthesized and characterized by elemental analyses, FT-IR, UV-Vis spectra and
90 citations
TL;DR: This work synthesizes an array of air-stable Ln2@C80(CH2Ph) dimetallofullerenes featuring a covalent lanthanide-lanthanide bond and explores the limiting case when the role of a radical bridge is played by a single unpaired electron.
Abstract: Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets. For lanthanides, the localized nature of 4f electrons usually results in weak exchange coupling. Mediating magnetic interactions between lanthanide ions via radical bridges is a fruitful strategy towards stronger coupling. In this work we explore the limiting case when the role of a radical bridge is played by a single unpaired electron. We synthesize an array of air-stable Ln2@C80(CH2Ph) dimetallofullerenes (Ln2 = Y2, Gd2, Tb2, Dy2, Ho2, Er2, TbY, TbGd) featuring a covalent lanthanide-lanthanide bond. The lanthanide spins are glued together by very strong exchange interactions between 4f moments and a single electron residing on the metal–metal bonding orbital. Tb2@C80(CH2Ph) shows a gigantic coercivity of 8.2 Tesla at 5 K and a high 100-s blocking temperature of magnetization of 25.2 K. The Ln-Ln bonding orbital in Ln2@C80(CH2Ph) is redox active, enabling electrochemical tuning of the magnetism. Dilanthanide complexes that possess radical bridges exhibit enhanced magnetic exchange coupling, affording molecular magnets with high blocking temperatures. Here, the authors explore a series of dilanthanide-encapsulated fullerenes where the radical bridge is taken to its limit and the role is played by a single unpaired electron.
89 citations
TL;DR: Under metal catalyst-free and exogenous-oxidant-free conditions, a series of C-3 aminated imidazo[1,2-a]pyridines were synthesized by electrochemical intermolecular oxidative C-H/N-H cross-coupling by using a catalytic amount of ferrocene as the mediator.
87 citations
TL;DR: This work performs scattering experiments of H atoms from graphene and observed a bimodal translational energy loss distribution and shows that the quasi-elastic channel involves scattering through the physisorption well where collision sites are near the centers of the six-membered C-rings.
Abstract: Viewing the atomic-scale motion and energy dissipation pathways involved in forming a covalent bond is a longstanding challenge for chemistry. We performed scattering experiments of H atoms from graphene and observed a bimodal translational energy loss distribution. Using accurate first-principles dynamics simulations, we show that the quasi-elastic channel involves scattering through the physisorption well where collision sites are near the centers of the six-membered C-rings. The second channel results from transient C–H bond formation, where H atoms lose 1 to 2 electron volts of energy within a 10-femtosecond interaction time. This remarkably rapid form of intramolecular vibrational relaxation results from the C atom’s rehybridization during bond formation and is responsible for an unexpectedly high sticking probability of H on graphene.
TL;DR: In this article, the authors focus on the intramolecular cyclization of molecules through C-O, C-N and C-S bonds forming C-H functionalizations with an emphasis on the literature after 2000.
Abstract: This review focuses on the intramolecular cyclization of molecules through C–O, C–N and C–S bonds forming C–H functionalizations with an emphasis on the literature after 2000. Intramolecular C–H functionalization reactions attract much interest because of the ease of reaction due to the proximity of reacting centers and favorable entropy over intermolecular reactions. Less by-product formation, high atom economy, ease of purification, and avoidance of prefunctionalization of substrates are the additional advantages. Hence, a number of research articles have been published in this field, but no review is available so far. This review includes the synthesis of various heterocycles involving C–O, C–N and C–S bond creation. This is the first review on the current topic which will motivate the readers to work in this area further.
TL;DR: The benefits of rotational spectroscopy for the structural and energetic assessment of inter-/intra-molecular interactions, which may help to move from fundamental research to applications in supramolecular chemistry and crystal engineering, are illustrated.
Abstract: In the last decade, experiment and theory have expanded our vision of non-covalent interactions (NCIs), shifting the focus from the conventional hydrogen bond to new bridging interactions involving a variety of weak donor/acceptor partners. Whereas most experimental data originate from condensed phases, the introduction of broadband (chirped-pulse) microwave fast-passage techniques has revolutionized the field of rotational spectroscopy, offering unexplored avenues for high-resolution studies in the gas phase. We present an outlook of hot topics for rotational investigations on isolated intermolecular clusters generated in supersonic jet expansions. Rotational spectra offer very detailed structural data, easily discriminating the isomeric or isotopic composition and effectively cancelling any solvent, crystal, or matrix bias. The direct comparison with quantum mechanical predictions provides insight into the origin of the inter- and intramolecular interactions with much greater precision than any other spectroscopic technique, simultaneously serving as test-bed for fine-tuning of theoretical methods. We present recent examples of rotational investigations around three topics: oligomer formation, chiral recognition, and identification of halogen, chalcogen, pnicogen, or tetrel bonds. The selected examples illustrate the benefits of rotational spectroscopy for the structural and energetic assessment of inter-/intramolecular interactions, which may help to move from fundamental research to applications in supramolecular chemistry and crystal engineering.
TL;DR: The progress of transition metal-catalyzed sp3 C-H activation/intramolecular C-N bond formation is summarized, and both the reaction development and mechanisms in numerous synthetically useful intramolescular sp3C-H catalytic aminations/amidations are introduced.
TL;DR: It is evident from the reaction Gibbs energy calculation that the above irreversible cyclotrimerizations are highly exothermic; therefore establishing that the intramolecular alkyne cyclotimerization is a powerful route to strained cyclic molecular strips.
Abstract: A belt-shaped [8]cycloparaphenylene (CPP) and an enantioenriched Mobius-shaped [10]CPP have been synthesized by high-yielding rhodium-catalyzed intramolecular cyclotrimerizations of a cyclic dodecayne and a pentadecayne, respectively. This Mobius-shaped [10]CPP possesses stable chirality and isolated with high enantiomeric purity. It is evident from the reaction Gibbs energy calculation that the above irreversible cyclotrimerizations are highly exothermic; therefore establishing that the intramolecular alkyne cyclotrimerization is a powerful route to strained cyclic molecular strips.
TL;DR: The results reveal the biosynthetic pathway of 1 and expand the repertoire of activities of Diels-Alder cyclases and biochemically characterized EupfF as the first intermolecular hetero-Diels- alderase from fungi.
Abstract: Diels-Alder reactions are among the most powerful synthetic transformations to construct complex natural products. Despite that increasing of enzymatic intramolecular Diels-Alder reactions have been discovered, natural intermolecular Diels-Alderases are rarely described. Here, we report an intermolecular hetero-Diels-Alder reaction in the biosynthesis of tropolonic sesquiterpenes and functionally characterize EupfF as the first fungal intermolecular hetero-Diels-Alderase. We demonstrate that EupfF catalyzed the dehydration of a hydroxymethyl-containing tropolone (5) to generate a reactive tropolone o-quinone methide (6) and might further stereoselectively control the subsequent intermolecular hetero-Diels-Alder reaction with (1E,4E,8Z)-humulenol (8) to produce enantiomerically pure neosetophomone B (1). Our results reveal the biosynthetic pathway of 1 and expand the repertoire of activities of Diels-Alder cyclases.
TL;DR: This study found that the lowest lying excited state (S1) of DM-7HIT is a sulfur nonbonding (n) to π* transition, which undergoes O-H bond flipping from S1(nπ*) to the non-H-bonded S'1( nπ*) state, followed by intersystem crossing and internal conversion to populate the T'1(* state.
Abstract: We report O–H----S hydrogen-bond (H-bond) formation and its excited-state intramolecular H-bond on/off reaction unveiled by room-temperature phosphorescence (RTP). In this seminal work, this phenom...
TL;DR: The dual function of the N-F bond as an effective oxidant and subsequent nitrogen source in intramolecular aliphatic C-H functionalization reactions is explored and a uniform catalysis manifold has been identified for the construction of both pyrrolidine and piperidine cores.
Abstract: The dual function of the N-F bond as an effective oxidant and subsequent nitrogen source in intramolecular aliphatic C-H functionalization reactions is explored. Copper catalysis is demonstrated to exercise full regio- and chemoselectivity control, which opens new synthetic avenues to nitrogenated heterocycles with predictable ring sizes. For the first time, a uniform catalysis manifold has been identified for the construction of both pyrrolidine and piperidine cores. The individual steps of this new copper oxidation catalysis were elucidated by control experiments and computational studies, clarifying the singularity of the N-F function and characterizing the catalytic cycle to be based on a copper(I/II) manifold.
TL;DR: Experimental data suggest that cationic cobalt complexes may be involved in the enantio-determining step, where cation-π interactions in the catalyst contribute to the asymmetric induction.
Abstract: Asymmetric intramolecular hydrofunctionalization of tertiary allylic alcohols is described. This metal hydride-mediated catalytic radical–polar crossover reaction delivers corresponding epoxides in...
TL;DR: A highly diastereo- and enantioselective cycloaddition of para-quinone methides to α-halogenated ketones was realized by bifunctional phosphonium salt catalysis, furnishing functionalized 2,3-dihydrobenzofurans in high yields and excellent stereoselectivities.
TL;DR: In this article, a Gaussian multi-peaks-fitting of Fourier transform infrared spectrum (FTIR) was used to analyze the formation of hydrogen bonds and their effects on the structures and properties of Silk Fibroin/Sodium Alginate composite films.
TL;DR: A palladium-catalyzed enantioselective intramolecular σ-bond cross-exchange between C-I and C-C bonds is realized, providing chiral indanones bearing an alkyl iodide group and an all-carbon quaternary stereocenter.
Abstract: A palladium-catalyzed enantioselective intramolecular σ-bond cross-exchange between C-I and C-C bonds is realized, providing chiral indanones bearing an alkyl iodide group and an all-carbon quaternary stereocenter. Pd/TADDOL-derived phosphoramidite is found to be an efficient catalytic system for both C-C bond cleavage and alkyl iodide reductive elimination. In addition to aryl iodides, aryl bromides can also be used for this transformation in the presence of KI. Density-functional theory (DFT) calculation studies support the ring-opening of cyclobutanones occuring through an oxidative addition/reductive elimination process involving PdIV species.
TL;DR: Benefiting from self-assembly induced solid state "olefin metathesis" reaction, it was observed, for the first time, that three BDOPV derivatives cocrystallized in one single crystal.
Abstract: Continuous band structure tuning, e.g., doping with different atoms, is one of the most important features of inorganic semiconductors. However, this can hardly be realized in organic semicondutors. Here, we report the first example of fine-tuning organic semiconductor band structures by alloying structurally similar derivatives into one single phase. By incorporating halogen atoms on different positions of the backbone, BDOPV derivatives with complementary intramolecular or intermolecular charge distributions were obtained. To maximize the Coloumbic attractive interactions and minimize repulsive interactions, they form antiparallel cofacial stacking in monocomponent or in alloy single crystals, resulting in efficient π orbital overlap. Benefiting from self-assembly induced solid state “olefin metathesis” reaction, it was observed, for the first time, that three BDOPV derivatives cocrystallized in one single crystal. Molecules with different energy levels serve like the dopants in inorganic semiconductors...
TL;DR: The nature of orbital interactions in a Carbonyl–carbonyl short contact is determined by the relative orientation of the two interacting carbonyl groups.
Abstract: Carbonyl-carbonyl (CO···CO) interactions are emerging noncovalent interactions found in many small molecules, polyesters, peptides and proteins. However, little is known about the effect of the relative orientation of the two carbonyl groups on the nature of these interactions. Herein, we first show that simple homodimers of acetone and formaldehyde can serve as models to understand the effect of relative orientations of the two carbonyl groups on the nature of CO···CO interactions. Further, from a comprehensive statistical analysis of molecules having inter- or intramolecular CO···CO interactions, we show that the molecules can be broadly categorized into six different structural motifs (I-VI). The analysis of pyramidality of the acceptor carbon atoms in these motifs and natural bond orbital (NBO) analysis suggest that the relative orientation of the two interacting carbonyl groups determines whether the orbital interaction between the two carbonyl groups would be n → π* or π → π* or a combination of both.
TL;DR: A formulation of single-molecule electroluminescence driven by electron transfer between a molecule and metal electrodes based on a many-body state representation of the molecule is presented and contributes to a microscopic understanding of optoelectronic conversion in single molecules on solid surfaces and in nanometer-scale junctions.
Abstract: Electron transport and optical properties of a single molecule in contact with conductive materials have attracted considerable attention because of their scientific importance and potential applications. With the recent progress in experimental techniques, especially by virtue of scanning tunneling microscope (STM)-induced light emission, where the tunneling current of the STM is used as an atomic-scale source for induction of light emission from a single molecule, it has become possible to investigate single-molecule properties at subnanometer spatial resolution. Despite extensive experimental studies, the microscopic mechanism of electronic excitation of a single molecule in STM-induced light emission has yet to be clarified. Here we present a formulation of single-molecule electroluminescence driven by electron transfer between a molecule and metal electrodes based on a many-body state representation of the molecule. The effects of intramolecular Coulomb interaction on conductance and luminescence spectra are investigated using the nonequilibrium Hubbard Green's function technique combined with first-principles calculations. We compare simulation results with experimental data and find that the intramolecular Coulomb interaction is crucial for reproducing recent experiments for a single phthalocyanine molecule. The developed theory provides a unified description of the electron transport and optical properties of a single molecule in contact with metal electrodes driven out of equilibrium, and thereby, it contributes to a microscopic understanding of optoelectronic conversion in single molecules on solid surfaces and in nanometer-scale junctions.
TL;DR: A metal-free intramolecular tandem sequence involving alkoxylation, Claisen rearrangement and lactone expansion has been achieved.
Abstract: Alkene carbooxygenation has attracted considerable attention over the past few decades as this approach provides an efficient access to various oxygen-containing molecules, especially the valuable O-heterocycles. However, examples of catalytic alkene carbooxygenation via a direct C–O cleavage are quite scarce, and the C–O cleavage in these cases is invariably initiated by transition metal-catalyzed oxidative addition. We report here a novel Bronsted acid-catalyzed intramolecular alkoxylation-initiated tandem sequence, which represents the first metal-free intramolecular alkoxylation/Claisen rearrangement. Significantly, an unprecedented Bronsted acid-catalyzed intramolecular alkene insertion into the C–O bond via a carbocation pathway was discovered. This method allows the stereocontrolled synthesis of valuable indole-fused bridged [4.2.1] lactones, providing ready access to biologically relevant scaffolds in a single synthetic step from an acyclic precursor. Moreover, such an asymmetric cascade cyclization has also been realized by employing a traceless chiral directing group. Control experiments favor the feasibility of a carbocation pathway for the process. In addition, biological tests showed that some of these newly synthesized indole-fused lactones exhibited their bioactivity as antitumor agents against different breast cancer cells, melanoma cells, and esophageal cancer cells.
TL;DR: It is demonstrated that entropic spring effects can lead to polymer refolding and reformation of the previously cleaved metal-ligand bonds, effectively repairing the intramolecular noncovalent cross-links, allowing for restoration of chemical bonds after mechanochemical events.
Abstract: Covalent macromolecules tend to fragment under mechanical stress through the mechanochemical scission of covalent bonds in the backbone. However, linear polymers that have been intramolecularly collapsed by covalent bonds show greater mechanochemical stability compared to other thermoplastics. Here, rhodium-π bonds are used for intramolecular collapse in order to show that mechanical stress can be removed from the polymer backbone and focused on weaker intramolecular cross-links, leading to polymer unfolding instead of mechanochemical events at the backbone. Moreover, given rhodium-π bonds form spontaneously, by changing the time interval between ultrasound pulses, we demonstrate that entropic spring effects can lead to polymer refolding and reformation of the previously cleaved metal–ligand bonds, effectively repairing the intramolecular noncovalent cross-links. These findings provide the first example of an intramolecular repairing mechanism in synthetic molecules in solution, allowing for restoration o...
TL;DR: A Cu-catalyzed enantioselective intramolecular Ullmann-type amination reaction for the synthesis of C–N atropisomers and the readily prepared N,N′-(cyclohexane-1,2-diyl)dipicolinamides showed high efficacy and stereoinduction.
Abstract: Catalytically asymmetric synthesis of atropisomeric compounds is an important research area in organic synthesis. However, in comparison with C–C atropisomers, the atropisomers caused by the restricted rotation of C–N single bonds have been given less attention because of the limited methods for accessing these compounds. Herein we report a Cu-catalyzed enantioselective intramolecular Ullmann-type amination reaction for the synthesis of C–N atropisomers. The C–N axial chirality was induced highly efficiently by the intramolecular adjacent C–N cross-coupling. The readily prepared N,N′-(cyclohexane-1,2-diyl)dipicolinamides showed high efficacy and stereoinduction (up to 99% ee).