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Catalytic enantioselective synthesis methodologies have been actively explored and developed owing to the significance of chiral molecules and their utilities. In particular, unnatural α-amino acids with tetrasubstituted stereogenic carbon centers (α-tertiary amino acids; ATAAs) are undoubtedly among the most valuable compounds. Asymmetric addition to an α-iminoester or α-iminoamide is widely recognized as a straightforward, powerful, and atom-economical strategy for accessing optically active α-amino acids and their derivatives. However, this type of chemistry, which relies on ketimine-type electrophiles, was quite limited only a few decades ago owing to low reactivities and difficulties associated with enantiofacial control. This feature article comprehensively overviews this research field and highlights the significant progress that has been made. In particular, it focuses on the chiral catalyst system and the transition state as the key parameters for such reactions. [ABSTRACT FROM AUTHOR]

We report the enantiodivergent reaction of ketimines derived from α‐ketoesters with malononitriles using a single chiral source. The reactions using an 8‐quinolinesulfonyl cinchona alkaloid catalyst in the presence and absence of Et2Zn gave both enantiomers in high yields with high enantioselectivities (53∼99% yield, 99:1∼3:97 er). The obtained malononitrile‐derived α‐amino acids were converted into various optically active compounds. A reaction mechanism is proposed to explain the observed enantiodivergency. [ABSTRACT FROM AUTHOR]

The robust motility through various physically disparate environments is a distinctive feature of spirochetes. The whole spirochetal cell body rotates and translocates without the help of any external apparatus. The surface-exposed adhesive molecules are more than a glue holding spirochetes to the surrounding substrate. The adhesins apparently play a significant role in switching between various motility states and translational modes in pathogenic spirochetes. The binding interactions of spirochetes with their environment are optimized not to interfere with the highly motile status of these pathogens. Adhesins mediate interactions that promote the penetration of host barriers. This invasion is a critical step in the dissemination of the pathogen within the host. Pathogenic spirochetes cause a range of serious human diseases such as Lyme disease (LD), syphilis, leptospirosis, relapsing fever (RF), and periodontal disease. Motility is a critical virulence factor for spirochetes. From the mechanical perspective of the infection, it has been widely believed that flagella are the sole key players governing the migration and dissemination of these pathogens in the host. Here, we highlight the important contribution of spirochetal surface-exposed adhesive molecules and their dynamic interactions with host molecules in the process of infection, specifically in spirochetal swimming and crawling migration. We believe that these recent findings overturn the prevailing view depicting the spirochetal body to be just an inert elastic bag, which does not affect spirochetal cell locomotion. [ABSTRACT FROM AUTHOR]

The enantioselective synthesis of chiral N,N‐acetals derived from α‐dicarbonyl compounds has been achieved. Good yields and enantioselectivities were observed for the reaction with various α‐dicarbonyl compounds with 2‐aminobenzamides using chiral bis(imidazoline)‐phosphoric acid catalysts. Based on these experimental investigations, a possible transition state is proposed to explain the origin of the asymmetric induction. [ABSTRACT FROM AUTHOR]

The bacterial flagellar motor accommodates ten stator units around the rotor to produce large torque at high load. But when external load is low, some previous studies showed that a single stator unit can spin the rotor at the maximum speed, suggesting that the maximum speed does not depend on the number of active stator units, whereas others reported that the speed is also dependent on the stator number. To clarify these two controversial observations, much more precise measurements of motor rotation would be required at external load as close to zero as possible. Here, we constructed a Salmonella filament‐less mutant that produces a rigid, straight, twice longer hook to efficiently label a 60 nm gold particle and analyzed flagellar motor dynamics at low load close to zero. The maximum motor speed was about 400 Hz. Large speed fluctuations and long pausing events were frequently observed, and they were suppressed by either over‐expression of the MotAB stator complex or increase in the external load, suggesting that the number of active stator units in the motor largely fluctuates near zero load. We conclude that the lifetime of the active stator unit becomes much shorter when the motor operates near zero load. [ABSTRACT FROM AUTHOR]

The enantioselective conjugate addition reaction of an α,α-dithioacetonitrile with nitroalkenes was catalysed by chiral bis(imidazoline)–palladium pincer-type complexes. The reaction was applicable to various nitroalkenes to afford products in good yield with high enantioselectivity. The obtained products can be converted to γ-lactam and biologically active rolipram. [ABSTRACT FROM AUTHOR]

2H‐Azirines are useful precursors for the synthesis of a variety of chiral aziridine and amine derivatives with a range of biological activities. Owing to the ring strain and the presence of a C=N double bond, 2H‐azirines are more reactive than other types of ketimine, and undergo a range of enantioselective reactions, including reduction and Diels–Alder reactions, as well as nucleophilic addition to the C=N double bond. Therefore, the enantioselective reactions of 2H‐azirines has become a hot topic, in particular within the last few years. In this Minireview, we focus on the enantioselective reactions of 2H‐azirines by using catalytic or stoichiometric amounts of chiral additives, the reaction mechanisms, and the applications of these reactions of 2H‐azirines and related compounds in organic synthesis. [ABSTRACT FROM AUTHOR]

An enantioselective aza-Friedel Crafts reaction of cyclic 4-aryl-3-oxo-1,2,5-thiadiazol-1,1-oxides as cyclic ketimines with indoles was developed. High enantioselectivities were observed for the reaction of various cyclic ketimines with indoles using chiral imidazoline–phosphoric acid catalysts. The obtained products can be converted to chiral α-amino amide and hydantoin. [ABSTRACT FROM AUTHOR]

The first highly enantioselective nucleophilic addition reaction of phosphites with 2 H-azirines has been developed. The reaction was applied to various 3-substituted 2 H-azirines using novel chiral bis(imidazoline)/ZnII catalysts to afford products in good yield with high enantioselectivity. The transformation of the obtained optically active aziridines showed that 2 H-azirines act as either α,β- or β,β-dicarbocationic amine synthons. [ABSTRACT FROM AUTHOR]

The first highly enantioselective nucleophilic addition reaction of phosphites with 2 H-azirines has been developed. The reaction was applied to various 3-substituted 2 H-azirines using novel chiral bis(imidazoline)/ZnII catalysts to afford products in good yield with high enantioselectivity. The transformation of the obtained optically active aziridines showed that 2 H-azirines act as either α,β- or β,β-dicarbocationic amine synthons. [ABSTRACT FROM AUTHOR]

Bacterial chemotaxis allows cells to swim toward a more favorable environment. Capillary assays are a major method for exploring bacterial responses to attractive and repellent chemicals, but the accumulation process obtained using a capillary containing chemicals has not been investigated fully. In this study, we quantitatively analyzed the response of Salmonella cells to serine as an attractant diffusing from a capillary placed in a cell suspension. Video microscopy showed that cells gradually accumulated near the tip of the capillary and thereafter directed flows were generated. Flow analysis using microspheres as tracers showed that the flow comprised millimeter-scale convection, which originated at the point source where serine was supplied by the capillary. The generation of convection was attributable to cell accumulation and gravitational force, thereby suggesting that it is a variant of bioconvection. We recorded the time courses of the changes in cell numbers and the convection flow speed at different positions near the capillary, which showed that the number of cells increased initially until an almost saturated level, and the convection flow speed then accelerated as the cell accumulation area increased in size. This result indicates that cell accumulation at the stimulation source and enlargement of the accumulation area were essential for generating the convection. [ABSTRACT FROM AUTHOR]

Organocatalytic enantioselective aza-Friedel-Crafts reactions of cyclic ketimines with pyrroles or indoles were catalyzed by imidazoline/phosphoric acid catalysts. The reaction was applied to various 3 H-indol-3-ones to afford products in excellent yields and enantioselectivities. The chiral catalysts can be recovered by a single separation step using column chromatography and are reusable without further purification. Based on the experimental investigations, a possible transition state has been proposed to explain the origin of the asymmetric induction. [ABSTRACT FROM AUTHOR]

Lactococcus garvieae is a well‐known fish pathogen that has low virulence in humans and is rarely isolated from the blood cultures of endocarditis patients. We describe herein the first reported case of transfusion‐transmitted L. garvieae sepsis caused by a contaminated platelet concentrate from a donor who consumed raw octopus before blood donation. Retrospective examination of the laboratory results of the index donor revealed that his haemoglobin levels had been steadily decreasing, which led to the detection of a latent colon cancer. The donors with colon lesions involving a latent cancer may relate an asymptomatic bacteremia. [ABSTRACT FROM AUTHOR]

The catalytic Mannich reaction of α-substituted α-isocyanoacetates with ketimines has been investigated. A variety of imidazolines containing congested vicinal tetra-substituted stereocenters were obtained in excellent yields with high diastereo- and enantioselectivity using cinchona alkaloid amide/Ni(ii) and base catalysts. [ABSTRACT FROM AUTHOR]

Mannose-binding lectin (MBL) is a key pattern recognition molecule in the lectin pathway of the complement system, an important component of innate immunity. MBL functions as an opsonin which enhances the sequential immune process such as phagocytosis. We here report an inhibitory effect of MBL on the motility of pathogenic bacteria, which occurs by affecting the energy source required for motility and the signaling pathway of chemotaxis. When Salmonella cells were treated with a physiological concentration of MBL, their motile fraction and free-swimming speed decreased. Rotation assays of a single flagellum showed that the flagellar rotation rate was significantly reduced by the addition of MBL. Measurements of the intracellular pH and membrane potential revealed that MBL affected a driving force for the Salmonella flagellum, the electrochemical potential difference of protons. We also found that MBL treatment increased the reversal frequency of Salmonella flagellar rotation, which interfered with the relative positive chemotaxis toward an attractive substrate. We thus propose that the motility inhibition effect of MBL may be secondarily involved in the attack against pathogens, potentially facilitating the primary role of MBL in the complement system. [ABSTRACT FROM AUTHOR]

We disclose herein an efficient enantioselective conjugate addition reaction between coumarin-3-carboxylic acids and malonic acid half thioesters (MAHTs). The reaction was catalyzed by N-heteroarenesulfonyl Cinchona alkaloid amides to afford double-decarboxylative conjugate addition products in good yield with high enantioselectivity. The reaction of various coumarin-3-carboxylic acids with MAHTs gave products in high yield with high enantioselectivity. [ABSTRACT FROM AUTHOR]

A direct enantioselective vinylogous Mannich reaction of ketimines with γ-butenolide has been developed. Good yields and enantioselectivities were observed for the reaction of various ketimines by using a cinchona alkaloid amide/Zn(OTf)2 catalyst and Et3N. Both enantiomers of the products could be obtained by using pseudoenantiomeric chiral catalysts. [ABSTRACT FROM AUTHOR]

Thefirst catalytic enantioselective addition of hydroperoxidesto ketimines derived from isatins has been developed. Excellent yieldsand enantioselectivities were observed for the reaction of variousketimines with peroxides using a cinchona alkaloid sulfonamide catalyst.Both enantiomers of products could be obtained by using pseudoenantiomericchiral catalysts. The obtained product can be converted to opticallyactive α-amino hydroperoxide. [ABSTRACT FROM AUTHOR]

The organocatalytic enantioselective decarboxylative Mannich reaction of malonic acid half thioesters (MAHTs) with cyclic N-sulfonyl ketimines by using N-heteroarenesulfonyl cinchona alkaloid amides afforded products with high enantioselectivity. Both enantiomers of the products could be obtained by using pseudoenantiomeric chiral catalysts. The reaction proceeds through a nucleophilic addition of the MAHTs to the ketimines prior to decarboxylation. [ABSTRACT FROM AUTHOR]

Highly enantioselectivedesymmetrization of aziridines with TMSNCShas been developed. Good yield and enantioselectivity were observedby using novel chiral imidazoline–phosphoric acid catalysts.The obtained product can be converted to a chiral β-aminothioland a β-aminosulfonic acid. [ABSTRACT FROM AUTHOR]

If a bacterium has motility, it will use the ability to survive and thrive. For many pathogenic species, their motilities are a crucial virulence factor. The form of motility varies among the species. Some use flagella for swimming in liquid, and others use the cell-surface machinery to move over solid surfaces. Spirochetes are distinguished from other bacterial species by their helical or flat wave morphology and periplasmic flagella (PFs). It is believed that the rotation of PFs beneath the outer membrane causes transformation or rolling of the cell body, propelling the spirochetes. Interestingly, some spirochetal species exhibit motility both in liquid and over surfaces, but it is not fully unveiled how the spirochete pathogenicity involves such amphibious motility. This review focuses on the causative agent of zoonosis leptospirosis and discusses the significance of their motility in liquid and on surfaces, called crawling, as a virulence factor. [ABSTRACT FROM AUTHOR]

The Salmonella flagellar motor consists of a rotor and about a dozen stator elements. Each stator element, consisting of MotA and MotB, acts as a proton channel to couple proton flow with torque generation. A highly conserved Asp33 residue of MotB is directly involved in the energy coupling mechanism, but it remains unknown how it carries out this function. Here, we show that the MotB( D33 E) mutation dramatically alters motor performance in response to changes in external load. Rotation speeds of the MotA/ B( D33 E) and MotA( V35 F)/ B( D33 E) motors were markedly slower than the wild-type motor and fluctuated considerably at low load but not at high load, whereas the rotation rate of the wild-type motor was stable at any load. At low load, pausing events were frequently observed in both mutant motors. The proton conductivities of these mutant stator channels in their 'unplugged' forms were only half of the conductivity of the wild-type channel. These results suggest that the D33 E mutation induces a load-dependent inactivation of the MotA/ B complex. We propose that the stator element is a load-sensitive proton channel that efficiently couples proton translocation with torque generation and that Asp33 of MotB is critical for this co-ordinated proton translocation. [ABSTRACT FROM AUTHOR]

Get selective! Enantioselective allylation of ketimines derived from isatins by using chiral 1,3‐bis(imidazolin‐2‐yl)benzene (Phebim)–PdII complexes afforded products with good enantioselectivity (see scheme). The reaction was applied to a wide variety of ketimines. The obtained product can be converted to homoallylic amines and a spirocyclic amine without the loss of enantiopurity. [ABSTRACT FROM AUTHOR]

Leptospires are a group of bacteria with a unique ultrastructure and a fascinating swimming behavior that cause a number of emerging and re-emerging diseases worldwide called leptospirosis. The unusual form of motility is thought to play a critical role in the infection process. However, the inhibition mechanism of antiserum on the motility of Leptospira to attenuate the infection efficiency is unknown. In this study, effect of antiserum on motility was quantitatively investigated by swimming speed. Relatively low concentration of antiserum was found to inhibit leptospiral motility, suggesting that the basic immunization can affect the infection efficiency. Recovery of motility a few hours later after the addition of antiserum was observed. This raises a hypothesis that Leptospira carries surface molecules bound with antibodies toward the cell end to escape and recovers the motility. [ABSTRACT FROM AUTHOR]

Electrostatic interactions between the stator protein MotA and the rotor protein FliG are important for bacterial flagellar rotation. Arg90 and Glu98 of MotA are required not only for torque generation but also for stator assembly around the rotor, but their actual roles remain unknown. Here we analyzed the roles of functionally important charged residues at the MotA-FliG interface in motor performance. About 75% of the motA(RgOE) cells and 45% of the motA(E98K) cells showed no fluorescent spots of green fluorescent protein (GFP)-MotB, indicating reduced efficiency of stator assembly around the rotor. The FliG(D289K) and FliG(R281V) mutations, which restore the motility of the motA(RgOE) and motA(E98K) mutants, respectively, showed reduced numbers and intensity of GFP-MotB spots as well. The FliG(D289K) mutation significantly recovered the localization of GFP-MotB to the motor in the motA(R9OE) mutant, whereas the FliG(R281V) mutation did not recover the GFP-MotB localization in the motA(E98K) mutant. These results suggest that the MotA-Arg90-FliG-Asp289 interaction is critical for the proper positioning of the stators around the rotor, whereas the MotA-Glu98-FliG-Arg281 interaction is more important for torque generation. [ABSTRACT FROM AUTHOR]

The organocatalytic enantioselective decarboxylative addition of malonic acid half thioesters to ketimines derived from isatins by using N-heteroarenesulfonyl cinchona alkaloid amides afforded products with high enantioselectivity. The products could be converted into optically active AG-041R. X-ray crystallographic analysis revealed that the hydrogen bonding between the sulfonimide proton and the 8-quinolyl nitrogen atom plays an important role in exerting the enantioselectivity of the reaction. [ABSTRACT FROM AUTHOR]

An organocatalytic enantioselective Mannich-type reaction of isocyanoacetate with N-sulfonylimines catalyzed by chiral thioureas derived from quinine yielded 2-imidazolines with high diastereo- and enantioselectivities (up to >99:1 dr. and 96% ee). This reaction provided a convenient route to access various imidazolines and related α,β-diamino acids having a quaternary carbon center in high enantiomeric purities. [ABSTRACT FROM AUTHOR]

MotA and MotB form a transmembrane proton channel that acts as the stator of the bacterial flagellar motor to couple proton flow with torque generation. The C-terminal periplasmic domain of MotB plays a role in anchoring the stators to the motor. However, it remains unclear where their initial binding sites are. Here, we constructed Salmonella strains expressing GFP-MotB and MotA-mCherry and investigated their subcellular localization by fluorescence microscopy. Neither the D33N and D33A mutations in MotB, which abolish the proton flow, nor depletion of proton motive force affected the assembly of GFP-MotB into the motor, indicating that the proton translocation activity is not required for stator assembly. Overexpression of MotA markedly inhibited wild-type motility, and it was due to the reduction in the number of functional stators. Consistently, MotA-mCherry was observed to colocalize with GFP-FliG even in the absence of MotB. These results suggest that MotA alone can be installed into the motor. The R90E and E98K mutations in the cytoplasmic loop of MotA (MotA), which has been shown to abolish the interaction with FliG, significantly affected stator assembly, suggesting that the electrostatic interaction of MotA with FliG is required for the efficient assembly of the stators around the rotor. [ABSTRACT FROM AUTHOR]

Abstract: A catalytic enantioselective desymmetrization of meso-N-(heteroarenesulfonyl)aziridines with TMSN3 using chiral Lewis acids afforded products with high enantioselectivity. As proof of the utility of this procedure, the precursor of selective κ-opioid agonist (1S,2S)-(−)-U-50,488 was synthesized. [Copyright &y& Elsevier]

Summary: The MotA/B complex acts as the stator of the proton-driven bacterial flagellar motor. Proton translocation through the stator complex is efficiently coupled with torque generation by the stator–rotor interactions. In Salmonella enterica serovar Typhimurium, the highly conserved Pro173 residue of MotA is close to the absolutely conserved Asp33 residue of MotB, which is believed to be a proton-binding site. Pro173 is postulated to be involved in coupling proton influx to torque generation. However, it remains unknown what critical function Pro173 carries out. Here, we characterize the motility and the torque–speed relation of the flagellar motor of the slow motile motA(P173A) mutant of Salmonella. Stall torque produced by the mutant motor was at the wild-type level, indicating that neither the number of stators in the motor nor the rotor–stator interaction is affected by the P173A substitution. In agreement with this, the motA(P173A) allele exerted a strong dominant-negative effect on wild-type motility. In contrast, high-speed rotation at low load was significantly impaired by the mutation, suggesting that the maximum rate of torque generation cycle is severely limited. Simulation of the torque–speed curve by a simple kinetic model indicated that the mutation reduces the rate of conformational changes of the MotA/B complex that switches the exposure of Asp33 to the outside and the inside of the cell, thereby slowing down the mechanochemical reaction cycle. Based on these results, we propose that Pro173 plays an important role in facilitating the conformational dynamics of the stator complex for rapid proton translocation and torque generation cycle. [Copyright &y& Elsevier]

Organocatalytic enantioselective aza-Friedel-Crafts alkylation of pyrroles with imines having heteroarylsulfonyl groups catalyzed by binaphthol monophosphoric acids afforded products with high enantioselectivity (up to 95% ee). [ABSTRACT FROM AUTHOR]

Organocatalytic enantioselective aza-Friedel-Crafts alkylation of pyrroles with imines having heteroarylsulfonyl groups catalyzed by binaphthol monophosphoric acids afforded products with high enantioselectivity (up to 95% ee). [ABSTRACT FROM AUTHOR]

Abstract: Bacterial flagella responsible for motility are driven by rotary motors powered by the electrochemical potential difference of specific ions across the cytoplasmic membrane. The stator of proton-driven flagellar motor converts proton influx into mechanical work. However, the energy conversion mechanism remains unclear. Here, we show that the motor is sensitive to intracellular proton concentration for high-speed rotation at low load, which was considerably impaired by lowering intracellular pH, while zero-speed torque was not affected. The change in extracellular pH did not show any effect. These results suggest that a high intracellular proton concentration decreases the rate of proton translocation and therefore that of the mechanochemical reaction cycle of the motor but not the actual torque generation step within the cycle by the stator–rotor interactions. [Copyright &y& Elsevier]

MotA and MotB form the stator of the proton-driven bacterial flagellar motor, which conducts protons and couples proton flow with motor rotation. Asp-33 of Salmonella enterica serovar Typhimurium MotB, which is a putative proton-binding site, is critical for torque generation. However, the mechanism of energy coupling remains unknown. Here, we carried out genetic and motility analysis of a slowly motile motB(D33E) mutant and its pseudorevertants. We first confirmed that the poor motility of the motB(D33E) mutant is due to neither protein instability, mislocalization, nor impaired interaction with MotA. We isolated 17 pseudorevertants and identified the suppressor mutations in the transmembrane helices TM2 and TM3 of MotA and in TM and the periplasmic domain of MotB. The stall torque produced by the motB(D33E) mutant motor was about half of the wild-type level, while those for the pseudorevertants were recovered nearly to the wild-type levels. However, the high-speed rotations of the motors under low-load conditions were still significantly impaired, suggesting that the rate of proton translocation is still severely limited at high speed. These results suggest that the second-site mutations recover a torque generation step involving stator-rotor interactions coupled with protonation/deprotonation of Glu-33 but not maximum proton conductivity. [ABSTRACT FROM AUTHOR]

Abstract: A catalytic enantioselective Mannich-type reaction of N-(2-pyridylsulfonyl)imines in the presence of chiral bis(oxazoline)s afforded the products with high enantioselectivity. Asymmetric induction was supposed to be efficiently controlled by a new chiral center on the sulfur dynamically induced through the discriminative coordination of a chiral Lewis acid to one of the sulfonyl oxygens. [Copyright &y& Elsevier]

Abstract: A catalytic enantioselective Strecker-type reaction to N-(2-pyridylsulfonyl)imines in the presence of chiral bis(oxazoline)s afforded the products with a high enantioselectivity. A dynamically induced new chiral center on the sulfur by discriminative coordination of a chiral Lewis acid to one of the sulfonyl oxygens efficiently controlled the enantioselectivity. [Copyright &y& Elsevier]

Abstract: The reaction of 1-[(2,4,6-triisopropylphenyl)sulfinyl]-2-naphthaldehyde with (trifluoromethyl)trimethylsilane using tetramethylammonium fluoride gave trifluoromethylated compounds in high yield with high diastereoselectivity. Desilylation and subsequent recrystallization yielded the enantiomerically and diastereomerically pure trifluoroethanol, which afforded chiral 1-(2-naphthyl)-2,2,2-trifluoroethanol after removal of the sulfinyl group. [Copyright &y& Elsevier]

Abstract: Enantioselective nucleophilic addition of Grignard reagents to N-(2-pyridylsulfonyl)imines in the presence of bis(oxazoline) afforded products with good enantioselectivity. Dynamically induced chirality on the sulfur by coordination of a chiral Lewis acid to a pyridyl nitrogen and one of the sulfonyl oxygens fixes the conformation of the complex and induces enantioselectivity. Since the 2-pyridylsulfonyl group can be easily removed after the addition reaction, it acts not only as a protecting group but also as an efficient stereocontroller. [Copyright &y& Elsevier]

The enantioselective reaction of α-seleno carbanions derived from bis(phenylseleno)acetal and bis(2-pyridylseleno)acetal in the presence of bis(oxazoline)s with various electrophiles gave products with high enantioselectivity. The enantioselective reaction of α-lithio benzyl 2-pyridyl selenide gave the products with stereochemistry reverse to that obtained in the reaction of α-lithio benzyl phenyl selenide. Mechanistic investigation suggests the enantiodetermination of these reactions at -78 °C depends on dynamic thermodynamic resolution. The enantioselective reaction was applied to the preparation of enantioenriched olefins and epoxide. [ABSTRACT FROM AUTHOR]

An enantioselective Strecker-type reaction of imines with Et2AlCN in the presence of chiral additives has been examined. The enantioselectivity varied depending on the substituents of the imino group as well as the chiral additives used. Thus, α-aminonitriles were obtained in good yields with good enantioselectivities in the reaction of N-benzylidenebenzhydrylamine with Et2AlCN and BINOL. The reaction with excess BINOL gave the aminonitrile with reversed configuration. [Copyright &y& Elsevier]

The enantioselective reaction of the α-thio carbanion derived from 1-phenyl-1-(phenylthio)-1-(tributylstannyl)methane with 4-substituted cyclohexanones in the presence of bis(oxazoline)s gave the products as a diastereomeric mixture. Each diastereomer obtained had high optical purity. The reaction of the α-seleno carbanion derived from the bis(phenylseleno)acetal also showed high enantioselectivity. The stereospecific elimination of the isolated diastereomers on treatment with methanesulfonyl chloride and triethylamine afforded axially chiral benzylidenecyclohexanes with high enantioselectivities up to 99% ee. [Copyright &y& Elsevier]

The enantioselective reaction of various α-lithiated dithioacetals with aldehydes or a ketone in the presence of bis(oxazoline)s was examined. Among them, unsymmetrical dithioacetals were found to be the best choice for attaining high enantioselectivity. The reaction of lithiated tert-butylthio(2-pyridylthio)methane with aldehydes proceeded with good diastereoselectivity as well as with good enantioselectivity. The enantioselective reaction was shown to proceed through dynamic thermodynamic resolution. Mercury(II) chloride effected hydrolysis of the dithioacetal moiety of the products to 2-hydroxyaldehydes, which were directly reduced to give the optically active 1,2diols. [ABSTRACT FROM AUTHOR]

Enantioselective hydrogen atom transfer to α-sulfonyl radicals generated from the alkyl radical addition to 2-propenyl and 1-phenylethenyl sulfones in the presence of chiral Lewis acids affords products with high enantioselectivity. The stereochemical course is discussed with the transition states involving selective coordination of a chiral Lewis acid to an enantiotopic sulfonyl oxygen. [Copyright &y& Elsevier]

The reactions of various (1-sulfinyl-2-naphthyl)methanimines with alkyllithium reagents were examined. Naphthylmethanimines bearing a 2,4,6-triisopropylphenylsulfinyl group gave the (RS*,S*)-products as a single diastereomer, possibly derived from the predominant rotamer around the C&z.sbnd;S bond axis. The reaction of chiral [1-(2,4,6-triisopropylphenylsulfinyl)-2-naphthyl]methanimine with MeLi and subsequent elimination of the sulfinyl group afforded optically active 1-(2-naphthyl)ethylamine. [Copyright &y& Elsevier]

Examines the role of in the work place, Purepargylic and allylic alcohols for 2-(Trimethylsilt)vinyl sulfoxides. Details on chiral from mixture of diastereomeric on election process to specify limitations; Calculation of beta-silyvinyl sulfoxide in the anitio sulfoxide; Separation of diastereomers.

Reports that nucleophilic reactions with Grignard reagents and the Mukaiyama aldol reactions of the naphthaldehydes having the (2,4,6-triisopropylphenyl)sulfinyl group produced products with high stereoselectivity. Changes in the stereochemistry of the products caused by the Lewis acids used; Carbonyl-face selective reactions.