Enantio- and diastereoselective boron conjugate addition to α-alkyl α,ß-unsaturated esters.

We developed a copper-catalyzed enantio- and diastereoselective boron conjugate addition to α-alkyl α,ß-unsaturated esters under base-free conditions. The approach showed excellent enantioselectivities (87-99% ee) and moderate to good conversions (51-99%), albeit with moderate diastereoselectivities (1 : 1-17 : 1 dr). The synthetic utility of this protocol was demonstrated.

Assessment of carbon emission and primary energy input of a gasoline combustion-powered 2.0 T SUV in China.

With the use of vehicles, large amounts of carbon dioxide are emitted by combustion of gasoline and energy consumes in their lifecycle. Therefore, the objective of this study is to evaluate the lifecycle carbon emission and primary energy input of a widely used sport utility vehicle (SUV) in China with the lifecycle assessment method. The results show that total petrol consumption of an SUV in lifetime is 21,300 kg; the CO2 emissions and primary energy input in the manufacturing, assembly, operation, and decommissioning phase are respectively 8857, 443, 54,925, and 443 kg and 123,413, 6171, 12,341, and 6171 MJ. The average CO2 emission intensity and energy input intensity of materials are respectively 2.74 kg/kg and 64.9 MJ/kg. The primary energy input of materials in manufacturing phase occupies 83.3%, and CO2 emission in use phase is 64,267.3 kg (occupied 92.62%), mainly attributed to the combustion of petrol.

Revisiting the Mg/TMSCl/Dipolar Solvent System for Dearomatic Silylation of Aryl Carbonyl Compounds: Substrate Scope, Transformations, and Mechanistic Studies.

Dearomatic silylation of arene derivatives is an intriguing synthetic target, which represents an elegant extension of Birch reduction and produces silylated cyclohexene derivatives with great potential of further transformation. Herein, we report a systematic study on dearomatic silylation of aryl carbonyl compounds with Mg and the TMSCl/NMP adduct. The protocol displays a wide range of substrate scope, including alkyl aryl ketones, aromatic amides, benzonitriles, tert-butyl benzoates, and even 2,2'-bipyridines. Synthetic utility is demonstrated using the products as versatile substrate in various transformations. The detailed mechanism is presented with both control experimental analyses and theoretical calculations. An unusual five-coordinated silicon dianion intermediate is first proposed and described here. The selectivity is influenced by the relative rates of single electron reductions (the TMSCl/NMP adduct versus the substrate) and the steric effects.

Rhodium-Catalyzed Ring Expansion of Azetidines via Domino Conjugate Addition/N-Directed α-C(sp3)-H Activation.

A facile synthetic method for 4-aryl-4,5-dihydropyrrole-3-carboxylates is developed, with a rhodium-catalyzed ring expansion strategy from readily available 2-(azetidin-3-ylidene) acetates and aryl boronic acids. Mechanistic investigations suggest a novel domino "conjugate addition/N-directed α-C(sp3)-H activation" process. The asymmetric catalytic synthesis of the 4-aryl-4,5-dihydropyrrole-3-carboxylate is realized by using QuinoxP* (91-97% ee). The synthetic utility of this protocol is demonstrated by the synthesis of 3,4-disubstituted or 2,3,4-trisubstituted pyrrolidines with excellent diastereoselectivities.

Rhodium catalyzed C-C bond cleavage/coupling of 2-(azetidin-3-ylidene)acetates and analogs.

The C-C bond cleavage/coupling of 2-(azetidin-3-ylidene)acetates with aryl boronic acids catalyzed by a rhodium complex was studied with a "conjugate addition/ß-C cleavage/protonation" strategy.

Duplication and diversification of lectin receptor-like kinases (LecRLK) genes in soybean.

Lectin receptor-like kinases (LecRLKs) play important roles in plant development and stress responses. Although genome-wide studies of LecRLKs have been performed in several species, a comprehensive analysis including evolutionary, structural and functional analysis has not been carried out in soybean (Glycine max). In this study, we identified 185 putative LecRLK genes in the soybean genome, including 123 G-type, 60 L-type and 2 C-type LecRLK genes. Tandem duplication and segmental duplication appear to be the main mechanisms of gene expansion in the soybean LecRLK (GmLecRLK) gene family. According to our phylogenetic analysis, G-type and L-type GmLecRLK genes can be organized into fourteen and eight subfamilies, respectively. The subfamilies within the G-type GmLecRLKs differ from each other in gene structure and/or protein domains and motifs, which indicates that the subfamilies have diverged. The evolution of L-type GmLecRLKs has been more conservative: most genes retain the same gene structures and nearly the same protein domain and motif architectures. Furthermore, the expression profiles of G-type and L-type GmLecRLK genes show evidence of functional redundancy and divergence within each group. Our results contribute to a better understanding of the evolution and function of soybean LecRLKs and provide a framework for further functional investigation of them.

Evolutionarily Conserved nodE, nodO, T1SS, and Hydrogenase System in Rhizobia of Astragalus membranaceus and Caragana intermedia.

Mesorhizobium species are the main microsymbionts associated with the medicinal or sand-fixation plants Astragalus membranaceus and Caragana intermedia (AC) in temperate regions of China, while all the Mesorhizobium strains isolated from each of these plants could nodulate both of them. However, Rhizobium yanglingense strain CCBAU01603 could nodulate AC plants and it's a high efficiency symbiotic and competitive strain with Caragana. Therefore, the common features shared by these symbiotic rhizobia in genera of Mesorhizobium and Rhizobium still remained undiscovered. In order to study the genomic background influencing the host preference of these AC symbiotic strains, the whole genomes of two (M. silamurunense CCBAU01550, M. silamurunense CCBAU45272) and five representative strains (M. septentrionale CCBAU01583, M. amorphae CCBAU01570, M. caraganae CCBAU01502, M. temperatum CCBAU01399, and R. yanglingense CCBAU01603) originally isolated from AC plants were sequenced, respectively. As results, type III secretion systems (T3SS) of AC rhizobia evolved in an irregular pattern, while an evolutionarily specific region including nodE, nodO, T1SS, and a hydrogenase system was detected to be conserved in all these AC rhizobia. Moreover, nodO was verified to be prevalently distributed in other AC rhizobia and was presumed as a factor affecting the nodule formation process. In conclusion, this research interpreted the multifactorial features of the AC rhizobia that may be associated with their host specificity at cross-nodulation group, including nodE, nodZ, T1SS as the possible main determinants; and nodO, hydrogenase system, and T3SS as factors regulating the bacteroid formation or nitrogen fixation efficiency.

Mechanically robust, chemically inert superhydrophobic charcoal surfaces.

We report a fast and cost-effective strategy towards the preparation of superhydrophobic composites where a double-sided adhesive tape is paved with charcoal particles. The composites are mechanically robust, and resistant to strong chemical agents.

Asymmetric Catalytic Enantio- and Diastereoselective Boron Conjugate Addition Reactions of α-Functionalized α,ß-Unsaturated Carbonyl Substrates.

An efficient catalytic system has been established for the asymmetric boron conjugate addition of B2pin2 onto α-functionalized (involving C, N, O, and Cl) α,ß-unsaturated carbonyls under mild, neutral conditions involving Cu[(S)-(R)-ppfa]Cl, AgNTf2, and alcohols. The dual additives of AgNTf2 and alcohols were found to play crucial roles for achieving high catalytic activity and enantio- and diastereoselectivity (up to 98% ee and 70:1 dr).

Group-assisted purification (GAP) chemistry for the synthesis of Velcade via asymmetric borylation of N-phosphinylimines.

A new approach to the anticancer drug Velcade was developed by performing asymmetric borylation of an imine anchored with a chiral N-phosphinyl auxiliary. Throughout the 7-step synthesis, especially in the imine's synthesis and in the asymmetric borylation reactions, operations and work-up were conducted in simple and easy ways without any column chromatographic purification, which defines the GAP (group-assisted purification) chemistry concept. It was found that the optically pure isomer (dr > 99:1) can be readily obtained by washing the crude mixture of the asymmetric borylation reaction with hexane; the chiral N-phosphinyl auxiliary can be easily recovered after deprotection is finished. Several other N-phosphinylimines were also investigated for the asymmetric borylation reaction. The absolute configuration of the borylation product was confirmed by single crystal X-ray diffraction analysis.

Comparative genomic analysis of N2-fixing and non-N2-fixing Paenibacillus spp.: organization, evolution and expression of the nitrogen fixation genes.

We provide here a comparative genome analysis of 31 strains within the genus Paenibacillus including 11 new genomic sequences of N2-fixing strains. The heterogeneity of the 31 genomes (15 N2-fixing and 16 non-N2-fixing Paenibacillus strains) was reflected in the large size of the shell genome, which makes up approximately 65.2% of the genes in pan genome. Large numbers of transposable elements might be related to the heterogeneity. We discovered that a minimal and compact nif cluster comprising nine genes nifB, nifH, nifD, nifK, nifE, nifN, nifX, hesA and nifV encoding Mo-nitrogenase is conserved in the 15 N2-fixing strains. The nif cluster is under control of a σ(70)-depedent promoter and possesses a GlnR/TnrA-binding site in the promoter. Suf system encoding [Fe-S] cluster is highly conserved in N2-fixing and non-N2-fixing strains. Furthermore, we demonstrate that the nif cluster enabled Escherichia coli JM109 to fix nitrogen. Phylogeny of the concatenated NifHDK sequences indicates that Paenibacillus and Frankia are sister groups. Phylogeny of the concatenated 275 single-copy core genes suggests that the ancestral Paenibacillus did not fix nitrogen. The N2-fixing Paenibacillus strains were generated by acquiring the nif cluster via horizontal gene transfer (HGT) from a source related to Frankia. During the history of evolution, the nif cluster was lost, producing some non-N2-fixing strains, and vnf encoding V-nitrogenase or anf encoding Fe-nitrogenase was acquired, causing further diversification of some strains. In addition, some N2-fixing strains have additional nif and nif-like genes which may result from gene duplications. The evolution of nitrogen fixation in Paenibacillus involves a mix of gain, loss, HGT and duplication of nif/anf/vnf genes. This study not only reveals the organization and distribution of nitrogen fixation genes in Paenibacillus, but also provides insight into the complex evolutionary history of nitrogen fixation.

Iridium-catalyzed asymmetric hydrogenation of α-substituted α,ß-unsaturated acyclic ketones: enantioselective total synthesis of (-)-mesembrine.

A highly efficient asymmetric hydrogenation of α-substituted α,ß-unsaturated acyclic ketones catalyzed by chiral spiro iridium complexes for the preparation of chiral 2-substituted allylic alcohols has been developed (ee up to 99.7%). This method provides a concise route to (-)-mesembrine (34% yield, 12 steps).

Paenibacillus taohuashanense sp. nov., a nitrogen-fixing species isolated from rhizosphere soil of the root of Caragana kansuensis Pojark.

A nitrogen-fixing bacterium, designated strain gs65(T), was isolated from a rhizosphere soil sample of Caragana kansuensis Pojark. Phylogenetic analysis based on a fragment of the nifH gene and the full-length 16S rRNA gene sequence revealed that strain gs65(T) is a member of the genus Paenibacillus. High levels of 16S rRNA gene similarity were found between strain gs65(T) and Paenibacillus borealis DSM 13188(T) (97.5 %), Paenibacillus odorifer ATCC BAA-93(T) (97.3 %), Paenibacillus durus DSM 1735(T) (97.0 %) and Paenibacillus sophorae DSM23020(T) (96.9 %). Levels of 16S rRNA gene sequence similarity between strain gs65(T) and the type strains of other recognized members of the genus Paenibacillus were below 97.0 %. Levels of DNA-DNA relatedness between strain gs65(T) and P. borealis DSM 13188(T), P. odorifer ATCC BAA-93(T) (97.3 %), P. durus DSM 1735(T) and P. sophorae DSM23020(T) were 35.9, 38.0, 34.2 and 35.5 % respectively. The DNA G+C content of strain gs65(T) was determined to be 51.6 mol%. The major fatty acids were found to be iso-C(14:0), anteiso-C(15:0) and iso-C(16:0). On the basis of its phenotypic characteristics and levels of DNA-DNA hybridization, strain gs65(T) is considered to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus taohuashanense sp. nov. is proposed. The type strain is gs65(T) (=CGMCC 1.12175(T) = DSM 25809(T)).

Chiral iridium spiro aminophosphine complexes: asymmetric hydrogenation of simple ketones, structure, and plausible mechanism.

The iridium complexes of chiral spiro aminophophine ligands, especially the ligand with 3,5-di-tert-butylphenyl groups on the P atom (1c) were demonstrated to be highly efficient catalysts for the asymmetric hydrogenation of alkyl aryl ketones. In the presence of KOtBu as a base and under mild reaction conditions, a series of chiral alcohols were synthesized in up to 97% ee with high turnover number (TON up to 10,000) and high turnover frequency (TOF up to 3.7×10(4)  h(-1)). Investigation on the structures of the iridium complexes of ligands (R)-1a and 1c by X-ray analyses disclosed that the 3,5-di-tert-butyl groups on the P-phenyl rings of the ligand are the key factor for achieving high activity and enantioselectivity of the catalyst. Study of the catalysts generated from the Ir-(R)-1c complex and H(2) by means of ESI-MS and NMR spectroscopy indicated that the early formed iridium dihydride complex with one (R)-1c ligand was the active species, which was slowly transformed into an inactive iridium dihydride complex with two (R)-1c ligands. A plausible mechanism for the reaction was also suggested to explain the observations of the hydrogenation reactions.

Highly enantioselective hydrogenation of alpha-arylmethylene cycloalkanones catalyzed by iridium complexes of chiral spiro aminophosphine ligands.

The highly efficient asymmetric hydrogenation of alpha-arylmethylene cycloalkanones catalyzed by Ir-complexes of chiral spiro aminophosphine ligands was developed, providing chiral exo-cyclic allylic alcohols at high yields with excellent enantioselectivities (up to 97% ee) and high turnover numbers (S/C up to 10,000). This new reaction provided an efficient method for the synthesis of the key intermediate of the active form of the anti-inflammatory loxoprofen.

Well-defined chiral spiro iridium/phosphine-oxazoline cationic complexes for highly enantioselective hydrogenation of imines at ambient pressure.

New chiral phosphine-oxazoline ligands (7, SIPHOX) with a rigid and bulky spirobiindane scaffold were synthesized, starting with optically pure 7-diphenylphosphino-7'-trifluoromethanesulfonyloxyl-1,1'-spirobiindane, in four steps in 40-64% overall yield. Iridium complexes of 7, the chiral analogues of the Crabtree catalyst, were generated by coordination of ligands 7 and [Ir(COD)Cl](2) in the presence of sodium tetrakis-3,5-bis(trifluoromethyl)phenylborate. The complexes were characterized by NMR, ESI-MS, and X-ray diffraction analysis. The Ir-SIPHOX complexes can catalyze the hydrogenation of acyclic N-aryl ketimines under ambient pressure with excellent enantioselectivities (up to 97% ee) and full conversions. This result represents the highest enantioselectivity and the first example of the hydrogenation of imines catalyzed by chiral analogues of the Crabtree catalyst at ambient pressure. Studies on the stability of the catalysts revealed that the catalysts Ir-SIPHOX are very stable and resistant to the formation of inactive trimers under hydrogenation conditions. On the basis of the X-ray diffraction analysis of the structures of catalysts and amine products, a rational explanation for the enantiocontrol of the chiral catalysts in the hydrogenation of imines is proposed.