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This paper proposes a power‐optimized column‐parallel cyclic analog to digital converter (ADC) for complementary metal oxide semiconductors (CMOS) image sensor readout circuits. The design combines a 2.5‐bit/cycle architecture with a comparator shutdown technique based on the comparator‐based switched‐capacitor (CBSC) circuits, which results in a significant reduction in the operating time of the threshold detection comparator compared with conventional CBSC circuits. This reduction in operating time leads to power savings as the threshold detection comparator can be shut down quickly. The paper also presents a comprehensive analysis of the nonideal factors of CBSC circuits and the coarse and fine conversion allocation scheme. The 10‐bit two‐stage comparator‐based cyclic ADC is designed in a 110 nm 1P4 M CMOS technology. Simulation results show that the effective number of bit (ENOB) is 9.7 bits, with each column consuming 103 μ$$ \upmu $$W of power. The proposed cyclic ADC has a figure of merit (FOM) of 123 fJ/conv‐step. Compared with conventional structures, the proposed design reduces the power consumption of the ADC by 34.3% while maintaining the same level of performance. [ABSTRACT FROM AUTHOR]

Let k$k$ be a number field. For a variety X$X$ over k$k$ that satisfies weak approximation with Brauer–Manin obstruction, we study the same property for smooth projective models of its symmetric products. Based on the same method, we also explore the property of weak approximation with Brauer–Manin obstruction for norm varieties. [ABSTRACT FROM AUTHOR]

All‐optical neural networks have advantages in higher throughput, higher speed as well as lower energy consumption compared to electrical neural networks. Optical neural networks have already shown great potential in various applications; however, the operation speed of the network is limited by the 2D detector as most optical neural networks rely on space to space projection. Here, a space to time projection approach to build diffractive deep neural network (D2NN) is proposed, which can project spatial intensity distribution into time‐domain intensity variation, thus bypassing the detection speed limit of 2D imaging device. Based on this scheme, high‐speed all‐optical logic gates are theoretically analyzed and experimentally realized. In this case, the network's operation speed is only limited by the photodetector (PD), which can reach GHz levels. Moreover, the method will show great advantage when it comes to wavelengths where 2D detectors are not achievable easily such as infrared, terahertz or microwaves. [ABSTRACT FROM AUTHOR]

In the ongoing quest to develop lithium‐ion batteries with superior capacity and enhanced safety, the focus has shifted toward all‐solid‐state batteries (SSBs) and nickel‐rich cathode materials. Despite their promise, these technologies face significant interface challenges, notably poor contact and low ion transport efficiency, leading to substantial stability issues. This review aims to provide a comprehensive analysis of both the advantages and the challenges associated with all‐solid‐state batteries. In addition, it discusses the benefits of single‐crystal application in SSBs, in terms of their kinetic performance, mechanical properties, and stability. The review concludes by proposing various strategies to optimize single‐crystal technologies, targeting the development of efficient nickel‐rich single‐crystal materials for use in all‐solid‐state batteries. These approaches offer the potential to address the core challenges currently faced by SSBs and pave the way for the next generation of high‐performance batteries. [ABSTRACT FROM AUTHOR]

A wideband and compact rat‐race coupler that covers 3 to 5 GHz is proposed for the fifth‐generation new radio N77/N78/N79 applications. The wideband characteristic is obtained by using cascaded two‐section topology and broadside‐coupled lines at each input/output port. Miniaturization of two‐section rings is achieved using meander microstrip lines. A fractional bandwidth of 50% and a size reduction of 60% are both reached. Good in‐phase and out‐of‐phase characteristics are obtained as well. The circuit can be easily fabricated using conventional printed circuit board process and suitable for mass production. [ABSTRACT FROM AUTHOR]

Here we report the design, synthesis, and characterization of bifunctional chemical ligands that induce the association of Ras with ubiquitously expressed immunophilin proteins such as FKBP12 and cyclophilin A. We show this approach is applicable to two distinct Ras ligand scaffolds, and that both the identity of the immunophilin ligand and the linker chemistry affect compound efficacy in biochemical and cellular contexts. These ligands bind to Ras in an immunophilin‐dependent fashion and mediate the formation of tripartite complexes of Ras, immunophilin, and the ligand. The recruitment of cyclophilin A to GTP‐bound Ras blocks its interaction with B‐Raf in biochemical assays. Our study demonstrates the feasibility of ligand‐induced association of Ras with intracellular proteins and suggests it as a promising therapeutic strategy for Ras‐driven cancers. [ABSTRACT FROM AUTHOR]

Here we report the design, synthesis, and characterization of bifunctional chemical ligands that induce the association of Ras with ubiquitously expressed immunophilin proteins such as FKBP12 and cyclophilin A. We show this approach is applicable to two distinct Ras ligand scaffolds, and that both the identity of the immunophilin ligand and the linker chemistry affect compound efficacy in biochemical and cellular contexts. These ligands bind to Ras in an immunophilin‐dependent fashion and mediate the formation of tripartite complexes of Ras, immunophilin, and the ligand. The recruitment of cyclophilin A to GTP‐bound Ras blocks its interaction with B‐Raf in biochemical assays. Our study demonstrates the feasibility of ligand‐induced association of Ras with intracellular proteins and suggests it as a promising therapeutic strategy for Ras‐driven cancers. [ABSTRACT FROM AUTHOR]

Here we report the design, synthesis, and characterization of bifunctional chemical ligands that induce the association of Ras with ubiquitously expressed immunophilin proteins such as FKBP12 and cyclophilin A. We show this approach is applicable to two distinct Ras ligand scaffolds, and that both the identity of the immunophilin ligand and the linker chemistry affect compound efficacy in biochemical and cellular contexts. These ligands bind to Ras in an immunophilin‐dependent fashion and mediate the formation of tripartite complexes of Ras, immunophilin, and the ligand. The recruitment of cyclophilin A to GTP‐bound Ras blocks its interaction with B‐Raf in biochemical assays. Our study demonstrates the feasibility of ligand‐induced association of Ras with intracellular proteins and suggests it as a promising therapeutic strategy for Ras‐driven cancers. [ABSTRACT FROM AUTHOR]

Abstract: Because of ultra‐broadband near‐infrared (NIR) emission bismuth‐activated glasses and fibers offer a new promising platform for novel photonic devices such as new type of optical amplifiers and broadly tunable fiber lasers. Yet, challenge remains to manipulate the NIR emission behavior of bismuth (Bi) in photonic glasses for efficient Bismuth‐doped fiber and fiber lasers. Here, by engineering phosphorus and aluminum's topology, broadly tunable NIR emission has been realized in Bismuth‐doped phosphate laser glass. Structural and optical analyses on 27Al magic‐angle spinning nuclear magnetic resonance (MAS NMR), 31P MAS NMR, fourier transform infrared (FTIR) and static emission spectra suggest that polymerization of glass network can be improved by proper addition of aluminum into the system, which can be evidenced by partial conversion of Q2 to Q3 species of phosphorus and the shift of P–O–P asymmetric stretching vibration toward lower frequency, and this turns out beneficial to Bi NIR emission. Embedding aluminum tetrahedra into phosphorus glass network can reduce the local crystal field around bismuth and therefore lead to the blueshift of Bi emission. This work presents new insights into the luminescent behavior of Bi ions in phosphate glass and it helps the design and fabrication of Bismuth‐doped glasses and fibers in future. [ABSTRACT FROM AUTHOR]

Accumulating evidence suggests that interaction between amyloid-β (Aβ) and cell membrane is crucial to the pathogenesis of Alzheimer's disease (AD), and thus an increasing understanding of the impact of membrane composition on Aβ-membrane interaction becomes essential for the mechanism elucidation of Aβ-membrane interaction and the early diagnosis of AD. In this work, electrically neutral phosphatidylcholine (PC) as the most major class of membrane phospholipids, including 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and Aβ(1-40) as the most common amyloid protein were selected as the research subjects, and a developed cantilever-based biosensor, on which liposomes comprised of PC lipids were immobilized, was applied to characterize in real time the interactions between Aβ(1-40) and membranes comprised of PC lipids with different hydrophobic acyl chains, and to evaluate the effect of cholesterol incorporated in membrane on Aβ-membrane interaction during the whole process of Aβ(1-40) fibrillization. The results illustrate that the interaction between Aβ(1-40) and PC membrane can be divided into three stages, which are related to the change in molecular states of Aβ. More importantly, it is found that membranes comprised of PC lipids with shorter saturated acyl chains show higher interaction ability with Aβ(1-40), and the incorporation of cholesterol into PC bilayer can remarkably accelerate and strengthen Aβ(1-40)-membrane interaction. These results confirm that hydrophobicity is the main driving force for the interactions between Aβ(1-40) and PC membranes. In return, the above results enlightened us to apply the current micro-cantilever immobilized with cholesterol-containing DPPC liposomes to challenge the detection of low-concentration Aβ(1-40). This time 50-nM Aβ(1-40) in aqueous solution has been effectively detected, suggesting that this proposed detection technique would contribute to Aβ detection and early diagnosis of AD in the future. [ABSTRACT FROM AUTHOR]

D-Desosamine is synthesized in 4 steps from methyl vinyl ketone and sodium nitrite. The key step in this chromatography-free synthesis is the coupling of (R)-4-nitro- 2-butanol and glyoxal (trimeric form) mediated by cesium carbonate, which affords in crystalline form 3-nitro-3,4,6- trideoxy-α-D-glucose, a nitro sugar stereochemically homologous to D-desosamine. This strategy has enabled the syntheses of an array of analogous 3-nitro sugars. In each case the 3-nitro sugars are obtained in pure form by crystallization. [ABSTRACT FROM AUTHOR]

D-Desosamine is synthesized in 4 steps from methyl vinyl ketone and sodium nitrite. The key step in this chromatography-free synthesis is the coupling of (R)-4-nitro-2-butanol and glyoxal (trimeric form) mediated by cesium carbonate, which affords in crystalline form 3-nitro-3,4,6- trideoxy-α-D-glucose, a nitro sugar stereochemically homologous to D-desosamine. This strategy has enabled the syntheses of an array of analogous 3-nitro sugars. In each case the 3-nitro sugars are obtained in pure form by crystallization. [ABSTRACT FROM AUTHOR]

Direct conversion of cyclohexane to adipic acid (AA) under mild conditions is an attractive technology in response to the increasing industrial demand of chemical intermediate AA. Exploring advanced free radical oxidation systems is the key to converting cyclohexane in a direct and mild manner. This study demonstrates that electrocatalytic water oxidation can quantitatively generate hydroxyl radicals (⋅OH) to selectively oxidize cyclohexane to AA by a vanadium oxide (VOx)‐platinum (Pt) composite catalyst coupled with persulfate (PS) redox mediator at the electrode/electrolyte interface under ambient temperature and pressure. The three active components of VOx, Pt, and PS can produce different concentrations of ⋅OH radicals alone or in combination, resulting in different AA selectivity and cyclohexane conversion, and the activity increased with the increase of free radical concentration before AA peroxidation. The optimized ternary oxidation system of VOx‐Pt‐PS achieved a cyclohexane conversion of 85 % with 95 % AA selectivity and the corresponding yield was 81 %, better than most traditional oxidation systems. Electrochemical interfaces‐driven radical oxidation provides opportunities to oxidatively convert many other inexpensive hydrocarbons to value‐added chemicals. [ABSTRACT FROM AUTHOR]

Reinforced concrete shear walls in multistory buildings often undergo the combined action of vertical and horizontal loads, with their failure primarily attributed to localized damage of the concrete at the bottom of edge elements, leading to premature loss of wall functionality. To enhance the performance of shear walls, this study explores the optimization of shear wall design from the perspective of the stress path within the wall, introducing a diagonally distributed reinforcements in shear walls (referred to as DDR shear walls). To investigate the seismic performance of DDR shear walls, we consider the effects of axial compression ratio, the inclination angle of distributed reinforcing bars, reinforcing bar spacing, and shear span ratio. We design 27 shear wall models with various parameter combinations and employ ABAQUS finite element analysis software to simulate the seismic performance. The simulation results reveal that the inclined distribution of reinforcing bars significantly enhances the seismic performance of shear walls. To achieve optimal structural performance, the inclination angle of reinforcing bars should be adjusted for different floor levels, with higher floors requiring a greater angle and lower floors a smaller one. Additionally, increasing the reinforcing bar spacing and altering the shear span ratio will have varying degrees of impact on the seismic performance of shear walls, necessitating rational design adjustments based on specific circumstances. Furthermore, the application of DDR shear walls in prefabricated construction can be considered to optimize construction processes. [ABSTRACT FROM AUTHOR]

Background: Aflatoxin B1 (AFB1) exposure is a crucial factor to initiate hepatocellular carcinoma (HCC). However, comprehensive microRNA (miRNA)‐message RNA (mRNA) regulatory network regarding AFB1‐associated HCC is still lacking. This work was aimed to identify miRNA‐mRNA network in primary human hepatocytes after AFB1 exposure. Methods: A miRNA expression dataset GSE71540 obtained from the gene expression omnibus (GEO) was used to identify differentially expressed miRNAs (DEMs) after AFB1 exposure using GEO2R. Target genes of these DEMs were identified using TargetScan V_7.2, miRDB, PITA, miRanda, and miRTarBase. Gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed at Database for Annotation, Visualization and Integrated Discovery (DAVID). miRNA‐mRNA regulatory network was established by analyzing three enriched KEGG pathways significantly correlated with HCC onset and then visualized at CytoScape. Results: In this work, nine upregulated and nine downregulated DEMs were identified. Functional enrichment analyses showed that these predicted target genes were significantly associated with cancer development. Analysis of three enriched pathways related to the onset of HCC identified 13 and nine target genes for upregulated DEMs and downregulated DEMs, respectively. Subsequently, the miRNA‐mRNA regulatory networks were constructed. Conclusions: In conclusion, miRNA‐mRNA regulatory network was established, which will help to understand the mechanism underlying the AFB1‐induced onset of HCC. [ABSTRACT FROM AUTHOR]

Solid‐state cooling fibers comprising an electrocaloric polymer, poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) terpolymer, spray‐coated on a conductive fiber core electrode, and a coaxially coated single‐walled carbon nanotubes outer electrode are reported. The fiber coolers can be less than 160 µm thin and more than 8 cm long. Measured cooling ΔT of the EC fibers is 0.7 °C at an electric field of 100 V µm−1 applied between the electrodes. The fiber coolers are flexible; 2000 cycles of repeated bending to a 2.5 mm curvature radius do not significantly degrade the cooling ΔT. Self‐actuated bending of the fibers is observed during the EC operation, which allows the EC fibers to move heat from one location to another without any additional driving mechanisms such as electromagnetic motors, pumps, or electrostatic actuation that are commonly used in conventional coolers. The self‐actuating EC fibers represent the first ever active cooler in a thin fiber form factor. [ABSTRACT FROM AUTHOR]

The loading of homogeneous catalysts with support can dramatically improve their performance in olefin polymerization. However, the challenge lies in the development of supported catalysts with well‐defined pore structures and good compatibility to achieve high catalytic activity and product performance. Herein, we report the use of an emergent class of porous material—covalent organic framework material (COF) as a carrier to support metallocene catalyst—Cp2ZrCl2 for ethylene polymerization. The COF‐supported catalyst demonstrates a higher catalytic activity of 31.1×106 g mol−1 h−1 at 140 °C, compared with 11.2×106 g mol−1 h−1 for the homogenous one. The resulting polyethylene (PE) products possess higher weight‐average molecular weight (Mw) and narrower molecular weight distribution (Ð) after COF supporting, that is, Mw increases from 160 to 308 kDa and Ð drops from 3.3 to 2.2. The melting point (Tm) is also increased by up to 5.2 °C. Moreover, the PE product possesses a characteristic filamentous microstructure and demonstrates an increased tensile strength from 19.0 to 30.7 MPa and elongation at break from 350 to 1400 % after catalyst loading. We believe that the use of COF carriers will facilitate the future development of supported catalysts for highly efficient olefin polymerization and high‐performance polyolefins. [ABSTRACT FROM AUTHOR]

Key step in the synthesis of D-desosamine and analogs (V) is the chromatography-free procedure for the coupling of chiral nitrobutanols (I) with glyoxal to give pure 3-nitro sugars by crystallization. [ABSTRACT FROM AUTHOR]

Bismuth-doped (Bi) glasses and fibers have raised considerable attention for broadband emission and tunable fiber lasers in the near infrared (NIR) region. However, they suffer from low efficiency and it remains challenging to enhance Bi NIR emission. Here, we propose a facile way to enhance and tune the Bi NIR emission by adjusting optical basicity and modulating the boron and aluminum coordination in borate glasses. We find that BO4 and AlO5 species favor Bi NIR emission, right followed by the analyses of static emission spectra, the Fourier transform infrared (FT-IR), and nuclear magnetic resonance (NMR) spectroscopy. Furthermore, abnormal Bi NIR luminescence phenomenon and boron anomaly were observed, which are attributed to the synthetic effect of B and Al coordination transformation. Besides, we find that BO4 tetrahedron plays a major role in enhancing Bi NIR emission at low Al content, while AlO5 hexahedron group will dominate at high Al concentration. Our investigation may give an insight into the luminescent behaviors of Bi in borate glasses and contribute to improving the performance of Bi-doped fiber and fiber lasers in future. [ABSTRACT FROM AUTHOR]

Summary: In the current research, we have adopted a pH shift treatment method that can significantly improve the solubility and emulsification of rice protein isolate (RPI) under neutral conditions. Our results showed that the RPI reached a quasi‐equilibrium state at 1 h after alkali shift treatment, and the solubility and emulsifying properties of RPI were significantly improved compared with the control. In addition, the particle size of RPI decreased considerably under the alkali shift treatment. The results of electron microscopy showed that the RPI aggregates were depolymerised and the particle size distribution was more uniform. The pH shift treatment induced the rearrangement of protein secondary structure, and the exposure of hydrophobic groups increase the surface hydrophobicity of RPI. The change in endogenous fluorescence spectrum, UV and the disulfide bond content all showed that the conformation of RPI changed significantly through pH shift treatment. In addition, it was found that the RPI treated under pH 10–11 shift possessed the best property to stabilise the emulsion. This study showed that under the condition of pH10 and pH11 shift treatment, the structural and functional properties of RPI were vastly improved, and the application of RPI in food was greatly ameliorated. [ABSTRACT FROM AUTHOR]

The interaction of 2D materials with ultrashort laser excitation generates fiber soliton pulses with extreme nonlinear absorption characteristics, which are essential for generating ultrafast pulses. However, searching for suitable nanomaterials to achieve versatile photonic properties is difficult. Factors such as cost, manufacturing process complexity, optical response time, and nonlinear absorption effects make the balance between high performance and low cost a constant challenge, greatly hindering the research and development of ultrafast photonics technology. For fiber soliton pulse systems, γ‐MnO2, as a transition metal oxide (TMO), shows excellent potential among many candidate nanomaterials due to its rich narrow‐band optoelectronic microstructural features and nonlinear optical properties. In this work, this fundamental trade‐off is overcome and γ‐MnO2 is investigated as a nonlinear optical material for multifunctional fiber soliton pulsed lasers. The outputs of conventional soliton pulses, 23rd order harmonic soliton‐molecule picosecond pulses, continuous and soliton pulse waves coexist in dual‐wavelength, and soliton rain pulses are obtained simultaneously, successfully achieving a technological breakthrough in nanophotonics and pulse dynamics. It is demonstrated that MnO2 has a broad application prospect for generating nonlinear effects such as fiber optic soliton pulses, which provides an effective and rich theoretical support for developing ultrafast photonics of narrow‐band optoelectronic materials. [ABSTRACT FROM AUTHOR]

To improve the low‐temperature activity and anti‐sintering ability of Ni‐based catalyst for CO2 methanation, nickel catalysts supported on ZrO2, CeO2 and Ce−Zr−O solid solutions are prepared via citrate complexation‐impregnation method, and characterized by BET, TPR, CO2‐TPD, H2‐TPD, XRD, XPS, TEM and ICP. The relationship between the structure and catalytic performance is also investigated systematically. The results show that Ni/Ce0.2Zr0.8O2 catalyst exhibits the highest CO2 conversion of 71 % at 250 °C and the highest stability, which is mainly attributed to the high dispersion of active metal nickel and its small particle size. The optimized interaction between Ce−Zr−O solid solution and Ni is in favor of the high dispersion and the stability of Ni nanoparticles on the surface, and enhances the sintering resistance of Ni catalyst. In addition, the similar TOF values of catalysts in different supports indicate that for improving low‐temperature activity of this system, the dispersion of Ni NPs is critical. [ABSTRACT FROM AUTHOR]

A broadband vertically interdigital‐capacitor (VIC) is proposed and fabricated in a 10‐layer low temperature co‐fired ceramic substrate. By interconnecting the open ends of interval fingers, the number of stop‐band structures is reduced and thus the spurs that limit the bandwidth are removed. With the orthogonally placed input/output ports, the amplitudes of transmission coefficient and reflection coefficient are also improved. Thus, the high frequency response of VIC is improved. The bandwidth and capacitance of the proposed VIC increased 225% and 28%, respectively. The proposed VIC is available to make compact microwave components in a wider frequency rage. Comparison and discussion are provided as well. [ABSTRACT FROM AUTHOR]

Cover Feature: Covalent Organic Framework-Supported Metallocene for Ethylene Polymerization (Chem. Eur. J. 54/2023) Covalent organic frameworks, ethylene polymerization, heterogenous polymerization, polyolefins, supported metallocenes Keywords: covalent organic frameworks; ethylene polymerization; heterogenous polymerization; polyolefins; supported metallocenes EN covalent organic frameworks ethylene polymerization heterogenous polymerization polyolefins supported metallocenes 1 1 1 09/29/23 20230926 NES 230926 B Covalent organic framework b (COF) particles with hydroxy groups and well-defined micropores have been synthesized and used as novel carriers to load a metallocene catalyst - Cp SB 2 sb ZrCl SB 2 sb . [Extracted from the article]

Abstract: Bismuth‐doped glasses and fibers with broadband near‐infrared (NIR) emission have garnered much attention on account of their potential applications in new fiber lasers and broadband amplifiers. Yet the realization of high gain from Bi‐doped fibers and highly efficient NIR emission from Bi‐doped glasses are still a stubborn puzzle. The enhancement of Bi NIR emission is normally based on modifying the glass composition and topology, which will change the structure of the glass over a wide range and alter the thermal or mechanical properties of the glass simultaneously, making it more complicated for the designing and fabricating of Bi fibers with good performance. Here, we find that a trace addition of Si3N4 can efficiently enhance the Bi NIR emission without changing the glass structure significantly, right followed by spectral and structural analysis. 27Al NMR measurement reveals that the short‐ to medium‐range order of this glass is unchanged. The EPMA measurement confirms the homogeneity of fabricated glass. The great enhancement and red‐shift under blue light excitation may originate from the conversion of Bi active centers to low valence. Our results indicate that the trace addition of nitride could be a facile and maneuverable way to control the valence of active ions in glasses, which may contribute to improving the performance of photonic glasses. [ABSTRACT FROM AUTHOR]

β-Hydroxy-α-amino acids figure prominently as chiral building blocks in chemical synthesis and serve as precursors to numerous important medicines. Reported herein is a method for the synthesis of β-hydroxy-α-amino acid derivatives by aldolization of pseudoephenamine glycinamide, which can be prepared from pseudoephenamine in a one-flask protocol. Enolization of ( R, R)- or ( S, S)-pseudoephenamine glycinamide with lithium hexamethyldisilazide in the presence of LiCl followed by addition of an aldehyde or ketone substrate affords aldol addition products that are stereochemically homologous with L- or D-threonine, respectively. These products, which are typically solids, can be obtained in stereoisomerically pure form in yields of 55-98 %, and are readily transformed into β-hydroxy-α-amino acids by mild hydrolysis or into 2-amino-1,3-diols by reduction with sodium borohydride. This new chemistry greatly facilitates the construction of novel antibiotics of several different classes. [ABSTRACT FROM AUTHOR]

β-Hydroxy-α-amino acids figure prominently as chiral building blocks in chemical synthesis and serve as precursors to numerous important medicines. Reported herein is a method for the synthesis of β-hydroxy-α-amino acid derivatives by aldolization of pseudoephenamine glycinamide, which can be prepared from pseudoephenamine in a one-flask protocol. Enolization of ( R, R)- or ( S, S)-pseudoephenamine glycinamide with lithium hexamethyldisilazide in the presence of LiCl followed by addition of an aldehyde or ketone substrate affords aldol addition products that are stereochemically homologous with L- or D-threonine, respectively. These products, which are typically solids, can be obtained in stereoisomerically pure form in yields of 55-98 %, and are readily transformed into β-hydroxy-α-amino acids by mild hydrolysis or into 2-amino-1,3-diols by reduction with sodium borohydride. This new chemistry greatly facilitates the construction of novel antibiotics of several different classes. [ABSTRACT FROM AUTHOR]

A facile, stereoselective preparation of syn-β-hydroxy-α-amino acids by an aldol reaction is described. [ABSTRACT FROM AUTHOR]