Understanding Structural Evolution in the Synthesis of Advanced Energy Materials

Developing a variety of in situ characterization techniques to unravel the structural/chemical evolution during the synthesis of various advanced energy materials for studying the relationship among those experimental conditions and the structure is the key to implement the controllable synthesis of battery materials.This perspective summarizes the recent studies into structural evolution during in situ synthesis of various advanced energy materials by synchrotron X-ray diffraction technique and forecasts the more extensive applications in the future.     

Polymer-supported synthesis of mono-substituted porphyrins

Anchoring of substituted benzaldehydes to soluble and insoluble polymers allows for the synthesis of mono-substituted tetraarylporphyrins without the production of di-, tri-, and tetra-substituted porphyrin side products. The exclusion of the aforementioned side products during the synthesis of mono-substituted tetraarylporphyrin acids greatly reduced the complexity during purification of the product.     

A selected ribozyme catalyzing diverse dipeptide synthesis

The sequence of events by which protein, RNA, and DNA emerged during early biological evolution is one of the most profound questions regarding the origin of life. The contemporary role of aminoacyl-adenylates as intermediates in both ribosomal and nonribosomal peptide synthesis suggests that they may have served as substrates for uncoded peptide synthesis during early evolution. We report a highly active peptidyl transferase ribozyme family, isolated by in vitro selection, that efficiently catalyzes dipeptide synthesis by using an aminoacyl-adenylate substrate. It was characterized by sequence and structural analysis and kinetic studies. Remarkably, the ribozyme catalyzed the formation of 30 different dipeptides, the majority of rates being within 5-fold that of the Met-Phe dipeptide required by the selection. The isolation of this synthetic ribozyme fosters speculation that ribozyme-mediated uncoded peptide synthesis may have preceded coded peptide synthesis.     

An insight into hexamethylenetetramine: a versatile reagent in organic synthesis

Hexamethylenetetramine is a versatile reagent in organic synthesis. It plays a major role in modern organic synthesis. This review focuses on hexamine reagent for its significant role in organic synthesis during the past decades and is able to provide a valuable perspective from synthetic point of view.     

电解合成芳香醛类化合物的研究进展

综述了电解合成芳香醛类化合物的研究进展情况,介绍了新技术在有机电解合成中的应用及发展趋势,着重对超声波技术在电解合成中的运用进行了评述。     

On the use of carboxamidomethyl esters (cam esters) in the synthesis of model peptides. scope and limitations

The usefulness of carboxamidomethyl esters (CAM esters) as a carboxyl protecting group for peptide synthesis was demonstrated. The synthesis of the chemotactic peptide For-Met-Leu-Phe-OH as well as the synthesis of Met-enkephalin using CAM ester as carboxyl terminal protection were performed. These esters showed good stability during acidolytic removal of BOC N-protecting group, during hydrogenolysis of Z N-protecting group and during removal of FMOC N-protecting group. CAM esters were selectively and rapidly cleaved by NaOH 0.5 N or by Na₂CO₃. However, we did not succeed in removing selectively the CAM ester when β-benzyl ester of aspartic acid was present in the sequence.     

Mass spectrometry feedback control for synthesis of polyhydroxyalkanoate granule microstructures in Ralstonia eutropha

Polyhydroxyalkanoate (PHA) granules with core-shell layered microstructure were synthesized in Ralstonia eutropha using periodic feeding of valeric acid into a growth medium containing excess fructose. The O2 consumption and CO2 evolution rates, determined by off-gas mass spectrometry, have been used as sensitive measures to indicate the type of nutrients utilized by R. eutropha during PHA synthesis. Domains of poly-3-hydroxybutyrate (PHB) were formed during polymer storage conditions when only fructose was present. Feeding of valeric acid (pentanoic acid) resulted in the synthesis of hydroxyvalerate (HV) monomers, forming a poly-3-hydroxybutyrate-co-valerate (PHBV) copolymer. The synthesis of desired polymer microstructures was monitored and controlled using online mass spectrometry (MS). The respiratory quotient (RQ) was unique to the type of polymer being synthesized due to increased O2 consumption during PHBV synthesis. MS data was used as the control signal for nutrient feeding strategies in the bioreactor. The core-shell structures synthesized were verified in cells using transmission electron microscopy after thin sectioning and staining with RuO4. It was demonstrated that the synthesis of core-shell microstructures can be precisely controlled utilizing a MS feedback control system.     

Recent progress on the total synthesis of natural products in China

An overview of natural products synthesis in Mainland China during the past 10 years is provided. This review only emphasizes the first total synthesis of molecules of contemporary interest and syntheses that helped to correct structures. In addition, some significant results on the novel synthesis and structure-activity relationship (SAR) studies of several natural products are introduced.     

A total synthesis of the ammonium ionophore, (−)-enniatin B

A nine-step (longest linear) batch total synthesis of the cyclic hexadepsipeptide (−)-enniatin B is described. The synthesis minimizes precipitation during reaction conditions for adaptability to flow synthesis. The route was used to prepare >100 mg of the natural product.     

N-trifluoroacetyl sialyl phosphite donors for the synthesis of alpha(2 --> 9) oligosialic acids

[reaction: see text] A new method for the synthesis of alpha(2 --> 9) oligosialic acids is developed using phosphite sialyl donors that are protected with a C-5 N-trifluoroacetyl (NHTFA) substituent. Compared with conventional donors, these donors gave a higher degree of alpha-anomeric selectivity during glycosidic bond formation and better yields during iterative sialylation in the synthesis of oligosialic acids.     

Unexpected decarbonylation during an acid-mediated cyclization to access the carbocyclic core of zoanthenol

An unusual loss of CO was observed during a key cyclization event in efforts toward the total synthesis of zoanthenol. The synthesis of the cyclization precursor and a proposed mechanism for decarbonylation are detailed.     

Protection of the indole nucleus of tryptophan in solid-phase peptide synthesis with a dipeptide that can be cleaved rapidly at physiological pH

The synthesis of a new derivative of tryptophan Fmoc-Trp(Boc-Sar-Sar)-OH is described. Fmoc-Trp(Boc-Sar-Sar)-OH is introduced into peptides by solid-phase peptide synthesis and during treatment with TFA at the end of the synthesis, the Boc group is cleaved and the peptide is obtained with the indole nucleus modified with the sarcosinyl-sarcosinyl (Sar-Sar) moiety. This modification will introduce a cationic charge that improves the solubility of the peptide during HPLC purification. The Sar-Sar moiety is cleaved upon exposure to physiological pH. The Boc-Sar-Sar group might, therefore, also find use in the design of pro-drugs of indole-containing compounds.     

Characterization by two-dimensional gel electrophoresis of host proteins whose synthesis is sustained or stimulated during the course of herpes simplex virus type 1 infection

Herpes simplex virus type 1 (HSV-1) gene expression is concomitant with a selective shutoff of host protein synthesis. While the synthesis of the vast majority of cellular proteins is inhibited immediately after infection, several cellular proteins continue to be synthesized, even during the late phase of infection. Because these cellular proteins may intervene in the life cycle of the virus, we undertook two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) analyses to evaluate the proportion of cellular proteins that is represented by these particular proteins. Human cells were infected with HSV-1. At different times after infection, proteins were labeled with 35S just prior to harvesting. The rate of synthesis of a set of 183 acidic host proteins, as well as that of ribosomal proteins, was measured during the course of infection, after separation by 2-D PAGE. As expected, HSV-1 induces a strong inhibition of host protein synthesis immediately after infection. However, the synthesis of basic ribosomal proteins and that of an unexpected high proportion of the sub-set of cellular proteins analyzed is sustained or stimulated during HSV-1 infection. A 2-D PAGE analysis outlining the expression patterns of these proteins at different times of infection is presented.     

A base-stable dithiomethyl linker for solid-phase synthesis of oligonucleotides

A novel linkage, useful for the synthesis of oligonucleotides is described. The linking function is compatible with all conditions used for oligonucleotide synthesis, orthogonal to all other protecting groups, but regenerates 3′-OH rapidly upon mild reduction under aqueous conditions. This method is employed in the removal of depurinated fragments during the synthesis of oligonucleotides.     

A Synthesis of Prostaglandins: Strategy and Reality

The prostaglandin synthesis developed in the Woodward Research Institute at Basel serves to provide an unusual look behind the scenes. A candid account is presented of the sometimes tortuous chronological sequence of ideas and experiments during work on a challenging synthesis.     

Protein synthesis in cell-free reticulocyte lysates on multi-hour incubation

Cell-free protein synthesis in rabbit reticulocyte lysate translation mixtures has been studied during multi-hour incubations. In an impaired lysate obtained from cells stored at 0°C before lysis, and showing a low initial rate of synthesis, translation could be stimulated by a factor of 4 by including RNase inhibitor and additional ATP and GTP. In translation mixtures prepared from normal lysates, protein synthesis could be improved by ∼50% by the addition of excess GTP. The observed increases in protein synthesis were obtained by improved maintenance of the initial rate of synthesis.     

Oligomeric guanidine synthesis assisted by TFA-sensitive arylsulfonylthiourea

Through arylsulfonyl activation of thiourea, efficient synthesis of oligomeric guanidines can be achieved in either solution or solid-phase. Incorporation of TFA-sensitive arylsulfonyl groups, such as Pbf, during the synthesis greatly simplifies deprotection procedures for obtaining the final oligomeric guanidine products.     

Synthesis and structure of a stabilized 10-membered cyclic enediyne

The synthesis and structure of an acetal protected 10-membered cyclic enediyne-1,2-diol rac-10 is reported. The conformational constrain of the unsaturated macrocycle by the acetal protection group prevents the thermal cyclization reaction of the endiyne during synthesis and purification.     

Using stop-flow lithography to produce opaque microparticles: synthesis and modeling

We report on modeling and experimental studies of the synthesis of opaque microparticles made via stop-flow lithography. Opaque magnetic beads and UV-absorbing dyes incorporated into hydrogel microparticles during synthesis changed the height and the degree of cross-linking of the polymer matrices formed. The effect of the concentration of these opaque materials on the particle height was determined experimentally and agreed well with model predictions based on the photopolymerization process over a wide range of UV absorbance. We also created particles with two independent anisotropies, magnetic and geometric, by applying magnetic fields during particle synthesis. Our work provides a platform for rational design of lithographic patterned opaque particles and also a new class of structured magnetic microparticles.     

The first total synthesis of sporiolide B

The first total synthesis of natural cytotoxic agent, sporiolide B, is described. d-Xylose was used as the chiral template to pre-control the absolute configuration during the synthesis. Yamaguchi esterification and ring closing metathesis greatly facilitate the target compound accomplishment.