Microwave‐Assisted Solid‐Phase Synthesis of Antifreeze Glycopeptides

Microwave‐assisted solid‐phase synthesis allows for the rapid and large‐scale preparation and structure–activity characterization of tandem repeating glycopeptides, namely monodispersed synthetic antifreeze glycopeptides (syAFGPs, H‐[Ala‐Thr(Galβ1,3GalNAcα1→)‐Ala]_n‐OH, n=2–6). By employing novel AFGP analogues, we have demonstrated that of the monodispersed syAFGP_n (n=2–6, degree of polymerization, DP=2–6, M_w=1257–3690 Da), syAFGP₅ (DP=5, M_w=3082 Da) and syAFGP₆ (DP=6, M_w=3690 Da) exhibit the ability to form typical hexagonal bipyramidal ice crystals and satisfactory thermal hysteresis activity. Structural characterization by NMR and CD spectroscopy revealed that syAFGP₆ forms a typical poly‐L ‐proline type II helix‐like structure in aqueous solution whereas enzymatic modification by sialic acid of the residues at the C‐3 positions of the nonreducing Gal residues disturbs this conformation and eliminates the antifreeze activity.     

Solid‐Phase Synthesis of a Seventh‐Generation Inverse Poly(amidoamine) Dendrimer: Importance of the Loading Ratio on the Resin

Here, this study overcomes the current barriers to efficient solid‐phase synthesis of high‐generation dendrimers by decreasing the loading ratio on the resin. G7 inverse poly(amidoamine) dendrimer is now prepared, for the first time, through a solid‐phase synthesis using only 50% of the available reactive sites and by choosing a large resin. This preparation takes only 15 d to afford highly pure product in 80% yield with precipitation being the only purification procedure used. The results clearly show the amount of the initial monomer loaded on the resin to be a vital factor for the ability to use solid‐phase synthesis to produce large dendrimers. This finding also sets stage for the applications of solid‐phase synthesis for the preparation of other macromolecules.

     

Efficient Automated Solid‐Phase Synthesis of DNA and RNA 5′‐Triphosphates

A fast, high‐yielding and reliable method for the synthesis of DNA‐ and RNA 5′‐triphosphates is reported. After synthesizing DNA or RNA oligonucleotides by automated oligonucleotide synthesis, 5‐chloro‐saligenyl‐N,N‐diisopropylphosphoramidite was coupled to the 5′‐end. Oxidation of the formed 5′‐phosphite using the same oxidizing reagent used in standard oligonucleotide synthesis led to 5′‐cycloSal‐oligonucleotides. Reaction of the support‐bonded 5′‐cycloSal‐oligonucleotide with pyrophosphate yielded the corresponding 5′‐triphosphates. The 5′‐triphosphorylated DNA and RNA oligonucleotides were obtained after cleavage from the support in high purity and excellent yields. The whole reaction sequence was adapted to be used on a standard oligonucleotide synthesizer.     

Efficient Formation of Luminescent Lanthanide(III) Complexes by Solid‐Phase Synthesis and On‐Resin Screening

Time‐resolved luminescence measurements of luminescent lanthanide complexes have advantages in biological assays and high‐throughput screening, owing to their high sensitivity. In spite of the recent advances in their energy‐transfer mechanism and molecular‐orbital‐based computational molecular design, it is still difficult to estimate the quantum yields of new luminescent lanthanide complexes. Herein, solid‐phase libraries of luminescent lanthanide complexes were prepared through amide‐condensation and Pd‐catalyzed coupling reactions and their luminescent properties were screened with a microplate reader. Good correlation was observed between the time‐resolved luminescence intensities of the solid‐phase libraries and those of the corresponding complexes that were synthesized by using liquid‐phase chemistry. This method enabled the rapid and efficient development of new sensitizers for Sm^III, Eu^III, and Tb^III luminescence. Thus, solid‐phase combinatorial synthesis combined with on‐resin screening led to the discovery of a wide variety of luminescent sensitizers.     

Facile Microwave‐Assisted Solid‐Phase Synthesis of Highly Fluorescent Nitrogen–Sulfur‐Codoped Carbon Quantum Dots for Cellular Imaging Applications

Carbon quantum dots (CQDs) have recently attracted significant attention for both their fundamental science and technological applications as a new class of fluorescent zero‐dimensional nanomaterials with a size below 10 nm. However, the reported methods of synthesis were generally less suitable for the large‐scale production of the CQDs with high‐fluorescent quantum yield (QY). In the paper, a novel one‐pot microwave‐assisted drying synthesis approach was presented to prepare CQDs with high QY of 61.3 % for the first time. The production yield of CQDs was 35±3 % in weight. The as‐prepared CQDs were characterized by various techniques such as TEM, AFM, XRD, XPS, FTIR spectroscopy, UV/Vis absorption spectroscopy, and fluorescence spectroscopy. The results showed that the high QY of CQDs was largely attributed to the dual doping of nitrogen and sulphur into CQDs. Such CQDs were then used as live‐cell imaging reagents due to their high QY, good water dispersibility, fine biocompatibility, high photostability, and low cytotoxicity.