Synthesis of C3-symmetric and C4-symmetric amino acid derivatives via Suzuki–Miyaura cross-coupling reaction

Synthesis and applications of symmetric amino acid derivatives

Symmetric α-amino acid derivatives can be used for the synthesis of intermolecularly linked peptides such as dimer-type peptides, and modified peptides in which two amino acids are intramolecularly linked. They are also synthetic intermediates for the total synthesis of natural products and functional molecules. These symmetric amino acid derivatives must be prepared based on organic synthesis. It is necessary to develop an optimal synthetic strategy for constructing the target symmetric amino acid derivative. In this review, we will introduce strategies for synthesizing symmetric amino acid derivatives. Additionally, selected applications of these amino acids in the life sciences will be described.

An overview of the synthetic strategies of C3-symmetric polymeric materials containing benzene and triazine cores and their biomedical applications

C3-symmetric star-shaped materials are an emerging category of porous organic polymers with distinctive properties such as permanent porosity, good thermal and chemical stability, high surface area, and appropriate functionalization that promote outstanding potential in various applications. This review is mostly about constructing benzene or s-triazine rings as the center of C3-symmetric molecules and using side-arm reactions to add functions to these molecules. Over and above this, the performance of various polymerization processes has been additionally investigated in detail, including the trimerization of alkynes or aromatic nitriles, polycondensation of monomers with specific functional groups, and cross-coupling building blocks with benzene or triazine cores. Finally, the most recent progress in biomedical applications for C3-symmetric materials based on benzene or s-triazine have been summarized.

Synthetic Approaches to Star-Shaped Molecules with 1,3,5-Trisubstituted Aromatic Cores

Herein, we summarize the synthetic approaches that have been developed for the synthesis of star-shaped molecules. Typically, to design such highly functionalized molecules, simple building blocks are first assembled through trimerization reactions, starting from commercially available starting materials. Then, these building blocks are synthetically manipulated to generate extended star-shaped molecules. We also discuss the syntheses of star-shaped molecules that contain 2,4,6-trisubstituted 1,3,5-triazine or 1,3,5-trisubstituted benzene rings as a central core and diverse substituted styrene, phenyl, and fluorene derivatives at their periphery, which endows these molecules with extended conjugation. A variety of metal-catalyzed reactions, such as Suzuki, Buchwald-Hartwig, Sonogashira, Heck, and Negishi cross-coupling reactions, as well as metathesis, have been employed to functionalize a range of star-shaped molecules. The methods described herein will be helpful for designing a wide range of intricate compounds that are highly valuable in the fields of supramolecular chemistry and materials science. Owing to space limitations, we will not cover all of the publications on this topic. Instead, we will focus on examples that were reported by our research group and other relevant recent literature. Apart from the trimerization sequence, this Minireview has been structured based on the key reactions that were used to prepare the star-shaped molecules and other higher analogues. Finally, some examples that do not fit into this classification are discussed.

Synthesis of C 3-symmetric star-shaped molecules containing α-amino acids and dipeptides via Negishi coupling as a key step

We demonstrate a new synthetic strategy toward star-shaped C₃-symmetric molecules containing α-amino acid (AAA) derivatives and dipeptides. In this regard, trimerization and Negishi cross-coupling reactions are used as the key steps starting from readily available 4’-iodoacetophenone and L-serine. These C₃-symmetric molecules containing AAA moieties are useful to design new ligands suitable for asymmetric synthesis and peptide dendrimers.

A propeller-like small molecule as a novel G-quadruplex DNA binder: The study of fluorescent sensing property and preferential interactions with human telo21 structure

A new propeller-like small molecule was synthesized with three terminal amino side groups. The molecule was found to be a selective nucleic acid binder towards telo21 G-quadruplex DNA compared with other representative nucleic acids including single-stranded DNA (dA21), duplex DNA (ds26) and RNA. The fluorescent signal of the molecule upon interaction with telo21 G-quadruplex structure shows remarkable enhancement (F_max /F₀  = 17.9) while interaction with other nucleic acids shows the signal enhancement which is less than 2.1. In addition, a good linear relationship of binding signal correlated with the concentration of telo21 DNA was obtained. Molecular docking study was also performed to acquire the binding behaviour and its interaction modes of the molecule with the structure of human telomeric DNA G-quadruplex. The modelling results show that the three conjugated terminal units (dimethylaminobenzyl groups) associated through the ethylene bridges with the central methylated pyridine ring formed a co-planar conformation upon stacking onto the G-quartets via pi-pi stacking interactions. This could be the key reason that the molecule shows excellent fluorescent signal of binding towards telo21 G-quadruplex DNA rather than other types of nucleic acids.

Diversity-oriented synthesis of medicinally important 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) derivatives and higher analogs

1,2,3,4-Tetrahydroisoquinoline-3-carboxylic acid (Tic) is a constrained analog of phenylalanine (Phe). The Tic unit has been identified as a core structural element present in several peptide-based drugs and forms an integral part of various biologically active compounds. This report covers the biological significance of the Tic core and provides a detailed account of various synthetic approaches available for the construction of Tic derivatives. Along with the traditional methods such as the Pictet-Spengler and Bischler-Nepieralski reactions, we cover various recent approaches such as enyne metathesis, [2 + 2 + 2] cycloaddition and the Diels-Alder reaction to generate Tic derivatives. In addition, syntheses of higher analogs of Tic are also discussed.

Star-Shaped Conjugated Systems

The present review deals with the preparation and the properties of star-shaped conjugated compounds. Three, four or six conjugated arms are attached to cross-conjugated cores, which consist of single atoms (B, C⁺, N), benzene or azine rings or polycyclic ring systems, as for example triphenylene or tristriazolotriazine. Many of these shape-persistent [n]star compounds tend to π-stacking and self-organization, and exhibit interesting properties in materials science: Linear and non-linear optics, electrical conductivity, electroluminescence, formation of liquid crystalline phases, etc.