Design, Synthesis, and Biological Evaluation of Desmuramyl Dipeptides Modified by Adamantyl-1,2,3-triazole

Di-mannosylation enhances the adjuvant properties of adamantane-containing desmuramyl peptides in vivo

Muramyl dipeptide (MDP) is the smallest essential peptidoglycan substructure capable of promoting both innate and adaptive immune responses. Herein, we report on the design, synthesis, and in vivo study of the adjuvant properties of two novel MDP analogs containing an achiral adamantyl moiety attached to the desmuramyl dipeptide (DMP) pharmacophore and additionally modified by one mannosyl subunit (derivative 7) or two mannosyl subunits (derivative 11). Mannose substructures were introduced in order to assess how the degree of mannosylation affects the immune response and nucleotide-binding oligomerization-domain-containing protein 2 (NOD2) binding affinity, compared to the reference compound ManAdDMP. Both mannosylated MDP analogs showed improved immunomodulating properties, while the di-mannosylated derivative 11 displayed the highest, statistically significant increase in anti-OVA IgG production. In this study, for the first time, the di-mannosylated DMP derivative was synthesized and immunologically evaluated. Derivative 11 stimulates a Th-2-polarized type of immune reaction, similar to the reference compound ManAdDMP and MDP. Molecular dynamics (MD) simulations demonstrate that 11 has a higher NOD2 binding affinity than 7, indicating that introducing the second mannose significantly contributes to the binding affinity. Mannose interacts with key amino acid residues from the LRR hydrophobic pocket of the NOD2 receptor and loop 2.

Flow Chemistry for Synthesis of 2-(C-Glycosyl)acetates from Pyranoses via Tandem Wittig and Michael Reactions

C-Glycosyl compounds (C-glycosides) are a class of saccharide derivatives with improved stability over their O-linked counterparts. This paper reports the synthesis of several trans-2-(C-glycosyl)acetates via a tandem Wittig-Michael reaction from pyranoses (cyclic hemiacetals) using continuous flow processing, which gave improvements compared to reactions conducted in round-bottom flasks. Products were isolated in yields of >60% from reactions of benzyl-protected xylopyranoses, glucopyranoses, and galactopyranoses at higher temperatures and pressures, which were superior to yields from batch procedures. A two-step procedure involving the Wittig reaction followed by Michael reaction (intramolecular oxa-Michael) of the unsaturated ester obtained in the presence of DBU was developed. Reactions of protected mannopyranose gave low yields in corresponding reactions in flow due to competing C-2 epimerization.

Emerging Aspects of Triazole in Organic Synthesis: Exploring its Potential as a Gelator

Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) - commonly known as the "click reaction" - serves as the most effective and highly reliable tool for facile construction of simple to complex designs at the molecular level. It relates to the formation of carbon heteroatomic systems by joining or clicking small molecular pieces together with the help of various organic reactions such as cycloaddition, conjugate addition, ring-opening, etc. Such dynamic strategy results in the generation of triazole and its derivatives from azides and alkynes with three nitrogen atoms in the five-membered aromatic azole ring that often forms gel-assembled structures having gelating properties. These scaffolds have led to prominent applications in designing advanced soft materials, 3D printing, ion sensing, drug delivery, photonics, separation, and purification. In this review, we mainly emphasize the different mechanistic aspects of triazole formation, which includes the synthesis of sugar-based and non-sugar-based triazoles, and their gel applications reported in the literature for the past ten years, as well as the upcoming scope in different branches of applied sciences.

Muramyl dipeptide-based analogs as potential anticancer compounds: Strategies to improve selectivity, biocompatibility, and efficiency

According to the WHO, cancer is the second leading cause of death in the world. This is an important global problem and a major challenge for researchers who have been trying to find an effective anticancer therapy. A large number of newly discovered compounds do not exert selective cytotoxic activity against tumorigenic cells and have too many side effects. Therefore, research on muramyl dipeptide (MDP) analogs has attracted interest due to the urgency for finding more efficient and safe treatments for oncological patients. MDP is a ligand of the cytosolic nucleotide-binding oligomerization domain 2 receptor (NOD2). This molecule is basic structural unit that is responsible for the immune activity of peptidoglycans and exhibits many features that are important for modern medicine. NOD2 is a component of the innate immune system and represents a promising target for enhancing the innate immune response as well as the immune response against cancer cells. For this reason, MDP and its analogs have been widely used for many years not only in the treatment of immunodeficiency diseases but also as adjuvants to support improved vaccine delivery, including for cancer treatment. Unfortunately, in most cases, both the MDP molecule and its synthesized analogs prove to be too pyrogenic and cause serious side effects during their use, which consequently exclude them from direct clinical application. Therefore, intensive research is underway to find analogs of the MDP molecule that will have better biocompatibility and greater effectiveness as anticancer agents and for adjuvant therapy. In this paper, we review the MDP analogs discovered in the last 10 years that show promise for antitumor therapy. The first part of the paper compiles the achievements in the field of anticancer vaccine adjuvant research, which is followed by a description of MDP analogs that exhibit promising anticancer and antiproliferative activity and their structural changes compared to the original MDP molecule.

Synthesis and Immunological Evaluation of Mannosylated Desmuramyl Dipeptides Modified by Lipophilic Triazole Substituents

Muramyl dipeptide (N-acetylmuramyl-L-alanyl-D-isoglutamine, MDP) is the smallest peptidoglycan fragment able to trigger an immune response by activating the NOD2 receptor. Structural modification of MDP can lead to analogues with improved immunostimulating properties. The aim of this work was to prepare mannosylated desmuramyl peptides (ManDMP) containing lipophilic triazole substituents to study their immunomodulating activities in vivo. The adjuvant activity of the prepared compounds was evaluated in the mouse model using ovalbumin as an antigen and compared to the MDP and referent adjuvant ManDMPTAd. The obtained results confirm that the α-position of D-isoGln is the best position for the attachment of lipophilic substituents, especially adamantylethyl triazole. Compound 6c exhibited the strongest adjuvant activity, comparable to the MDP and better than referent ManDMPTAd.