Expedient synthesis of imino-C-nucleoside fleximers featuring a one-pot procedure to prepare aryl triazoles.

Nucleoside analogues such as the antiviral agents galidesivir and ribavirin are of synthetic interest. This work reports a "one-pot" preparation of similar fleximers using a bifunctional copper catalyst that generates the aryl azide in situ, which is captured by a terminal alkyne to effect triazole formation.

Galidesivir Triphosphate Promotes Stalling of Dengue-2 Virus Polymerase Immediately Prior to Incorporation.

Millions of people are infected by the dengue and Zika viruses each year, resulting in significant morbidity and mortality. Galidesivir is an adenosine nucleoside analog that can attenuate flavivirus replication in cell-based assays and animal models of infection. Galidesivir is converted to the triphosphorylated form by host kinases and subsequently incorporated into viral RNA by viral RNA polymerases. This has been proposed to lead to the delayed termination of RNA synthesis. Here, we report direct in vitro testing of the effects of Galidesivir triphosphate on dengue-2 and Zika virus polymerase activity. Galidesivir triphosphate was chemically synthesized, and inhibition of RNA synthesis followed using a dinucleotide-primed assay with a homopolymeric poly(U) template. Galidesivir triphosphate was equipotent against dengue-2 and Zika polymerases, with IC50 values of 42 ± 12 µM and 47 ± 5 µM, respectively, at an ATP concentration of 20 µM. RNA primer extension assays show that the dengue-2 polymerase stalls while attempting to add a Galidesivir nucleotide to the nascent RNA chain, evidenced by the accumulation of RNA products truncated immediately upstream of Galidesivir incorporation sites. Nevertheless, Galidesivir is incorporated at isolated sites with low efficiency, leading to the subsequent synthesis of full-length RNA with no evidence of delayed chain termination. The incorporation of Galidesivir at consecutive sites is strongly disfavored, highlighting the potential for modulation of inhibitory effects of nucleoside analogs by the template sequence. Our results suggest that attenuation of dengue replication by Galidesivir may not derive from the early termination of RNA synthesis following Galidesivir incorporation.

An Isomer of Galidesivir That Potently Inhibits Influenza Viruses and Members of the Bunyavirales Order.

We report for the first time the antiviral activities of two iminovirs (antiviral imino-C-nucleosides) 1 and 2, structurally related to galidesivir (Immucillin A, BCX4430). An iminovir containing the 4-aminopyrrolo[2,1-f][1,2,4-triazine] nucleobase found in remdesivir exhibited submicromolar inhibition of multiple strains of influenza A and B viruses, as well as members of the Bunyavirales order. We also report the first syntheses of ProTide prodrugs of iminovir monophosphates, which unexpectedly displayed poorer viral inhibition than their parent nucleosides in vitro. An efficient synthesis of the 4-aminopyrrolo[2,1-f][1,2,4-triazine]-containing iminovir 2 was developed to enable preliminary in vivo studies, wherein it displayed significant toxicity in BALB/c mice and limited protection against influenza. Further modification of this anti-influenza iminovir will therefore be required to improve its therapeutic value.

Synthesis and Antibacterial Analysis of Analogues of the Marine Alkaloid Pseudoceratidine.

In an effort to gain more understanding on the structure activity relationship of pseudoceratidine 1, a di-bromo pyrrole spermidine alkaloid derived from the marine sponge Pseudoceratina purpurea that has been shown to exhibit potent biofouling, anti-fungal, antibacterial, and anti-malarial activities, a large series of 65 compounds that incorporated several aspects of structural variation has been synthesised through an efficient, divergent method that allowed for a number of analogues to be generated from common precursors. Subsequently, all analogues were assessed for their antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Overall, several compounds exhibited comparable or better activity than that of pseudoceratidine 1, and it was found that this class of compounds is generally more effective against Gram-positive than Gram-negative bacteria. Furthermore, altering several structural features allowed for the establishment of a comprehensive structure activity relationship (SAR), where it was concluded that several structural features are critical for potent anti-bacterial activity, including di-halogenation (preferable bromine, but chlorine is also effective) on the pyrrole ring, two pyrrolic units in the structure and with one or more secondary amines in the chain adjoining these units, with longer chains giving rise to better activities.

Development, synthesis and biological investigation of a novel class of potent PC-PLC inhibitors.

Phospholipases are enzymes that are involved in the hydrolysis of acyl and phosphate esters of phospholipids, generating secondary messengers that have implications in various cellular processes including proliferation, differentiation and motility. As such inhibitors of phospholipases have been widely studied for their use as anti-cancer therapeutics. Phosphatidylcholine-specific phospholipase C (PC-PLC) is implicated in the progression of a number of cancer cell lines including aggressing triple-negative breast cancers. Most current studies on PC-PLC have utilised D609 as the standard inhibitor however it is known to have multiple failings, including poor stability in aqueous media. 2-Morpholinobenzoic acids were recently identified using vHTS as a potential class of lead compounds, with improvements over D609. In this work 129 analogues in this class were prepared and their PC-PLC inhibitory activity was assessed. It was found that the majority of these novel compounds had improved activity when compared to D609 with the most potent inhibitors completely inhibiting enzyme activity. It was determined that the best compound/s contained a morpholino and 2-substituted N-benzyl moieties with these findings explained using molecular modelling. The compounds reported here will allow for improved study of PC-PLC activity.

Incorporation of 'click' chemistry glycomimetics dramatically alters triple-helix stability in an adiponectin model peptide.

Adiponectin (Adpn) has been shown to be a possible therapeutic for Type II diabetes, however the production of a therapeutic version of Adpn has proved to be challenging. Biological studies have highlighted the importance of the glycosylated lysine residues for the formation of bioactive high molecular weight oligomers of Adpn. Through the use of 'click' glycopeptide mimetics, we investigated the role of glycosylated lysine and serine residues for the formation of triple helical structures of the collagenous domain of Adpn, in the context of a collagen model peptide scaffold. The physical properties of the unglycosylated lysine and serine peptides are compared with their glycosylated analogues. Our results highlight the crucial role of lysine residues for formation of the triple helical structure of Adpn, possibly due to the extension of both intra- and interstrand hydrogen bonding networks. Strikingly, we observed a significant decrease in thermal stability upon incorporation of triazole-linked analogues of glycosylated lysine residues into the adiponectin collageneous domain, indicating possible uses of 'click' glycomimetics for bioengineering applications.