Synthesis of a Hexavalent Betulinic Acid Derivative as a Hemagglutinin-Targeted Influenza Virus Entry Inhibitor

Abstract

Naturally occurring pentacyclic triterpenes, such as betulinic acid (BA) and its derivatives, exhibit various pharmaceutical activities and have been the subject of great interest, in particular for their antiviral properties. Here, we found a new anti-influenza virus conjugate, hexakis 6-deoxy-6-[4-N-(3β-hydroxy-lup-20­(29)-en-28-oate)­aminomethyl-1H-1,2,3-triazol-1-yl]-2,3-di-O-acetyl-α-cyclodextrin (CYY1-11, 1), in a mini library of pentacyclic triterpene–cyclodextrin conjugates by performing a cell-based screening assay and then exploring the underlying mechanisms. Our results showed that conjugate 1 possessed a high-level activity against the influenza virus A/WSN/33 with an IC50 value of 5.20 μM (SI > 38.4). The study of the mechanism of action indicated that conjugate 1 inhibited viral replication by directly targeting the influenza hemagglutinin protein (K D = 1.50 μM), thus efficiently preventing the attachment of the virion to its receptors on host cells and subsequent infection. This study suggests that multivalent BA derivatives have possible use as a new class of influenza virus entry inhibitors.

Facial Synthesis and Bioevaluation of Well-Defined OEGylated Betulinic Acid-Cyclodextrin Conjugates for Inhibition of Influenza Infection

“…Designed bifunctional amino alkyne linkers of different lengths (1, 2, 4, 6 and 8 OEG units) 26-30 were prepared from commercially available 2-azidoethanol 20, di(ethylene glycol) 8, tetra(ethylene glycol) 9, hexa(ethylene glycol) 10 or octa(ethylene glycol) 11 in 27-64% yields over four steps according to conventional methods (Scheme 1) [30,31]. Compound 31 could be accessed by synthesis from the cheaper precursor betulin, as reported previously [25,32]. Subsequent activation of the carboxylic acid by using TBTU/DIPEA in THF gave compound 32 in 83% yield, which was then subjected to aminolysis with commercially available propargylamine or bifunctional aminoalkyne linkers 26-30 to afford BA derivatives 33-38 bearing a terminal alkynyl group at the C-28 position (Scheme 2), and their structures were characterized with 1 H and 13 C NMR (Supplementary Materials).…”

“…In addition, the CC 50 was not determined for 51 because the dose-response curve was not achieved at the highest concentration tested (200 µM), displaying over 38.4-fold selectivity. Detailed studies on the biological activities of 51 have been described by Chen et al [25]. The CC 50 values of conjugates 69-71 in MDCK cell were also not determined because they had a value over 100 µM, in other words they were also not cytotoxic.…”

“…Based on these literature results of the antiviral activities of lupane-type triterpenoids and our interest in the development of natural products as potential anti-influenza agents [13,24,25], it was valuable to design and synthesize a variety of multivalent triterpenoid conjugates to disclose the relationship between their structure and activity. In our recent study, we found that one multivalent BA-α-cyclodextrin (CD) conjugate, CYY1-11, showed good anti-influenza activity (IC 50 = 5.20 µM) against A/WSN/33 virus [25].…”

“…Based on these literature results of the antiviral activities of lupane-type triterpenoids and our interest in the development of natural products as potential anti-influenza agents [13,24,25], it was valuable to design and synthesize a variety of multivalent triterpenoid conjugates to disclose the relationship between their structure and activity. In our recent study, we found that one multivalent BA-α-cyclodextrin (CD) conjugate, CYY1-11, showed good anti-influenza activity (IC 50 = 5.20 µM) against A/WSN/33 virus [25]. In the present work, we further describe the synthesis of a range of well-defined hexa-, hepta-and octavalent BA derivatives based on α-, βand γ-CD scaffolds, respectively, with varying OEG chains (0, 1, 2, 4, 6 and 8 OEG units) as linkers via click chemistry.…”

<p>Research Progress on Classical Traditional Chinese Medicine Jieyu Pills in the Treatment of Depression</p>

“…Betulinic acid is one of the main effective ingredients of JF. Studies have shown that it has therapeutic effects on various diseases, such as influenza virus infection, 82 glioblastoma, 83 ischemic stroke, 84 and a variety of malignant tumors. 85,86 In addition, betulinic acid has unique effects on improving AD and combating anxiety/depression.…”