## 4 Conclusions  
The aim of this research was to initially assess the impact of the substituents introduced into the betulin system and their location on the antiviral activity of the tested derivatives. 30-Phosphonate (allyl isomers) derivatives of betulin, betulinic acid (**4** and **5**, respectively), and 3-carboxyed betulinic acid (**7a**, **7b**) do not show activity against the tested viruses. From a series of derivatives containing a diethylphosphonate group at position C29  
Figure 8: Analysis of bonding between ligands ((**A**)—compound **3**; (**B**)—betulin **1**) and adenain. Hydrogen bonds are marked in green, hydrophobic in gray. Figure 7: Docked poses of betulin **1** (green) and compound **3** (light blue) in the active site of adenain. * _[PERSON] et al. (2022)_ [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Risk perception associated with an emerging agri-food risk in Europe: Plant viruses in agriculture. _Agric. Food Secur._**2022**, _11_, 21. [CrossRef] [PubMed]
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