Comparison of Antiviral Medicines - Are There Pyrimidine-based Antivirals?

Some have core based on purine, such as aciclovir and entecavir. Several examples are shown below. It's interesting to note that antivirals in this group are structurally similar to the nucleotides adenine and guanine. That implies there are antivirals based similar to cytosine and thymine, which are pyrimidines. 

Ribavirin has only one nitrogen ring. Atazanavir has one nitrogen ring of a different sort, as does lamivudine. 

Nevirapine and its cousins have a triple ring structure. Note the cyclopropyl group, also found in other antivirals. 

Oseltamivir has no ring nitrogen atoms. 

Daclatasvir is a rare symmetrical antiviral. In general, it is rare for any medicine to be symmetrical. It has two imidazole rings. Ombitasvir is symmetrical and like daclatasvir is belongs to the NS5A inhibitor group. Velpatasvir has two imidazole rings, but is asymmetrical. 

Here are some with fluorine. Like telaprevir, efavirenz also has a cyclopropyl group. 

Darunavir has sulfur, as does ritonavir in ring (thiazole) form. 

Protease inhibitors form a family of antivirals. Many contain sulfur, fluorine, or phosphorus. Asunprevir contains two cyclopropyl groups.

This combo has a very high cure rate against HepC and belongs to the NS5A inhibitor group. 

Telaprevir is an antiviral containing pyrazine (not pyrimidine) as a functional group. 

To summarize, most antivirals are either based on purine or are protease inhibitors. Here I will note I only has two semesters of organic chemistry in college in the course of earning my BS in chemical engineering. I got an A in the first semester and a C in the second semester.