Prominent in the current stage of drug development, antiviral compounds can be efficiently prepared through cycloaddition reactions. This review reports the use of 1,3-dipolar cycloaddition reactions of selected 1,3dipoles, in particular azides, in the light of their application for the preparation of key intermediates in the design and synthesis of compounds that were tested for their antiviral activities against a variety of viruses. The products obtained from these pericyclic reaction approaches were tested for their activities in terms of blocking the virus replication and the relevant biological data are highlighted.

Regioisomeric nor-nucleoside analogues, brominated at the anthracene ring, have been prepared and phosphorylated according to different protocols affording a variety of phosphate and phosphonate derivatives. Chiral phosphorus derivatives were also obtained as inseparable mixtures of diastereisomers. The synthetic methods are described and found to be reliable and robust, affording nor-nucleosides and nornucleotides, available in large amounts for in vitro antiviral evaluation.

The generation and trapping of two new nitrosocarbonyl intermediates bearing carbohydrate-based chiral substituents is achieved by the mild oxidation of the corresponding nitrile oxides with tertiary amine N-oxides. Their capture with suitable dienes and alkenes afforded the corresponding hetero Diels–Alder cycloadducts and ene adducts from fair to excellent yields. The entire methodology looks highly promising by the easy conversion of aldoximes into hydroxymoyl halides, widening the access to nitrosocarbonyls, versatile tools in organic synthesis.

1,2,4‐Oxadiazole[4,5‐a]piridinium salts add alcohols and alkoxides to undergo electrocyclic ring opening affording alkoxybutadienyl 1,2,4‐oxadiazole derivatives. The pyridinium salts represent a special class of Zincke salts that are prone to rearrange to give alkoxybutadienyl 1,2,4‐oxadiazoles when treated with suitable nucleophiles or, alternatively, to give pyridones in the presence of bicarbonate. The pivotal tuning of the experimental conditions leads to a straightforward synthesis of valuable 1,2,4‐oxadiazole derivatives. The mechanism is also discussed in the light of previous observations.

Cyclopenta[d]isoxazoline aminols were used for the synthesis of β-turn mimics.