Abstract: Peptidomimetic N5-methyl-N2-(nonanoyl-L-leucyl)-L-glutaminate derivatives, triazaspiro[4.14]nonadecane derivatives and similar compounds for use in methods of inhibiting the replication of noroviruses and coronaviruses in a biological sample or patient, for use in reducing the amount of noroviruses or coronaviruses in a biological sample or patient, and for use in treating norovirus and coronavirus in a patient, comprising administering to said biological sample or patient a safe and effective amount of a compound represented by formulae I or II, or a pharmaceutically acceptable salt thereof. The present description discloses the synthesis and characterisation of exemplary compounds as well as pharmacological data thereof (e.g. page 99 to page 271; examples 1 to 3; compounds A1 to A104 and B1 to B66; tables A to E).