This invention describes compounds and pharmaceutical compositions useful as inhibitors of ubiquitination. The compounds and compositions of the invention are useful as inhibitors of the biochemical pathways of organisms in which ubiquitination is involved. In particular, the compounds and compositions are useful for treating diseases caused by viruses such as poxviruses and retroviruses. The invention further provides for methods of treating smallpox, Herpes virus and HIV infection in patients using the compounds and compositions of the invention.