To some, the smell of blackcurrants and blackcurrants bushes is apparently strongly reminiscent of cat urine. Of cat urine. This is due to the presence of a number of thiol-containing compounds. One of the key aroma components, is 4-methoxy-2-methyl-2-butanethiol. Another, 4-thio-4-methylpentan-2-one, is more commonly known as ‘cat ketone’, because it’s also present in cat urine. At low concentrations, is smells of blackcurrant, whereas higher concentrations are less pleasant!