It is produced by typical esterification procedures with usual catalysts such as HCl or H2SO4, and is rather slow, usually done for 20+hr at 100°C or a bit higher. Validol, the anxiety medication containing a roughly 25% solution of menthol in menthyl isovalerate is prepared essentially in one step, in which the amount of menthol added before conducting the acid catalysed esterification is in an excess such that the resulting solution of the yielded ester has around 25% menthol, simplifying the procedure.
Esterification, typically using catalysts like HCl or H2SO4, is a slow process that usually takes 20+ hours at temperatures of 100°C or higher.  Validol, an anxiety medication containing menthol in menthyl isovalerate, is prepared in one step with excess menthol added before acid-catalyzed esterification to yield a solution around 25% menthol.