Abstract: There is provided a process for the preparation of a compound of formula (I): which process comprises reaction of a compound of formula (II): with either a compound of formula (III): or acrylamide, followed, in the latter case, by reaction of the resulting intermediate of formula (IV): with an alcohol of formula R2—OH and an agent that promotes, or agents that in combination promote, rearrangement and oxidation of the compound of formula IV to an intermediate isocyanate, which may then react with the alcohol of formula R2—OH, and wherein R1, R2 and R16 have meanings given in the description