A process for the preparation of a dihydroxypyrimidine compound of formula: in which R1 and R2 are identical or different and are a hydrogen atom, a C1-C4-alkyl group or an aryl group, comprising in a first stage, converting, as a substrate, a compound of formula: in which R2 has the meaning mentioned above and R3 is ???CN or COOR4, in which R4 is a C1-C4-alkyl group, using microorganisms of the s