A process for the preparation of an intermediate of formula I, wherein the stereogenic center marked with an * is either in - or -configuration at marked center, or it is in racemic form, and wherein R 1 and R 2 are identical or different, and are independently selected from (i) hydrogen; (ii) alkyl residues optionally chiral, having from 1 to 12 carbon atoms, wherein the alkyl residues are optionally aryl and/or aryloxy substituted; (iii) alkyloxy residues optionally chiral, having from 1 to 12 carbon atoms, wherein the alkyloxy residues are optionally aryl substituted; (iv) aryl residues optionally chiral, having from 6 to 24 carbon atoms, wherein the aryl residues are optionally alkyl and/or alkyloxy substituted; (v) aryloxy residues optionally chiral, having from 6 to 24 carbon atoms, wherein the aryloxy residues are optionally alkyl substituted; (vi) benzyl; (vii) alkaloyl residues optionally chiral, having from 2 to 13 carbon atoms, wherein the alkaloyl residues are optionally aryl substituted; (viii) aroyl residues optionally chiral, having from 7 to 25 carbon atoms, wherein the aryloxy residues are optionally alkyl substituted; (ix) alkoxycarbonyl residues optionally chiral, having from 2 to 13 carbon atoms; (x) aryloxycarbonyl residues optionally chiral, having from 7 to 25 carbon atoms; (xi) tosyl; (xii) silyl residues optionally chiral, having from 3 to 15 carbon atoms; and (xiii) silyloxy residues optionally chiral, having from 3 to 15 carbon atoms; wherein R 3 is selected from alkyl residues having from 1 to 6 carbon atoms; the process comprising the steps of: (a) providing an intermediate of formula II, (b) reacting the intermediate of formula II with an amine of formula III, HNR 1 R 2 wherein R 1 and R 2 are as defined above, in a protic solvent, particularly in water; or in a mixture of protic solvents, wherein the mixture particularly comprises water; or without adding of solvents in step (b); to obtain an intermediate of formula I. (i) hydrogen; (ii) alkyl residues optionally chiral, having from 1 to 12 carbon atoms, wherein the alkyl residues are optionally aryl and/or aryloxy substituted; (iii) alkyloxy residues optionally chiral, having from 1 to 12 carbon atoms, wherein the alkyloxy residues are optionally aryl substituted; (iv) aryl residues optionally chiral, having from 6 to 24 carbon atoms, wherein the aryl residues are optionally alkyl and/or alkyloxy substituted; (v) aryloxy residues optionally chiral, having from 6 to 24 carbon atoms, wherein the aryloxy residues are optionally alkyl substituted; (vi) benzyl; (vii) alkaloyl residues optionally chiral, having from 2 to 13 carbon atoms, wherein the alkaloyl residues are optionally aryl substituted; (viii) aroyl residues optionally chiral, having from 7 to 25 carbon atoms, wherein the aryloxy residues are optionally alkyl substituted; (ix) alkoxycarbonyl residues optionally chiral, having from 2 to 13 carbon atoms; (x) aryloxycarbonyl residues optionally chiral, having from 7 to 25 carbon atoms; (xi) tosyl; (xii) silyl residues optionally chiral, having from 3 to 15 carbon atoms; and (xiii) silyloxy residues optionally chiral, having from 3 to 15 carbon atoms; (a) providing an intermediate of formula II, (b) reacting the intermediate of formula II with an amine of formula III, HNR 1 R 2 wherein R 1 and R 2 are as defined above, in a protic solvent, particularly in water; or in a mixture of protic solvents, wherein the mixture particularly comprises water; or without adding of solvents in step (b); to obtain an intermediate of formula I.