Patent ID: 7846887

Claim:
A method of producing a compound of formula (I) wherein R 1 and R 2 are independently selected from the group consisting of linear and branched C 1 -C 14 alkyl and alkenyl, cycloalkyl and cycloalkenyl, optionally substituted, comprising 5-14 carbon atoms, and spirobicycloalkyl and spirobicycloalkenyl, optionally substituted, comprising 8-13 carbon atoms; R 3 and R 4 are independently selected from the group consisting of hydrogen, phenyl, linear and branched C 1 -C 6 alkyl and alkenyl, cycloalkenyl, optionally substituted, comprising 5-12 carbon atoms, and cycloalkenylalkyl, optionally substituted, comprising 6-14 carbon atoms; R 6 and R 7 are independently selected from hydrogen, linear and branched C 1 -C 6 alkyl and alkenyl, and cycloalkyl, optionally substituted, comprising 3-14 carbon atoms; or at least one of the pairs R 1 and R 7 , R 2 and R 6 , R 3 and R 7 , R 4 and R 6 forming together with the carbon atoms to which they are attached a mono- or bicyclic ring system comprising 5 to 10 carbon atoms; and R 5 is selected from the group consisting of linear and branched C 1 -C 5 alkyl, and C 7 -C 10 aralkyl, optionally substituted with 1, 2 or 3 hetero atoms selected from N, S and O; the method comprising the step of : admixing an 2-amino-3-mercapto propionic acid ester of formula (II) or a salt thereof wherein R 5 has the same meaning as given above; with at least 2 equivalents of a substituted 3-buten-2-one of formula (IIIa and IIIb) wherein R 1 to R 4 , R 6 and R 7 have the same meaning as given above.