The title compound has been prepared by solid phase synthesis. Attachment of (R)-2-butylsuccinic acid 1-fluorenylmethyl ester (I) to ArgoGel resin under Mitsunobu conditions affords the succinate-bound resin (II). Subsequent deprotection with piperidine in DMF leads to the acid-resin (III), which is further activated as the pentafluorophenyl ester (IV) upon treatment with pentafluorophenyl trifluoroacetate. Coupling of active ester (IV) with L-proline tert-butyl ester (V) furnishes amide (VI). Finally, cleavage of the resin by means of hydroxylamine in aqueous dioxane provides the target hydroxamic acid.
In an alternative procedure, (R)-2-butylsuccinic acid 4-methyl ester (I) is coupled to L-proline tert-butyl ester (II) to afford amide (III). Then, displacement of the methyl ester group with hydroxylamine gives rise to the desired hydroxamic acid.