Selective reduction of a carboxyl group with diborane. Synthesis of specifically carbon-14 labelled D,L-2-Amino-4-(2-aminoethoxy)butanoic acid

Abstract

Specific labelling of the title compound was achieved through intermediate 3a, methyl 2-(2-phthalimidoethoxy)acetate, derived from methyl bromoacetate-2-14C. Conversion to the corresponding acid (4) was followed with selective diborane reduction which provided 2-(2-phthalimidoethoxy)ethanol-2-14C (5). Treatment with thionyl chloride yielded the chloride 6 which is identical with the intermediate used in the nonlabelled synthesis and reaction with sodium ethyl phthalimidomalonate provided the title compound after hydrolytic work-up.