Some Stereochemical Aspects of the Strecker Synthesis and the Bucherer-Bergs Reaction

Both the Strecker and Bucherer–Bergs reactions convert the norbornane keto ester methyl bicyclo[2.2.1]hept-6-one-2-endo-carboxylate into the lactam 6-endo-aminobicyclo[2.2.1]heptane-2-endo-carboxylic acid-γ-lactam-6-exo-carboxylic acid. This lactam is unusually stable and cannot be hydrolyzed to the corresponding amino acid. The stereochemistry in the Strecker reaction, in which the amino group is endo, is contrary to that expected from literature precedent. The stereochemistry in the Bucherer–Bergs reaction, in which the amino group is also endo, has been confirmed by X-ray crystallographic analysis of the intermediate spirohydantoin (±)-bicyclo[2.2.1]heptane-2-endo-carboxylic acid-6-spiro-5′-hydantoin.