A concise synthesis of both E-isomers of 2S-amino-3-(20-aminomethyl-cyclopropyl)propionic acid, new methano-Llysines, is described. The synthetic route includes nine steps from L-methionine, with a key step involving the cyclopropanation of an intermediate E-allylic alcohol. The resultant hydroxymethylcyclopropanes were readily separated and converted into the title a-amino acids. The stereochemistry around the cyclopropane rings was deduced by conducting the cyclopropanation in the presence of N,N,N 0,N 0 -tetramethyl-D-tartaric acid diamide butylboronate, a chiral controller which is known to favour the production of S-hydroxymethyl cyclopropanes from allylic alcohols.

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