Radical cyclization in heterocycle synthesis. Part 13: Sulfanyl radical addition-cyclization of oxime ethers and hydrazones connected with alkenes for synthesis of cyclic β-amino acids
A combination of sulfanyl radical addition-cyclization of the oxime ethers and hydrazones connected with alkenes and subsequent conversion of a phenylsulfanylmethyl group to a carboxyl group provides a novel method for the construction of the cyclic β-amino acids. Upon treatment with thiophenol in the presence of AIBN, the oxime ethers and hydrazones smoothly underwent sulfanyl radical addition-cyclization to give the 2-(phenylsulfanylmethyl)cycloalkylamine. This method was successfully applied to the practical synthesis of 2-aminocyclopentanecarboxylic acid and 4-amino-3-pyrrolidinecarboxylic acid.
A concise synthesis of rigidified β-amino acids via sulfanyl radical addition-cyclization of oxime ethers and hydrazones
A new route to the rigidified cyclic β-amino acids such as cispentacin has been developed by sulfanyl radical addition-cyclization of the alkenyl-tethered-oxime ethers and hydrazones.