Synthesis of All the Diastereomers of 2-Amino-3-hydroxy-4,5-dimethylhexanoic Acid

Herein, we describe an efficient stereoselective synthesis of all the diastereomers of 2-amino-3-hydroxy-4,5-dimethylhexanoic acid. The -branched carbon skeleton was set up by reaction of Garner's aldehyde with 2-lithio-3-methyl-2-butene. Hydrogenation (Pd/C catalyst) of the tetrasubstituted olefin proceeded smoothly with acceptable stereoselectivity, depending on the diastereomer hydrogenated. The final compounds were then obtained in 12-18% overall yield through intramolecular cyclization, Jones oxidation, and hydrolysis in 5-7 steps from Garner's aldehyde.