Synthesis of potassium 2,3,4-trihydroxy-2-methylbutanoate: a leaf-closing substance of Leucaena leucocephalam

Starting from citraconic anhydride (), a six step synthesis of leaf closing substance (±)-erythro potassium 2,3,4-trihydroxy-2-methyl-butanoate () has been described with 29% overall yield via diesterification, OsO4-dihydroxylation, acetonide protection, regioselective mono hydrolysis of unhindered ester moiety, borane–dimethylsulfide induced chemoselective reduction of carboxylic group and hydrolysis pathway. Surprisingly, the sodium borohydride reduction of monoester and lithium borohydride reduction of furnished the undesired regioisomer .