Stereoselective Synthesis of meso- and l,l-Diaminopimelic Acids from Enone-Derived α-Amino Acids.

The stereoselective synthesis of meso-diaminopimelic acid (meso-DAP), the key cross-linking amino acid of the peptidoglycan cell wall layer in Gram-negative bacteria, and its biological precursor, l,l-DAP, is described. The key step involved stereoselective reduction of a common enone-derived amino acid by substrate- or reagent-based control. Overman rearrangement of the resulting allylic alcohols, concurrent alkene hydrogenation and trichloroacetamide reduction, and subsequent ruthenium-catalyzed arene oxidation completed the synthesis of each stereoisomer. The synthetic utility of this approach was demonstrated with the efficient preparation of an l,l-DAP-derived dipeptide.

Ligand-Enabled Copper-Mediated Radioiodination of Arenes.

The discovery of a copper precatalyst that facilitates the key mechanistic steps of arene halodeboronation has allowed a step change in the synthesis of radioiodine-containing arenes. The active precatalyst [Cu(OAc)(phen)2]OAc was shown to perform room temperature radio-iododeboronation of aryl boronic acids with 1-2 mol % loadings and 10 min reaction times. These mild conditions enable particularly clean reactions, as demonstrated with the efficient preparation of the radiopharmaceutical and SPECT tracer, meta-iodobenzylguanidine (MIBG).