Total synthesis of [13C2]-labelled phytosiderophores of the mugineic and avenic acid families

We herein report the synthesis of 13C2-labelled natural products from the mugineic acid and avenic acid family. These phytosiderophores (“plant iron carriers”) are built up from non-proteinogenic amino acids and play a key role in micronutrient uptake in gramineous plants. In this work two central building blocks are prepared from labelled starting materials (13C2-bromoacetic acid, 13C2-glycine) and further employed in our recently reported divergent, branched synthetic strategy delivering eight isotopically labelled phytosiderophores. The required labelled building blocks (13C2-L-allylglycine and a related hydroxylated derivative), were prepared via enantioselective phase-transfer catalysis and enantio- and diastereoselective aldol condensation with a chiral auxiliary respectively, both potentially valuable themselves for other synthetic routes towards labelled (natural) products.