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

We, herein, report the synthesis of ¹³C₂-labeled 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 labeled starting materials (¹³C₂-bromoacetic acid, ¹³C₂-glycine) and further employed in our recently reported divergent, branched synthetic strategy delivering eight isotopically labeled phytosiderophores. The required labeled 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 toward labeled (natural) products.