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

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