The acyloxyallylation of unprotected aldoses was first demonstrated more than a decade ago as a potentially elegant two-carbon homologation of reducing sugars (upon ozonolysis); however, its application in real case syntheses remained scarce. Following up on such a successful showcase and to answer several pending questions about this attractive transformation, we engaged in an in depth methodological reinvestigation. The epimeric tetroses l-erythrose and d-threose in unprotected and protected form were successfully applied to the indium and also zinc-mediated acyloxyallylation, with the latter being a first for an unprotected sugar. The investigation largely benefited from the choice of these more exotic starting materials as it allowed unambiguous identification/quantification of the hexose-products which are available as authentic reference materials. The observed diastereoselectivities indicate a strong substrate control (stereochemistry at O2), and the influence of the reagent’s structure on the selectivity was investigated in great detail. A strong facial diastereodivergence between related protected and unprotected structures was demonstrated and an unexpected, pronounced principle difference in performance between indium and zinc was revealed.

Examples of strong substrate governance and tuning of selectivity between two borderline scenarios by successful catalyst design are reported.

A series of substituted imidazoquinolines, a structurally related chemotype to pyrazoloquinolinones, a well-known class of GABAA ligands, was prepared via two synthetic procedures and the efficiency of these procedures were compared. One method relies on classical heterocyclic synthesis, the other one aims at late-stage decoration of a truncated scaffold via direct C–H functionalization. A pharmacological evaluation disclosed that one of the synthesized derivatives showed interesting activity on a α1β3 containing receptor subtype. Graphical abstract

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.