Synthesis and chiroptical properties of a new type of chiral depsipeptide dendrons

Metal‐Induced Chiral Folding of Depsipeptide Dendrimers

“…Synthesis of the depsipeptide dendrimers: To induce a preferred chiral folding motif in the new type of chiral depsipeptide dendrons that we reported recently, [43] the conformational flexibility needs to be reduced. The depsipeptide dendrons are based on natural and non-natural tartaric acid building blocks, which are connected to w-aminocaproic acid spacers through ester and amide bonds (Scheme 1).…”

“…[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] Recently, we introduced the concept of chiral depsipeptide dendrimers as peptide or protein mimetics. [34,43] This new class of dendrimers closely resembles the structures of natural depsipeptides, which consist of a-hydroxy and a-amino acids connected by ester and amide linkages. [44] We have demonstrated that the conformation within the dendrons is very sensitive to environmental conditions (solvent and temperature) and that a chiral secondary structure might be stabilized in non-protic solvents such as acetonitrile.…”

“…[43] In 6, the focal functionality is a hydroxy group instead of a protected amine functionality (Scheme 3), because it turned out that comparatively long reaction times are required and the hydroxy-terminated dendron proved to be more stable towards decomposition than the corresponding second-generation analogue of 5. Moreover, the stereogenic centers in 7 are in closer proximity to the central EDTA core, which should lead to more stereoselective formation of chiral metal complexes.…”

“…[44] We have demonstrated that the conformation within the dendrons is very sensitive to environmental conditions (solvent and temperature) and that a chiral secondary structure might be stabilized in non-protic solvents such as acetonitrile. [43] However, no specific folding motif could be found. We also showed that chirality transfer from the dendron to the focal functionality takes place.…”

“…We also showed that chirality transfer from the dendron to the focal functionality takes place. [43] We now report on depsipeptide dendrimers that diastereoselectively fold upon metal complexation in a well-defined manner, leading to a chiral secondary structure in the region of the ethylenediaminetetraacetic acid (EDTA)-derived core. In analogy to what is commonly found in metallo-proteins, the metal ions cause a particular arrangement of the organic backbone.…”