Synthesis and Photochromic Properties of Azobenzene‐Derived Glycomacrolactones

Reversible photocontrol of glycosides and glycoconjugates structures is a very attractive approach to modulate, in a spatiotemporal way, the various properties and biological activities of carbohydrates. We have synthesized three new azobenzene‐derived glycomacrolactones from thioglycopyranosides. The synthesized cyclic glycoazobenzenes can be reversibly photoisomerized between E and Z isomers with high fatigue resistance. A 1 H NMR spectroscopic study shows that E → Z isomerization of glycomacrocycles induces large conformational change of the macrocyclic structures, without changing sugar 4 C 1 chair conformation. The Z ‐glycoazobenzenes can be thermally converted back to the E ‐isomers. Interestingly, these 16 to 17‐membered Z ‐glycomacrolactones display higher thermal stability than the reported macrocyclic azobenzenes, the half‐life varying from 37 to 72 days. The excellent photoswitching property and bistability of the synthesized glycoazobenzenes open a new opportunity for the convergent synthesis of diastereomers of glycomacrocycles. Furthermore, chiroptical properties have been observed for both E and Z glycomacrolactones. The geometry of different isomers of macrocycles has been optimized with DFT calculations. Theoretical CD spectra obtained by TD‐DFT suggest that the E and Z glycomacrocycles adopt preferentially ( P ) helical structure for the azobenzene moiety.