Intramolecular crankshaft-type rearrangement in a photoisomerised glycoconjugate

High-resolution NMR spectroscopy revealed that a novel glycoconjugate, consisting of two β-glucopyranoses attached to a quinazolinone-like structure, exhibited photoisomerization around the –N–N[double bond, length as m-dash] and [double bond, length as m-dash]CH–C– bonds of the –N–N[double bond, length as m-dash]CH–C– linkage in the same timeframe (the so-called “crankshaft rotation”) upon exposure to UV light. Experimental NMR data combined with DFT calculations discovered that the attachment of carbohydrate residues to photoactive compounds significantly changed the isomerization process and intramolecular rearrangement compared to the unglycosylated system, while the overall molecular structure remained virtually unchanged.