Design and studies of novel polyoxysterol-based porphyrin conjugates

New types of steroid-porphyrin conjugates derived from 20-hydroxyecdysone (20E) and 24-epibrassinolide (EBl) were synthesized. An exceptional regioselectivity in the reaction of both steroids with porphyrin boronic acids was found to give side-chain-conjugated boronic esters as sole products. UV–Vis-, fluorescence and NMR spectroscopy yielded similar data for all the studied compounds confirming the solvent driven supramolecular assembly with formation of J-aggregates. CD measurements of water diluted solutions showed a clear difference between 20E and EBl conjugates. The latter showed a strong supramolecular chirality, whereas 20E J-aggregates did not.

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► Steroid–porphyrin conjugates have been synthesized.
► Side-chain-conjugated boronic esters were formed as sole products.
► Spectral studies confirmed the solvent driven formation of J-aggregates.
► 24-Epibrassinolide conjugates showed a strong supramolecular chirality.