Background: Synthesis of lipophilic mitochondria-targeted antioxidants is a topical problem
of modern biochemistry. The so-called "radical sponges" effect is a very high ability of fullerene C60 and
its derivatives to catch free radicals. The experiments showed that the fullerene derivatives increase resistance
of animals towards oxidative stress and prevent passing of neurodegenerative processes.
Objective: Synthesis of lipophilic fullerene C60
conjugates based on maleopimaric acid derived from resin.
Methods: Synthesis of new diterpene containing fullerene C60
conjugates based on the bromo- and
chloromethylketones by primary functionalization of the fullerene core by the Bingel cyclopropanation
reaction was shown. Bromo- and chloromethylketones were obtained from methyl maleopimarateproteinogenic
amino acids condensation products by the Arndt-Eistert reaction.
Results: Diazoketones and chloromethylketones were received from carboxylic acids and corresponding
chlorides under Arndt-Eistert reaction conditions. Chloromethylketones formed due to a Nierenstein
side reaction. The IR spectra of diazo compounds 2a-e contained a strong absorption band for the
diazo group at 2103-2115 cm–1
. The reaction of diazoketones with HBr produced bromomethylketones
in excellent yield. Bromo- and chloromethylketones were reacted with fullerene C60
in the presence of
1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) in toluene to give diterpene containing fullerene conjugates.
Fullerene conjugates formed 6% oil solutions in different sunflower oils. The structures of all
compounds obtained were proved using 2D NMR HSQC, HMBC, COSY, NOESY experiments.
Conclusion: Rosin-based methanofullerenes were synthesized for the first time under Bingel conditions by
[2+1]-cyclopropanation of the chloro- and bromomethylketones to fullerene C60
in the presence of DBU. In
our case chloromethylketones gave better yields in the Bingel reaction than bromomethylketones. The obtained
diterpene containing fullerene conjugates have the ability to dissolve in sunflower oils.