Green solvent-free synthesis of new N-heterocycle-L-ascorbic acid hybrids and their antiproliferative evaluation.

Aim: The authors' aim was to improve the application of copper-catalyzed azide-alkyne cycloaddition in the synthesis of hybrids containing biologically significant nucleobases and L-ascorbic acid scaffolds by introducing an environmentally friendly and waste-free ball mill. Results: Two series of hybrids with a purine, pyrrolo[2,3-d]pyrimidine or 5-substituted pyrimidine attached to 2,3-dibenzyl-L-ascorbic acid via a hydroxyethyl- (15a-23a) or ethylidene-1,2,3-triazolyl (15b-23b) bridge were prepared by ball milling and conventional synthesis. The unsaturated 6-chloroadenine L-ascorbic acid derivative 16b can be highlighted as a lead compound and showed strong antiproliferative activity against HepG2 (hepatocellular carcinoma) and SW620 (colorectal adenocarcinoma) cells. Conclusion: Mechanochemical synthesis was superior in terms of sustainability, reaction rate and yield, highlighting the advantageous applications of ball milling over classical reactions.