Enzymatic synthesis of novel N-heterocycle-containing troxerutin derivatives

Using vinyl-troxerutin esters (troxerutinOCO(CH2)nCOOCHCH2, n = 3, 4, 7, 8, 11) and N-heterocyclic amines (piperazine, methylpiperazine, piperidine, and morpholine) as substrates, twenty novel N-heterocycle-containing troxerutin derivatives were synthesized through enzymatic reaction. The products were characterized by 1H NMR, 13C NMR, ESI-MS and FT-IR. Among the ten kinds of commercially available enzymes tested, lipase LS-10 produced the highest yield (58%). Investigation of water content and different medium showed that pyridine containing water lower than 2% was the efficient medium. Increasing of the molar ratio of morpholine to vinylglutaryl-troxerutin to 6:1 produced the highest yield. The carbon chain length of vinyl-troxerutin esters did not show significant effect and the yields reached plateau after reaction at 50 °C for 24 h.