In order to search for new antiplatelet agents with higher potency, a series of tetramethylpyrazine ( TMP) /chalcone hybrids ( 2-26) were synthesized and evaluated based on the principle of bioisostere and hybrid-ization. They exerted inhibitory activity against adenosine diphosphate ( ADP )-induced and arachidonic acid ( AA)-induced platelet aggregation to varied extent. Among them, compound 8 was the most potent with IC50 of 0. 14 mmol/L on ADP-induced platelet aggregation ( 9. 1 folds of TMP and 10. 5 folds of chalcone ) and 0. 09 mmol/L on AA-induced platelet aggregation ( 8. 8 folds of TMP and 10. 0 folds of chalcone) , which was superior to clinically used anti-platelet drug aspirin ( ASP, IC50 =0. 15 mmol/L) .

The novel oleanolic acid derivatives 2a-2e were synthesized by introducing an α, β-unsaturated ketone moiety to C-ring of oleanolic acid(OA)via a nine-step reaction sequence, yielding an active CDDO-Me analogue(1), followed by coupling of C3-OH of 1 with various aliphatic and aromatic carboxylic acids, respectively. Derivatives 3a-3e were synthesized by substituting C-1 of compounds 2a-2e with bromine. The target compounds were characterized by IR, MS and 1H NMR spectra. All the target compounds showed strong inhibitory effects against two tumor cell lines(HepG2 and A549)to a varying extent. The anti-proliferative activities of active compounds 3b and 3c(IC50=6. 13±1. 16 μmol/L and IC50=5. 49±1. 03 μmol/L, respectively)against HepG2 and A549 were more potent than compound 1 and comparable to the positive control CDDO-Me. In addition, all the target compounds displayed much weaker anti-proliferative activity against the two tumor cell lines than that against normal BEAS-2B cells. Compound 3c showed ten-fold selective inhibition against HepG2 relative to BEAS-2B cells, and is thus worthy of further study.