Dihydroxy stilbene derivatives were designed based on lithospermic acid B and were prepared from 4-(chloromethyl)benzoicacid. The inhibitory activities of the novel compounds against protein tyrosine phosphatase 1B (PTP1B) were evaluated. 3,4-Dihydroxy stilbene carbonyl compounds (7, 11b, 27b) inhibited PTP1B with IC50 values comparable to molybdate, while the conjugation-extended compound (15b) showed