Preparation And Structure-Activity Relationship Study Of PTP1B Inhibitors

Protein tyrosine phosphatase 1B(PTP1B), as a typical non-receptor type member of the family of PTPs(protein tyrosine phosphatases, PTP), is a key element in the negative regulation of insulin signaling pathway,and also has been a novel drug target for diabetes and obesity.Discovery for highly effective inhibitors of PTP1B has a promising application in diabetes and obesity therapy.Bis-(2,3-dibromo-4,5-dihydroxy-phenyl)-methane (BDDPM) is a natural bromophenol with significant inhibition against PTP1B (IC₅₀=2.4μmol/L), which was isolated from the ethanol extract of red algae Rhodomela confervoides. In vivo anti-hypoglycemic effects on streptozotocin-diabetes in male Wistar rats (STZ-DM) fed with high fat diet revealed that the STZ-DM treated with medium-dose and high-dose algae ethanol extract showed remarkable reductions in fasting blood glucose as compared with the STZ-DM control. So it is necessary to develop BDDPM pharmacological study in vivo, however, above 30g BDDPM is needed. Thus, in this thesis two medthods extraction from algae and total organic synthesis were evaluated to the prepartion of BDDPM.Firstly, 7.8g BDDPM was isolated from EtOAc-soluble portion of 50kg red alga R. confervoides by chromatography including normal phase silica gel, Sephadex LH-20 gel and recrystallization. Then its structure was elucidated by spectroscopic methods including IR, MS and NMR. The results revealed that it is too hard to isolate BDDPM from R. confervoides, which contains too much constituent which makes separation and purification process of BDDPM taking a lot of money and time. In additon, the collection of raw material is easily affected by natural, noncontrollable factors, such as shortage of raw materials. So this method is not suitable for the preparation of BDDPM. Secondly, in this thesis starting from the readily accessible materials, a linear sequence of five steps (Friedel-Crafts acylation, Bromine reaction,Carbonyl reduction, Demethylation) was designed and applied to synthesize the targeting compound BDDPM in 23.6% overall yield. Moreover, the synthesized target compound shown nearly the same PTP1B inhibitory activity as the natural ingredients and all the other synthesized compounds demonstrated moderate to good PTP1B inhibitory activity in colorimetric assay.In addition by comparing of PTP1B inhibition of four series compound, the preliminary structure-activity relationship of the screened compounds were revealed. First, the existence of carbonyl functional group on such compounds signifcantly lower rate of their PTP1B inhibition. Second, in the majority of those compounds, when the hydroxy functional groups to be protected by methoxy group their PTP1B inhibitory activity strengthening at a certain degree. Third, the presence of one or more bromines on the benzyl ring is benefite to PTP1B inhibitory activity and the increasing of bromine number on benzyl ring could obviously upgrade potency of PTP1B inhibitory activity. However, in this thesis it is not obvious to see a structure–activity pattern of selective compounds; more analogues need to be prepared further.Finally, 30g BDDPM was successfully synthesized by five steps, which laid foundation for further pharmaceutical research.