Development of potent non-acylhydrazone inhibitors of intestinal sodium-dependent phosphate transport protein 2b (NaPi2b).

Inhibition of intestinal sodium-dependent phosphate transport protein 2b (NaPi2b), responsible for intestinal phosphate absorption, is considered to reduce serum phosphate levels, making it a promising therapeutic approach for hyperphosphatemia. Previously, we aimed to identify new drugs for hyperphosphatemia treatment and obtained zwitterionic compound 3 (IC50 = 64 nM) as a potent selective inhibitor of intestinal NaPi2b. This small-molecule compound is gut-restricted owing to its almost membrane-impermeable property. However, when compound 3, containing an acylhydrazone structure, is exposed to plasma, it is easily metabolized and likely produces an acetylhydrazine compound. Clinical studies have shown that acetylhydrazine is a risk factor for hepatic toxicity owing to its microsomal metabolism, wherein toxic reactive intermediates are formed. Therefore, in this study, we aimed to obtain potent NaPi2b inhibitors without an acylhydrazone structure to reduce the risk of hepatic toxicity. We developed compound 18, an anilide compound with zwitterionic property having potent phosphate uptake inhibitory activity in vitro (IC50 = 14 nM) and low bioavailability (FaFg = 5.9%). Oral administration of compound 18 in rats showed a reduction in phosphate absorption comparable to that observed with lanthanum carbonate, a clinically effective phosphate binder used in hyperphosphatemia treatment. Moreover, combined administration of compound 18 and lanthanum carbonate resulted in an additive effect on phosphate absorption inhibition in rats. Our findings suggest that combination therapy with lanthanum carbonate and compound 18 will not only provide better treatment outcomes for hyperphosphatemia but also reduce gastrointestinal side effects in patients.

Discovery of Gut-Restricted Small-Molecule Inhibitors of Intestinal Sodium-Dependent Phosphate Transport Protein 2b (NaPi2b) for the Treatment of Hyperphosphatemia.

NaPi2b is primarily expressed in the small intestine, lungs, and testes and plays an important role in phosphate homeostasis. The inhibition of NaPi2b, responsible for intestinal phosphate absorption, is considered to reduce serum phosphate levels, making it a promising therapeutic approach for hyperphosphatemia. Using a novel phosphate uptake inhibitor 3 (IC50 = 87 nM), identified from an in-house compound collection in human NaPi2b-transfected cells as a prototype compound, we conducted its derivatization based on a Ro5-deviated strategy to develop orally administrable small-molecule NaPi2b inhibitors with nonsystemic exposure. Consequently, compound 15, a zwitterionic compound with a potent in vitro phosphate uptake inhibitory activity (IC50 = 64 nM) and a low membrane permeability (Pe < 0.025 × 10-6 cm/s), was developed. Compound 15 showed a low bioavailability (F = 0.1%) in rats and a reduction in phosphate absorption in the rat intestinal loop assay comparable to sevelamer hydrochloride, a clinically effective phosphate binder for treating hyperphosphatemia.

Development of Dihydrodibenzooxepine Peroxisome Proliferator-Activated Receptor (PPAR) Gamma Ligands of a Novel Binding Mode as Anticancer Agents: Effective Mimicry of Chiral Structures by Olefinic E/ Z-Isomers.

A novel class of PPARγ ligand 1 (EC50 = 197 nM) with a dibenzoazepin scaffold was identified through high-throughput screening campaign. To avoid the synthetically troublesome chiral center of 1, its conformational analysis using the MacroModel was conducted, focusing on conformational flip of the tricyclic ring and the conformational restriction by the methyl group at the chiral center. On the basis of this analysis, scaffold hopping of dibenzoazepine into dibenzo[ b, e]oxepine by replacing the chiral structures with the corresponding olefinic E/ Z isomers was performed. Consequently, dibenzo[ b, e]oxepine scaffold 9 was developed showing extremely potent PPARγ reporter activity (EC50 = 2.4 nM, efficacy = 9.5%) as well as differentiation-inducing activity against a gastric cancer cell line MKN-45 that was more potent than any other well-known PPARγ agonists in vitro (94% at 30 nM). The X-ray crystal structure analysis of 9 complexed with PPARγ showed that it had a unique binding mode to PPARγ ligand-binding domain that differed from that of any other PPARγ agonists identified thus far.

Brønsted acid-promoted hydrocyanation of arylalkenes.

Nonactivated arylalkenes are effectively converted to tertiary benzylic nitriles in the presence of triflic acid and trimethylsilyl cyanide. The hydrocyanation reactions result in good to excellent yield when electron-donating groups are substituted on the benzene ring. The reaction conditions are mild and relatively safe, notably without need for handling hazardous hydrogen cyanide gas, providing simple and easy access to tertiary benzylic nitriles. The reaction was applied to the preparation of a PDE4 inhibitor (3) as well as a series of analogues.

Total synthesis of ecteinascidin 743.

The total synthesis of ecteinascidin 743 (1), an extremely potent antitumor agent, has been accomplished. The synthesis features Ugi's 4CC reaction, intramolecular Heck reaction, phenol-aldehyde cyclization, and acid-induced intramolecular sulfide formation.