Improved performance by replacing iminodiacetic residues with glyceryl residues in symmetrically branched oligoglycerols.

Synthesis of a symmetrically branched diglycerol (BGL002, involving one iminodiacetic residue) as a G2 dendron, and the tetradecaglycerol (BGL014, involving one iminodiacetic residue) as a G4 dendron, is described. Several members of the BGL family of G2-G4 dendrons were assembled, with G2 bearing four hydroxyl groups at the terminus region, G3 bearing eight, and G4 bearing sixteen. It is noteworthy that triglycerol (BGL003, including no iminodiacetic residue), has a water-solubility ten times higher than BGL002, and the liposome surrounded by BGL014 has a duration period in blood vessel roughly two times longer than the liposome surrounded by dodecaglycerol (BGL012, including three iminodiacetic residues).

Modification of protein with BGL06, a novel branched oligoglycerol derivative.

A branched oligoglycerol derivative, BGL06, with a cascade-like structure of glycerol units was used as a novel reagent for protein modification. Modification reaction with a recombinant human granulocyte-colony stimulating factor derivative, ND28, was carried out successfully in aqueous conditions to obtain a coupled form, BGL06-ND28. Characterization of the modified ND28 suggests that two types of products were obtained by controlling the reaction; one was H(BGL06)-ND28, a highly modified version coupled with 4.34 molecules of BGL06 units on average, and the other was L(BGL06)-ND28, a moderately modified version coupled with 2.58 molecules of BGL06 units on average, respectively. The properties of these products were compared to the known polyethylene glycol (PEG)-modified ND28. In the cell proliferation assays, unlike PEGylation, modification with BGL06 did not produce a significant loss of biological activity even when the modification extent was elevated. Under such conditions, 76.0% of the activity was in fact maintained for H(BGL06)-ND28, while PEGylated ND28 retained only 24.6% of biological activity in vitro even though the extent of modification was smaller. In addition, H(BGL06)-ND28 showed comparable thermostability to a 20 kDa PEG-modified counterpart. Therefore, the BGL06 derivative will be a useful alternative as a protein modification reagent where PEGylation is not effective.

S6 Kinase- and ß-TrCP2-Dependent Degradation of p19Arf Is Required for Cell Proliferation.

The kinase mTOR (mammalian target of rapamycin) promotes translation as well as cell survival and proliferation under nutrient-rich conditions. Whereas mTOR activates translation through ribosomal protein S6 kinase (S6K) and eukaryotic translation initiation factor 4E-binding protein (4E-BP), how it facilitates cell proliferation has remained unclear. We have now identified p19(Arf), an inhibitor of cell cycle progression, as a novel substrate of S6K that is targeted to promote cell proliferation. Serum stimulation induced activation of the mTOR-S6K axis and consequent phosphorylation of p19(Arf) at Ser(75). Phosphorylated p19(Arf) was then recognized by the F-box protein ß-TrCP2 and degraded by the proteasome. Ablation of ß-TrCP2 thus led to the arrest of cell proliferation as a result of the stabilization and accumulation of p19(Arf). The ß-TrCP2 paralog ß-TrCP1 had no effect on p19(Arf) stability, suggesting that phosphorylated p19(Arf) is a specific substrate of ß-TrCP2. Mice deficient in ß-TrCP2 manifested accumulation of p19(Arf) in the yolk sac and died in utero. Our results suggest that the mTOR pathway promotes cell proliferation via ß-TrCP2-dependent p19(Arf) degradation under nutrient-rich conditions.

Diastereoselective intramolecular carbamoylketene/alkene [2 + 2] cycloaddition: enantioselective access to pyrrolidinoindoline alkaloids.

A novel and highly diastereoselective intramolecular carbamoylketene/alkene [2 + 2] cycloaddition has been developed, and the methodology was successfully applied to the enantioselective syntheses of (-)-esermethole and Takayama's intermediate for (+)-psychotrimine.

Enantioselective total syntheses of pygmaeocins B and C.

The first enantioselective total syntheses of pygmaeocins B and C have been accomplished using an efficient and highly diastereoselective intramolecular Heck cyclization for the construction of a quaternary stereogenic center and the functionalized A-ring of the natural products as the key step.

Design and synthesis of highly potent and selective human peroxisome proliferator-activated receptor alpha agonists.

A combination of benzoxazole, phenoxyalkyl side chain, and phenoxybutyric acids was identified as a highly potent and selective human peroxisome proliferator-activated receptor alpha (PPARalpha) agonist. The synthesis, structure-activity relationship (SAR) studies, and in vivo activities of the representative compounds are described.