Chemical synthesis of a glycoprotein having an intact human complex-type sialyloligosaccharide under the Boc and Fmoc synthetic strategies

The chemical synthesis of complex glycoproteins is an ongoing challenge in protein chemistry. We have examined the synthesis of a single glycoform of monocyte chemotactic protein-3 (MCP-3), a CC-chemokine that consists of 76 amino acids and one N-glycosylation site. A three-segment native chemical ligation strategy was employed using unprotected peptides and glycopeptide. Importantly, the synthesis required the development of methods for the generation of sialylglycopeptide-alphathioesters. For the sialylglycopeptide-alphathioester segment, we examined and successfully implemented approaches using Fmoc-SPPS and Boc-SPPS. To avoid use of hydrogen fluoride, the Boc approach utilized minimal side chain protection and direct thiolysis of the resin bound peptide. Using these strategies, we successfully synthesized a glycoprotein having an intact and homogeneous complex-type sialyloligosaccharide.     

Stereoselective and efficient total synthesis of optically active tetrodotoxin from D-glucose

A stereoselective and efficient total synthesis of optically active tetrodotoxin (TTX) is described. A polyfunctionalized key cyclitol compound containing branched-chains for the synthesis of TTX was prepared from D-glucose employing the Henry reaction (Nitro aldol reaction) as the key transformation. Stereoselective construction of the alpha-azido-aldehyde branched-chain was achieved via the key spiro alpha-chloroepoxide intermediate.     

Theoretical Studies on the First Hyperpolarizabilities of One-dimensional Donor-bridge-acceptor Chromophores and New Applications of BLA in Determining Molecular First Hyperpolarizabilities

We present a quantum-chemical analysis of the relationship between the bond length alteration （BLA） and the static first hyperpolarizability of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures. The calculated results show that the parameter BLA can be considered as an indicator to evaluate the molecular first hyper- polarizability. Along the direction of molecular ground-state dipole moments, the evolutions of BLA can be classified into three categories： the first is a non-monotonic line, which represents most chromophores; the second is monotonic increasing; and the third, contrarily, is monotonic decreasing. On the whole, the first hyperpolarizabilities of these studied chromophores are the monotonic functions of BLA along the direction of dipole moments. Therefore, the first hyperpolarizability of these 1D chromophores can be preliminarily evaluated in terms of the development of BLA without a rigorous computation. In other words, one can roughly estimate the relative magnitude of the first hyperpolarizability according to the optimized geometry.     

Theoretical Studies on the Binding of Cd~（2＋） to Uracil and Its Thio-derivatives

The interaction of Cd2+ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory(DFT) calculations.For uracil and 2,4-dithiouracil,where the two basic sites are the same,Cd2+ attachment to the heteroatom at position 4 is preferred.However,for the systems where both types of basic centers,a carbonyl and a thiocarbonyl groups,are present,Cd2+ association with sulfur is favorable.The enhanced stability of these enolic and thiol forms comes from Cd2+ interaction with two basic sites simultaneously,which thereby triggers a significant aromatization of the ring.More significantly,the Cd2+ binding energy with uracil and its thio-derivatives is larger than the tautomerization barriers connecting the diketo-like forms with the corresponding enolic-like tautomers.Consequently,when associated with Cd2+,all tautomers are energetically accessible and should be observed in the gas phase.     

Role of interstitial voids in oxides on formation and stabilization of reactive radicals: interstitial HO2 radicals in F2-laser-irradiated amorphous SiO2

A procedure to produce stable hydroperoxy radicals (HO*2) in bulk amorphous SiO(2) (a-SiO(2)) has been developed. Oxygen molecules incorporated in the interstitial voids in a-SiO(2) react with mobile hydrogen atoms (H(0)) generated by the photolysis of silanol (SiOH) groups with F(2)-laser light (lambda = 157 nm, hnu = 7.9 eV), resulting in the efficient creation of interstitial HO*2. The high yield of HO*2 suggests that the collisions of the reaction intermediate with the void wall play an important role in dissipating the excess energy of the intermediate instead of the triple collision observed in the gas phase reaction. The resultant HO*2 is thermally stable up to 100 degrees C.