Amino acids and peptides. LIV. Application of 2-adamantyl derivatives as protecting groups to the synthesis of peptide fragments related to Sulfolobus solifataricus ribonuclease. I.

The 2-adamantyloxycarbonyl group was employed for the protection of the epsilon-amino group of Lys and the hydroxyl group of Tyr, and the 2-adamantyl ester was employed for the protection of the beta-carboxyl group of Asp in order to construct eight peptide segments as building blocks for the preparation of peptide fragments related to the sequence of Sulfolobus solifataricus Ribonuclease. The usefulness of the above protecting groups developed in our laboratory was confirmed.     

MercuryII-mediated formation of thymine-HgII-thymine base pairs in DNA duplexes

The very specific binding of the HgII ion unexpectedly and significantly stabilizes naturally occurring thymine-thymine base mispairing in DNA duplexes. Following this finding, we prepared DNA duplexes containing metal-mediated base pairs at the desired sites, as well as novel double helical architectures consisting only of thymine-HgII-thymine pairs.     

A one-dimensional coordination polymer, BBDTA.InCl4: possible spin-Peierls transition with high critical temperature of 108 K

We have studied the crystal structure and magnetic properties of the organic radical cation salt, BBDTA.InCl4. This material formed a one-dimensional coordination polymer. Magnetic measurements indicated the spin-Peierls transition-like behavior at 108 K, which was higher than those typically observed for the other organic spin-Peierls materials. The structural aspects of the lattice distortion from X-ray diffraction measurements at 50 K have been discussed.     

Preparation of floating drug delivery system by plasma technique

A novel intragastric floating drug delivery system (FDDS) has been prepared by pulsed plasma-irradiation on the double-compressed tablet of 5-Fluorouracil (5-FU) as a core material with outer layer composed of a 68/17/15 weight ratio of Povidone (PVP), Eudragit RL (E-RL) and NaHCO3. The plasma heat flux caused the thermal decomposition of NaHCO3 to generate carbon dioxide and the resultant gases were trapped in bulk phase of outer layer, so that the tablets turned to have a lower density than the gastric contents and remained buoyant in simulated gastric fluid for a prolonged period of time. In addition, the release of 5-FU from the tablet is sustained by occurrence of plasma-induced crosslink reaction on the outer layer of tablet and the release rate of 5-FU can be well controlled by plasma operational conditions.     

Phosphazene base-promoted halogen-zinc exchange reaction of aryl iodides using diethylzinc

The use of catalytic t-Bu-P4 base dramatically improved the performance of halogen-zinc exchange of aryl iodides, and the arylzinc derivatives were functionalized under copper-free reaction conditions.     

Phosphazene base-catalyzed condensation of trimethylsilylacetate with carbonyl compounds

The t-Bu-P4 base was found to be an excellent catalyst for the condensation of trimethylsilylacetate or trimethylacetonitrile with carbonyl compounds to form functionalized alkenes and beta-enaminoesters were also synthesized by the condensation with formanilides.     

Construction and structural characterization of versatile lactosaminoglycan-related compound library for the synthesis of complex glycopeptides and glycosphingolipids

We have established a facile and efficient protocol for the preparative-scale synthesis of various compound libraries related to lactosaminoglycans: cell surface oligosaccharides composed of N-acetyllactosamine as a repeating disaccharide unit, based on chemical and enzymatic approaches. Substrate specificity and feasibility of a bacterial glycosyltransferase, Neisseria meningitidis beta1,3-N-acetylglucosaminyltransferase (LgtA), were investigated in order to synthesize various key intermediates suited for the construction of mammalian O-glycopeptides and glycosphingolipids containing poly-N-acetyllactosamine structures. Recombinant LgtA exhibited the highest glycosyltransferase activity with strongly basic conditions (pH = 10, glycine-NaOH buffer) and a broad range of optimal temperatures from 20 to 30 degrees C. Interestingly, it was found that LgtA discriminates L-serine and L-threonine and functions both as a core-1 beta1,3-N-acetylglucosaminyltransferase and core-2 beta1,3-N-acetylglucosaminyltransferase toward Fmoc-Ser derivatives, while LgtA showed only core-2 beta1,3-N-acetylglucosaminyltransferase activity in the presence of Fmoc-Thr derivatives. Combined use of LgtA with human beta1,4-galactosyltransferase allowed for controlled sugar extension reactions from synthetic sugar amino acids and gave synthetic lactosaminoglycans, such as a decasaccharide derivative, Galbeta(1 --> 4)GlcNAcbeta(1 --> 3)Galbeta(1 --> 4)GlcNAcbeta(1 --> 3)Galbeta(1 --> 4)GlcNAcbeta(1 --> 3)Galbeta(1 --> 4)GlcNAcbeta(1 --> 6)[Galbeta(1 --> 3)]GalNAcalpha1 --> Fmoc-Ser-OH (6), and a dodecasaccharide derivative, Galbeta(1 --> 4)GlcNAcbeta(1 --> 3)Galbeta(1 --> 4)GlcNAcbeta(1 --> 3)Galbeta(1 --> 4)GlcNAcbeta(1 --> 6)[Galbeta(1 --> 4)GlcNAcbeta(1 --> 3)Galbeta(1 --> 4)GlcNAcbeta(1 --> 3)Galbeta(1 --> 3)]GalNAcalpha1 --> Fmoc-Ser-OH (9). A partially protected pentasaccharide intermediate, GlcNAcbeta(1 --> 3)Galbeta(1 --> 4)GlcNAcbeta(1 --> 6)[Galbeta(1 --> 3)]GalNAcalpha1 --> Fmoc-Thr-OH (11), was applied for the microwave-assisted solid-phase synthesis of a MUC1-related glycopeptide 19 (MW = 2610.1). The findings suggest that this sugar extension strategy can be employed for the modification of lactosyl ceramide mimetic polymers to afford convenient precursors for the synthesis of various glycosphingolipids.     

Coordination symmetry-dependent structure restoration function of one-dimensional MOFs by molecular respiration

One-dimensional metal-organic compounds with cis, trans symmetry-controlled counter anions were synthesized (cis compound {[Cu(azpy)(H2O)2(OTs)2]*2H2O*(acetone)} (1) and trans compound {[Cu(H2O)4Cu(azpy)2(OTs)2(H2O)2]*2(OTs)*2H2O*2EtOH} (2)). Only 2, having trans conformation, exhibited a complete structure-restoration effect with a mechanism involving layering of molecular "bricks" of water and solvent molecules.     

Oxidation of gem-borylsilylalkylcoppers to acylsilanes with air

[reaction: see text] 1-Boryl-1-silylalkylcoppers react with molecular oxygen in the presence of pyridine to afford acylsilanes efficiently. The one-pot process consists of two reactions: alkylation of 1-boryl-1-chloro-silylmethyllithium with Grignard reagents in the presence of copper(I) cyanide and aerobic oxidation of the alkylcopper species. This procedure enables us to access the divergent synthesis of acylsilanes.