One-pot synthesis of sialo-containing glycosyl amino acids by use of an N-trichloroethoxycarbonyl-beta-thiophenyl sialoside

We describe an efficient synthesis of 2,6- and 2,3-sialyl T antigens linked to serine in a one-pot glycosylation. We first investigated the glycosidation of thiosialosides by varying the N-protecting group. Modification of the C-5 amino group of beta-thiosialosides into the N-9-fluorenylmethoxycarbonyl, N-2,2,2-trichloroethoxycarbonyl (N-Troc), and N-trichloroacetyl derivatives enhanced the reactivity of these compounds towards glycosidation. Addition of a minimum amount of 3 A molecular sieves was also effective in improving the yield of alpha-linked sialosides. Next, we conducted one-pot syntheses of the glycosyl amino acids by using the N-Troc sialyl donor. The N-Troc derivative can be converted into the N-acetyl derivative without racemization of the amino acids. Branched-type one-pot glycosylation, initiated by regioselective glycosylation of the 3,6-dihydroxy galactoside with the N-Troc-beta-thiophenyl sialoside, provided the protected 2,6-sialyl T antigen in good yield. Linear-type one-pot glycosylation, initiated by chemoselective glycosylation of galactosyl fluoride with the N-Troc-beta-thiophenyl sialoside, afforded the protected 2,3-sialyl T antigen in excellent yield. Both protected glycosyl amino acids were converted into the fully deprotected 2,6- and 2,3-sialyl T antigens linked to serine in good yields.     

Metal-complex assemblies constructed from the flexible hinge-like ligand H2bhnq: structural versatility and dynamic behavior in the solid state

Novel metal-complex assemblies constructed from the flexible hinge-like ligand H(2)bhnq (H(2)bhnq=2,2'-bi(3-hydroxy-1,4-naphthoquinone)) have been synthesized. The X-ray crystal structures of these compounds reveal that four types of architectures are accessible by variation of the metal ions. In copper(II) compounds 1-3, the chelating bhnq(2-) ions bridge copper(II) centers to form one-dimensional zigzag chains. The chains of 1-3 are arranged by hydrogen-bonding interactions and stacking interactions to produce porous structures. Cobalt(II) and zinc(II) compounds 4 and 5 form one-dimensional helical chains. In 4 and 5, the crystal packing induces spontaneous resolution of the helical chains with chiral cavities formed perpendicular to the helices. Nickel(II) compounds 6 and 7 form cyclic tetramers. The fourth architecture, a dimer (compound 8), is obtained by the reaction of zinc(II) and bhnq(2-) in MeOH. In these compounds, changes of the dihedral angles and the metal-coordination mode of the bhnq(2-) ion induce the structural versatility. The assemblies of the zigzag chains of the copper(II) compounds exhibit reversible vapochromic behavior. UV/Vis, powder X-ray diffraction, EPR, and adsorption isotherm measurements indicate that this vapochromic behavior is based on the hinge-like flexibility of the bhnq(2-) ion.     

Triple hydrogen bonds direct crystal engineering of metal-assembled complexes: the effect of a novel organic-inorganic module on supramolecular structure

Novel triply hydrogen bonded suprastructures based on [M(tdpd)2(L)2]2- (H2tdpd=1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile, L=solvent) and melamine-analogous cations have been synthesized and characterized. The use of anions containing two AAA sets from [M(tdpd)2(L)2]2- together with cations containing one DDD set (A=hydrogen-bond acceptor, D=hydrogen-bond donor) leads to the formation of complementary triply hydrogen bonded modules in the solid state. In all cases, the building module is further extended via additional hydrogen-bonding interactions to produce a tape, and tapes are assembled into sheets. These results show that a hydrogen-bonded module consisting of different kinds of building blocks, one of which is a metal complex that includes hydrogen-bond acceptor sites and the other is a hydrogen-bond donor molecule, will be attractive for constructing metal-containing supramolecular systems by the self-assembly technique.     

One-loop surface tension on a boundary inλφ 4 theory

We calculate quantum corrections to the vacuum energy in ⁴ theory with a tachyonic mass term in a half space, where the scalar field is required to satisfy the Dirichlet boundary condition on the surface. It is found that the one-loop self-energy diagram includes a finite energy portion, representing a repulsive surface tension on the boundary.     

Synthesis of di-branched heptasaccharide by one-pot glycosylation using seven independent building blocks

[reaction: see text] We describe an efficient synthesis of di-branched heptasaccharide 1 having phytoalexin elicitor activity in soybeans by one-pot glycosylation. The synthesis involves chemo- and regioselective sequential six-step glycosylations using seven independent building blocks and sequential removal of acyl- and benzyl ether-type protecting groups. The coupling of seven building blocks requires only four chemoselective activitable leaving groups of glycosyl donors. Both the glycosylation and deprotection reactions can be achieved utilizing a parallel manual synthesizer.     

First observation of the P-wave spin-singlet bottomonium states hb(1P) and hb(2P)

We report the first observations of the spin-singlet bottomonium states h(b)(1P) and h(b)(2P). The states are produced in the reaction e(+)e(-)→h(b)(nP)π(+)π(-) using a 121.4 fb(-1) data sample collected at energies near the Υ(5S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We determine M[h(b)(1P)]=(9898.2(-1.0-1.1)(+1.1+1.0)) MeV/c(2) and M[h(b)(2P)]=(10,259.8±0.6(-1.0)(+1.4)) MeV/c(2), which correspond to P-wave hyperfine splittings ΔM(HF)=(+1.7±1.5) and (+0.5(-1.2)(+1.6)) MeV/c(2), respectively. The significances of the h(b)(1P) and h(b)(2P) are 5.5σ and 11.2σ, respectively. We find that the production of the h(b)(1P) and h(b)(2P) is not suppressed relative to the production of the Υ(1S), Υ(2S), and Υ(3S).     

Numerical simulation of 2D granular particles and its analyses by means of the micropolar fluid model

Numerical simulations of two-dimensional granular flows under uniform mean shear and external body torque were performed following the setting of the authors’ previous study [10]. Convergence of the stresses with the increase of coarse-graining length is investigated. Difference R between vorticity field and spin field is controlled by the external torque and the stresses for the region R > 0 is obtained as well as those for R < 0. The symmetry of the stresses under the change of the sign of R is discussed.