Review of Measurements of Fusion Neutrons and X-Rays in Muon Catalyzed d–t Fusion at RIKEN-RAL – Details of the Detection System

Precise measurements of the absolute yields and the disappearance rates were carried out for both the X-rays from the (αμ)⁺ ion formed by muon to alpha sticking after the muon catalyzed fusion and for the fusion neutrons from ³He-free liquid and solid D/T mixtures. While the αμ X-ray yield does not contradict the values predicted by the atomic-process theories, the effective sticking probability (ω _s ) obtained by neutron measurement is much smaller than that from any of the calculations published so far, suggesting, e.g., enhanced reactivation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Strong intramolecular ferromagnetic couplings in nickel(II) and copper(II) complexes chelated with tert-butyl 5-methoxy-2-pyridyl nitroxide

We successfully isolated a new paramagnetic bidentate ligand tert-butyl 5-methoxy-2-pyridyl nitroxide (meopyNO). Complexation of nickel(II) and copper(II) perchlorates with meopyNO gave the corresponding ML₂-type bis-chelated compounds. The magnetic studies showed that they were ground high-spin molecules with 2J/k_B = +288(5) and +178(3) K for [M(meopyNO)₂(H₂O)₂] · (ClO₄)₂ (M = Ni and Cu, respectively), where the spin Hamiltonian is defined as H = ?2J(S₁ · S₂ + S₂ · S₃). From the crystallographic analysis, the torsion angles (?) around M–O–N–C_2py were 4.2(3)° and 6.87(19)°, respectively, being so small that the orthogonality between the magnetic radical π1 and the metal dσ orbitals would be guaranteed.     

Synthetic Studies on Tumor-Associated Antigens: Efficient Syntheses of Lea and Sialyl-Lea Oligosaccharides,and Their Deaminated Analogs1

ABSTRACT

Efficient syntheses of tumor-associated Le^a, sialyl Le^a and their deaminated analogs are described. The suitably protected D-glucosamine (4) or D-glucose (5) derivative was successively coupled with the methyl-1-thioglycosides (glycosyl donors) of D-galactose (6) and L-fucose (11) in high yields by using N-iodosuccinimide/trifluoromethanesulfonic acid (NIS/TfOH) as the glycosyl promoter. The resulting trisaccharides (12 and 13) were each converted, by deprotections, to the Le^a determinant (17) and its deaminated analog (18), and by further glycosylation with the phenyl-2-thioglycoside of N-acetylneuraminic acid (25), to the sialyl-Le^a determinant (30) and its deaminated analog (31), respectively.     

Synthetic Studies on Sialoglycoconjugates 7: Synthesis of N-Acetylneuraminic Acid Derivatives and Analogs

ABSTRACT

Various types of the O-protected derivatives and the 9-bromo analogs of methyl [2-(trimethylsilyl)ethyl 5-acetamido-3, 5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosid]onate were synthesized from methyl [2-(trimetnyl-silyl)ethyl 5-acetamido-4, 7-di-O-acetyl-3, 5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosid]onate (1) or methyl [2-(trimethylsilyl)ethyl 5-acetamido-8, 9-di-O-isopropylidene-D-glycero-α-D-galacto-2-nonulopyranosidlonate (3).     

Synthesis of Sialyl-α-(2→3)-Neolactotetraose Derivatives Containing Different Sialic Acids: Molecular Probes for Elucidation of Substrate Specificity of Human α1,3-Fucosyltransferases

ABSTRACT

A series of sialyl-α-(2→3)-neolactotetraose derivatives containing N-acetyl-(NeuAc), N-glycolyl- (NeuGc) and N-butanoylneuraminic acid, and 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN) have systematically been synthesized as molecular probes for elucidation of substrate specificity of human α1,3-fucosyltransferases (Fuc-TVII and Fuc-TVI). 2-Methyl-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-D-glucopyrano)-[2',1':4,5]-2-oxazoline (1) was coupled with 2-(trimethylsilyl)ethyl (2,4,6-tri-O-benzyl-β-D-galactopyranosyl)-(1 → 4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (2) to give a trisaccharide 3 which, upon successive O-deacetylation, benzylidenation and reductive opening of the benzylidene group, afforded a common glycosyl acceptor 5. Glycosylation of 5 with sialyl-α-(2→3)-galactose donors 6-8, 19 and 21 gave the corresponding pentasaccharides 22-25, which were converted to a series of sialyl-α-(2→3)-neolactotetraose derivatives 30-33. In the competitive enzyme assay, the NeuGc derivative 32 showed the most potent activity for Fuc-TVII, while the KDN derivative 31 was less active than the standard NeuAc derivative 30. In contrast, the N-butanoylation of neuraminic acid enhanced the activity for Fuc-TVI.     

A facile method for synthesizing selenoglycosides based on selenium-transfer to glycosyl imidate

A facile reaction for constructing selenoglycosides has been developed based on the transacetalization reaction between a selenoacetal and a glycosyl imidate. Glycosyl imidates were activated with TMSOTf to produce oxocarbenium ion, which reacted with benzyloxymethyl alkyl (aryl) selenide, providing alky (or aryl) selenoglycosides in high yields. Furthermore, this reaction was utilized in the synthesis of 2-(trimethylsilyl)ethylselenoglycoside, which, upon treatment with TBAF in the presence of an electrophile, was transformed into other selenoglycosides.