Design and synthesis of fluorescence-labeled closo-dodecaborate lipid: its liposome formation and in vivo imaging targeting of tumors for boron neutron capture therapy

The fluorescence-labeled closo-dodecaborane lipid (FL-SBL) was synthesized from (S)-(+)-1,2-isopropylideneglycerol as a chiral starting material. FL-SBL was readily accumulated into the PEGylated DSPC liposomes prepared from DSPC, CH, and DSPE-PEG-OMe by the post insertion protocol. The boron concentrations and the fluorescent intensities of the FL-SBL-labeled DSPC liposomes increased with the increase of the additive FL-SBL, and the maximum emission wavelength of the liposomes appeared at 531 nm. A preliminary in vivo imaging study of tumor-bearing mice revealed that the FL-SBL-labeled DSPC liposomes were delivered to the tumor tissue but not distributed to hypoxic regions.     

Structural diversity in the coordination of 1,4‐dihydro‐1,4‐diarsinine as a cyclic ditopic organoarsenic ligand to metal ions

A number of different complexation structures of cis‐1,4‐dihydro‐1,4‐dimethyl‐2,3,5,6‐tetrakis(t‐butoxycarbonyl)‐1,4‐diarsinine (cis‐DHDAtBu) with gold(I) and iridium(III) were synthesized and characterized by ¹H, ¹³C NMR spectra, X‐ray crystallography, and elemental analysis. Mono‐ and di‐nuclear gold(I) chloride complexes with cis‐DHDAtBu were obtained by simple addition of gold(I) chloride to cis‐DHDAtBu. A hetero‐trinuclear gold‐platinum‐gold complex (PtAu₂Cl₄(cis‐DHDAtBu)₂) was obtained by complexation of a mononuclear platinum(II) complex (trans‐PtCl₂(cis‐DHDAtBu)₂), which was obtained by complexation of cis‐DHDAtBu with a half‐equimolar amount of PtCl₂(PhCN)₂, with a twice‐equimolar amount of gold(I) chloride. An iridium(III) complex with cis‐DHDAtBu (IrCl₃(cis‐DHDAtBu)₂) was prepared from hydrated iridium(III) chloride and cis‐DHDAtBu. The complex comprises a five‐membered chelate cis‐DHDAtBu and an usual monodentate cis‐DHDAtBu. The interior angles at around the arsenic and the As–C—C bond angles were significantly varied from 113.4° to 129.4° in the present crystal. These observations suggest that the flexibility of the bond angles at around the arsenic center is inherent property in the present organoarsenic compounds. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 23:16–26, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20747     

Ru(II)-Pheox catalyzed N-H insertion reaction of diazoacetamides: synthesis of N-substituted α-aminoamides

An efficient protocol for the preparation of α-aminoamides was developed via the Ru(II)-dm-Pheox catalyzed N-H insertion reaction of various diazoacetamides with several amines, including aniline. This catalytic N-H insertion reaction was also applied to the synthesis of 2-(2-methylquinolin-4-ylamino)-N-phenylacetamide, a potential antileishmanial agent.     

The braid index is not additive for the connected sum of 2-knots

Any -dimensional knot can be presented in a braid form, and its braid index, , is defined. For the connected sum of -knots and , it is easily seen that holds. Birman and Menasco proved that the braid index (minus one) is additive for the connected sum of -dimensional knots; the equality holds for -knots. We prove that the equality does not hold for -knots unless or is a trivial -knot. We also prove that the -knot obtained from a granny knot by Artin's spinning is of braid index , and there are infinitely many -knots of braid index .

     

Notable temperature effect on the stereoselectivity in the photochemical [2+2] cycloaddition reaction (Paternò-Büchi reaction) of 2,3-dihydrofuran-3-ol derivatives with benzophenone

A notable temperature effect (nonlinear Eyring plot) on stereoselectivity, trans-configured oxetane 2 versus cis-configured oxetane 2, is reported in the photochemical [2+2] cycloaddition reaction (Paternò-Büchi reaction) of 2,3-dihydrofuran-3-ol derivatives 1 with benzophenone.     

Synthesis, structure, and magnetic properties of Li-doped manganese-phthalocyanine, Li(x)[MnPc] (0 < or = x < or = 4)

We report on the first synthesis of Li-intercalated manganese-phthalocyanine (MnPc) in the bulk form and on the evolution of the structural and magnetic properties as a function of Li concentration, x. We find that solid beta-MnPc, which comprises rodlike assemblies of individual planar molecules, is best described as a glassy one-dimensional ferromagnet without three-dimensional ordering and that it can be quasi-continuously intercalated with Li up to x = 4, forming an isosymmetrical series of Li(x)[MnPc] phases. Inserted Li+ ions strongly bond to pyrrole-bridging nitrogen atoms of the Pc rings, thereby disrupting the ferromagnetic Mn-N(a)...Mn superexchange pathways. This gradually induces a crossover of the intrachain exchange interactions from ferromagnetic to antiferromagnetic as the doping level, x, increases coupled with a spin-state transition of the Mn2+ ions from intermediate spin, S = 3/2, to high spin, S = 5/2.     

Asymmetric synthesis of methyl (-)-13-oxo-15,16-dinorlabda-8(17),11E-dien-19-oate, methyl ester of a potent suppressor toward carcinogenic promotor

Asymmetric synthesis of methyl ester (4) of (-)-13-oxo-15,16-dinorlabda-8(17),11E-dien-19-oic acid (1), which exhibited the most potent activity for the prevention of incipient carcinogenesis among the isolated diterpenes from Thuja standishii and its related plants, was achieved by using methyl (-)-1,4a-dimethyl-5-oxodecahydronaphthalene-1-carboxylate (5) as a strating material, which was easily prepared on gram scale by baker's yeast-catalyzed asymmetric reduction.     

Subcellular topological effect of particle monolayers on cell shapes and functions

We studied topological effects of subcellular roughness displayed by a closely packed particle monolayer on adhesion and growth of endothelial cells. Poly(styrene-co-acrylamide) (SA) particles were prepared by soap-free emulsion copolymerization. Particle monolayers were prepared by Langmuir–Blodgett deposition using particles, which were 527 (SA053) and 1270 nm (SA127) in diameter. After 24-h incubation, cells tightly adhered on a tissue culture polystyrene dish and randomly spread. On the other hand, cells attached on particle monolayers were stretched into a narrow stalk-like shape. Lamellipodia spread from the leading edge of cells attached on SA053 monolayer to the top of the particles and gradually gathered to form clusters. This shows that cell–cell adhesion became stronger than cell–substrate interaction. Cells attached to SA127 monolayer extended to the reverse side of a particle monolayer and engulfed particles. They remained immobile without migration 24 h after incubation. This shows that the inhibition of extensions on SA127 monolayer could inhibit cell migration and cell proliferation. Cell growth on the particle monolayers was suppressed compared with a flat TCPS dish. The number of cells on SA053 gradually increased, whereas that on SA127 decreased with time. When the cell seeding density was increased to 200,000 cells cm⁻², some adherent cells gradually became into contact with adjacent cells. F-actin condensations were formed at the frame of adherent cells and the thin filaments grew from the edges to connect each other with time. For the cell culture on SA053 monolayer, elongated cells showed a little alignment. Cells showed not arrangement of actin stress fibers but F-actin condensation at the contact regions with neighboring cells. Interestingly, the formed cell monolayer could be readily peeled from the particle monolayer. These results indicate that endothelial cells could recognize the surface roughness displayed by particle monolayers and the response was dependent on the pitch of particle monolayers.     

Highly efficient alkylation to ketones and aldimines with Grignard reagents catalyzed by zinc(II) chloride

A highly efficient alkylation to ketones and aldimines with Grignard reagents in the presence of catalytic trialkylzinc(II) ate complexes derived from ZnCl2 (10 mol %) in situ was developed. This simple Zn(II)-catalyzed alkylation could minimize the well-known but serious problems with the use of only Grignard reagents, which leads to reduction and aldol side products, and the yield of desired alkylation products could be improved.