Intravenous administration of 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxy chroman (gamma-CEHC) to rats and determination of its plasma concentration and urinary sodium excretion

A natriuretic hormone, 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxy chroman (gamma-CEHC) was administered intravenously to male Sprague-Dawley rats and the plasma concentration of gamma-CEHC along with urinary sodium (Na+) excretion was investigated. The plasma gamma-CEHC concentrations were fluorimetrically determined by a column-switching HPLC method consisting of both phenyl and octadecyl silica columns, following a pre-column fluorescence derivatization with a fluorescence reagent, 4-N,N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ). In rats fed with a high-NaCl (8.0%) diet, plasma gamma-CEHC concentrations rapidly decreased by 20% in 15-45 min after the administration of gamma-CEHC, while Na+ excretion gradually increased with time. Considering these results, the Na+ excretion effect appeared not to be associated with plasma gamma-CEHC concentration. In addition, attempts were made to examine a main urinary metabolite of gamma-CEHC, a large amount of 6-O-sulfated gamma-CEHC found to be present in the urine using an HPLC-tandem mass spectrometry. Thus, it is plausible that gamma-CEHC was easily metabolized to 6-O-sulfated metabolite and excreted into urine in rats.     

Synthesis and Properties of Spiro-double Sila[7]helicene: The LUMO Spiro-conjugation

A double helicene with a spiro-Si linker ( 4 ) was synthesized by four successive nucleophilic substitutions on SiCl₄. Its (P,P), (M,M) and (P,M) isomers were isolated and characterized by single crystal X-ray analysis. Due to the central spirosilabi[fluorene] moiety, the two helicene units in 4 are symmetrically and nearly perpendicularly arranged. (P,P)- 4 and (M,M)- 4 exhibit unique optical properties attributable to the LUMO spiro-conjugation between the two sila[7]helicene units.     

Synthesis of 1,2-bisalkylidenecyclopentanes from 1,6-allenynes via stereoselective addition of nucleophiles to ruthenacyclopentenes

Ruthenium-catalyzed cyclization of 1,6-allenynes occurs via the addition of heteroatom nucleophiles to ruthenacyclopentenes, providing functionalized 1,2-bisalkylidenecyclopentanes in a highly regio- and stereoselective manner.     

Stereoselective total synthesis of acremomannolipin A and its anomer,the potent calcium signal modulators with a novel glycolipid structure: role of the stereochemistry at the anomeric center on the activity

A full account of stereoselective total synthesis of a novel glycolipid, acremomannolipin A (1), the potent calcium signal modulator isolated from Acremonium strictum, by employing the stereoselective β-mannosylation of 4,6-O-benzylidene-protected mannosyl sulfoxide with d-mannitol as the key reaction is described. The α-anomer (epi-1) of 1 was also synthesized selectively. The calcium modulating activity was reduced upon inversion of the configuration at the anomeric center, indicating that the β-configuration of the mannose moiety is preferable for the activity.     

Anion- and cation-exchange MicroHPLC utilizing poly(methacrylates)-coated monolithic silica capillary columns.

A novel method was developed for the preparation of highly efficient anion- and cation-exchange microHPLC columns using an on-column polymerization of methacrylates having amine or sulfonic acid functional groups onto monolithic silica capillary columns modified with 3-methacryloxypropyltriethoxysilane as the anchor groups. The chromatographic evaluation of the columns using nucleic acids, nucleotides, and inorganic anions as samples showed the characteristics of the ion-exchange-type stationary phases. These columns exhibited higher separation efficiency when compared with the conventional particle-packed columns. A capillary column for the simultaneous anion- and cation-exchange separation could be prepared by a step-by-step functionalization. The advantages of this column preparation will include: (1) no need of column packing; (2) no need of the preparation of silane reagents possessing anion- and cation-exchange functionalities; (3) the amount of immobilized polymer could be controlled by changing polymerization conditions. These columns should be suitable for the separation of biologically active compounds by the microHPLC modes.     

Paramagnetic-diamagnetic phase transition accompanied by coordination bond formation-dissociation in the dithiolate complex Na[Ni(pdt)2]·2H2O

Bis(2,3-pyrazinedithiolate)nickel complex Na[Ni(pdt)(2)]·2H(2)O formed one-dimensional stacks of the Ni(pdt)(2) units and showed strong antiferromagnetic interactions along the stacking direction. A first-order phase transition between the paramagnetic and diamagnetic states, which was driven by dimerization of the Ni(pdt)(2) units, accompanied by coordination bond formation, was observed.     

Side chain effect on the double helix formation of ethynylhelicene oligomers

Three series of ethynylhelicene oligomers with different side chains were synthesized: (P)-bD-n (n = 2-6) with branched alkyloxycarbonyl side chains; (P)-S-n (n = 2-7) with decylsulfanyl side chains; and (P)-DF-n (n = 4, 6, 8, 10) with alternating decyloxycarbonyl and perfluorooctyl side chains. The double helix formation of these side chain derivatives was compared to that of (P)-D-n with decyloxycarbonyl side chains. CD, UV-vis, and vapor pressure osmometry (VPO) studies showed that (P)-bD-n formed double helices as well as (P)-D-n. CD studies in trifluoromethylbenzene at different temperatures and concentrations indicated that the stability of the aggregate of (P)-bD-6 was similar to that of (P)-D-6. Bulkiness of side chains had little effect on aggregation, which indicated that π-π interactions of the aromatic moiety were essential for double helix formation. (P)-S-n were random coils in all solvents examined except in trifluoromethylbenzene. Whereas (P)-D-7 formed a double helix at 1 × 10(-3) M in toluene, (P)-S-7 was a random coil. This result indicated that the double helix forming ability of (P)-S-n was substantially lower than that of (P)-D-n. Based on the previous observation that (P)-F-n formed a more stable double helix than (P)-D-n, the order of stability may be summarized as follows: (P)-F-n > (P)-D-n and (P)-bD-n >(P)-S-n. The lower stability of (P)-S-n compared to that of (P)-F-n was ascribed to the softness and/or the electron-rich nature at the m-phenylene moiety. (P)-DF-n did not form a stable double helix. It was speculated that a regular alternating arrangement of soft/hard or electron-rich/deficient moieties is important for stable double helix formation. Side chains of ethynylhelicene oligomers can play significant roles in determining the stability of double helices.