D3h‐Symmetric Porphyrin‐Based Rigid Macrocyclic Ligands for Multicofacial Multinuclear Complexes in a One‐Nanometer‐Sized Cavity

The one‐step synthesis of D_3h‐symmetric cyclic porphyrin trimers 1 composed of three 2,2′‐[4,4′‐bis(methoxycarbonyl)]bipyridyl moieties and three porphyrinatozinc moieties was achieved from a nickel‐mediated reductive coupling of meso‐5,15‐bis(6‐chloro‐4‐methoxycarbonylpyrid‐2‐yl)porphyrinatozinc. Although cyclic trimers 1 were obtained as a mixture that included other cyclic and acyclic porphyrin oligomers, an extremely specific separation was observed only for cyclic trimers 1 when using columns of silica gel modified with pyrenylethyl, cyanopropyl, and other groups. Structural analysis of cyclic trimers 1 was carried out by means of NMR spectroscopy and X‐ray crystallography. Treatment of an η³‐allylpalladium complex with a cyclic trimer gave a tris(palladium) complex containing three η³‐allylpalladium groups inside the space, which indicated that the bipyridyl moieties inside the ring could work as bidentate metalloligands.     

Preparation of a cyclodextrin dimer linked with a bis(picolinyl)cystine moiety and its intra- and intermolecular inclusion behavior

A novel cyclodextrin (CD) dimer linked with a bis(picolinyl)cystine (Cys) moiety was prepared by the coupling of Boc-protected Cys with amino-modified CDs, followed by deprotection of the Boc groups and bispicolinylation. The dimer showed less affinity to an organic guest molecule compared to that of a native CD monomer. It was attributed to an intramolecular inclusion of the pyridine moiety into CD cavity. The dimer caused significant increase of its organic guest affinity by an addition of a copper ion. The included pyridine group may come out of a CD cavity to bind the copper ion and the two CDs included cooperatively and intermolecularly a guest molecule with high affinity.     

Reactions of hydropolysilanes with alcohols catalysed by tris(triphenylphosphine)chlororhodium

[RhCl(PPh₃)₃] is a very effective catalyst for the cleavage of Si-Si bonds by alcohols.     

Spacer effect of appended moieties for molecular recognition in doubly-sodium anthranilate modified γ-cyclodextrin

-Cyclodextrin with two sodium anthranilate moieties (1) has been prepared as a sensor for detecting organic compounds including terpenoids and steroids. Compound1 shows a pure monomer fluorescence whose intensity is increased or decreased upon addition of the guest species examined. In this system, the sodium anthranilate moieties act either as a spacer, which enables the cyclodextrin to form a 1:1 host-guest complex by narrowing the -cyclodextrin cavity, or as a hydrophobic cap.1 recognizes steroids with much higher sensitivity than terpenoids, in which the appended moieties act as a hydrophobic cap for terpenoids and a spacer for steroids, respectively.     

Structures of Ganoderic Acid A and B,Two New Lanostane Type Bitter Triterpenes from Ganoderma lucidum (FR.) KARST.

The structures of two new bitter triterpenes, ganoderic acid A and B. isolated from a mushroom Ganoderma lucidum (FR.) Karst. (Polyporaceae) were determined as 1 and 2 on the basis of spectral data. Ganoderic acid A is a novel highly oxidized triterpene bearing a boat-shaped A-ring of lanostane.     

Medicinal flowers. VI. Absolute stereostructures of two new flavanone glycosides and a phenylbutanoid glycoside from the flowers of Chrysanthemum indicum L.: their inhibitory activities for rat lens aldose reductase

Two new flavanone glycosides, (2S)- and (2R)-eriodictyol 7-O-beta-D-glucopyranosiduronic acids, and a new phenylbutanoid glycoside, (2S, 3S)-1-phenyl-2,3-butanediol 3-O-beta-D-glucopyranoside, were isolated from the flowers of Chrysanthemum indicum L. cultivated in China together with eight flavonoids. The absolute stereostructures of the new compounds were determined on the basis of chemical and physicochemical evidence. Both of the new flavanone glycosides were found to show inhibitory activity for rat lens aldose reductase.     

Prenylated xanthones from Garcinia xanthochymus

A new prenylated xanthone, 1,3,5,6-tetrahydroxy-4,7,8-tri(3-methyl-2-butenyl)xanthone (1), was isolated from the wood of Garcinia xanthochymus together with a known xanthone, garciniaxanthone E (2). Their structures were determined by spectroscopic analysis. Compounds 1 (3 microM) and 2 (10 microM) elicited marked enhancement of nerve growth factor-mediated neurite outgrowth in PC12D cells.     

Total synthesis of gambierol

[structure: see text] The first total synthesis of gambierol, a marine polycyclic ether toxin, has been achieved. The synthesis features the Pd(PPh3)4/CuCl/LiCl-promoted Stille coupling for the stereoselective construction of the sensitive triene side chain that includes a conjugated (Z,Z)-diene moiety.     

Autocorrelated 13c-13c double quantum coherence two-dimensional nmr spectroscopy: Utilization of a modified version of the technique as an adjunct in the total assignment of the 1h- and 13c-nmr spectra of the mutagen phenanthro[3,4-b]thiophene

Development of successively higher field nmr spectrometers has facilitated the study of increasingly more complex molecules, although smaller molecules such as phenanthro[3,4-b]thiophene still offer very substantial assignment problems because of the highly congested nature of their ¹H- and ¹³C-nmr spectra. Assignments of such spectra, if they are to be unequivocal, frequently require the utilization of two-dimensional nmr spectroscopic techniques. Total assignments of the ¹H- and ¹³C-nmr spectra of phenanthro[3,4-b]thiophene are reported. Assignments were based on a conventional high resolution 500 MHz ¹H-nmr spectrum, autocorrelated two-dimensional ¹H-nmr spectra (COSY), two-dimensional ¹H-¹³C chemical shift correlation spectra and a modified version of autocorrelated ¹³C-¹³C double quantum coherence two-dimensional nmr spectroscopy. From NOE measurements, a separation of 1.99 Å between H1 and H11 was computed, suggesting that phenanthro[3,4-b]thiophene has a pronounced helical conformation in solution.     

Dansyl-Modified γ-Cyclodextrin as a fluorescent sensor for molecular recognition

The crystal structure of thiamine iodide sesquihydrate has been determined by X-ray diffraction methods as a host-guest model for coenzyme-substrate interactions. The asymmetric unit contains two chemical units. Both the thiamine molecules A and B, which are crystallographically independent, assume the usualF conformation and have a disordered hydroxyethyl side chain. An iodide anion (or a water molecule) bridges the pyrimidine and thiazolium rings of molecule A (or B) by forming a hydrogen bond with the amino group and an electrostatic contact with the thiazolium ring to stabilize the molecular conformation. In the crystal the thiamine molecules self-associate to form a pipe-like polymeric structure, in which four thiamine hosts surround an iodide guest and hold it through C(2)-H...I hydrogen bonds and thiazolium...I electrostatic interactions. Crystal data: C₁₂H₁₇N₄OS⁺·I^– · 1.5 H₂O, monoclinic,P2₁/c, a=12.585(2), b=25.303(5), c=12.030(2) Å, =115.15(1)°,V=3468(1) ų,Z=8,D _c=1.606 g cm^–3,R=0.045 for 3328 observed reflections. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP. 82156 (13 pages).