Synthesis and biological evaluation of rigid polycyclic derivatives of the Diels-Alder adduct tricyclo[6.2.1.02,7]undeca-4,9-dien-3,6-dione

Part of our research program concentrates on the discovery of new bioactive compounds prepared either by total synthesis or molecular transformation of compounds with bioactivity profiles. In this work we have focused our interest on chemical transformations of the Diels-Alder adduct tricyclo[6.2.1.0(2,7)]undeca-4,9-dien-3,6-dione in order to obtain cage-like compounds and derivatives, followed by an evaluation of their biological activity.     

Relativistic effects and the halogen dependencies in the 13C chemical shifts of CH4−nIn,CH4−nBrn,CCl4−nIn,and CBr4−nIn (n=0–4)

Linear and nonlinear halogen dependencies of the ¹³C magnetic shielding constants of CH_4−nI_n, CH_4−nBr_n, CCl_4−nI_n, and CBr_4−nI_n were fairly reproduced by the ab initio generalized unrestricted Hartree–Fock (GUHF)/finite perturbation (FP) method including spin‐orbit (SO) interaction and spin‐free relativistic (SFR) terms. As seen from the experimental trends, the calculated ¹³C chemical shifts in CCl_4−nI_n and CBr_4−nI_n depend linearly on n=0–4, while those in CH_4−nI_n and CH_4−nBr_n depend nonlinearly. We found that both the linear and nonlinear dependencies are due to the relativistic effects, and especially due to the Fermi–Contact (FC) term originating from the SO interaction. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 528–536, 2001     

Benzylic triflates prepared in‐situ: novel initiators for mono‐, bi‐ and trifunctional living poly(THF)s

Mono‐, bis‐, and tris(trifluoromethanesulfonate ester)s ((triflate ester)s) were prepared by the reaction of benzyl alcohol ( 1 ), 1,4‐bis(hydroxymethyl)benzene ( 2 ) and 1,3,5‐tris(hydroxymethyl)benzene ( 3 ) with trifluoromethanesulfonic anhydride in the presence of 2,6‐di‐tert‐butylpyridine. These benzylic triflate esters were applied in‐situ for the living polymerization of tetrahydrofuran (THF). The subsequent end‐capping reaction with a suitable nucleophile proceeded quantitatively to produce mono, bi‐ and, in particular, novel trifunctional telechelic poly(THF)s, respectively.     

Effects of chloride ions on electrochemical reactions of manganese(III) complexes

Electrochemical reactions of manganese(III) complexes, Mn^III(L)X (L; salen, salpn, 5-NO₂–salen or 5-NO₂–salpn, X; Cl, Br or NO₂) and Mn^III(L’)₂X (L’; N-Bu-sal, N-Oct–sal, N-Oct–5-Br–sal or N-Oct–5-NO₂–sal, X; Cl or Br), were investigated by voltammetry at a glassy carbon electrode in the absence/presence of Cl⁻ in acetonitrile solution. By the addition of Cl⁻, oxidation processes of Mn^III(L)X and Mn^III(L’)₂X have been found to be improved from quasi-reversible to reversible, and their oxidation products, [Mn^IV(L)X]⁺ and [Mn^IV(L’)₂X]⁺, were stabilized by the combination with Cl⁻ resulting in [Mn^IV(L)Cl₂] and [Mn^IV(L’)₂Cl₂], respectively. On the other hand, the reduction processes of Mn^III(L)X and Mn^III(L’)₂Cl were not so significantly affected by Cl⁻ as those observed for their oxidation. Other types of manganese(III) complexes and iron(III) complex were also investigated. The present study may clarify the role of Cl⁻ being involved in OEC (oxygen-evolving center) in photosystem II.     

Synthesis of the DFGH ring system of Type B Physalins: Highly Oxygenated,Cage‐Shaped Molecules

Let the dominos fall : Synthesis of the complex DFGH ring system of the title compounds has been accomplished. The approach features simple treatment of the key intermediate with a Brønsted base to afford the tetracyclic cage‐shaped target in one pot through a four‐step domino transformation (see scheme; Mc= monochloromesylate, MOM=methoxymethyl).

     

Syntheses of model compounds related to an antigenic epitope in pectic polysaccharides from Bupleurum falcatum L. (II)

Stereocontrolled syntheses of model compounds related to a major antigenic epitope against antibupleurum 2IIc/PG-1-IgG from antiulcer pectic polysaccharide are described. A trisaccharide derivative (13) was prepared as a precursor and a novel and simple approach for the rational design of a glycocluster and glycodendrimer was developed, through the syntheses of the fluorescence-labeled glycocluster (2) and glycodendrimer (3).     

Enhancement of molecular-shape selectivity in high-performance liquid chromatography through multi-anchoring of comb-shaped polymer on silica

Poly(octadecylacrylate) having plural trimethoxysilyl groups in the side chain (co-ODA(n)) was newly synthesized and immobilized onto silica through these groups. The liquid chromatographic behavior of silica-supported co-ODA(n) (Sil-co-ODA(n)) was investigated and compared with that of Sil-ODA(n), in which poly(octadecylacrylate) was immobilized through a terminal trimethoxy group at one side of the polymer main chain. Sil-co-ODA(n) showed higher selectivity for molecular shape, especially molecular planarity of PAHs than Sil-ODA(n).     

Synthesis and structure of diastereomers of pentenocin B produced by Trichoderma hamatum FO-6903

All diastereomers of pentenocin B, an inhibitor of interleukin-1β converting enzyme produced by Trichoderma hamatum FO-6903, were synthesized in chiral forms starting from l-threonine. Absolute configurations of natural pentenocin B were clarified to be 4S, 5R, and 6R.