Experimental and theoretical studies of the molecular and crystal structures of trialkoxy- and chlorodialkoxy-stibanes

The molecular structures of triisopropoxystibane, Sb((OPr)-Pr-i)(3), and chlorodiisopropoxystibane, SbCl((OPr)-Pr-i)(2), were determined in the solid state by single crystal X-ray diffraction. Sb((OPr)-Pr-i)(3) forms discrete centrosymmetric dimers in the solid state via Sb . . .O-Sb interactions, leading to pseudo trigonal bipyramidal configurations of the four co-ordinate Sb atoms, while SbCl((OPr)-Pr-i)(2) forms chains via Sb . . .O-Sb and Sb . . . Cl-Sb bridges, resulting in five-co-ordinate Sb atoms with pseudo octahedral configurations. Comparison of the solid state structures and the density functional optimized molecular structures of Sb(OMe)(3), SbCl(OMe)(2) and their dimers reveal…

Stereoselective Conjugate Addition of Mixed Organoaluminum Reagents to ?,?-Unsaturated N-Acyloxazolidinones Derived from Carbohydrates.

The stereoselective synthesis of β-branched carboxylic acid derivatives was accomplished by conjugate addition of mixed organoaluminum reagents to chiral α,β-unsaturated N-acyloxazolidinones. Mixed organoaluminum reagentswere generated in situ by transmetalation of Grignard or organolithium compounds with methylaluminum dichloride. Efficient stereocontrol was achieved using different bicyclic glycosamine-derived oxazolidinones, yielding alternatively (R)- or (S)-configured β-branched carboxylic acid derivatives.

Inhibitors of inducible NO synthase expression: total synthesis of (S)-curvularin and its ring homologues.

(S)-Curvularin and its 13-, 14-, and 16-membered lactone homologues were synthesized through a uniform strategy in which a Kochi oxidative decarboxylation and ring-closing metathesis reactions constitute the key processes. In the evaluation of the anti-inflammatory effects of the synthesized compounds in assays using cells stably transfected with a human iNOS promoter-luciferase reporter gene construct, the 14- and 16-membered homologues showed a slightly higher inhibitory effect towards iNOS promoter activity than curvularin itself. However, the larger ring homologues also exhibited higher cytotoxicity, manifest in downregulated eNOS promoter activity. In contrast, the di-O-acetyl and 4-ch…

ChemInform Abstract: Inhibitors of Inducible NO Synthase Expression: Total Synthesis of (S)-Curvularin (Ia) and Its Ring Homologues.