Studien zum synthetischen Zugang zu Ripostatinen und deren Analoga

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Total Synthesis of Ripostatin A

The first total synthesis of the bacterial RNA-polymerase inhibitor ripostatin A (<b>1</b>) was achieved. The route utilizes a cyclic methyl acetal intermediate and a sequence of a double Stille cross-coupling reaction followed by a ring-closing metathesis for the construction of the macrolactone ring. Additionally, an unprecedented formation of the 4-methoxy substituted tetrahydropyrans was observed during the acid catalyzed acetalization of the β,δ-dihydroxyketone

The synthesis and electrorheological properties of BaTiO3-coated PMMA microspheres

Coated-PMMA microspheres consisting of poly (methyl methacrylate)(PMMA) core and barium titanate (BaTiO3) shell were synthesized by the modified sol-gel processing and then adopted as an electrorheological (ER) materials. The structure and morphology of coated powders were characterized by SEM and FT-IR; the shear stress of the suspensions of coated-PMMA particles and pure PMMA particles in silicone oil with a 20 vol\% were investigated. The results show that the BaTiO3 coated PMMA microspheres based suspension in silicone oil exhibited typical ER behavior and stronger ER effects