The convergent synthesis of a benzofuran analog of the carbacyclic ansa compound kendomycin has been achieved by assembling three major fragments by means of epoxide opening and directed ortho lithiation. The crucial tetrahydropyran ring was formed by a highly stereoselective cationic cyclization. Analysis of all synthesized tetrahydropyran-arene compounds reveals a hindered sp(2)-sp(3) rotatio...

Recent advances in studies of the kinetics of chemical processes in dilute polymer solutions include in— vestigations of hindered rotation in the backbone of flexible chain molecules, of ionic reactions in polyelectrolyte solu— tions, kinetic effects reflecting the local medium in the polymer domain, neighboring group effects in reactiorof polysaccharides and diffusion—controlled intramolecular...

Surprisingly stable formamide rotamers were encountered in the tetrahydroisoquinoline and morphinan series of alkaloids. We investigated the hindered rotation around the amide bond by dynamic high-performance liquid chromatography (DHPLC) and kinetic measurements of the interconversion of the rotamers which can readily be separated by HPLC as well as TLC. The experimental results of the differe...

A number of vibrational-tunneling-rotational (VTR) transitions in the range of 195-298 GHz belonging to theΣ00 → Π10 hindered rotation band in Rg·ND3 (Rg = Ne, Kr) complexes are observed in absorption in a free supersonic jet, using the pulsed fast scan submillimeter wave spectroscopic technique (FASSST). The data obtained in this experiment, combined with previously obtained data on the Ar·ND3...