Polymerizations of racemic mixtures of epoxides or episulfides may lead to stereoregular polymers through a stereoselective process, and to optically active polymers through a stereoelective process that gives either atactic or isotactic polymers. Monomers that have been most studied are propylene oxide, propylene sulfide and t-butyl thiirane, and their polymerization with insoluble initiators ...

Unsymmetrically substituted allenes (1,2-dienes) are inherently chiral and can be prepared in optically pure form. Nonetheless, to date the allene framework has not been incorporated into ligands for asymmetric catalysis. Since allenes project functionality differently than either tetrahedral carbon or chiral biaryls, they may create complementary chiral environments. This study demonstrates th...

Epoxide hydrolase (EH) enzymes catalyze the hydration of racemic epoxides to yield their corresponding vicinal diols. These enzymes present different enantio- and regioselectivity depending upon either the substrate structure or the substitution pattern of the epoxide ring. In this study, we computationally investigate the Bacillus megaterium epoxide hydrolase (BmEH)-mediated hydrolysis of race...

Differently substituted β-hydroxy- and β-amino dialkyl alkyl-aryl tellurides selenides have been prepared through ring-opening reactions of epoxides aziridines with selenium- or tellurium-centered nucleophiles. The antioxidant properties the cytotoxicity such compounds investigated on normal human dermal fibroblasts. Most studied exhibited a low number them proved to be non-toxic, not showing a...

Kinetic resolution of a series fluorinated styrene oxide derivatives was studied using halohydrin dehalogenase. A mutant HheC-W249P catalysed nucleophilic ring-opening with azide and cyanide ions excellent enantioselectivity (E-values up to >200), which gives access various enantiopure ?-substituted alcohols epoxides. It found that the enzyme tolerates substrates in concentrations over 50 mM. H...

in this work, new biodegradable abcba type pentablock copolymers with different mole ratio of l-lactide and ppdo-b-peg-b-ppdo triblock copolymer were synthesized and characterized. in the first step, ppdo-b-peg-b-ppdo triblock copolymer was synthesized via a ring-opening polymerization of p-dioxanone (pdo) monomer with poly (ethylene glycol) (peg) using stannous octoate (sn(oct)2) as the cataly...

A conceptually new, simple and practical method for the syn-nucleophilic displacement of aryl and vinyl epoxides and aryl aziridines with (substituted) phenols, using aryl borates as activating nucleophiles under neutral conditions, is reported.

Reactivity ratios were evaluated for anionic ring-opening copolymerizations of ethylene oxide (EO) with either allyl glycidyl ether (AGE) or ethylene glycol vinyl glycidyl ether (EGVGE) using a benzyl alkoxide initiator. The chemical shift for the benzylic protons of the initiator, as measured by (1)H NMR spectroscopy, were observed to be sensitive to the sequence of the first two monomers adde...