Methylene-Bridged Bis(imidazoline)-Derived 2-Oxopyrimidinium Salts as Catalysts for Asymmetric Michael Reactions
作者:Andrey E. Sheshenev、Ekaterina V. Boltukhina、Andrew J. P. White、King Kuok Mimi Hii
DOI:10.1002/anie.201300614
日期:2013.7.1
In nothing flat: The title salts, having planar nitrogen centers, were utilized successfully as phase‐transfer catalysts for asymmetricMichaelreactions of tert‐butyl glycinate benzophenone Schiff base with vinyl ketone and chalcone derivatives, thus providing excellent levels of diastereo‐ and enantiocontrol (see scheme).
New Chiral Zwitterionic Phosphorus Heterocycles: Synthesis, Structure, Properties and Application as Chiral Solvating Agents
作者:Andrey E. Sheshenev、Ekaterina V. Boltukhina、Anastasiya A. Grishina、Ivana Cisařova、Ilya M. Lyapkalo、King Kuok Mimi Hii
DOI:10.1002/chem.201300062
日期:2013.6.17
A family of new chiral zwitterionic phosphorus‐containing heterocycles (zPHC) have been derived from methylene‐bridged bis(imidazolines). These structures were unambiguously determined, including single‐crystal XRD analysis for two compounds. The stability, acid/base and electronic properties of these dipolar phosphorusheterocycles were subsequently investigated. zPHCs can be successfully employed
Addition reactions of dicyanomethyl tert-butyldimethylsilyl ether (H–MAC–TBS) to optically active tert-butanesulfinimides afforded α-amino acid precursors in excellent yields and with high diastereoselectivities.
Stereoselective Synthesis of Constrained Azacyclic Hydroxyethylene Isosteres as Aspartic Protease Inhibitors: Dipolar Cycloaddition and Related Methodologies toward Branched Pyrrolidine and Pyrrolidinone Carboxylic Acids
[GRAPHICS]The synthesis of three vicinally substituted azacyclic carboxylic acids in enantiopure form was achieved from a common (x-amino aldehyde originating from (L)-leucine. Pyrrolidines and pyrrolidinones were elaborated from a,beta-unsaturated gamma-hydroxy-delta-amino acids via azomethine ylide 1,3dipolar addition and conjugate addition/cyclization strategies, respectively. The azacyclic amino acids were incorporated in a pseudopeptide now encompassing a hydroxyethylene isostere. Low nanomolar inhibition of BACE1, an enzyme implicated in the cascade of events leading to plaque formation in Alzheimer's disease, was found with a pyrrolidinone analogue.
A new synthetic route to tert-butyloxycarbonylaminoacyl-4-(oxymethyl)phenylacetamidomethyl-resin, an improved support for solid-phase peptide synthesis
作者:Alexander R. Mitchell、Stephen B. H. Kent、Martin Engelhard、R. B. Merrifield