- Recoverable Dendritic Phase-Transfer Catalysts that Contain (+)-Cinchonine-Derived Ammonium Salts
-
Four new phosphorus dendrimeric phase-transfer catalysts are prepared that contain 12 (+)-cinchoninium salts on the surface obtained by the quaternisation of the quinuclidinic N atom. The asymmetric alkylation of a glycinate Schiff base with benzyl bromide is used as a benchmark reaction, and the dendrimeric catalyst that contains an allyl group on the O-9 hydroxy group of the cinchonine units is the most active. The recovery and reuse of the catalyst are possible for five consecutive runs without loss of activity and with only a slight decrease in enantioselectivity. If other electrophiles are used, substituted benzyl bromides give better results than other activated alkyl bromides to afford the corresponding R amino acid derivatives. A comparison of these results with those reported previously for similar cinchoninium salts shows that dendrimers could be a better support than other polymers for this type of organocatalysis.
- Rull, Jordi,Jara, José Juan,Sebastián, Rosa M.,Vallribera, Adelina,Nájera, Carmen,Majoral, Jean-Pierre,Caminade, Anne-Marie
-
p. 2049 - 2056
(2016/07/07)
-
- Toward a rational design of peptide inhibitors of ribonucleotide reductase: Structure-function and modeling studies
-
Mammalian ribonucleotide reductase, a chemotherapeutic target, has two subunits, mR1 and mR2, and is inhibited by AcF1TLDADF7, denoted P7. P7 corresponds to the C-terminus of mR2 and competes with mR2 for binding to mR1. We report re
- Pender,Wu,Axelsen,Cooperman
-
-
- Multiply substituted DTPA derivatives and their metal complexes, and their metal complexes, pharmaceutical agents that contain these complexes, their use in diagnosis and therapy, as well as process for the production of pharmaceutical agents
-
The invention relates to new, multiply substituted diethylenetriaminepentaacetic acid derivatives, their complexes and complex salts, that contain an element of atomic numbers 20-32, 39-51 or 57-83, pharmaceutical agents that contain these compounds, their use as contrast media and antidotes, and process for the production of pharmaceutical agents.
- -
-
-