Department of Chemistry
Seminar Announcement
Date/Time/Venue
Title/Speaker
20 Jan (Thu)
10am – 11am
Directed Assembly of C4-Symmetric
Vanadate-Centered Quadruplexes:
Synergistic Ion-specific Transport and
Asymmetric Catalysis
@ S8 Level 3
Executive
Classroom
Professor Chen Chien-Tien
National Tsing Hua University, Taiwan
Host : Asst Prof Huynh Han Vinh
About the Speaker
Professor Chen Chien-Tien, b 1964 in Taipei, Taiwan. National TsingHua Univ. (BS 1986; MS 1988), Univ. of Illinois at Urbana-Champaign
(Ph.D. 1994, Prof. S. Denmark), Scripps Research Institute (Postdoc.
1995, Prof. B. Sharpless) Associate Prof. (1995), Professor (2000-),
Research Chair of NTNU (2008-2009), Distinguished Professor of
NTHU (2010-). Research filed: (synergistic) asymmetric catalysis,
organic optoelectronic materials and LC-based optical switches,
DNA photocleavages, and nanoparticle-encapsulated dendritic
probes, directed assembly for synergistic ion-specific transport.
Abstract
We have developed a series of N-Salicylidene-based L-a-amino acids as chiral auxiliaries
for chiral vanadyl(V) methoxide complex synthesis. These configurationally well-defined
complexes have been examined for kinetic resolution of 2o alcohols. They serve as efficient
and highly enantioselective catalysts for asymmetric aerobic oxidation of a-hydroxy acid,
phosphonic acid, and ketone derivatives at ambient temperature. The asymmetric
inductions of the oxidation process are in the range of 50 - > 500 in terms of selectivity
factors (krel) in most instances. X-ray crystallographic analysis of an adduct between Nbenzyl-mandelamide and the catalyst allows for probing the origin of the nearly exclusive
asymmetric control in the oxidation process. In the case of the 3,5-di-tert-butyl and 3,5dihalo- substituted analogs, pentanuclear C4-symmetric complexes were formed when
potassium salts were employed instead of the corresponding sodium salts. The complexes
work synergistically in the asymmetric aerobic oxidations of various racemic a-hydroxy acid
and ketone derivatives with excellent selectivity factors. A directed assembly process to form
C4-symmetric, vanadate-centered helical quadruplexes, for the first time, from a given chiral
oxidovanadium(V) complex allows for highly efficient K+-, Ag+, Ba2+, Pb2+, Hg2+, and (chiral)
ammonium ion-specific transports from aqueous phase into organic solvents, reminiscent of
the K+ specific transport exerted by four homochiral glycine residues of the opening site in
KcsA membrane protein.
References:
(a) Weng, S.-S.; Shen, M.-W.; Kao, J.-Q.; Munot, Y. S.; Chen, C.-T. Proc. Natl. Acad. Sci. U.S.A. 2006, 103,
3522. (b) Pawar, V. D.; Weng, S.-S.; Bettigeri, S.; Kao, J.-Q.; Chen, C.-T. J. Am. Chem. Soc. 2006, 128, 6308.
(c) Chen, C.-T. and Lee, W.-Z. J. Org. Chem. 2007, 72, 8175. (d) Chen, C.-T.; Lin, Y.-H.; Kuo, T.-S. J. Am.
Chem. Soc. 2008, 130, 12843. (e) Lee, W.-Z. and Chen, C.-T. et al. Organometallics 2009, 28, 652. (f) C.-T.
Chen, J.-Q. Kao, S. B. Salunke, Y.-H. Lin; Organic Lett. 2010, 12, on web (Dec. 6).
All are Welcome