Strychnos 1990 - 2004 - Crops for the Future
Strychnos 1990 - 2004 - Crops for the Future
Strychnos 1990 - 2004 - Crops for the Future
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Author<br />
Title<br />
Year<br />
Source title<br />
Reference<br />
Shibasaki, M., T. Iida and Y. M. A. Yamada<br />
Development of multifunctional asymmetric catalysts and <strong>the</strong>ir application to prac<br />
1998<br />
Journal of Syn<strong>the</strong>tic Organic Chemistry Japan<br />
56(5): 344-356<br />
Abstract<br />
This article focuses on a new concept in catalytic asymmetric syn<strong>the</strong>sis, which was first realized by<br />
<strong>the</strong> use of heterobimetallic complexes. As such complexes function at <strong>the</strong> same time as both a Lewis<br />
acid and a Bronsted base, similar to enzymes, <strong>the</strong>y make possible a variety of efficient catalytic<br />
asymmetric reactions. This "heterobimetallic" concept has proven to be applicable to a variety of<br />
new asymmetric catalyses. We have already succeeded in asymmetric nitroaldol reactions catalyzed<br />
by <strong>the</strong> LaLi(3)tris (binaphthoxide) complex (LLB) and asymmetric Michael reactions catalyzed by<br />
<strong>the</strong> LaNa(3)tris (binaphthoxide) complex (LSB). Now <strong>the</strong> LLB catalyst could also be applied<br />
efficiently to <strong>the</strong> tandem inter-intramolecular asymmetric nitroaldol reaction, af<strong>for</strong>ding a<br />
syn<strong>the</strong>tically useful bicyclic product with four newly generated chiral carbons in one pot.<br />
Fur<strong>the</strong>rmore we succeeded in <strong>the</strong> first direct asymmetric aldol reactions of aldehydes with<br />
unmodified ketones (up to 94% ee) by using a catalytic amount of LLB. While LLB was also<br />
effective in <strong>the</strong> hydrophosphonylation of aldehydes, asymmetric hydrophosphonylations of imines<br />
were efficiently catalyzed by <strong>the</strong> LnK(3)tris (binaphthoxide) complex (LnPB:Ln=rare earth metal<br />
such as La, Yb) (up to 96% ee). On <strong>the</strong> o<strong>the</strong>r hand, alkali metal free lanthanum complexes prepared<br />
from Ln(O-i-Pr)(3) (Ln=La or Yb) and 1,1'-binaphthol (BINOL) or 3-hydroxymethyl-BINOL were<br />
excellent catalysts <strong>for</strong> <strong>the</strong> asymmetric epoxidation of alpha,beta-unsaturated ketones (up to 94% eel.<br />
We also developed ano<strong>the</strong>r type of heterobimetallic catalysts featuring group 13 elements such as Al<br />
or Ga as a central metal. Among <strong>the</strong>m, <strong>the</strong> AlLibis(binaphthoxide) complex (ALB) is an effective<br />
catalyst <strong>for</strong> asymmetric Michael reactions of malonates or Horner-Wadsworth-Emmons reagents (up<br />
to 99% ee) and <strong>for</strong> asymmetric tandem Michael-aldol reactions. Applications bi this catalyst to<br />
syn<strong>the</strong>ses of biologically important compounds such as 11-deoxy-PGF(1 alpha) and tubifolidine are<br />
also described. Fur<strong>the</strong>rmore <strong>the</strong> GaLibis (binaphthoxide) complex (GaLB) in combination with<br />
molecular sieves 4 A was found to be an efficient catalyst <strong>for</strong> asymmetric ring openings of a variety<br />
o f e p o x i d e s w i t h t - B u S H ( u p t o 9 7 % e e ) .<br />
Author<br />
Title<br />
Year<br />
Source title<br />
Reference<br />
Abstract<br />
Shimizu, S., K. Ohori, T. Arai, H. Sasai and M. Shibasaki<br />
Catalytic asymmetric syn<strong>the</strong>sis of tubifolidine<br />
1998<br />
Journal of Organic Chemistry<br />
63(21): 7547-7551<br />
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