H.-J. Cristau et al. / Journal of Organometallic Chemistry 690 (2005) 2472–2481
2481
nature of the catalyst. As shown in Scheme 22, the pure
a-aminobenzyl phenylphosphinic acid 11 is obtained
using formic acid in presence of palladium on charcoal.
Acknowledgements
This work was supported by the SSTD-KBRI-
SFERE program, the EGIDE program, the Centre Na-
´
tional de la Recherche Scientifique and the Ministere de
lÕEducation Nationale de lÕEnseignement Superieur et de
la Recherche.
2.2.3. Synthesis from enantiopure 1(S),2(R)-
diphenylethanolamine [14]
´
Based on the chemistry developed in the preceding
part from the racemic starting material, we are now
elaborating the synthesis of diastereoisomerically and
enantiomerically pure functional a-aminophosphinic
acids (Scheme 23).
References
Starting from the enantiomerically pure 1(S),2(R)-
diphenylethanolamine, the formation of the corresponding
imine with benzaldehyde occurs almost quantitatively.
Then the base-catalysed addition of methyl phosphinate
followed by cyclisation through transesterification af-
fords two diastereoisomers (ratio 75/25), and the major
dextrogyre product can be isolated by crystallisation. Its
Michael addition on the trans methyl cinnamate affords
also two diastereoisomers (ratio 85/15), which can be
separated chromatographically.
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preparation.
[15] H.J. Cristau, J. Monbrun, M. Tillard, D. Virieux, J.L. Pirat, in
preparation.
These reactions exhibit generally a good to excellent
kinetic diastereoselectivity which can often be predicted
by molecular models of the transition states.
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