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the electrode surface, and other researchers
have pointed out that Miller's results are not
always reproducible. Later on, in order to solve
problems such as the instability of electrodes
modified with chiral adsorbance and the low
density of modified chiral compounds, chiral
polymer-modified electrodes were developed.
For instance, Nonaka, Fuchigami and
co-workers prepared various electrodes coated
with optically active poly(amino acid)s and
applied these to the asymmetric reduction of
olefins. They obtained 43% ee in the reduction
of 4-methylcumarin at a cathode coated with
poly( L -valine) as shown in Figure 5.9 [39].
Figure 5.9 Asymmetric reduction using chiral
polymer-modified electrode
Subsequently, a graphite felt electrode modified
with 2,2,6,6-tetramethylpiperidin-1-yloxyl
(TEMPO) was developed and applied to
enantioselective oxidative coupling of
2-naphthol, 2-methoxynaphthalene and
10-hydroxyphenanthrene in the presence of
(−)-sparteine as a chiral base. The
enantioselectivity of the coupling products was
very high (98%) [40,41]. It has been considered
that high asymmetric yield cannot be expected
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