helical PDPyMMA also shows an analogous chiral recognition with a slightly
higher durability against solvolysis by methanol [19].
6 Polyacrylamides and Polymethacrylamides
Blacshke and coworkers synthesized various poly(meth)acrylamide (5, 6) gels
through the radical copolymerization of (meth)acrylamides bearing optically active
side groups, with ethylene diacrylate as a crosslinker, and used the gels for the
resolution of many racemic pharmaceuticals by column chromatography [20]. The
authors pointed out that the structure constructed during the polymerization plays a
key role in the chiral recognition of the gels. Therefore, when the same chiral side
groups were attached onto a poly(acryloyl chloride) gel, the obtained gel exhibited
a much lower chiral recognition.
We synthesized chiral polymers with different tacticities by the radical polymerization of the optically active methacrylamide 21 (Fig. 8) in the absence and
presence of a Lewis acid, Yb(OTf) 3 [21]. The polymerization without the Lewis
acid at À20
C afforded the syndiotactic polymer with a triad tacticity mm/mr/
rr ¼ ~0/13/87, whereas in the presence of the Lewis acid, the isotactic polymer
with mm/mr/rr ¼ 87/13/~0 was obtained. These two tactic polymers exhibited
different chiral recognitions as the CSPs in HPLC, as shown in Table 1. The
isotactic polymer could not resolve any of the three racemates, although two
racemates were resolved on the highly syndiotactic polymer. In the isotactic
O
CH 2 O
CH 2 O
Me
Me
Me
Me
O
O
O
O
Cl
Cl
Cl
Cl
Cl
N
3
CH 3
CH 3
O O O
O
CH 2
CH 2
O
n
9
Si
CH 3
CH 3
Cl
Cl
Cl
Cl
H H
N
N
O O
R
R
O
O
O O
H
t-Bu
t-Bu
t-Bu
P C P
t-Bu
t-Bu
t-Bu
NO 2
N
H
H COOR
CN
H 3 C
(CH 3 ) 2 CHOOC
O
C
HO
O
N
N
OH
OH
O
O
R
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl Cl Cl
Cl
Cl
Cl
S
S
O 2 N
N(CH 3 ) 2
CH 2
(CO) 3 Fe
N
N
Fe
Noyori (1982)
Iwamura (1983)
Nakazaki (1983)
Nozoe (1984)
(1985)
Yamamoto (1984)
Harada (1985)
Tajiri (1983)
Hatano (1985)
Yamamoto (1985)
Matsumoto (1985)
Yoshifuji (1986)
Tokuma (1987)
Clark (1987)
Mislow (1989)
Vecchi (1990)
Rapopport (1992)
Irurre (1995)
Mislow (1984)
Feringa (1994)
Feringa (1997)
Aida (2003)
Fig. 7 Compounds resolved on poly(triphenylmethyl methacrylate) PTrMA column
398
Y. Okamoto