formed by CD derivatives with substituents sensitive to
light or heat have yet to be reported. Herein we report
pseudo-rotaxanes formed by 6-stilbene-amide-R-CD (6-
StiNH-R-CD) and an alkyl chain with pyridinium end caps
(Figure 1) where threading of the axle into the cavity of
6-StiNH-R-CD is controlled by light.
The axle molecule (Py2Dec) and trans-6-StiNH-R-CD
were prepared according to the previously reported
methods.13a,16 Stilbene derivatives show photoinduced
isomerization; irradiating with UV and visible light in-
duces isomerization from trans to cis and from cis to trans,
respectively.17 After photoirradiation with visible light
(λ = 340 nm), 92% of trans-6-StiNH-R-CD was isomer-
ized to cis-6-StiNH-R-CD (trans/cis = 8:92). However, the
trans form was recovered by irradiating at λ = 254 nm.
Figure 1. (a) Chemical structures of 6-StiNH-R-CD and Py2Dec
as an axis molecule. (b) Photoisomerization of 6-StiNH-R-CD.
blocks have been achieved by controlling the rotary
movement.9À12 We have previously reported that the
direction of the faces of R-CD by the terminal group of
the axle molecule controls the linear movement of
R-cyclodextrin (R-CD) on pseudo[2]rotaxane with dicatio-
nic axle molecules.13a,b Upon complexation of modified
R-CDs as host molecules for guest molecules consisting of
an alkyl chain with pyridinium end caps, we have con-
trolled complex formation and dissociation by pH re-
sponses of the functional groups on modified R-CDs.13c
Although numerous types of CD-based pseudo-rotaxanes
and rotaxanes have been prepared in the past two decades,14
there are few reports on the threadingÀdethreading of CD-
based pseudo-rotaxanes.15 Moreover, pseudo-rotaxanes
(9) Shukla, R.; Deetz, M. J.; Smith, B. D. Chem. Commun. 2000,
2397.
(10) (a) Koumura, N.; Zijlstra, R. W. J.; Delden, R. A. van; Harada,
N.; Feringa, B. L. Nature 1999, 401, 152. (b) Koumura, N.; Geertsema,
E. M.; Meetsma, A.; Feringa, B. L. J. Am. Chem. Soc. 2000, 122, 12005.
(c) Feringa, B. L. Acc. Chem. Res. 2001, 34, 504.
Figure 2. Partial 1H NMR of Py2Dec (4.0 mM) (a) in the absence
of 6-StiNH-R-CD, (b) in the presence of trans-6-StiNH-R-CD
(4.0 mM), and (c) in the presence of cis-6-StiNH-R-CD in D2O
(4.0 mM) at 30 °C.
(11) (a) Kelly, T. R.; De Silva, H.; Silva, R. A. Nature 1999, 401, 150.
(b) Kelly, T. R.; Silva, R. A.; De Silva, H.; Jasmin, S.; Zhao, Y. J. Am.
Chem. Soc. 2000, 122, 6935. (c) Kelly, T. R. Acc. Chem. Res. 2001, 34,
514.
Based on the isomerization of 6-StiNH-R-CD des-
cribed above, Py2Dec was mixed with trans-6-StiNH-R-
CD or cis-6-StiNH-R-CD at room temperature. 1H
NMR spectroscopy in D2O monitored the formation of
pseudo-rotaxanes. These 6-StiNH-R-CDs were isolated
by preparative reversed phase HPLC. Figure 2 shows
the partial H NMR spectra of Py2Dec, Py2Dec/trans-6-
StiNH-R-CD, and Py2Dec/cis-6-StiNH-R-CD. After 10 min,
equilibrium of the complexation was reached. Mixing
(12) (a) Leigh, D. A.; Wong, J. K. Y.; Dehez, F.; Zerbetto, F. Nature
2003, 424, 174. (b) Bottari, G.; Dehez, F.; Leigh, D. A.; Nash, P. J.;
Perez, E. M.; Wong, J. K. Y.; Zerbetto, F. Angew. Chem., Int. Ed. 2003,
42, 5886. (c) Hannam, J. S.; Lacy, S. M.; Leigh, D. A.; Saiz, C. G.;
Slawin, A. M. Z.; Stitchell, S. G. Angew. Chem., Int. Ed. 2004, 43, 3260.
(13) (a) Oshikiri, T.; Takashima, Y.; Yamaguchi, H.; Harada, A.
J. Am. Chem. Soc. 2005, 127, 12186. (b) Oshikiri, T.; Takashima, Y.;
Yamaguchi, H.; Harada, A. Chem.;Eur. J. 2007, 13, 7091. (c) Omori,
K.; Takashima, Y.; Yamaguchi, H.; Harada, A. Chem. Lett. 2011, 40,
758.
1
(14) (a) Nepogodiev, S. A.; Stoddart, J. F. Chem. Rev. 1998, 98, 1959.
(b) Harada, A. Acc. Chem. Res. 2001, 34, 456. (c) Wenz, G.; Han, B.-H.;
Muller, A. Chem. Rev. 2006, 106, 782. (d) Harada, A.; Hashidzume, A.;
Yamaguchi, H.; Takashima, Y. Chem. Rev. 2009, 109, 5974.
(15) (a) Mirzoian, A.; Kaifer, A. E. Chem.;Eur. J. 1997, 3, 1052. (b)
Mirzoian, A.; Kaifer, A. E. Chem. Commun. 1999, 1603.
(16) Nishimura, D.; Oshikiri, T.; Takashima, Y.; Hashidzume, A.;
Yamaguchi, H.; Harada, A. J. Org. Chem. 2008, 73, 2496.
(17) (a) Irie, M. Chem. Rev. 1999, 100, 1685. (b) Takeshita, K.; Irie,
M. J. Org. Chem. 1998, 63, 6643. (c) Takeshita, K.; Irie, M. J. Chem.
Soc., Chem. Commun. 1996, 1807.
Org. Lett., Vol. 13, No. 16, 2011
4357