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Threading Cyclodextrin Rings on Polymer Chains.

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1 ; 412, 138062-63-2;4d, 138062-64-3;4e, 138062-65-4;4f, 138062-66-5;
4g,
138062-67-6;4h, 138062-68-7;ClCH,COCl, 79-04-9;CH3CH0, 75-07-0;
C,H,CHO, 123-38-6;C,H,CHO, 123-72-8;C,H,CHO, 110-62-3;
CH,NH,,
74-89-5;
C,H,NH,, 75-04-7;
C3H,NH,, 107-10-8;
proline acylase, 86352-21-8.
[l] P. A. Plattner, U. Nager, Helv. Chim. Acro 1948,31,665-671;J. C . Sheehan, H. G. Zachau, W. B. Lawson, J Am. Chem. Soc. 1957, 79, 39333934;ibid. 1958,80,3349-3355;H. Vanderhaeghe, G. Parmentier, ihid.
1960,82,4414-4422;
E W. Eastwood. B. K. Snell, A. Todd, .IChem. Soc.
1960,2286-2292;H. Brockmann, Angew. Chrm. 1960,72,939-947;J.4.
Shoji, K. Tori, H. Otsuka, .I Org. Chem. 1965, 30. 2772-2776; H.
Kleinkauf, H. von Dohren in Regularion of Srcondary Metabolite Formuifon (Eds.: H. Kleinkauf, H. von Dohren, H. Dornauer. G. Nesemann),
VCH. Weinheim, 1986,p. 173-207,and references cited therein.
[2] T. Hoshino, Justus Liebigs Ann. Chem. 1935,520, 31 -34.
[3] K. A. Schellenherg, J. Org. Chem. 1963.28,3259-3261; P.Quitt, J. Hellerbach, K. Vogler, Helv. Chim. Acru 1963,46, 327-333;M. Ebdta, Y Tdkahashi, H. Otsuka, Bull. Chem. Soc. Jprr. 1966,39,2535-2538.
141 W. Leuchtenherger, U. Plocker, Ullmanns Encykl. Ind. Chem. 5 . Aufl.
1985-1990,Band A9, p. 423-429,and references cited therein; W. Leuchtenberger, U. Plocker, Chem. Ing. Tech. 1988, 60,16-23,and references
cited therein.
I S ] J. Kdmphuis, W. H. J. Boesten, Q. B. Broxterman, H. F. M. Hermes,
J. A. M. van Balken, E. M. Meijer, H. E. Shoemaker, Adv. Biochem. Eng.
Biotechnol. 1990,42. 133-186,and references cited therein.
161 U. Groeger, K.Drauz, H. Klenk, Angew. Chem. 1990, 102, 428-429;
Angew. Chem. Inr. Ed. Engl. 1990. 29, 417-419, and references cited
therein.
[7] K. Drauz, U.Groeger. M. Schafer, H. Klenk, Chem.-Zrg. 1991, 115,97101.
[S] S. M. Birnbaum, L. Levintow, R. B. Kingsley, J. P. Greenstein, J. B i d .
Chem. 1952,194,455-470;S.-C. J. Fu,S . M. Birnbaum, J. Am. Chem. Soc.
1953, 75, 918-920;H. K. Chenault, J. Dahmer, G. M. Whitesides, ibid.
1989. lil, 6354-6364;M.Sugie, H. Suzuki, Agric. Biol. Chem. 1980,44,
1089-1095;S. Kang, Y Minematsu, Y Shimohigashi, M. Waki, N. Izumiya. Mem. Fat. Sei. Kyushu Univ. Ser. C16 1987,61-68.
acid (N-CIAc-L-pipecolicacid)
[9] Whereas N-C1Ac-~-piperidine-2-carboxylic
is a good substrate, N-C1Ac-piperidine, N-C1Ac-piperidine-3-carboxylic
acid, and N-ClAc-piperidine-4-carhoxylicacid are not hydrolyzed.
[lo] A. Yaron, D. Mlynar, Biochem. Biophy.7. Res. Commun. 1968. 32, 658663.
of many cyclodextrin rings on a polymer chain has never
been unequivocally proven.
We report here the first threading of cyclodextrin rings on
poly(iminooligomethy1ene)s. Since the resulting polymeric
inclusion compounds are highly soluble in water, the kinetics
of the threading and unthreading could be examined for the
first time. The structure of these polymeric inclusion compounds could be clearly proven by their conversion to polyrotaxane~.[~I
Poly(iminoundecamethy1ene) 2 a and poly(iminotrimethylene-iminodecamethylene) 2 b were obtained in almost
quantitative yields by reductions of poly( 11-undecaneamide)
and poly(trimethy1enedecanediamide) with BH, . Me$.@]
Polymers 2 a and 2b are soluble in water at pH values < 6.
No indication of aggregation was observed for solutions
with sufficient ion strength.L71The degree of polymerization
for 2 a was P,, = 43 j,5 (number average); for 2b, P,,=
23 rf: 2 and P, = 60 & 12 (weight average).[*]
2a k=l=ll
2b k=10. 1=3
The reactions of the polymeric guest molecules 2 a and 2 b
with hosts 1a and heptakis(2,6-di-O-methyl)-~-cyclodextrin
(1 c) were conducted under homogeneous conditions['] and
could thus be followed by 'H NMR spectroscopy and viscometry. The 'H NMR spectrum of a mixture of l a and
2aL7] differs distinctly from the spectra of the individual
components (Fig. 1 a-c). The signal at 6 = 3.95 attributed to
Threading Cyclodextrin Rings on Polymer
Chains""
By Gerhard Wenz* and Bruno Keller
The ability of cyclodextrins like a-cyclodextrin (1 a) and
a-cyclodextrin (1 b) to include smaller guest molecules has
been the subject of numerous investigations['l since
Cramer's extensive work in this area.rZ1Depending on its
ring size, a cyclodextrin molecule has room for one or two
guest molecules;[31if the guest is long enough, one or two
cyclodextrin rings may be threaded along it.[41The stringing
4
la n=6, R=H
lb n=7, R=H
lc n=7, R=Me
[*) Dr. G. Wenz, DipLChem. B. Keller
[**I
Max-Planck-Institut fur Polymerforschung
Ackermannweg 10,D-W-6500Mainz 1 (FRG)
This research was supported by the Bundesminister fur Forschung und
Technologie (BE0 0319055A), Henkel KGaA, and Wacker-Chemie
GmbH. We thank B. Muller for the light-scattering measurements, A.
Kuhn for GPC measurements, and Prof. Dr. G. Wegner for helpful discussions.
Angew. Chem. I n f . Ed. Engl. 31 (1992) No. 2
0 VCH
5
t
I
L
1
3
I
I
2
I
I
1
-6
Fig 1. Part of the 'H NMR spectra at 20" for a) la, b) 2a,c) 45 mM l a +
45 mM 2a after 5 min. d) 45 mM 1 a + 45 mM 2a after 3.5 h, e) 4a[7]:
W = water, Ac = acetate.
Verlagsgesellschafr mbH, W-6940 Weinheim, 1992
0570-0833/92j0202-0197
$3.50+ ,2510
197
a hydrogen in the cavity (H-3) vanishes, while a new signal
at 6 = 3.85 arises. Similarly the signal of H-1 is shifted from
6 = 5.04 to 6 = 5.08. This shift could be attributed to conformational changes in 1 a upon inclusion. In addition, new
signals at 6 = 3.10,1.75, and 1.50 show up and are attributed
to included 2a (H-a', H - b , and H-c', respectively).
The observed downfield shifts of 'H NMR signals of the
guest molecule upon inclusion are not u n u ~ u a l . [It~ lis more
surprising that the chemical shifts of these new signals do not
depend on the concentrations of 1 a and 2a. In general the
inclusion of low-molecular-weight guests is revealed by the
continuous shift of the signals of one component upon variation of the concentration of the other due to signal averaging.l'O1Since this averaged signal is not seen in the reaction
of 1 a with 2a, the individual inclusion steps must be slow on
the NMR time scale. Averaged NMR signals were also not
observed for the inclusion of a,o-bis(1-pyridinium)alkanes
in 1a. This was attributed to the steric hindrance of the bulky
cationic end-groups.lgl In our case the cationic ammonium
groups (at pH 4.6) apparently also present steric barriers for
the host molecules. Even more surprising is the change in the
'H NMR spectra of 1 a with 2a or 2b over time. The spectrum of the system 1 a + 2 a is stable after 1.5 h (Fig. 1d);["]
that of 1 a + Zb, after 170 h.
Viscosity measurement~~'~
also provide support for the
slow equilibration (Fig. 2). System 1 a + 2 a has a constant
viscosity after 2 h;r''l l a + 2b, after 210 h. In comparison,
the reaction of the larger host 1 c with 2 a or 2 b is complete
after the mere mixing of the components.
la2a
laZb
4a k = l = l l , z=0.025, y=O.lO
4b k=10, 1=3. z=0.25, y=0.67
Scheme 1
equilibrium reaction analogous to the formation of monomeric ones. Thus the continuous removal of l a from the
equilibrium mixture should lead to the dissociation of
1 a . 2 a and 1 a 2 b. In order to observe this dissociation we
The
removed 1 a from the equilibrium mixture by
total concentration of cyclodextrin was determined by optical rotation measurements (Fig. 3). Although the dialysis of
free 1 a was complete after 1.3 h,[I3]the dialysis of the equilibrium mixture of 1 a ' 2 a proceeded much more slowly after a fast initial period. This fast rate at the onset is due to
excess 1 a, the slow progression thereafter, due to the slow
dissociation of 1 a . 2a. The unthreading of all the rings takes
15 h for 1 a . 2a;[I31 this process is far from complete after
two weeks for 1 a . 2 b.
R.
t
0'25
0.200.0
0.5
1.0
1.5
2.0
2.5
t [hl
b
o*]
0 .o 0
5
15
10
t [hl
OL9
50
-
150
100
f
IU
200
Fig. 2. Specific viscosity qSpat 25" for a) 11.8 mM 1 a
9.5 mM 1 a + 9.5 mM 2 b as a function of time t .
250
+ 11.8 mM 2 a and b)
The extremely long reaction times of l a with 2 a and 2b
implies a mode of inclusion in which the rings are strung on
the polymer chain, since each individual ring molecule must
find a chain end in order to be threaded. Once strung along
the polymer chain the rings must move towards the middle
of the chain to make room for the next rings.
The formation of the polymeric inclusion compounds
I a . 2a and 1 a . 2b according to Scheme 1 should be an
198
25
-
Fig. 3. Dialysis experiments[l2]: Optical rotation a as a function of time I for
a) 11.8 mM I a, b) the polymeric inclusion compound 1a . 2 a from 23 mM 1 a
and 15.4mM 2a, and c) the crude polyrotaxane 4 a from 23 mM I a and
15.4 mM 2 a after reaction with nicotinoyl chloride.
t
0.184
0
20
(G) VCH VerluggeseNschaft mbH. W-694U Weinheim, 1992
The low rates of formation and dissociation of these polymeric inclusion compounds and the marked dependence on
the structures of the host and guest molecules may be indications for the threading but do not provide conclusive proof.
Complex equilibria could also exist for nonspecific aggregates of host and guest molecules. By closing the polymer
chain, however, one should be able to differentiate between
the threaded and aggregated host molecules. Threaded rings
become permanently bound upon closure of the chain; rings
simply attached along the chain do not.
To completely close a polymeric inclusion compound, two
bulky substituents must be attached to the ends of the chain.
The attachment of at least two "blocking groups" at arbitrary positions on the chain would prevent unthreading
0570-0A'33j92j0202-0198 3 3.50+ ,2510
Angew. Chem. Inr. Ed. Engl. 31 (1992) No. 2
along a part of the chain and would be much easier to carry
out. The nicotinoyl group was chosen as a blocking group
since it is sufficiently hydrophilic. After the reaction of
nicotinoyl chloride. HCI 3 with 1 a . 2b the reaction mixture
was dialyzed. The optical rotation of the mixture did not
approach zero but rather stabilized at 0.065 (Fig. 3). Thus
permanently bound a-cyclodextrin is present in product 4 a.
The integration of the signals of the 'H NMR spectrum of
4a (Fig. 3 d) indicates a concentration of 10 mol YUcyclodextrin and 2.5 mol% nicotinoyl groups. The absence of the
signal at 6 = 5.04 indicates that all the a-cyclodextrin units
are threaded. All the cyclodextrin signals are sharp and identical to those of 1 a . 2 a. Since the structure of these rings is
retained and since the rings are bound permanently, we believe that 4a is a polyrotaxane.
Only those rings on the chain between the two blocking
groups remain threaded. The probability of finding at least
two blocking groups on one chain increases with the conversion x of the blocking reaction. Thus the relative amount y
of permanently bound rings should increase with x. This is
the case. From the reaction of l a 2b with 3 polyrotaxane
4b is obtained in 43% yield with x = 25 mol% blocking
groups and y = 67 mol% cyclodextrin rings per basic unit.
The molecular mass of 4b"I M , = 55000 & 5000 gmol-'
was found by light scattering; this corresponds to a degree of
polymerization P, = 55 & 5, in good agreement with that of
2b (P,, = 60 &12). Thus 37 cyclodextrin rings are permanently threaded in 4b. By this synthesis of polyrotaxanes 4a
and 4 b we demonstrate not only the threading of rings 1 a on
the chains 2a and 2 b but also a promising new approach to
polyrotaxanes.
Experimental Procedure
2 a : Reprecipitated[h] Nylon 1 1 (6.0 g, 32.8 mmol, Aldrich) was suspended in
dry THF (100 mL) and heated to reflux under inert gas. A 2 M solution of
BH, . Me,S in TH F (55 mL, 110 mmol, Aldrich) was added dropwise over 1 h.
The reaction mixture was heated 1 d at reflux. The THF was distilled off, water
(100 mL) added, and the mixture heated at reflux 1 h. The reaction mixture was
allowed to cool to 20" and glacial acetic acid (60 mL) was added. The mixture
was stirred 1 h at room temperature and heated 3 h at reflux. The cooled
solution was added dropwise to a 10% NaOH solution (2 L). The precipitate
was removed by filtration, washed with water, dried in vacuum, and extracted
with CHCI, in a Soxhlet apparatus. The extract was added dropwise to diethyl
ether (1 L). Polymer 2a precipitated and was filtered and dried in vacuum.
Yield 5.2 g (94%), white powder, m.p. = 108 '; Elemental analysis : C 78.03, H
13.56, N 8.38;calculated forC,,H2,N:C78.03,H 13.69.N8.27;Viscometry[7]
(using Huggins' plot of the specific viscosity): [q] = 91.7 mLg-', k , = 0.28;
' H NMR (300 MHz, HOD)[7]: 6 =1.29 (m. 14H; H-c to H-f), 1.65 (m, 4 H ;
H-h), 3.00 (t. '4H.H) =7.8 Hz, 4H; H-a); "C NMR (75.46 MHz, CDCI,
TMS): 6 = 27.4 (C-c), 29.6 (C-d, e, f), 30.2 (C-b), 50.2 (C-a); 1R (CHCI,-film)
V [cm-']= 3273 (N-H), 2920 (C-H), 1463 (C-H), 1128 (C-N).
2b: Poly(trimethylenedecanediamide)[l4] (6.0 g) was converted to 2b in an
analogous manner to the preparation of 2 a from Nylon 11. Yield 5.04 g (95 %),
white powder, m.p. = 86°C; Elemental analysis C 73.40, H 13.05, N 12.91,
calculated for C,,H,,N: C 73.52, H 13.29, N 13.19; Viscometry (see 2a):
[q] = 81.8 m Lg- ', k , = 0.18; 'H NMR(HOD)[7]: 6 =1.30 (m, 12H; H-c bis
H-e). 1.66 (m, 4 H ; H-b), 2.09 (m, 2H; H-B), 3.03 (t. 'J(H,H) =7.7 Hz, 4 H ;
H-a), 3.11 (t, 3J(H.H) =7.9Hz, 4H; H-A); "CNMR (CDCI,, TMS):
6 = 27.4 (C-c), 29.6 (C-d, e), 30.2 (C-b), 30.5 (C-B), 48.6 (C-A), 50.2 (C-a); IR
(CHCI, film): i. [cm-'1 = 3260 (N-H), 2919 (C-H). 1467 (C-H), 1129 (C-N).
4a: Polymer 2a (0.13 g, 0.77 mmol) and 1 a (1.12 g, 1.16 mmol) were dissolved
in huffer(71 (20 mL). The solution was stirred at 20" for 24 h. The pH of the
solution was adjusted to 6.3 with NaHCO,, and 3 (0.286 g, 1.6 mmol, Aldrich)
was added in small portions. During this addition the pH of the solution was
held between 5.7 and 6.4 by further addition of NaHCO,. After 16 h the
solution was diluted to 50 mL and dialyzed with 2% acetic acid (24 h) until
the optical rotation remained constant and with water (2 h) [12]. The product
was then freeze-dried. Yield: 0.148 g (71 %), white solid; Elemental
analysis: C 63.23, H 10.38, N 4.99, calculated for (C,,H,,N),(C,,H,o03,),,,(C,H,NO),,,,(C,H,O),,,:
C 63.21. H 10.47, N 4.80; 1H NMR (HOD)[7]:
6 = 1.30(m, 13.6H; H-c to H-f), 1.50(m,0.4H; H-c'), 1.65 (m, 3.6H; H-b), 1.75
(m,0.4H;H-b),1.95(~,1.5H;acetate),3.00(t,'J(H,H)
=7.7Hz,3.6H;H-a),
3.10 (m. 0.4 H ; H-a'), 3.67 (m. 1.ZH; H-2', H - 4 ) , 3.85 (m, 1.8H; H-3'. H-S,
H-6'), 5.09 (m, 0.6H; H-l'), 7.6, 8.0, 8.6 (3m, 0.1H; nic.).
Angew Chem. Inl. Ed. Engl. 31 (1992) No. 2
0 VCH
4b: Polymer 2b (0.29 g, 1.37 mmol) and cyclodextrin 1 a (4 g, 4.1 mmol) were
added to a buffer solution[7] (20 mL) and stirred at 20" for 14 d. Compound 3
(0.79 g, 4.4 mmol) was added in small portions and the pH of the solution was
maintained between 5 and 7 by addition of 5 M KOH. After 16 h the reaction
was worked up analogously to that leading to 4a. Yield: 0.565 g (43%). white
solid; Elemental analysis C48.94, H 7.43, N 3.11, calculated for (C,,HZ8N2),(C36H60030)o
,,(C,H,NO), 25(C6HdO),: C 50.65%, H 7.70%. N 3.12%;
'H NMR (HOD)[7]: 6 = 1.29, 1.50, 1.65, 1.75 (4m, 16H; H-b, H-c', H-b to
H-e), 1.95 (s, 6H; acetat). 2.08 (m, 2 H ; H-B), 3.00, 3.10 (2m, 5.6H; H-a. H-A,
H-a'),3.2-3.5(m,2H; -CH2-NR-C=O),3.67(m,SH;
H-2',H-4').3.86 (m.
12H; H-3', H-S, H-61, 5.09 (m. 4 H ; H-l'), 7.60 (m, 0.25H; nic.), 7.95 (m,
0.25H; nic.), 8.62 (m, 0.5H; nic.). nic. = nicotinoyl.
Received: August 14, 1991 [Z48721E]
German version: Angew. Chem. 1992, 104, 201
[l] Review: J. Szejtli, Cyclodexfrin Technology in Topics i n Inclusion Science
(Ed.: J. E. D. Davies), Kluwer, Dordrecht, 1988.
[2] F. Cramer, Chem. Ber. 1951,84,851-854; F. Cramer, F. M. Henglein, rbid.
1957, 90, 2567-71 ; F. Cramer, Einschluaverhindungen, 1st ed., Springer,
Heidelberg, 1954, pp. 1 - 113 .
[3] O.S. Tee, M. Bozzi, J. Am. Chem. SOC.1990, 112, 7815-7816; H.-J.
Schneider, N. K. Sangwan, Angew. Chem. 1987, 99, 924-925; Angebc.
Chem. Int. Ed. Engl. 1987, 26, 896.
[4] R. I. Gelb, L. M. Schwartz, D. A. Laufer, J. Am. Chem. Soc. 1978, 100,
5875-5879; B. Klingert, G. Rihs, Organometallics 1990, 9, 1135-1141.
[5] Several syntheses of rotaxanes: First synthesis of a rotaxane: I. T. Harrison, S. Harrison, J; Am. Chem. Soc. 1967, 89, 5723-5724. Main-chain
polyrotaxanes: N. Ogata, K. Sanui, J. Wada, J; Po/vm. Sci. Po/Fm. Left.
Ed. 1976, 14, 459-62; H. W. Gibson, P. Engen, P. Lecavalier. Polym.
Prepr. ( A m . Chem. Sor. Div. Pol.vm. Chem.) 1988, 29, 248-9. Side-chain
polyrotaxanes: M. Born, H. Ritter, Makromol. Chem. Rapid. Commun.
1991, 12,471-476.
[6] Analogous to T. Perner, R. C. Schulz, Br. P d y m . J. 1987, 19, 181-188.
[7] Solvent: 0.1 M sodium acetate buffer, pH = 4.6.
[8] P, was determined by vapor pressure osmometry (Knauer) in CHCI,. Pw
by gel permeation chromatography (columns: TSKGPW from Toyo Soda)
with 0.5 M sodium acetate bufferiacetonitrile 80/20 (v/v).
[9] H. Saito, H. Yonemura, H. Nakamura, T. Matsuo, Chem. Leff. 1990,
535-538.
[lo] D. J. Wood, F. E. Hruska, W. Saenger, J. Am. Chrm. Sor. 1977.99. 173540.
[ll] The height of the signal reached >95% of the final height.
[12] The dialysis was carried out at 20" in 2 % acetic acid with a hollow fiber
membrane module (Reichelt, Thomapor LD-OC02). The polymer solution
(50 mL) was circulated with a peristaltic pump (flow rate 8.5 mLmin-I).
The optical rotation was measured continuously with a polarimeter (Polarmonitor IBZ-Messtechnik, Braunschweig); drift < 0.002"per day.
[13] The cyclodextrin concentration is reduced to t 5 % of the starting concentration.
[14] Synthesis analogous to W. R. Ssrenson. J. Chem. Educ. 1965,42. 8-12.
Selectivity Control By Temperature Variation
in the Formation of Lsotactic vs. Syndiotactic
Polypropylene with a Titanocene/Alurnoxane
Catalyst**
By Gerhard Erker* and Cornelia Fritze
The syndioselective polymerization of a-olefins with vanadium catalysts probably proceeds by a different mechanism
(2-1 insertion) than with Ziegler
A few homogeneous catalyst systems based on the group 4 metallocenes,
which direct the usual mode of polymerization (1-2 insertion), have led to the production of syndiotactic polypropylene as
In the past the few exceptional cases of syn[*I Prof. Dr. G. Erker, DipLChem. c. Fritze
Organisch-Chemisches lnstitut der Universitat
Corrensstrasse 40, D-W-4400 Munster (FRG)
[**I This work was supported by the Fonds der Chemischen Insdustrie, the
Alfred-Krupp-von-Bohlen-und-Halbach
Stiftung, and the Bundesminister
fur Forschung und Technologie.
Verlagsgesellschafi mbH. W-6940 Weinheim, 1992
0570-0833/92/0202-0199$3.50+.25/0
199
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