COMMUNICATIONS
10 min, then acetonitrile:iPrOH (1:1) (100%) for 5 min, then acetonitri-
le:iPrOH (1:1) (100%) !acetonitrile:1% NH4OAc(aq) (1:1) (100%) in
2 min). A diode array detector was used for the detection. Rt 10.39 (2),
Rt 12.05 (9), Rt 12.20 min (10). In all reactions, carotenoids 1 (Rt
14.0 min) and 8 (Rt 15.3 min) were completly consumed after 24 h.
released from the receptor, are then extracted into the organic
phase, aliquots of which were subjected to HPLC conditions
developed for the analysis of carotene dioxygenase enzyme
studies.[15] The reaction products were identified by retention
time (co-injection with authentic samples) and by their UV
spectra; external calibration curves were used for the
quantification. The ratio of reaction products is given in
Scheme 3.
Received: November 11, 1999 [Z14254]
[1] J. A. Olson, N. I. Krinsky, FASEB J. 1995, 9, 1547 ± 1550, and
references therein.
[2] X.-D. Wang, G.-W. Tang, J. G. Fox, N. I. Krinsky, R. M. Russel, Arch.
Biochem. Biophys. 1995, 285, 8 ± 16.
It is evident that 1 is not only cleaved at the central double
bond but also at C(12') C(11') to give 12'-apocarotenal 9 and
at C(10') C(9') to give 10'-apocarotenal 10. The combined
[3] J. A. Olson, J. Nutr. 1989, 119, 105 ± 108.
yield of aldehydes 2, 9, and 10 was 30%, which compares well
with the efficiency of b,b-carotene 15,15' dioxgenase which
gives retinal 2 in 20 ± 25%.[4] Most interestingly, the double
bond in closest proximity to the central one in 1,
[4] G. Wirtz, PhD Thesis, Universität Basel (Switzerland), 1998.
[5] G. Wirtz, A. Giger, R. K. Müller, H. Schneider, W.-D. Woggon,
unpublished results.
[6] R. R. French, W.-D. Woggon, J. Wirz, Helv. Chim. Acta. 1998, 81,
1521 ± 1527.
C(14') C(13'), remains untouched. We postulated that this
[7] Q.-X. Guo, T. Ren, Y.-P. Fang, Y.-C. Liu, J. Incl. Phenom. Mol. Recog.
Chem. 1995, 22, 251 ± 256.
phenomenon is related to interactions between the end-
groups of 1 and the cyclodextrin moieties, such that a lateral
movement of 1 within the binding pocket exposes only three
[8] S. Takagi, T. K. Miyamoto, Inorg. Chim. Acta. 1990, 173, 215 ± 221.
[9] R. R. French, P. Holzer, W.-D. Woggon, unpublished results.
[10] J. T. Groves, T. E. Nemo, J. Am. Chem. Soc. 1983, 105, 5786 ± 5791.
[11] E. N. Jacobsen in Comprehensive Organometallic Chemistry II, Vol. 12
(Eds.: G. W. Wilkinson, F. G. A. Stone, E. W. Abel, L. S. Hegadus),
Pergamon, New York, 1995, chap. 11.1.
double bonds to the reactive Ru O group (Figure 1b). If this
hypothesis is true, one would expect a carotenoid with one
modified end-group to demonstrate a different selectivity in
double-bond cleavage. Accordingly, we investigated the
oxidation of synthetic carotenoid 8,[16] a substrate of the
native enzyme,[17] under identical conditions. The selectivity
[12] C.-J. Liu, W.-Y. Yu, C.-M. Che, C.-H. Yeung, J. Org. Chem. 1999, 64,
7365 ± 7374.
[13] 6A-O-(p-Tosyl)-b-cyclodextrin was obtained from Cyclodextrin Tech-
nologies Development, Inc., Gainsville, FL 32068, USA.
[14] The free-base ªtransº-porphyrin could be isolated by column chro-
matography (silica gel, chloroform 1% ethanol) from a mixture of
six porphyrins obtained after porphyrin condensation and subsequent
O-deprotection. For physical data for 4, see Experimental Section.
[15] G. Wirtz, C. Bornemann, W.-D. Woggon, Autumn meeting of the
Society for Biochemistry and Molecularbiology, Jena, Germany, 1998.
[16] M. G. Leuenberger, PhD Thesis in preparation, Universität Basel
(Switzerland).
for C(15) C(15') cleavage is almost exclusive when one of the
cyclohexene end-groups of b,b-carotene 1 is replaced by an
ortho-dimethylphenyl group, supporting the relationship
between substrate mobility and selectivity. This suggests that
stronger hydrophobic interactions between the aromatic end-
group of 8 and the b-cyclodextrin cavity are responsible for
stabilizing the 1:1 inclusion complex with the central double
bond under the reactive ruthenium center.
[17] C. Bornemann, M. G. Leuenberger, W.-D. Woggon, unpublished
results.
We have demonstrated the selective cleavage of carote-
noids to provide retinal 2 with a supramoleclular enzyme
mimic which shows an unusual reactivity towards olefins in
the presence of TBHP. Work is currently underway to mimic
the reactivity and selectivity of the enzymes responsible for
excentric cleavage of b,b-carotene 1.[18]
[18] P. Holzer, PhD Thesis in preparation, Universität Basel (Switzerland).
The Spatial Demand of Dendrimers:
Deslipping of Rotaxanes**
Experimental Section
Physical data for 4. lmax 414 (100%), 534 (10%) 570 (4%); 1H NMR
(600 MHz, 258C, [D6]DMSO): d 8.61 (d, 4H, H-2,8,12,18, J 4.5 Hz),
8.56 (d, 4H, H-3,7,13,17, J 4.5 Hz), 8.06 (m, 4H, H-2'',6''), 7.94 (m, 4H,
H-3'',5''), 7.58 (m, 4H, H-2',6'), 7.33 (m, 4H, H-3',5'), 5.9 ± 5.6 (br. m, 28H,
2OH), 5.0 ± 4.8 (m, 14H, anomeric H), 4.7 ± 4.4 (m, 12H, 1OH), 3.8 ± 3.25
(m, 84H, b-CD (H-2,3,4,5,6,6')), 2.65 (s, 6H, ArCH3); MALDI-TOF-MS:
Gosia M. Hübner, Guido Nachtsheim, Qian Yi Li,
Christian Seel, and Fritz Vögtle*
Dendrimers are generally not rigid molecules because of
the flexibility of their building blocks,[1] and this makes it
difficult to compare their size with that of voluminous, but
rather rigid ªconventionalº molecules. Recently we described
the effect of slight changes in the size of wheels and stoppers
m/z: 3007 [M ], 3024 [MH2O]; HPLC (LiChrospher 100Rp-18 (5 mm),
250-4) Rt 9.43 min (20 ± 60% acetonitrile in 20 min, flow 1.5 mLmin 1).
General procedure for cleavage reactions: A 25-mL round-bottomed flask
which had been purged with argon and fitted with an egg-shaped magnetic
stir bar was charged with a solution of dimer 4 (2.3 mg, 10 Mol-%) in H2O
(1 mL). TBHP (30 mL of a 70% solution in water, 30 equiv with respect to
1) was added. b,b-Carotene 1 (4 mg) was dissolved in hexane/chloroform
(9/1; 10 mL) and added to the reaction flask to produce a biphasic system.
The reaction system was closed and stirred vigorously to ensure good
mixing of the two phases. At different times during the reaction, stirring
was stopped to allow phase separation. Aliquots (20 mL) of the organic
phase were taken and subjected to HPLC analysis (LiChrospher 100 Rp-18
5 mm, length  ID 125 mm  4.6 mm, 258C, 1 mLmin 1, gradient: aceto-
nitrile:1% NH4OAc(aq) (1:1) (100%) !acetonitrile:iPrOH (1:1) (100%) in
[*] Prof. Dr. F. Vögtle, Dipl.-Chem. G. M. Hübner, Dr. G. Nachtsheim,
Dipl.-Chem. Q. Y. Li, Dr. C. Seel
Â
Kekule-Institut für Organische Chemie und Biochemie der Universität
Gerhard-Domagk-Strasse 1, 53121 Bonn (Germany)
Fax: (49)228-735662
[**] We thank Dr. S. Höger, MPI für Polymerforschung, Mainz, for
discussions. This work was supported by the Deutsche Forschungsge-
meinschaft (Vo 145/47-1).
Angew. Chem. Int. Ed. 2000, 39, No. 7
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