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New Chiral PorphyrinsЧSyntheses and Molecular Recognition of Amino Acid Esters.

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Casanova. G. A. Olah. J. A m . Chem. Suc. 1992. 114. 3076; H.-U. Siehl.
F.-P. Kaufmdnn, ibid. 1992. 114, 4937.
[6] R. A. Cox. K. Yates. J. A m . Chem. Suc. 1978. 100, 3861. R. A. Cox, Acc.
(%cw?. Res. 1987. 20. 27.
[7] R. A. Cox, K. Yates, Can. J. Chem. 1981, 59. 2116; A. J. Kresge, H. J.
Chen. G. L. Capen, M . F. Powell. b i d , 1983, 61, 249.
[XI J. R. Keeffe, A. J. Kresge in Techniqueso/Chemis[ry, Vul. V I Investrgulion
of Rules und Mechanisms of Reuctions, 4th ed. (Ed. C. F. Bernasconi).
Wiley. New York, 1986. Part 1. Chapter XI.
[9] a ) W. Drenth. H. Hogeveen, R e d . Truv. Chim. Puys-Bus 1960, 79, 1002;
E. J. Stamhuts. W. Drenth, ihid. 1963. 82, 385; D. S. Noyce. M. A.
Matesich, M. D. Schtavelli, P. E. Peterson, J. A m . CArm. Suc. 1965. 87,
2295: D. S . Noyce. M. D. Schiavelli, ibid. 1968. 90. 1023. b) N. Banait, M.
Hojatti. P. Findlay, A. J. Kresge. Cun. J. Chem. 1987, 65, 441.
[lo] R. W. Bott, C. Eaborn. D. R. M. Walton, J. Chen?.SOC.1965, 384; D. S .
Noyce. M. D. Schiavelli, J. A m . Chem. So(,. 1968, 90, 1020.
[ l l ] Y. Lucchini, G. Modend, J. Am. Chrm. Sor. 1990. 112, 6291.
I121 A. J. Kresge. J. B. Tobin. J. P / i n . Org. Chem. 1991, 4. 587.
of these products is clearly demonstrated by their circular
dichroism (CD) spectra, which show completely symmetric
Cotton effects in the region of the Soret bands. The
analogous reaction with 4-nitroisophthaloyl chloride gave,
following chromatographic separation, meso-2 and 2/ent-2;
the enantiomers could be separated again by HPLC.14]
All compounds were characterized by 'H NMR spectroscopy and fast atom bombardment mass spectrometry
(FAB-MS).
In spite of the slight difference between the bridging positions of 1 (para) and 2 (mefa),the topological structures of
these porphyrins were expected to be quite different; the
angles between planes of the porphyrin and the bridging
benzene units in 1 and 2 are predicted by calculations to be
approximately 0" and 70-80", respectively (see Fig. 2).I5I
New Chiral Porphyrins-Syntheses and Molecular
Recognition of Amino Acid Esters
By Yasuhisu Kuroda,* Yusuke Kato, Takuji Higashioji,
and Hisanobu Ogoshi*
Synthetic chiral porphyrins have attracted much interest
as model compounds for the chiral environments of heme
proteins."' We report herein a new synthetic route to chiral
porphyrins and their chiral recognition behavior. Since the
required synthetic building blocks are achiral atropisomeric
tetraarylporphyrins with ortho-substituted phenyl groups
and simple bridging reagents, the route is suitable for the
preparation of a series of chiral porphyrins for the systematic
investigation of molecular recognition properties. Our synthetic scheme is based on the following strategy (Fig. 1).
e c
Fig. 2. Ball-and-stick molecular models of one each of the sets of enantiomers
lien!-1 (left) and 2/ent-2 (right) (see ref. [ 5 ] ) .
X = NH2
meso-1
l/ent-1
NO.
2 = CONH
CI
0
0
Fig. 1. Schematic representation of the synthesis of chiral porphyrins
When the a,a,P$ atropisomers of tetraarylporphyrins are
doubly bridged with an unsymmetric, difunctionalized
reagent, a mixture of a meso porphyrin and a pair of enantiomeric porphyrins with a C, symmetry axis parallel to the
porphyrin plane may result,['] which may be separated by
chromatography. For example, the reaction of a,a,P$tetrakis(orfho-aminophenyl) porphyrin with nitroterephthaloloyl chloride in T H F gave two doubly bridged porphyrins,
meso-1 and llent-1, which could be purified by silica gel
c h r ~ m a t o g r a p h yThe
.~~~
product with the larger R, value on
a silica gel TLC plate was further resolved into the enantiomers 1 and ent-1 on a chiral HPLC column. The chirality
[*] Prof. Dr. Y Kuroda. Prof. Dr. H. Ogoshi, Y. Kato, T. Higashioji
Department of Synthetic Chemistry
Kyoto University
Sakyo-ku. Kyoto 606 (Japan)
Telefdx: Int. code +(75)753-4979
Angew. Chem. I n / . Ed. Engl. 1993. 32, No. 5
We attempted to evaluate the chiral recognition abilities of
1 and 2 by determining the association constants of the adducts formed by their Zn complexes and amino acid methyl
esters.[61Titration experiments indicate that various types of
amino acid methyl esters form 1 :1 complexes with 1-Zn and
2-Zn (Table 1). The following interesting aspects of the molecular recognition are clear: a) coordination of the amino acid
to meso-1-Zn is hindered significantly compared with that to
TPP-Zn, by the benzene bridge; b) in contrast, meso-2-Zn
shows a high affinity for amino acids, while the affinity for
corresponding simple amines is low; c) the chiral porphyrins
2 and ent-2 show significant chiral recognition for amino
acids.
Upon complex formation, the 'H NMR signals of the protons of the amino acid ester exhibit upfield shifts that are
dependent on their distance from the amino group. For example, valine shows upfield shifts of A6 = 6.2, 2.2, 2.2, and
0.9 for C,-H, C,-H, CH, (iPr), and CH, (ester), respectively.
The electronic spectra of these Zn porphyrins also show a
clear redshift of the Soret bands (ca. 8 nm) upon addition of
the amino acid, while the corresponding uncomplexed porphyrins do not. These observations strongly indicate coordination of the amino group on the Zn atom. Comparison of
association constants for amino acids esters and the corresponding amines strongly indicates that the methoxycar-
Q VCH Vrrlug.~~esell.~cliuft
mhH. W-6940 Weinheim, I993
0570-0833i93i0505-0723$ 10.00f ,2510
723
Table 1 Association constants K, for the adducts of Zn porphyrin complexes and amino acld esters [a]
Substrate
meso-2-Zn
K, [M ’1 [bl
(+)-2-Zn [c]
8800 (300)
10000 (500)
14000 (500)
14000 (500)
7 000 (300)
2 800 (200)
5400 (500)
3900 (100)
2300 (200)
4100 (100)
2 200 (100)
2 300 (100)
4100 (100)
1 700 (100)
~
HCR~R*-NH,
TPP-Zn
R’ = C0,Me [dl
R2 = Ph
R2 = PhCH,
R‘ = 3,4-(OMe),C,H,CH,
R 2 = (CH,),CH
R‘ = H
R 2 = Ph
RZ = 3,4-(OMe),C,H,CH,
R’ = (CH,),CH
2 100 (100)
2600 (100)
2 500 (I 00)
2000 (100)
3700 (100)
13000 (500)
5 900 (200)
meso-1-Zn
-
900 (100)
1100 (100)
-
( - )-2-Zn [c]
11 000 (1 000)
15 000 ( 1000)
24000 (600)
22000 (800)
-
[a] I n CHCI,, at 15 ’C. [b] No statistical correction for the plane symmetry of ( + ) - Z and (-)-2 was applied. Standard deviations are given in parentheses. [c] Absolute
configurations of these enantiomeric porphyrins were not determined. The signs ( + ) and (-)are based on the CD spectra in the Soret region (see ref. [4]). [d] All amino
acids used in this work have L configuration
bony1 group participates in the attractive interaction between 2-Zn and the substrate. This attractive interaction is
best explained by a hydrogen bond between the carbonyl
oxygen atom of the amino acid ester and amide hydrogen
atom of 2-Zn; upon coordination of the amino group to the
Zn atom these two atoms are only 1.9 8, apart. This hydrogen bonding is confirmed by the observation in the ‘H N M R
titration experiments that two signals for amide N H protons
shift upon addition of valine methyl ester from 6 = 6.76/7.34
to 7.4517.65. Existence of the hydrogen bond is further supported by a result from preliminary IR spectroscopic measurements: upon addition of the amino acid, the N H stretching bond of the amide groups in 2/ent-2-Zn, originally
observed 3403 cm-’, shifts to 3305 cm-’; this can be explained by the formation of a NH . . .O hydrogen bond.”’
Since chiral recognition logically requires a t least a spatially oriented three-point interaction, the observed chiral recognition for amino acid esters suggests that there is a significant
difference between the hydrogen-bonding abilities of the two
amide groups at the 1- and 3-positions of the bridging benzene ring in 2/enr-2-Zn. Thus, the amino acid receptor 2lent2-Zn utilizes three kinds of interactions: coordination of the
Zn atom, hydrogen bonding, and steric repulsion. Interestingly, these three interactions correspond to three characteristic elements of amino acids: the amino group (coordination), the carboxyl group (hydrogen bonding), and the side
chain (steric repulsion).
The new synthetic route to chiral porphyrins reported here
is expected to be widely applicable for various structural
variations. Preliminary studies on chiral recognition show
that, in contrast with chiral crown ethers,[*] chiral porphyrins differentiate between neutral amino acid esters.
Received: October 13, 1992
Revised version: January 14, 1993 [Z 5622 IE]
German version: Angew. Chem. 1993, 105, 774
[ l ] a) J. T. Groves, R. S. Myers, J. Am. Chem. SOC. 1983, 105, 5791; b) D.
Mansuy, P. Battioni, J:P. Renaud, P. Guerin, J Chem. Soc. Chem. Com-
mun. 1985, 155; c) H. Ogoshi, K. Saita, K. Sakurai, T. Watanabe, H. Toi, Y.
Aoyama, Y. Okamoto. Tetrahedron Lett. 1986,27,6365; d) Y. Aoyama. K.
Saita, H. Toi. H. Ogoshi. Y. Okamoto. ihid. 1987,28,4853;e) B. Boitrel. A.
Lecas, E. Rose, J. Chem. Soc. Chem. Commun. 1989,349; f) S. O’Malley, T.
Kodadek, J. Am. Chem. Soc. 1989. 111,9116; g) K. Konishi, T. Sugino, T.
Aida, S. Inoue, ibid. 1991, 113,6487; h) Y. Naruta, F. Tani, N. Ishihara, K.
Maruyama, ibid. 1991, 113, 6865.
[2] If the a,a,a,a-atropisomer is doubly bridged, other chiral porphyrins may be
obtained in which the C , symmetry axis is perpendicular to the porphyrin
plane.
[31 Very similar reactions of the a.a,a.u-atropisomer with isophthaloyl chloride
and 5-nitroisophthaloyl dichloride have been reported; the products were,
however, not chiral. See, a) J. P. Collman, R. R. Gagne, C. A. Reed, T. R.
Halbert, G. Lang, W T. Robinson, J Am. Chem. Sot..1975,97.1427; b) J. P.
724
8 VCH
Verlagsgesellschafi mbH, W-6940 Weinheim, 1993
Collman, J. I. Brauman, J. P. Fitzgerald, P. D. Hampton. Y Naruta, T.
Michida. Bull. Chem. Soc. Jpn. 1988, 61, 47.
[4] HPLC conditions and CD data: HPLC: column/solvent/separation factor
a/resolution factor R,: CD spectra: [@I ~ - ‘ c m - ’(2. [nm]): l/ent-l: YMC,
A-K43/CH2CIz-EtOH(97:3)/1.64/1.57; k2.0 x 10’ (434); Z/en1-2:Daicel,
Chiralcel OD/hexane:EtOH (1 : 1)/2.98/1.98; f5.8 x 10’ (424).
[5] These angles were estimated from MO calculations (AM1 in MOPAC Version 6.02, J. J. P. Stewart, QCPEBuN. 1989.9.10) and molecular mechanics
calculations using Dreiding-I force field (NMRgraf, Molecular Simulations, Inc).
[6] a) Y. Aoyama, T. Uzawa, K. Saita, Y. Tanaka, H. TOI,H. Ogoshi. Tetrahedron Letl. 1988, 29, 5271; b) Y Aoyama, A. Yamagishi, M. Asagawa, H.
Toi, H. Ogoshi, J. Am. Chem. Soc. 1988, 110,4076; ibid. 1990, 112, 3145.
[7] L. J. Bellamy, The Infra-red Spectra of Complex Molecules, Wiley, New
York, 1958, pp. 203-233, 252-255.
[8] a) E. B. Kyba, K. Kenji, L. R. Sousa, M. G. Siege], D. J. Cram, J. Am.
Chem. Soc. 1973,95,2692; b) S. C. Peacock, L. A. Domeier, F. C. A. Gaeta,
R. C. Helgeson, J. M. Timko. D. J. Cram. ibid. 1978, 100, 8190, and references therein.
The Synthesis and Ab Initio Structure
Determination of Zn,O(BO,), , a Microporous
Zincoborate Constructed of “Fused” Subunits
of Three- and Five-Membered Rings**
By William 7: A . Harrison,* Thurman E. Gier,
and Galen D. Stucky
Substitution of boron for aluminum and/or silicon in zeolite molecular sieves has long been a topic of interest.“ - 3 1 A
rare example of complete boron substitution for both Si and
A1 is provided by “boralite”, Zn,O(BO,),
a direct topological analogue of the aluminosilicate sodalite-type framework found in, for example, Na,OH(AISiO,), .Is1
In general,
however, boron atoms, which usually substitute for aluminum atoms, have only been introduced into aluminosilicate molecular sieves in small quantities, although the technological implications of such doping reactions are extremely important, as in the boron/MFI zeolite.[61
[*I
[**I
Dr. W. T. A. Harrison
Department of Chemistry, University of Houston
Houston, TX 77204-5641 (USA)
Telefax: Int. code +(713)743-2787
Dr. T. E. Gier, Prof. Dr. G. D. Stucky
Department of Chemistry, University of California
Santa Barbara, CA 93106-9510 (USA)
This work was supported in part by the Office of Naval Research and the
National Science Foundation (Grant No. DMR 9208 51 1). We thank Dr.
V. I. Srdanov (UCSB) for carrying out the powder-second-harmonic-generation test.
0570-0833/93/0505-0724$10.00+ .25/0
Angew. Chem. I n / . Ed. Engl. 1993, 32, No. 5
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