Synthesis of two calix[4]arene diamide derivatives for extraction of chromium(VI)

Article abstract of DOI:10.1016/j.tet.2005.08.072

The synthesis of four diamide derivatives of the p-tert-butylcalix[4]arenes from the reaction of 5,11,17,23-tetra-tert-butyl-25,27-diethoxycarbonylmethoxy- 26,28-dihydroxycalix[4]arene 2 with various primary amines were reported. The ¹H and

Full text of DOI:10.1016/j.tet.2005.08.072

Tetrahedron 61 (2005) 10443–10448
Synthesis of two calix[4]arene diamide derivatives for extraction
of chromium(VI)
*
Selahattin Bozkurt, Aysegul Karakucuk, Abdulkadir Sirit and Mustafa Yilmaz
Department of Chemistry, Selc¸uk University, 42031 Konya, Turkey
Received 16 May 2005; revised 27 July 2005; accepted 18 August 2005
Available online 9 September 2005
Abstract—The synthesis of four diamide derivatives of the p-tert-butylcalix[4]arenes from the reaction of 5,11,17,23-tetra-tert-butyl-25,27-
diethoxycarbonylmethoxy-26,28-dihydroxycalix[4]arene 2 with various primary amines were reported. The 1H and 13C NMR, data showed
that the synthesized compounds exist in the cone conformation. The complexing properties of these compounds toward Cr2O27K/HCr2O7K
anions are also studied. It has been observed that receptors 5 and 6 are better extractant than the compounds 3 and 4. The protonated alkyl
ammonium form of 5 and 6 is an effective extractant for transferring HCr2OK7 /Cr2O72K anions from an aqueous phase into a dichloromethane
layer.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
calix[4]arene anion receptors, although such host molecules
are still relatively rare. Several studies on anion coordi-
nation have reported using calixarene based chelating
units.4–10 For example, a few excellent approaches
emphasized by Beer et al.5 regarding calixarene based
anion receptors, and the work highlighted by Gale6 for anion
and ion-pair receptor chemistry are complimentary studies
in the field of anion coordination. Among anions, chromate
and dichromate anions are important because of their high
toxicity,9a,b and also because of their presence in soils and
waters.9c Chromium(VI) is a carcinogen in humans and
animals, with chromates and dichromates being both
mutagenic and genotoxic. Chromium(VI) requires intra-
cellular reduction for activation, and this in vivo reduction
can produce several reactive intermediates such as
chromium(V) and chromium(IV) that can target and
damage DNA.9d Chromate and dichromate (CrO24K and
Cr2O27K) are dianions with oxide functionalities at their
periphery. Nevertheless, since the periphery of the anions
has oxide moieties, these are potential sites for hydrogen
bonding to the host molecule. Recently we have demon-
strated that the amine base derivatives of calix[4]arenes are
very effective toward chromate and dichromate anions.6–10
The main focus of this work is the design of new calixarene-
based ionophores that effectively bind anions and can be
useful for multiple applications such as laboratory, clinical,
environmental, and industrial process analysis. In our
previous work,10 we have extended the field of research of
design structures based on a calix[4]arene platform for the
extraction of dichromate anions. Herein, we report synthesis
and extraction studies of new designed calix[4]arene
platform with alkyl amide derivatives on their lower rim.
Much attention has been paid in recent years to chemical
separation techniques that involve the design and synthesis
of new extraction reagents for metal ions. This attention
results in part from environmental concerns, efforts to save
energy, and recycling at the industrial level. In this respect,
supramolecular chemistry has provided solutions in the
search for molecular structures that can serve as building
blocks for the production of sophisticated molecules by
anchoring functional groups oriented in such a way that they
delineate a suitable binding site.1
Calixarenes are a family of cyclic oligomers prepared from
formaldehyde and para-substituted phenols via cyclic
condensation under alkaline conditions. It was suggested
that the calixarenes could be regarded as the third generation
of supramolecules, after crowns and cyclodextrins.1,2 These
phenol-based macrocycles have proven to be excellent
ligands for the formation of stable complexes with cations,
anions, or neutral molecules.3
The molecular recognition of anionic guest species by
positively charged or electron deficient neutral abiotic
receptor molecules is an area of intense current interest. The
importance of favorable amine, amide, or imide (–NH2/OC–
NH/OC]N) hydrogen bonding interactions for anion
binding has recently been exploited in the design of
Keywords: Calix[4]arene; Dichromate anions; Solvent extraction; Diamide.
*
Corresponding author. Tel.: C90 332 2232774; fax: C90 332 2410520;
e-mail: myilmaz@selcuk.edu.tr
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.08.072

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S. Bozkurt et al. / Tetrahedron 61 (2005) 10443–10448
2. Results and discussion
The new compounds 3–6 were characterized by a
1
combination of IR, H NMR, 13C NMR, FAB-MS, and
elemental analysis. The formation of diamide derivatives of
calix[4]arene 3–6 was confirmed by the appearance of the
characteristic amide bands at about 1684 cmK1 in their IR
spectra, and by the disappearance of ester carbonyl band at
1755 cmK1 in the IR spectra. The conformational charac-
teristics of calix[4]arenes were conveniently estimated by
the splitting pattern of the ArCH2Ar methylene protons in
2.1. Design and synthesis of the new hosts
In this work, we extend our previous studies and explore the
binding properties of calix[4]arene amide derivatives 3–6
towards anions such as dichromate. To achieve the desired
goal, p-tert-butylcalix[4]arene 1 was chosen as the
precursor.11 A synthetic scheme was developed to enable
its derivatization: the synthetic route is depicted in
Scheme 1. The synthesis of compounds 1 and 2 is based
on previously published procedures,12 compounds 4–6 are
reported for the first time while compound 3 was previously
obtained from the acid chloride derivative of calix[4]-
arene.10d In the synthesis of calix[4]arene amides, the
aminolysis reaction of calix[4]arene esters is a new facile
method.13 Therefore, following the strategy outlined in
Scheme 1; 5,11,17,23-tetra-tert-butyl-25,27-diethoxycarbo-
nylmethoxy-26,28-dihydroxycalix[4]arene 2 was refluxed
with, respectively, benzyl amine, furfuryl amine, 3-mor-
pholino propyl amine and 3-ethylamino-1-propyl amine in
toluene/MeOH (1:2) mixture to give corresponding amide
derivatives of p-tert-butyl calix[4]arene 3–6 in 75–80%
yield.
1
the H and 13C NMR spectroscopy.1
1H and 13C NMR data showed that compounds 3–6 have a
cone conformation. A typical AB pattern was observed for
the methylene bridge ArCH2Ar protons at 3.19 and
3.72 ppm (JZ13.4 Hz) for 3, 3.30 and 3.91 ppm (JZ
13.3 Hz) for 4, 3.35 and 4.04 ppm (JZ13.3 Hz) for 5 and
3.32 and 4.05 ppm (JZ13.2 Hz) for 6 in 1H NMR and two
signals covering a range of d 31.63 and 30.98 ppm in 13C
NMR. The high field doublets at 3.19 ppm for 3, 3.30 ppm
for 4, 3.35 ppm for 5 and 3.32 ppm for 6 were assigned to
the equatorial protons of methylene groups, whereas the low
field signals at 3.72 ppm for 3, 3.91 ppm for 4, 4.04 ppm for
5 and 4.05 ppm for 6 were assigned to the axial protons in
1
the H NMR.
Scheme 1. (a) K2CO3/acetone, EtBrOAc, reflux, 24 h; (b) Primary amine, MeOH/toluene (1:1), reflux.

S. Bozkurt et al. / Tetrahedron 61 (2005) 10443–10448
10445
2.2. Two-phase solvent extraction
HCr2OK7 . This monoanion will have a smaller free energy
of hydration than does the dianionic form Cr2O27K. As a
result, there is a smaller loss in hydration energy as HCr2O7K
is transferred from the aqueous phase into the dichloro-
methane phase. An additional advantage of HCr2OK7 over
Cr2O27K is that for the former only one sodium ion needs to
be coextracted to maintain charge balance, whereas for
Cr2O27K two sodium ions are extracted, with additional loss
of hydration energy. For the calix[4]arene amides 5 and 6
we discount the possibility that increased extraction at lower
pH values when compared to 3 and 4, is due to protonation
of the amine nitrogens.
Chromate and dichromate anions are important because of
their high toxicity9b and their presence in soils and waters.9a,c
For a molecule to be effective as a host, it is necessary that
its structural features are compatible with those of the guest
anions. The chromate and dichromate (Cr2O27K/HCr2O7K)
ions are dianions where the periphery of the anions have
oxide moeties. It is known that calix[4]arenes with amino
functionalities on their lower rim are efficient extractants for
oxoanions.8b,c,10a,b These oxides alter potential sites for
hydrogen bonding to the host molecule.
Because the pKa of protonated amides (R-C(OHC)NH2) is
approximately K1, the protonated form of calix[4]arene
amid derivatives 3 and 4 are not expected to be present in
significant concentration in aqueous solutions having pH
values in the 1.5–4.5 range.
We were interested in synthesizing new calix[4]arene
diamide derivatives in the cone conformation and to
examining their extraction properties for dichromate ions.
The present work determines the strategic requirements for
two-phase extraction measurements. A preliminary evalua-
tion of the extraction efficiencies of 3–6 has been carried out
by solvent extraction of Na2Cr2O7 from water into
dichloromethane at different pH values. The results are
summarized in Table 1.
By contrast, amines 5 and 6 are expected to be protonated in
these acidic aqueous solutions (generally the pKa of
protonated amines is around 10–11).
Table 1. Percentage extraction of dichromate by extractants 3, 4, 5 and 6 at
different pH valuesa
Dichromate anion extracted (%)
PH
Compound
1.5
2.5
3.5
4.5
3
4
5
6
8.2
6.1
35.9
b
3.1
3.7
1.0
2.1
81.6
3.6
1.0
1.3
19.0
!0.1
23.5
87.8
a Aqueous phase, [metal dichromate]Z1!10K4 M; organic phase,
dichloromethane, [ligand]Z1!10K3 M or solid phase [ligand]Z1!
10K3 M at 25 8C, for 1 h. The percentage extraction is given by [initial
aqueous anion]K[final aqueous anion]/[initial aqueous anion]!100.
b Partly soluble at this pH.
From the extraction data (Fig. 1), the percentage of
dichromate extracted increased by lowering the pH of the
aqueous phase. This pH dependence can be explained by
anion hydration. In aqueous solutions having a lower pH the
dichromate will be primarily in its protonated form
Figure 2. Extraction percentrage of dichromate anions with 3, 4, 5 and 6 at
pH 1.5–4.5.
The extraction data (Fig. 2) showed that the extractant 6 is
more effective for the extraction of dichromate anions at low
pH (1.5–4.5) because 5 and 6 contains a protonable amine
binding site appropriate for anion binding at low pH.
Therefore, it can be demonstrated that because of the proton
transfer to the nitrogen atom of the amine unit in 5 and 6,
protonated complex is formed in the two phase extraction
system. Upon addition of NaOH to the aqueous layer, the
deprotonated calixarene in the CH2Cl2 is no longer an
effective host molecule for Cr2O27K and the dianion then
migrates back into the aqueous layer in a reversible process
(Scheme 2).
All data have been analyzed using the classical slope
analysis method. Assuming that the extraction of an anion
AnK by the receptor LHnC is according to following
Figure 1. Plots of extraction (E%) versus pH following the two phase
solvent extraction of dichromate with compounds 3, 4, 5 and 6.

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S. Bozkurt et al. / Tetrahedron 61 (2005) 10443–10448
Scheme 2. The proposed interactions of compound 6 with HCr2OK7 and Cr2O72K ions.
equilibrium:
approximately equal to 1 (at pH 1.5 for ligand 5 and at pH
2.5 for ligand 6), suggesting that these ligands 5 and 6 form
1:1 complexes with the dichromate anion.
nðLHnC
The extraction constant Kex is then defined by:
Þ
org CnAnaKq #ððLHnCÞn; AnnKÞorg
(1)
(2)
(3)
However, it is well known that at more acidic conditions
Na2Cr2O7 is converted into H2Cr2O7 and after ionization in
an aqueous solution it exists in the HCr2OK7 /Cr2O72K form.
At higher acidic conditions HCr2OK7 and Cr2O72K dimers
become the dominant Cr6C form and pKa and pKa values
½ððLHnCÞn; AnnKÞꢀorg
Kex
Z
½AnKꢀnaq½LHnCꢀnorg
Eq. 2 can be re-written as;
1
2
of these equations are 0.74 and 6.49, respectively. It is
apparent to us that the ligands 5 and 6 form complex mostly
with HCr2OK7 ion. This has allowed us to consider that
mostly the Eqs. 4 and 5 this simultaneous extraction of 1:1
complexes according to the following equilibria:
log DA Z log Kex Cn log½LHnCꢀorg
where DA is defined as the ratio of the analytical
concentration of the anion AnK in both phases:
Kex
ðLHCÞorg CHCr2OK7aq#ðLHC; HCr2OK7 Þorg
(4)
(5)
DAZ[A]org/[A]aq
Ke0x
Consequently a plot of the log DA versus log[L] may lead to
a straight line with a s[L]lope that allows for the
determination of the stoichiometry of the extracted species,
where is defined as the analytical concentration of the ligand
in the organic phase. Figure 3 exhibits the extraction into
dichloromethane at different concentrations of 5 and 6 with
dichromate, respectively. A linear relationship between
log DA versus log[L] is observed with the slope of the line
for extraction of dichromate anion by ligands 5 and 6 being
ðLH22C
Þ
org CCr2O27Kaq#ðLH22C; Cr2O72KÞorg
According to these assumptions, the extraction constant has
been calculated from the experimental data with similar Kex
0
and Kex values using Eq. 3. Calculations of these constant
values lead to log KexZlog Kex0Z3.12G0.2 for 5 and
log KexZlog Kex0Z4.58G0.2 for 6.
3. Conclusion
In conclusion, the synthesis and complexation ability of four
calix[4]arene based receptors 3–6 were studied. The
spectroscopic data indicated that these compounds (3–6)
adopt the cone conformation. The complexation studies
show that compounds 5 and 6 are better receptors for
Cr2O27K/HCr2OK7 anions compared with 3 and 4. Morever,
the extraction properties of 5 and 6 are enhanced in the
acidic medium for Cr2O27K/HCr2O7K anions due to their
protonation from the extraction phenomenon it could be
concluded that the complexation of Cr2O27K/HCr2O7K
depend on the nature and aggregation of the ions round
the receptor. This is a particularly important feature if it is
desirable to recover the particular metal in pure form and
Figure 3. Log D versus log[L] for the extraction of dichromate by the
ligand 5 and 6 from an aqueous phase into dichloromethane at 25 8C.

S. Bozkurt et al. / Tetrahedron 61 (2005) 10443–10448
10447
reuse the extractant. The calixarene based receptors could
be proved to find remarkable applications in the design of
chemical sensors, using an electrochemical transduction/as
conventional ion selective electrodes (ISE) and solid-state
sensors (ISFETs).
where A0 and A are the initial and final concentrations of the
dichromate ion before and after the extraction, respectively.
4.2. General procedure for the synthesis of compound 3,
4, 5 and 6
An appropriate primary amine (20.0 mmol) was dissolved in
1:2 toluene/MeOH mixture (60 mL) and added dropwise to
a solution of 5,11,17,23-tetra-tert-butyl-25,27-diethoxycar-
bonylmethoxy-26,28-dihydroxycalix[4]arene 2 (4.0 mmol)
in 20 mL toluene with continuous stirring at room
temperature for about 30 min. Then the reaction mixture
was refluxed and the reactions were monitored by TLC.
After the substrate had been consumed the solvent was
evaporated under reduced pressure and the residue was
triturated with MeOH to give a crude product. The crude
products were purified by flash chromatography (SiO2,
CH2Cl2/Hexane 2:1) and recrystallized from CH2Cl2/
MeOH.
4. Experimental
Melting points were determined on an Electrothermal 9100
apparatus in a sealed capillary and are uncorrected. H and
1
13C NMR spectra were recorded on a Bruker 400 MHz
spectrometer in CDCl3 with TMS as an internal standard. IR
spectra were obtained on a Perkin Elmer 1605 FTIR
spectrometer using KBr pellets. UV–vis spectra were
obtained on a Shimadzu 160A UV–vis spectrophotometer.
Elemental analyses were performed using a Leco CHNS-
932 analyzer. FAB-MS spectra were taken on a Varian
MAT 312 spectrometer. A Crison MicropH 2002 digital pH
meter was used for the pH measurements.
4.2.1. Compound 3. White crystals; yield 79%; mp 248–
1
250 8C; IR (KBr): 3353 (OH), 1684 (CO) cmK1; H NMR
Analytical TLC was performed using Merck prepared plates
(silica gel 60 F254 on aluminum). Flash chromatography
separations were performed on a Merck Silica Gel 60
(230–400 Mesh). All reactions, unless otherwise noted,
were conducted under a nitrogen atmosphere. All starting
materials and reagents used were of standard analytical
grade from Fluka, Merck and Aldrich and used without
further purification. Toluene was distilled from CaH2 and
stored over sodium wire. Other commercial grade solvents
were distilled, and then stored over molecular sieves.
Anions were used as their sodium salts. The drying agent
employed was anhydrous MgSO4. All aqueous solutions
were prepared with deionized water that had been passed
through a Millipore milli-Q Plus water purification system.
Compounds 1 and 2 were synthesized according to
previously described methods.12
(CDCl3): d 8.80 (t, 2H, NH), 7.21 (s, 2H, OH), 7.18 (m, 10H,
ArH), 6.93 (s, 4H, ArH), 6.72 (s, 4H, ArH), 4.45 (d, 4H,
NHCH2), 4.29 (s, 4H, OCH2CO), 3.72 (d, 4H, JZ13.4 Hz,
ArCH2Ar), 3.19 (d, 4H, JZ13.4 Hz, ArCH2Ar), 1.20 (s,
18H, C(CH3)3), 0.88 (s, 18H, C(CH3)3); 13C NMR (CDCl3):
d 167.91 (C]O), 149.29, 148.96, 148.12, 142.68, 136.87,
128.94, 128.53, 127.54, 126.79, 126.99, 125.32, 125.00,
123.24 (ArC), 96.20 (C(CH3)3), 77.28, 76.96 (OCH2),
76.64, 74.65 (NHCH2), 31.70, 30.93 (ArCH2Ar); FAB-MS
m/z: (966.4) [MCNa]C. Anal. Calcd for C62H74N2O6
(943.3): C, 78.95%; H, 7.91%; N, 2.97%. Found: C,
78.68%; H, 7.76%; N, 2.86%.
4.2.2. Compound 4. White crystals; yield 78%; mp 289–
1
291 8C; IR (KBr): 3326 (OH), 1684 (CO) cmK1; H NMR
(CDCl3): d 9.01 (t, 2H, NH), 7.22 (d, 2H, OH), 7.10 (d, 2H,
ArH), 7.01 (s, 4H, ArH), 6.82 (s, 4H, ArH, ph), 6.23 (s, 4H,
ArH, ph), 4.54 (d, 4H, NHCH2), 4.45 (s, 4H, OCH2CO),
3.91 (d, 4H, JZ13.3 Hz, ArCH2Ar), 3.30 (d, 4H, JZ
13.3 Hz, ArCH2Ar), 1.21 (s, 18H, C(CH3)3), 0.96 (s, 18H,
C(CH3)3); 13C NMR (CDCl3): d 167.79 (C]O), 149.41,
148.83, 148.02, 142.79, 137.05, 132.28, 128.61, 128.23,
127.83, 126.94, 126.10, (ArC), 96.22 (C(CH3)3), 77.32,
76.88 (OCH2), 76.56, 74.64 (NHCH2), 31.74, 30.91
(ArCH2Ar); FAB-MS m/z: (946.1) [MCNa]C. Anal.
Calcd for C58H70N2O8 (923.2): C, 75.46%; H, 7.64%; N,
3.03%. Found: C, 75.69; H, 7.27%; N, 3.23%.
4.1. Analytical procedure
The dichromate anion extraction experiments of calix[4]
arene daimide derivatives 3, 4, 5 and 6 were studied by
liquid–liquid extraction experiments following Pedersen’s
procedure.14 Into a vial was pipetted an aqueous solution
(10 mL) containing sodium dichromate at a concentration of
1!10K4 M, a few drops of 0.01 M KOH/HCl solution in
order to obtain the desired pH at equilibrium and 10 mL of
1!10K3 M calixarene ligand in CH2Cl2.The mixture was
shaken vigorously in a stoppered glass tube with a
mechanical shaker for 2 min and then magnetically stirred
in a thermostated water bath at 25 8C for 1 h, and finally
left standing for an additional 30 min. The concentration
of dichromate ion remaining in the aqueous phase was
then determined spectrophotometrically as described
previously.10b Blank experiments showed that no dichro-
mate extraction occurred in the absence of calix[4]arene.
The percent extraction (E%) was calculated from the
absorbance A of the aqueous phase measured at 346 nm
(for pH 1.5–4.5) using the following expression:
4.2.3. Compound 5. White crystals; yield 76%; mp 244–
1
246 8C; IR (KBr): 3351 (OH), 1686 (CO) cmK1; H NMR
(CDCl3): d 8.87 (t, 2H, NH), 7.79 (s, 2H, OH), 7.00 (s, 4H,
ArH), 6.86 (s, 4H, ArH), 4.50 (s, 4H, OCH2CO), 4.04 (d,
4H, JZ13.3 Hz, ArCH2Ar), 3.54 (b, 8H, OCH2CH2N),
3.36–3.41 (m, 4H, NHCH2CH2CH2N), 3.35 (d, 4H, JZ
13.3 Hz, ArCH2Ar), 2.18 (m, 8H, NCH2CH2O), 2.30 (m,
4H, NHCH2CH2CH2N), 1.75 (b, 4H, NHCH2CH2CH2N),
1.19 (s, 18H, C(CH3)3), 0.97 (s, 18H, C(CH3)3); 13C NMR
(CDCl3): d 167.82 (C]O), 149.38, 148.65, 148.57,
143.34, 132.22, 127.06, 126.24, 125.62 (ArC), 96.16
(C(CH3)3), 77.25 (OCH2), 76.93 (NHCH2CH2CH2N),
A0 KA
ðE%Þ Z
!100
A0

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S. Bozkurt et al. / Tetrahedron 61 (2005) 10443–10448
(b) Scheerder, J.; Van Duynhoven, J. P. M.; Engbersen, J. F. J.;
Reinhoudt, D. N. Angew Chem., Int. Ed. 1996, 35, 1090–1093.
5. (a) Redman, J. E.; Beer, P. D.; Dent, S. W.; Drew, M. G. B.
Chem. Commun. 1998, 2, 231–232. (b) Cooper, J. B.; Drew,
M. G. B.; Beer, P. D. J. Chem. Soc., Dalton Trans. 2000,
2721–2728. (c) Beer, P. D.; Cooper, J. B. Calixarene Based
Anion Receptors. In Calixarenes in Action; Mandolini, L.,
Ungaro, R., Eds.; Imperial College: London, 2000;
pp 111–143. (d) Matthews, S. E.; Beer, P. D. Calixarene-Based
76.62 (NHCH2CH2CH2N), 74.83 (NHCH2CH2CH2N),
56.27 (OCH2CH2N), 53.58 (OCH2CH2N), 31.63, 30.97
(ArCH2Ar); FAB-MS m/z: (1040.4) [MCNa]C. Anal.
Calcd for C62H88N2O8 (1017.41): C, 73.19%; H, 8.72%;
N, 5.51%. Found: C, 73.38%; H, 8.66%; N, 5.40%.
4.2.4. Compound 6. White crystals; yield 78%; mp 179–
1
180 8C; IR (KBr): 3353 (OH), 1684 (CO) cmK1; H NMR
(CDCl3): d 8.76 (t, 2H, NH), 7.62 (s, 2H, OH), 7.00 (s, 4H,
ArH), 6.83 (s, 4H, ArH), 4.48 (s, 4H, OCH2CO), 4.05 (d,
4H, JZ13.2 Hz, ArCH2Ar), 3.42 (q, 4H, NHCH2CH2CH2N),
3.32 (d, 4H, JZ13.2 Hz, ArCH2Ar), 2.35 (t, 4H,
NHCH2CH2CH2N), 2.28 (q, 8H, NCH2CH3), 1.66 (p, 4H,
NHCH2CH2CH2N), 1.18 (s, 18H, C(CH3)3), 0.96 (s, 18H,
C(CH3)3), 0.81 (t, 12H, NCH2CH3); 13C NMR (CDCl3): d
167.70 (C]O), 149.40, 148.77, 148.40, 143.13, 132.30,
127.14, 126.17, 125.57 (ArC), 96.16 (C(CH3)3), 77.25
(OCH2), 76.93 (NHCH2CH2CH2N), 76.62 (NHCH2CH2-
CH2N), 74.84 (NHCH2CH2CH2N), 50.84, 46.70
(CH3CH2N), 31.63, 30.98 (ArCH2Ar), 11.65 (CH3CH2N);
FAB-MS m/z: (1012.5) [MCNa]C. Anal. Calcd for
C62H92N4O6 (989.45): C, 75.26%; H, 9.37%; N, 5.66%.
Found: C, 75.12%; H, 9.48%; N, 5.72%.
¨
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Acknowledgements
We thank the Research Foundation of Selcuk University,
Konya-Turkey (BAP 2002/131) for financial support of this
work.
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