Synthesis and structure investigation of stabilized aromatic oligoamides and their interaction with g quadruplex structures 4

110

Chapter 4

Synthesis of Folded Circular Aromatic Pentamers with Tunable
Interior Structure

4.1 Introduction
Macrocyclic structures with persistent shape have unique structural features, special
physical properties, and chemical behavior that differ from their acyclic
counterparts.
1,2
In particular, persistent-shaped aromatic macrocycles have attracted
wide attention due to their defined structures and functions. Usually, the shape
persistency and rigidity of these macrocyclic motifs are induced by covalent force,
3

intrinsic conformational bias of the backbone
4
and built-in hydrogen-bonds.
5,6,7

Particularly, multiple-center H-bonding has become a top strategy for designing
tailor-made macrocyclic aromatic foldmers due to its robustness and predictablity.
6,7

Owning to their specific structural features, these aromatic macrocycle have enabled
extensive applications in chemistry and biology. For example, their well-defined
cavities may serve as species binder
8
or ion transporter across cell membrane.

9

Aligning rigid macrocycles into columnar assemblies should lead to organic
nanotube.
10
However, until now, few synthetic macrocyclic systems allow systematic
fine-tuning of interior properties while maintain overall topographic feature. Herein, a
series of 5-fold symmetric aromatic circular oligoamides with tunable interior
functional groups were designed and synthesized.
111

4.2 Results and Discussion
4.2.1 Design and Computational Molecular Modeling of Circular Pentamer 1
In chapters 2 and 3, we showed that the oligoamide backbone requires five
repeating units per helical turn in forming a helical structure. Accordingly, the
end-to-tail cyclization of a crescent acyclic pentamer into a circular structure might
not impose much angle strain on the backbone and may result in a planar
conformation. To testify this speculation, ab initio calculation of the designed circular
aromatic pentamer 1 was performed with Gaussian 98 at the B3LYP/6-31G level.
a) b)





Figure 4.1. Structure predicted by ab intio calculation of circular pentamer 1. (a) top view and (b) side
view.

As shown in Figure 4.1, circular pentamers adopts almost planar structure with an
appreciable cavity size.

Similar to helical oligoamides, the most stable circular pentamer
prefers the
up-down-up-down-up fashion in terms of orientation of five interior methyl
side chains.

4.2.2 Synthesis of Circular Pentamer 1

A highly rigid and structurally well defined circular pentamer 1 was synthesized by
Dr. Bo Qin.
11
This pentamer was efficiently obtained by circlizing the acyclic
112

pentamer 5a using BOP as the amide coupling reagent.
Scheme 4.1. Synthesis of circular pentamer 1
a

N
H
O
O
N
N
O
H
O
O O
O
H
O

O
N
H
O
O
2
N
O
O
N
O
N
O
N
O
N
N
O
O
O
O
O
O
H
H
H
H
H
1
a, b, c

5a

a
a) 10% Pd/C, 40˚C, THF; b) 1M KOH, MeOH; c) BOP, DIEA, CH
2
Cl
2,
61% (in total).

4.2.3 One-Dimensional
1
H NMR Study of Circular Pentamer 1
1
H NMR was firstly examined to confirm the identity of circular pentamer 1
(Firgure 4.2). The
1
H NMR spectrum of 1 revealed five sets of proton signals
corresponding to the methoxy groups (4.09 ppm), aromatic (9.00 ppm, 8.02 ppm &
7.45 ppm), and amide protons (10.89 ppm) that are in excellent agreement with the
symmetrical structure of 1. In particular, the amide protons of 1 resonating at the very
low field

(10.88-10.89 ppm) are a diagnostic indicator of the presence of strong
H-bonding interactions, leading to the rigidification of the amide linkages and a
crescent aromatic backbone.

Figure 4.2.
1
H NMR spectrum (500 MHz, 298 K, CDCl
3
) of pentamer 1 at 5 mM.


4.2.4 Solid State Structure of Pentamer 1
Single crystal of 1, grown by Dr Qin Bo, was obtained by slow evaporation of 1 in
113

mixed solvents.
11
Consistent to ab initio caculation, the molecules adopted an almost
flat disc arrangement (Firgure 4.3). All the five methoxy oxygen atoms and amide
protons point inward and contribute to the formation of a continuous intramolecularly
Hydrogen-bonded network (NH•••OMe = 1.9-2.4 Å). The size of the cavity is 2.85 Å
in radius. After deducting a covalent radius of 1.4 Å for oxygen atom, the actual
radius is 1.45 Å, which is almost the same as K
+
(~1.4 Å). The geometrical feature of
circular pentamer 1 made it a potential candidate as cation-binding medium.
a) b) c)

Figure 4.3. Crystal structure of pentamer 1. (a) top view with interior methoxy methyl groups omitted
for clarity of view, (b) top view and (c) side view both with methoxy methyl groups in CPK
representations.

4.2.5 Design of Circular Pentamer 8
According to the crystal structure of 1, the methyl groups form two hydrophobic

caps above and below the pentameric plane. These hydrophobic caps might prevent 1
from binding to metal cations, such as Na
+
and K
+
. We hypothesised that the
replacement of methoxy groups with hydroxyl groups should greatly reduce the steric
hindrance and hydrophobicity imparted by the interior methyl groups in 1.
Furthermore, it has been well established that the fluoride atom can act as a good
proton acceptor. Considering the similarity of the F•••H-N to O•••H-N motif,
replacing hydroxyl groups with fluorine may form a new rigid, well-established
114

conformation. Finally, considering the bad solubility of oligoamides, the introduction
of hydrophobic side chains should enhance the solubility of the pentamer.

4.2.6 Synthesis of Circular Pentamer 8
The synthetic details for oligoamides have been discussed in Chapter 2. Herein, we
focus on discussing two types of new reactions. 1) Protection of hydroxyl group with
Benzyl group. To introduce hydroxyl groups into pentamers’ interior, benzyl
protecting group (Bn) was used for protecting hydroxyl groups in case the coupling
between amine and phenol group. Similar to alkylation, Benzyl protection was
realized by reacting monomer with benzyl bromide and potassium carbonate

in
acetone. Since benzyl bromide was hard to remove, no more than 1.1 equiv of the
benzyl bromide was used. Removal of benzyl protecting groups readily proceeded by
catalytic hydrogenation, using Pd-C as the catalyst in MeOH/THF under one
atmosphere of hydrogen gas. This allows us to introduce three OH groups into the
resulting pentamer molecule. 2) Reduction of nitro group into amine by iron powder.

Since benzyl group could be easily moved by catalytic hydrogenation, method to
reduce NO
2
group using Pd/C could not be used. Instead, reduction was carried out by
using iron powder and glacial acetic acid, a highly efficient method for reduction of
NO
2
into NH
2
.



115

Scheme 4.2. Synthesis of circular pentamer 8
a

R
OH
COOCH
3
O
2
N
R
OBn
COOCH
3
O

2
N
R
OBn
COOHO
2
N
8a, 8c 8b, 8d
1f, 8a, 8b
:R=OC
8
H
17
1o, 8c, 8d: R=CH
3
1f, 1o
a
b

H
3
COOC N
H
O
O
Bn NO
2
O
Bn
8e

N
H
O
F
NO
2
N
O
H
O
Bn
O O
O
Bn
8g
N
H
O
F
N
N
O
H
O
Bn
O O
O
Bn
H
O

F
O
2
N
8h
N
H
O
F
N
N
O
H
O
Bn
O O
O
Bn
H
O
F
N
H
O
O
2
N
O
Bn
OC

8
H
17
OBn
COOCH
3
O
2
N
8a
OC
8
H
17
OC
8
H
17
C
8
H
17
O
OC
8
H
17
c, e
C
8

H
17
O
OC
8
H
17
C
8
H
17
O
OC
8
H
17
8i
c, d
c, e
c, f
c, g, h
O
N
O
N
O
N
O
N
NH

O
O
O
O
F
F
Bn
Bn
H
H
H
H
Bn
OC
8
H
17
C
8
H
17
O
O
N
O
N
O
N
O
N

N
O
O
O
O
F
F
H
H
H
H
H
H
H
H
OC
8
H
17
C
8
H
17
O
8m
8
i

a
a). K

2
CO
3
/ BnBr, DMF, 60
o
C, 4 h, 88~90%; b). NaOH, MeOH/H
2
O, reflux, 2 h, 84~91%; c). Fe,
AcOH/EtOH, reflux, 2h, 78%; d) ethyl carbonochloridate, 4-methylmorpholine, CH
2
Cl
2
, 8b, overnight,
74%; e) 8f, SOCl
2
, reflux, Pyridine/CH
2
Cl
2
, 56%; f) 8d, SOCl
2
, reflux, Pyridine/CH
2
Cl
2
, 72%; g) KOH,
Dioxane/H
2
O, RT, overight; h) BOP, DIEA, CH
2

Cl
2
, 2h, 35%; i) H
2
, Pd/C, THF/MeOH, 40

o
C, 3h,
40%.

To study the intramolecular H-bonds in 8,
1
H NMR spectra was first examined. As
mentioned, amide protons typically exhibit a substantial downfield shift due to the
formation of intramolecular H-bonds. Surprisingly, only three amide protons resonate
116

at chemical shifts larger than 10 ppm in CDCl
3
. According to previous study, these
signals should be the amides adjacent to interior hydroxyl group. In comparison, two
amide protons adjacent to fluorine element were less downfield (7~9 ppm). This
experimental observation suggests that the three-centered F•••H-N hydrogen-bonding
motif is weaker than O•••H-N hydrogen-bonding motif. This may because the small
radius of fluorine make it is hard to be a hydrogen acceptor as the distance of
F•••H-N and O•••H-N in our design is fixed. However, by addition of DMSO-d
6
into
CDCl
3

(1:1)
,
the two amide protons adjacent to fluorine also demonstrated chemical
shift more than 10 ppm as a result of the H-bonding ability of DMSO.


4.2.7 Crystal Structure of a Tetramer and Computational Molecular Modeling of
Circular Pentamer 8
To demonstrate the existence of intramolecular hydrogen-bonds that restrict the
rotational freedom of the aryl-amide bonds to enforce a crescent structure, X-ray
crystallography of tetramer 8h was obtained by slow evaporation of 8h in mixed
solvents of 1:1 dichloromethane and methanol. The X-ray results showed that the
presence of the bulky benzyloxy group does not disrupt the crescent-shaped
conformation. In addition, the H-bond distances of F•••NH and OH•••NH are no
more than 2.3 Å, indicating the formation of intramolecular hydrogen bonds.
However, numerous attempts to obtain single crystal structure of pentamer 8 were
unsuccessful.

117







Figure 4.4. X-ray crystal structure of tetramer 8h.

Since our previous study showed that ab initio molecular calculation has
consistently allowed us to reliably predict the 3D topography of helical and circular

oligomers, modeling with the B3LYP/6-31G basis set of circular pentamer 8 was
performed. The modeling result showed that the interior cavity dimension of cyclic
pentamer 8 is about 5.64 Å (Figure 4.5), suggesting that the replacement of interior
methoxy groups with hydroxyl or fluorine groups increasingly opened the interior
cavity. Moreover, pentamer 8 still folds into a roughly planar disk arrangement akin to
pentamer 1.
a) b)







Figure 4.5. Structure predicted by ab intio calculation of circular pentamer 8. (a) top view and (b) side
view.
118

4.3 Conclusion
X-ray diffraction results of 1 illustrated that the pentamer was almost planar with
intramolecular hydrogen-bonding between the amide protons and methoxy oxygen
atoms to rigidify the amide linkage. A new generation of circular pentamer 8 was
successfully synthesized that folds based on intromolecular F•••N-H H-bonds. The
planar structure and the interior cavity of these macrocycles may give arise to their
potential applications in chemical and biological settings.

4.4 Experimental Section
Compound 1:
Compound 5a (0.442 g, 0.559 mmol) was reduced by catalytic hydrogenation in THF
(50 mL) at 50

o
C, using Pd-C (0.75 g, 20%) as the catalyst for 3 hours. The reaction
mixture was then filtered and the solvent removed in vacuo to give a brown liquid 1x.
Yield: 0.425 g, quantitative. Compound 1x (0.425 g, 0.558 mmol) was dissolved in
hot methanol (5 mL) to which 1M KOH (1.20 mL, 1.20 mmol) was added. The
mixture was heated under reflux for 2 hours and then quenched with water (20 mL).
The aqueous layer was neutralized with 1M KHSO
4
(1.2 mL). The precipitated crude
product 1y was collected by filtration. Compound 1y (0.763 g, 1.0 mmol) and BOP
(0.88 g, 2.0 mmol) were dissolved in CH
2
Cl
2
(3.2 ml) at 0
o
C. DIEA (0.5 ml, 3.0
mmol) was added and the reaction mixture was stirred continuously for 1 hr at 0
o
C,
then stirred at room temperature for 2 hours. Removal of solvent in vacuo gave the
crude product, which was purified by flash column chromatography on silica gel
119

using CH
2
Cl
2
/CH
3

CN (1:10) as the eluent to give a pure white product 1. Yield: 0.465
g, 62%; Decomposition in 340-345
o
C;
1
H NMR (500 MHz, CDCl
3
) δ 10.88 (s, 5H),
9.00 (d, 5H, J = 8.2, 1.5), 8.02 (d, 5H, J = 8.0, 1.5), 7.44 (t, 5H, J = 8.1), 4.09 (s, 15H).

13
C NMR (125 MHz, CDCl3) δ 162.3, 146.5, 132.9, 126.6, 126.2, 125.6, 124.3, 63.3.
HRMS-EI: exact mass calculated for [M]
+ (
C
40
H
35
N
5
O
10
): m/z 745.2384, found: m/z
745.2387.
Compound 8a:
Methyl 2-hydroxy-3-nitro-5-(octyloxy)benzoate (8.12 g, 25.0 mmol) was dissolved in
anhydrous DMF (100 mL), to which anhydrous K
2
CO
3

(14.00 g, 0.1 mol) and
benzene bromide (3.1 mL, 26.0 mmol) was added. The mixture was heated under
reflux for 60
o
C hours. CH
2
Cl
2
(200 mL) was then added and the reaction mixture was
filtered. The solvent was removed in vacuo and the concentrate was dissolved in
CH
2
Cl
2
(200 mL), washed with water (2 x 100 mL) and dried over anhydrous Na
2
SO
4
.
Removal of CH
2
Cl
2
gave the pure product 8a as a red liqid. Yield: 9.40 g, 90%. Yield:
1.76 g, 85%.
1
H NMR (500 MHz, CDCl
3
): δ 7.56 (d, 1H, J = 3.2 Hz), 7.47 (d, 2H, J =
6.9 Hz), 7.44 (d, 1H, J = 3.8 Hz), 5.11 (s, 2H), 3.99 (t, 2H, J = 6.3 Hz), 3.88 (s, 3H),

1.29 (m, 12H), 0.91 (t, 3H, J = 13.5 Hz).
13
C NMR (75 MHz, CDCl
3
): δ 190.36,
164.85, 154.52, 145.97, 144.65, 136.04, 128.65, 128.57, 128.48, 128.42, 121.57,
114.06, 78.56, 69.22, 52.72, 50.74, 31.73, 29.19, 29.14, 28.91, 25.85, 22.60, 14.02.
HRMS-ESI: calculated for [M+Na]
+
(C
23
H
29
NO
6
Na): m/z 438.1887 found: m/z
438.1868.
120

Compound 8b:
8a (1.25 g, 3.0 mmol) was dissolved in hot MeOH (20 mL), to which 1N NaOH (6
mL, 6.0 mmol) was added. The mixture was heated under reflux for 1 h and then
quenched with water (20 mL). The aqueous layer was neutralized by addition of 1M
HCl (8 mL). The precipitated crude product was collected by filtration, which was
recrystallized from MeOH to give a yellow solid 8b. Yield: 0.90 g, 91%.
1
H NMR
(500 MHz, CDCl
3
): δ 7.82 (d, 1H, J = 3.2 Hz), 7.60 (d, 1H, J = 3.2 Hz), 7.47 (m, 2H),

7.41 (m, 3H), 5.14 (s, 2H), 4.93 (t, 2H, J = 6.4 Hz), 1.81 (m, 3H), 1.46 (m, 3H),
1.30(m, 6H), 0.90 (t, 3H, J = 6.9 Hz).
13
C NMR (75 MHz, DMSO-d6): δ 165.62,
154.01, 145.53, 144.01, 135.89, 129.12, 127.90, 121.11, 113.20, 68.68, 31.25, 28.72,
28.66, 28.45, 25.38, 22.12, 13.62. HRMS-ESI: calculated for [M]
+
(C
23
H
29
NO
6
): m/z
400.1887 found: m/z 400.1868.
Compound 8c:
Methyl 2-hydroxy-3-nitro-5-(octyloxy)benzoate (1.05 g, 5.0 mmol) was dissolved in
anhydrous DMF (20 mL), to which anhydrous K
2
CO
3
(3.0 g, 21.7 mol) and benzene
bromide (0.7 mL, 5.8 mmol) was added. The mixture was heated under reflux for 60
o
C hours. CH
2
Cl
2
(50 mL) was then added and the reaction mixture was filtered. The
solvent was removed in vacuo and the concentrate was dissolved in CH

2
Cl
2
(50 mL),
washed with water (2 x 50 mL) and dried over anhydrous Na
2
SO
4
. Removal of
CH
2
Cl
2
gave the pure product 8c as a red liquid. Yield: 1.32 g, 88%.
1
H NMR (300
MHz, CDCl
3
): δ 7.73 (d, 1H, J = 2.0 Hz), 2.2 (d, 1H, J = 2.2 Hz), 7.36 (m, 2H), 7.23
121

(m, 3H), 5.00 (s, 2H), 3.75 (s, 3H), 2.27 (s, 3H).
13
C NMR (75 MHz, CDCl
3
): δ
164.86, 149.06, 145.36, 135.94, 135.85, 134.39, 128.57, 128.52, 128.34, 127.49,
78.33, 52.50, 20.35. MS-ESI: calculated for [M+Na]
+
(C

16
H
15
NO
5
Na): m/z 324.0950,
found: m/z 324.0952.
Compound 8d:
8c (1.2 g, 4.0 mmol) was dissolved in hot MeOH (20 mL), to which 1N NaOH (8 mL,
8.0 mmol) was added. The mixture was heated under reflux for 1 h and then quenched
with water (20 mL). The aqueous layer was neutralized by addition of 1M HCl (10
mL). The precipitated crude product was collected by filtration, which was
recrystallized from MeOH to give a yellow solid 8d. Yield: 0.97 g, 84%.
1
H NMR
(500 MHz, CDCl
3
): δ 8.15 (d, 1H, J = 1.9 Hz), 7.91 (d, 1H, J = 1.9 Hz), 7.49 (m, 2H),
7.43 (m, 3H), 5.19 (s, 2H), 2.49 (s, 3H).
13
C NMR (75 MHz, CDCl
3
): δ 165.88,
148.53, 145.04, 135.89, 135.74, 133.87, 128.37, 127.97, 77.71, 20.06. MS-ESI:
calculated for [M-H]
+
(C
15
H
13

NO
5
): m/z 286.0794 found: m/z 286.0742.
Compound 8e:
8a (1.0 g, 2.4 mmol) was first dissolved in ethanol (20 mL), to which acetic acid (5.0
mL), and iron powder (0.6 g, 10.7 mmol) was added. The reaction was stirred and
heated under reflux for 2 hours. The reaction mixture was then filtered and the filtrate
solvent was removed in vacuo. The residue after solvent removal was dissolved in
CH
2
Cl
2
(30 mL), washed with water (2 x 30 mL), and dried over anhydrous Na
2
SO
4
.
Removal of CH
2
Cl
2
solvent gave pure amine which was immediately used for the
next coupling. Acid 8b (1.0 g, 2.5 mmol) was dissolved in CH
2
Cl
2
(20 mL) to which
122

4-methylmorpholine, NMM (0.43 mL, 3.5 mmol) and ethyl chloroformate (0.36 mL,

3.0 mmol) was added at 0
o
C. The reaction mixture was stirred for at least 15 min then
a solution of above amine (0.85 g, 2.2 mmol) dissolved in CH
2
Cl
2
(20 mL) was added.
The reaction mixture was allowed to stir continuously overnight at room temperature.
The reaction mixture was washed with 1M KHSO
4

(30 mL), followed by saturated
NaHCO
3
(30 mL) and saturated NaCl (30 mL). Drying over Na
2
SO
4
and removal of
solvent in vacuo gave the crude product, which was recrystallized from methanol to
give the pure product 8e as a white solid. Yield: 1.32 g, 78%.
1
H NMR (500 MHz,
CDCl
3
) δ 9.73 (s, 1H), 8.32 (d, 1H, J = 2.0), 7.62 (d, 1H, J = 0.9), 7.42 (d, 1H, J =
3.0), 7.30 (d, 1H, J = 6.9), 7.10~7.20 (m, 10H), 4.91 (s, 2H), 3.92 (s, 2H), 4.00 (m,
4H), 3.92 (s, 3H), 1.80 (m, 2H), 1.46 (m, 2H), 1.27 (m, 8H), 0.88 (m, 3H).
13

C NMR
(125 MHz, CDCl
3
) δ 165.81, 161.64，155.11, 155.08, 145.26, 142.11, 141.79, 136.19,
133.87, 133.48, 131.50, 129.70，128.96, 128.85, 128.56, 128.42, 128.34, 128.30,
124.22, 120.38, 114.35, 111.80, 110.88, 79.59, 77.7, 69.24, 68.61, 52.29, 31.80, 31.76,
29.33, 29.23, 29.17, 28.93, 26.02, 25.86, 22.65, 22.62, 14.07, 14.06. HRMS-ESI:
calculated for [M+Na]
+
(C
45
H
56
N
2
O
9
Na): m/z 791.3878 found: m/z 791.3906.
Compound 8g:
8e (0.32 g, 0.42 mmol) was first dissolved in ethanol (5 mL), to which acetic acid (1
mL), and iron powder (0.1 g, 2.1 mmol) was added. The reaction was stirred and
heated under reflux for 2 hours. The reaction mixture was then filtered and the filtrate
solvent was removed in vacuo. The residue after solvent removal was dissolved in
CH
2
Cl
2
(10 mL), washed with water (2 x 10 mL), and dried over anhydrous Na
2
SO

4
.
123

Removal of CH
2
Cl
2
solvent gave pure amine which was immediately used for the
next coupling. Acid 8f (0.15 g, 0.6 mmol) was dissolved in thionyl chloride (1 mL)
and the mixture was heated under reflux for 2 h. The solvent was removed in vacuo
and anhydrous ether (2 x 15 mL) was added and removed again. The solvent was then
removed in vacuo and saturated with nitrogen gas before addition of 5 mL dry CH
2
Cl
2
.
The above amine (0.27 g, 0.36 mmol) was dissolved in 5 mL dry CH
2
Cl
2
and pyridine
(0.1 mL, 1.2 mmol) before addition to the reaction mixture above. The reaction
mixture was stirred at 50
o
C for 6 hours and then was washed with aq NaHCO
3
(50
mL). Drying over anhydrous Na
2

SO
4
and removal of solvent in vacuo gave the crude
product which was purified by flash column chromatography (silica gel as the
stationary phase) using hexane/ethyl acetate (4:1) as the eluent to give pure 8g as
yellow solid. Yield: 0.18 g, 74%.
1
H NMR (300 MHz, CDCl
3
) δ 10.26 (s, 1H), 8.80 (d,
1H, J = 3.2), 8.67 (d, 1H, J = 11.1), 8.44~8.55 (m, 4H), 7.69~7.72 (m, 4H), 7.61 (d,
1H, J = 3.2), 7.47~7.56 (m, 6H), 5.23 (s, 2H), 5.11 (s, 2H), 4.33 (m, 1H), 4.24 (s, 3H),
2.10 (m, 2H), 1.19 (m, 8H), 1.68 (m, 2H), 1.62 (m, 8H), 1.18 (m, 3H).
13
C NMR (125
MHz, CDCl
3
) δ 165.84, 162.98, 158.88， 156.07, 155.31, 155.23, 141.73, 139.79,
137.04, 136.89, 136.42, 134.63, 133.93, 133.12, 132.48, 129.23, 129.06, 128.77,
128.68, 128.60, 128.56, 128.42, 127.57, 124.77, 124.73, 124.28, 124.19, 124.14,
112.23, 111.71, 111.49, 111.29, 111.21, 110.82, 79.44, 78.51, 77.80, 68.68, 68.63,
60.37, 52.42, 52.34, 31.81, 29.33, 29.23, 22.65, 14.08. HRMS-ESI: calculated for
[M+Na]
+
(C
52
H
60
FN
3

O
10
Na): m/z 928.4155 found: m/z 928.4148.
Compound 8h:
124

8g (1.20 g, 1.32 mmol) was first dissolved in ethanol (20 mL), to which acetic acid (4
mL), and iron powder (0.4 g, 7.0 mmol) was added. The reaction was stirred and
heated under reflux for 2 hours. The reaction mixture was then filtered and the filtrate
solvent was removed in vacuo. The residue after solvent removal was dissolved in
CH
2
Cl
2
(30 mL), washed with water (2 x 30 mL), and dried over anhydrous Na
2
SO
4
.
Removal of CH
2
Cl
2
solvent gave pure amine which was immediately used for the
next coupling. Acid 8b (0.37 g, 2.0 mmol) was dissolved in thionyl chloride (1.5 mL)
and the mixture was heated under reflux for 2 h. The solvent was removed in vacuo
and anhydrous ether (2 x 30 mL) was added and removed again. The solvent was then
removed in vacuo and saturated with nitrogen gas before addition of 10 mL dry
CH
2

Cl
2
. The above amine (1.06 g, 1.21 mmol) was dissolved in 10 mL dry CH
2
Cl
2
and pyridine (0.32 mL, 4 mmol) before addition to the reaction mixture above. The
reaction mixture was stirred at 50
o
C for 6 hours and then was washed with aq
NaHCO
3
(30 mL). Drying over anhydrous Na
2
SO
4
and removal of solvent in vacuo
gave the crude product which was further purified by flash column chromatography
(silica gel as the stationary phase) using hexane/ethyl acetate (2:1) as the eluent to
give pure 8h as white solid. Yield: 0.91 g, 72%.
1
H NMR (300 MHz, CDCl
3
) δ 10.04
(s, 1H), 8.71~8.83 (m, 2H), 8.66 (d, 2H, J = 3.0), 8.52 (d, 2H, J = 3.0), 7.97 (m, 1H),
7.77 (m, 1H), 7.55~7.61 (m, 4H), 7.37~7.48 (m, 5H), 7.04~7.34 (m, 5H), 5.12 (m,
2H), 5.03 (m, 2H), 4.25 (m, 2H), 4.17 (s, 3H), 2.03 (m, 2H), 1.71 (m, 2H), 1.50 (m,
8H), 1.11 (m, 3H).
13
C NMR (125 MHz, CDCl

3
) δ 165.83, 163.13, 160.41, 159.44,
156.14, 155.30, 154.23, 152.13, 151.56, 149.60, 141.79, 139.47, 138.29, 137.54,
125

136.47, 134.80, 133.90, 132.79, 129.91, 129.00, 128.94, 128.66, 128.41, 128.22,
128.15, 127.70, 127.23, 126.25, 126.01, 125.91, 125.25, 125.31, 125.16, 125.11,
124.13, 123.78, 123.69, 121.66, 121.58, 111.66, 111.25, 110.82, 110.73, 78.92, 77.86,
68.68, 68.63, 52.33, 31.82, 29.34, 29.25, 29.22, 26.02, 22.66, 14.09. HRMS-FAB:
calculated for [M]
-
(C
16
H
23
NO
6
): m/z 1041.4545 found: m/z 1041.4461.
Compound 8i:
8h (0.18 g, 0.15 mmol) was first dissolved in ethanol (2 mL), to which acetic acid (0.4
mL), and iron powder (0.1 g, 1.78 mmol) was added. The reaction was stirred and
heated under reflux for 2 hours. The reaction mixture was then filtered and the filtrate
solvent was removed in vacuo. The residue after solvent removal was dissolved in
CH
2
Cl
2
(5 mL), washed with water (2 x 5 mL), and dried over anhydrous Na
2
SO

4
.
Removal of CH
2
Cl
2
solvent gave pure amine which was immediately used for the
next coupling. Acid 8b (0.1 g, 0.35 mmol) was dissolved in thionyl chloride (0.5 mL)
and the mixture was heated under reflux for 2 h. The solvent was removed in vacuo
and anhydrous ether (2 x 5 mL) was added and removed again. The solvent was then
removed in vacuo and saturated with nitrogen gas before addition of 3 mL dry CH
2
Cl
2
.
The above amine (0.14 g, 0.14 mmol) was dissolved in 3 mL dry CH
2
Cl
2
and 3ml
DMF and pyridine (0.05 mL, 0.7 mmol) before addition to the reaction mixture above.
The reaction mixture was stirred at 60
0
C for 6 hours and then was washed with aq
NaHCO
3
(10 mL). Drying over anhydrous Na
2
SO
4

and removal of solvent in vacuo
gave the crude product which was further purified by flash column chromatography
(silica gel as the stationary phase) using hexane/ethyl acetate (2:1) as the eluent to
126

give pure 8i as white solid. Yield: 0.1 g, 56%.
1
H NMR (300 MHz, CDCl
3
) δ 9.75 (s,
1H), 9.55 (s, 1H), 8.55~8.67 (m, 2H), 8.42 (d, 2H, J = 3.2), 8.30 (d, 1H, 2H, J = 3.2),
8.28 (m, 2H), 7.85~7.93 (m, 2H), 7.65 (m, 1H), 7.32~7.39 (m, 2H), 7.28 (d, 1H, 2H, J
= 1.9), 7.24 (d, 1H, 2H, J = 5.3), 7.17~7.22 (m, 3H), 7.05 (m, 2H), 6.93~7.02 (m, 5H),
5.11 (s, 1H), 4.83 (s, 1H), 4.80 (s, 1H), 4.02 (m, 4H), 3.89 (m, 3H), 2.49 (s, 3H), 1.82
(m, 2H), 1.48 (m, 2H), 1.30 (m, 8H), 0.88 (m, 3H).
13
C NMR (125 MHz, CDCl
3
) δ
165.69, 163.10，161.19, 161.00, 160.73, 156.09, 155.24, 152.19, 148.92, 147.57,
144.17, 141.74, 139.32, 136.80, 136.41, 135.75, 134.60. 133.87, 132.81, 129.91,
129.38, 129.25, 129.10, 128.89, 128.72, 128.62, 128.36, 128.15, 127.73, 127.30,
126.56, 126.44, 126.29, 126.03, 125.32, 125.03, 123.97, 121.88, 121.74, 120.76,
120.61, 120.23, 116.27, 111.69, 111.12, 110.78, 110.68, 80.12, 78.99, 78.61, 77.76,
77.18, 68.59, 52.20, 31.80, 29.66, 29.32, 29.22, 25.99, 22.64, 20.69, 14.07.
HRMS-FAB: calculated for [M]
-
(C
74
H

76
F
2
N
5
O
13
): m/z 1280.5408 found: m/z
1280.4984.
Compound 8m:
8i (0.1 g, 0.08 mmol) was first dissolved in ethanol (1 mL), to which acetic acid (0.1
mL), and iron powder (0.04 g, 0.7 mmol) was added. The reaction was stirred and
heated under reflux for 2 hours. The reaction mixture was then filtered and the filtrate
solvent was removed in vacuo. The residue after solvent removal was dissolved in
CH
2
Cl
2
(2 mL), washed with water (2 x 3 mL). Removal of CH
2
Cl
2
solvent gave pure
amine 8j. Compound 8j was dissolved in dioxane (2 ml) to which 1M KOH (0.4 ml,
0.4 mmol) was added. The mixture was heated at 50
0
C overnight and then quenched
127

with water (4 ml). The aqueous layer was neutralized with 1M KHSO

4
(0.4ml) and
extracted with DCM (2 x 5 mL). Removal of CH
2
Cl
2
solvent gave pure compound 8k.
Compound 8k (0.073 g, 0.06 mmol) and BOP (0.066 g, 0.15 mmol) were dissolved in
CH2Cl2 (2 ml) and stirred for 30min, DIEA (0.05 ml, 0.3 mmol) was added and the
reaction mixture was stirred at room temperature for 6 hours. Removal of solvent in
vacuo gave the crude product, which was purified by flash column chromatography
on silica gel using DCM/MeOH (50:1) as the eluent to give a pure white product 8m.
Yield: 34 mg, 35%.
1
H NMR (500 MHz, CDCl
3
) δ 10.50 (s, 1H), 10.44 (s, 1H), 9.77
(s, 1H), 8.98~9.12 (m, 2H), 8.91 (m, 1H), 8.84 (m, 1H), 8.70 (d, 1H, J = 1.4), 8.50 (d,
1H, J = 1.4), 8.35 (d, 1H, J = 1.4), 7.97 (m, 1H), 7.85 (m, 1H), 7.65 (d, 1H, J = 1.4),
7.40~7.48 (m, 3H), 7.37 (d, 1H, J = 1.4), 7.23 (d, 2H, J = 6.9), 5.18 (m, 2H), 4.87 (m,
2H), 4.83 (m, 2H), 4.09 (m, 4H), 2.49 (s, 3H), 1.87 (m, 2H), 1.50 (m, 2H), 1.35 (m,
8H), 0.89 (m, 3H).
13
C NMR (125 MHz, CDCl
3
) δ 165.77, 164.04, 163.15, 161.20,
160.74, 156.12, 155.25, 151.99, 148.77, 141.73, 139.37, 136.32, 135.47, 134.60,
133.90, 132.83, 129.00, 128.84, 128.76, 128.56, 128.36, 128.18, 127.64, 127.44,
126.41, 126.22, 125.97, 125.56, 126.22, 125.06, 124.01, 121.45, 121.04, 120.35,
111.65, 111.21, 110.88, 110.71, 78.94, 77.72, 68.62, 52.25, 31.79, 29.67, 29.32, 29.22,

25.99, 22.64, 20.98, 14.07. HRMS-FAB: calculated for [M]
-
(C
74
H
76
F
2
N
5
O
13
): m/z
1218.5404 found: m/z 1218.4984.
Compound 8:
8m (20 mg, 0.016 mmol) was reduced by catalytic hydrogenation in THF/MeOH (2
ml/2 ml) at 40
0
C, using Pd/C (10 mg, 50%) as the catalyst for 3 h. The reaction
128

mixture was then filtered and the solvent removed in vacuo to give the pure yellow
solid.
1
H NMR (500 MHz, DMSO-d
6
) δ 10.60 (s, 1H), 10.48 (s, 1H), 9.97 (s, 1H),
8.11(m, 1H), 8.01 (m, 1H), 7.88 (m, 1H), 7.75 (m, 2H), 7.60 (m, 1H), 7.37 (m, 4H),
7.11 (m, 1H), 7.03 (m, 1H), 6.69 (m, 1H), 3.92 (m, 4H), 2.20 (s, 3H), 1.75 (m, 2H),
1.70 (m, 2H), 1.25 (m, 8H), 0.88 (m, 3H).

13
C NMR (75 MHz, DMSO) δ 170.50,
169.90, 166.71, 163.94, 162.01, 155.52, 155.01, 152.10, 151.65, 147.06, 146.80,
138.67, 130.69, 130.21, 129.65, 128.59, 127.98, 127.76, 127.27, 127.09, 126.84,
126.68, 125.40, 124.45, 124.49, 119.78, 117.13, 116.18, 115.04, 113.09, 110.83,
110.45, 108.62, 69.27, 69.16, 54.62, 53.79, 32.29, 30.04, 29.81, 29.71, 26.59, 26.52,
26.16, 23.13, 21.65, 14.99, 13.50. HRMS-FAB: calculated for [M]
-
(C
74
H
76
F
2
N
5
O
13
):
m/z 948.4073 found: m/z 948.3992.

129

Reference:

1. (a) Meng, Q.; Hesse, M. Top. Curr. Chem. 1992, 161, 107. (b) Sessler, J.; Burrell, A. Top. Curr.
Chem. 1992, 161, 177. (c) Bernhardt, P. V.; Moore, E. G. Aust. J. Chem. 2003, 56, 239.
2. (a) Grave, C.; Schlu¨ter, A. D. Eur. J. Org. Chem. 2002, 3075. (b) Ho¨ger, S. Chem. Eur. J. 2004,
10, 1320. (c) Zhang, W.; Moore, J. S. Angew. Chem., Int. Ed. 2006, 45, 4416.
3. Zhang, W.; Moore, J. S. Angew. Chem., Int. Ed. 2006, 45, 4416.
4. Holub, J. M.; Jang, H. J.; Kirshenbaum, K. Org. Lett. 2007, 9, 3275.
5. (a) Gellman, S. H. Acc. Chem. Res. 1998, 31, 173. (b) Hill, D. J.; Mio, M. J.; Prince, R. B.; Hughes,
T. S.; Moore. J. S. Chem. Rev. 2001, 101, 3893. (c) Cheng, R. P.; Gellman, S. H.; DeGrado, W. F.
Chem. ReV. 2001, 101, 3219. (d) Huc, I. Eur. J. Org. Chem. 2004, 17. (e) Li, Z. T.; Hou, J. L.; Li,
C.; Yi, H. P. Chem. Asian J. 2006, 1, 766. (f) Gong, B. Acc. Chem. Res. 2008, 41, 1376. (g) Horne,
W. S.; Gellman, S. H. Acc. Chem. Res. 2008, 41, 1399. (h) Li, X.; Wu, Y D.; Yang, D. Acc. Chem.
Res. 2008
, 41, 1428. For some selected H-bonded macrocyles, see: (i) Srinivasan, A.; Ishizuka, T.;
Osuka, A.; Furuta, H. J. Am. Chem. Soc. 2003, 125, 878. (j) Jiang, H.; Leger, J. M.; Guionneau, P.;

Huc, I. Org. Lett. 2004, 6, 2985.
6.
(a) Yuan, L.; Feng, W.; Yamato, K.; Sanford, A. R.; Xu, D.; Guo, H.; Gong, B. J. Am. Chem. Soc.
2004, 126, 11120. (b) Xing, L. Y.; Ziener, U.; Sutherland, T. C.; Cuccia, L. A. Chem. Commun.
2005, 5751. (c) Zhang, A. M.; Han, Y. H.; Yamato, K.; Zeng, X. C.; Gong, B. Org. Lett. 2006, 8,
803. (d) Qin, B.; Chen, X. Y.; Fang, X.; Shu, Y. Y.; Yip, Y. K.; Yan, Y.; Pan, S. Y.; Ong, W. Q.;
Ren, C. L.; Su, H. B.; Zeng, H. Q. Org. Lett. 2008, 10, 5127. (e) Berni, E.; Dolain, C.; Kauffmann,
B.; Lger, J M.; Zhan, C.; Huc, I. J. Org. Chem. 2008, 73, 2687. (f) Zhu, Y. Y.; Li, C.; Li, G. Y.;
Jiang, X. K.; Li, Z. T. J. Org. Chem. 2008, 73, 1745. (g) Ahn, H. C.; Yun, S. M.; Choi, K. Chem.
Lett. 2008, 37, 10.
7. (a) Feng, W.; Yamato, K.; Yang, L. Q.; Ferguson, J. S.; Zhong, L. J.; Zou, S. L.; Yuan, L. H.;
Zeng, X. C.; Gong, B. J. Am. Chem. Soc. 2009, 131, 2629. (b) Ferguson, J. S.; Yamato, K.; Liu, R.;
He, L.; Zeng, X. C.; Gong, B. Angew. Chem., Int. Ed. 2009, 48, 3150. (c) Yang, L. Q.; Zhong, L. J.;
Yamato, K.; Zhang, X. H.; Feng, W.; Deng, P. C.; Yuan, L. H.; Zeng, X. C.; Gong, B. New J.
Chem. 2009, 33, 729. (d) Li, F.; Gan, Q.; Xue, L.; Wang, Z M.; Jiang, H. Tetrahedron Lett. 2009,
50, 2367.
8. Zhu, Y. Y.; Li, C.; Li, G. Y.; Jiang, X. K.; Li, Z. T. J. Org. Chem. 2008, 73, 1745.
9. Helsel, A. J.; Brown, A. L.; Yamato, K.; Feng, W.; Yuan, L. H.; Clements, A. J.; Harding, S. V.;
Szabo, G.; Shao, Z. F.; Gong, B. J. Am. Chem. Soc. 2008, 130, 15784.
10. Bing Gong, Chem. Eur. J. 2001,7
, 4337.
11. Qin, B.; Chen, X. Y.; Fang, X.; Shu, Y. Y.; Yip, Y. K.; Yan, Y.; Pan, S. Y.; Ong, W. Q.; Ren, C. L.;
Su, H. B.; Zeng, H. Q. Org. Lett. 2008, 10, 5127.
12. Babb, D. A., ARKIVOC 2004, 2003, 164.