JOURNAL OF CHEMICAL RESEARCH 2010 483
Table 1 Synthetic comparison of molecular tweezers 4a–k
between microwave irradiation and conventional heating
C41H56N2O8: C, 69.86; H, 8.01; N; 3. 97. Found C, 69.74; H, 7.98; N
3.94%.
4g: White solid, yield 94%, m.p. 90–92 °C, [α]2D0+123.1 (c 0.13,
CH2Cl2); IR (KBr)(cm–1): 3350, 2944, 2854, 1730, 1612, 1542, 1450,
1220, 1056; 1H NMR (400 MHz, CDCl3) δ: 7.34 (s, 1H, ArH), 7.23–
7.10 (m, 5H, ArH), 6.90–6.84 (m, 2H, ArH), 6.67 (s, 1H, CONH),
6.42 (s, 1H, CONH), 5.10 (s, 1H, 12β–H), 4.67–4.63 (m, 1H, 3β–H),
3.64 (s, 3H, COOCH3), 2.35 (s, 3H, ArCH3), 2.31 (s, 3H, ArCH3), 0.93
(s, 3H, 19–CH3), 0.89 (d, J = 6.4 Hz, 3H, 21–CH3), 0.76 (s, 3H, 18–
CH3); ESI–MS m/z (%): 695.6 [(M+Na)+, 100]. Anal. Calcd for
C41H56N2O6: C, 73.18; H, 8.39; N 4.16. Found C, 72.96; H 8.37; N
4.14%.
a
Compd.
Conventional
method
Microwave
method
tc/tw
Time/min Yield/% Time/min Yield/%
4a
4b
4c
4d
4e
4f
4g
4h
4i
540
600
660
660
600
660
660
720
720
720
720
65
73
70
67
71
69
66
72
71
68
65
20
23
21
24
23
21
24
25
25
25
25
93
95
94
92
95
91
94
95
93
96
94
27
26
31
28
26
31
28
29
29
29
29
4h: White solid, yield 95%, m.p. 101–102 °C, [α]2D0+100.0 (c 0.13,
CH2Cl2); IR (KBr)(cm–1): 3344, 2946, 2875, 1718, 1596, 1526, 1448,
1
1220, 1092; H NMR (400 MHz, CDCl3) δ: 7.40 (d, J = 8.8 Hz, 2H,
4j
4k
ArH), 7.30 (d, J = 8.8 Hz, 4H, ArH), 7.25 (d, J = 8.8 Hz, 2H, ArH),
6.76 (s, 1H, CONH), 6.53 (s, 1H, CONH), 5.11 (s, 1H, 12β–H), 4.68–
4.62 (m, 1H, 3β–H), 3.64 (s, 3H, COOCH3), 0.92 (s, 3H, 19–CH3),
0.88 (d, J = 6.0 Hz, 3H, 21–CH3), 0.76 (s, 3H, 18–CH3); ESI–MS m/z
(%): 735.4 [(M+Na)+, 100]. Anal. Calcd for C39H50Cl2N2O6: C, 65.63;
H, 7.06; N 3.92. Found C, 65.50; H, 7.04; N 3.90%.
a tc, Conventional method needs time; tw, microwave method
needs time.
4i: White solid, yield 93%, m.p. 95–97 °C, [α]2D0+125.7 (c 0.12,
CH2Cl2); IR (KBr)(cm–1): 3343, 2942, 2883, 1716, 1586, 1530, 1484,
1218, 1062; 1H NMR (400 MHz, CDCl3) δ: 7.57 (s, 1H, ArH), 7.48 (s,
1H, ArH), 7.31 (s, 1H, ArH), 7.24–7.18 (m, 3H, ArH), 7.06–7.00 (m,
2H, ArH), 6.87 (s, 1H, CONH), 6.57 (s, 1H, CONH), 5.11 (s, 1H,
12β–H), 4.69–4.63 (m, 1H, 3β–H), 3.65 (s, 3H, COOCH3), 0.94
(s, 3H, 19–CH3), 0.87 (d, J = 6.4 Hz, 3H, 21–CH3), 0.75 (s, 3H, 18–
CH3); ESI–MS m/z (%): 735.4 [(M+Na)+, 100]. Anal. Calcd for
C39H50Cl2N2O6: C, 65.63; H, 7.06; N 3.92. Found C, 65.72; H, 7.08; N
3.93%.
Table 2 Association constants (Ka) and Gibbs free energy
changes (–∆G°) for the inclusion complexes of guests with
molecular tweezers 4a, 4b and 4e in CHCl3 at 25 oC
Host
Guest
Ka/L mol–1
–∆G°/kJ mol–1
4a
p-Nitroaniline
Aniline
p-Methoxyaniline
p-Nitroaniline
Aniline
1148.3
546.5
368.5
5191.2
1756.3
3832.4
776.1
629.3
536.5
17.45
15.61
14.63
21.18
18.50
20.43
16.48
15.96
15.56
4b
4e
4j: White solid, yield 96%, m.p. 105–106 °C, [α]2D0+103.3 (c 0.15,
CH2Cl2); IR (KBr)(cm–1): 3350, 2944, 2875, 1720, 1584, 1522, 1477,
p-Methoxyaniline
p-Nitroaniline
Aniline
1
1218, 1048; H NMR (400 MHz, CDCl3) δ: 7.44 (d, J = 8.8 Hz, 2H,
ArH), 7.40 (d, J = 8.8 Hz, 2H, ArH), 7.36 (d, J = 8.8 Hz, 2H, ArH),
7.25 (d, J = 8.8 Hz, 2H, ArH), 6.79 (s, 1H, CONH), 6.56 (s, 1H,
CONH), 5.10 (s, 1H, 12β–H), 4.68–4.64 (m, 1H, 3β–H), 3.64 (s, 3H,
COOCH3), 0.91 (s, 3H, 19–CH3), 0.86 (d, J = 6.4 Hz, 3H, 21–CH3),
0.75 (s, 3H, 18–CH3); ESI–MS m/z (%): 825.5 [(M+Na)+, 100]. Anal.
Calcd for C39H50Br2N2O6: C, 58.36; H, 6.28; N, 3.49. Found C, 58.20;
H, 6.30; N 3.51%.
p-Methoxyaniline
Table 3 Association constants(Ka) and Gibbs free energy
changes (–∆G0) for the inclusion complexes of amino acid
methyl esters with molecular tweezers 4a, 4b, 4e in CHCl3 at
25 oC
4k: White solid, yield 94%, m.p. 97–98 °C, [α]2D0+82.8 (c 0.17,
CH2Cl2); IR (KBr)(cm–1): 3342, 2946, 1718, 1582, 1526, 1480, 1217,
1050; 1H NMR (400 MHz, CDCl3) δ: 7.72 (s, 1H, ArH), 7.62 (s, 1H,
ArH), 7.39 (s, 1H, ArH), 7.28 (s, 1H, ArH), 7.19–7.11 (m, 4H, ArH),
6.94 (s, 1H, CONH), 6.63 (s, 1H, CONH), 5.10 (s, 1H, 12β–H), 4.66–
4.64 (m, 1H, 3β–H), 3.65 (s, 3H, COOCH3), 0.89 (s, 3H, 19–CH3),
0.88 (d, J = 6.4 Hz, 3H, 21–CH3), 0.77 (s, 3H, 18–CH3); ESI–MS m/z
(%): 825.3 [(M+Na)+, 100]. Anal. Calcd for C39H50Br2N2O6: C, 58.36;
H, 6.28; N 3.49. Found C, 58.25; H, 6.26; N 3.47%.
Host
Guest
Ka/L mol–1 –∆G°/kJ mol–1
KD/KL
4a
D-Phe-OMe
L-Phe-OMe
D-Tyr-OMe
L-Tyr-OMe
D-Phe-OMe
L-Phe-OMe
D-Tyr-OMe
L-Tyr-OMe
D-Phe-OMe
L-Phe-OMe
D-Tyr-OMe
L-Tyr-OMe
328.23
126.41
483.15
287.36
242.63
143.39
335.92
216.41
123.15
53.54
14.35
11.98
15.30
14.02
13.60
12.30
14.40
13.32
11.92
9.86
2.60
1.68
1.69
1.55
2.30
4.92
4b
4e
Conventional method for the preparation of molecular tweezers 4a–k
Triphosgene (0.11 g, 0.37 mmol)was added to a solution of methyl
deoxycholate 2 (0.2 g, 0.5 mmol) in dry CH2Cl2 (20 mL) and dry pyri-
dine (0.2 mL) at room temperature. It was then refluxed for 5 h. Inter-
mediate 3 was formed and without separation, aromatic amines (1.5
mmol) and dry pyridine (0.2 mL) were added directly to the mixture
and the reflux was continued for 4–7 h. The solvent was removed and
the residue was diluted with ethyl acetate (30 mL) and washed with
10% NaHCO3 (15 mL×3), brine (15 mL×3), and finally dried over
anhydrous Na2SO4. The solvent was evaporated to give the crude
product. The crude product was purified by column chromatography
on silica gel H with dichloromethane/ethyl acetate as eluant.
298.26
60.63
14.11
10.17
2H, ArH), 7.23 (s, 1H, CONH), 6.93 (s, 1H, CONH), 5.16 (s, 1H,
12β–H), 4.70 (br, s, 1H, 3β–H), 3.65 (s, 3H, COOCH3), 0.93 (s, 3H,
19–CH3), 0.91 (d, J = 6.8 Hz, 3H, 21–CH3), 0.77 (s, 3H, 18–CH3);
ESI–MS m/z (%): 757.3 [(M+Na)+, 100]. Anal. Calcd for C39H50N4O10:
C, 63.75; H, 6.86; N, 7. 62. Found C, 63.51; H, 6.88; N, 7.65%.
4f: White solid, yield 91%, m.p. 83–85 °C, [α]2D0+121.6 (c 0.15,
CH2Cl2); IR (KBr)(cm–1): 3346, 2949, 2843, 1732, 1606, 1547, 1468,
1222, 1044; 1H NMR (400 MHz, CDCl3) δ: 7.24–7.15 (m, 5H, ArH),
6.99 (d, J = 8.0 Hz, 1H, ArH), 6.84 (d, J = 8.0 Hz, 2H, ArH), 6.82–
6.58 (m, 2H, CONH), 5.11 (s, 1H, 12β–H), 4.65 (br, s, 1H, 3β–H),
3.81 (s, 3H, ArOCH3), 3.78 (s, 3H, ArOCH3), 3.65 (s, 3H, COOCH3),
0.91 (s, 3H, 19–CH3), 0.89 (d, J = 6.4 Hz, 3H, 21–CH3), 0.75 (s, 3H,
18–CH3); ESI–MS m/z (%): 727.6 [(M+Na)+, 100]. Anal. Calcd for
We thank the Natural Science Foundation of the State Ethnic
Affairs Commission of P.R.China (Project No.09XN08) for
the financial support.
Received 28 June 2010; accepted 23 July 2010
Paper 1000229 doi: 10.3184/030823410X12812894581758
Published online: 7 October 2010