38
B. Xu et al. / Bioorganic Chemistry 56 (2014) 34–40
with concentrated hydrochloric acid, and partitioned between
ethyl acetate and water. The organic phase was separated and
washed with brine, dried over Na2SO4 and evaporated in vacuo to
afford the compound III which was directly engaged in the next
step without further purification. To a solution of compound III
H-300, 700), 7.29–7.03 (m, 9H, H-400, 600, H-5, 9, H-50-90), 6.63 (d,
J = 8.4 Hz, 2H, H-6, 8), 4.65 (m, 1H, H-2), 4.50 (m, 1H, H-20), 3.58
(s, 3H, OCH3), 3.09–2.81 (m, 4H, H-3, 30), 2.34 ppm (s, 3H, Ar-
13
CH3); C NMR (100 MHz, DMSO: d 171.9 (C-1), 171.9 (C-10),
166.1 (C-100), 155.7 (C-7), 141.2 (C-500), 137.1 (C-40), 131.3 (C-200),
130.2 (C-5, 9), 129.2 (C-60, 80), 128.7 (C-400, 600), 128.4 (C-4), 128.3
(C-50, 90), 127.5 (C-300, 700), 126.6 (C-70), 114.9 (C-6, 8), 56.2 (C-2),
54.9 (C-20), 51.9 (OCH3), 36.6, 36.2, 21.0 ppm (Ar-CH3); ESI–HRMS:
m/z [M + Na]+ Calcd for C27H28N2O5Na: 483.1896, Found 483.1888.
(1.0 mmol), L-tyrosine methyl ester hydrochloride (or L-phenylala-
nine methyl ester hydrochloride) (1.1 mmol) and NMM (2.3 mmol)
in CH2Cl2 (50 mL) was added dropwise IBCF (1.1 mmol) at 0 °C. The
mixture was stirred for 30 min and the bulk of CH2Cl2 was
removed in vacuo. The residue was dissolved in ethyl acetate and
washed sequentially with water, 5% HCl, saturated NaHCO3 solu-
tion and brine, dried with Na2SO4. Removal of the solvent gave a
residue which was recrystallized from ethyl acetate to afford target
compound 1–13.
4.2.6. N-(N-benzoyl-L-tyrosyl)-L-phenylalanine methyl ester (5)
(Colorless needle, yield 50.7%) mp: 200.0–202.0 °C, EI-MS m/z:
446 (M+), 325, 240, 180, 163, 147, 120, 105 (100), 91, 77; 1H
NMR (400 MHz, DMSO): d 9.19 (s, 1H, Ar-OH), 8.52–8.47 (m, 2H,
NHCO ꢁ 2), 7.76 (d, J = 6.8 Hz, 2H, H-300, 700), 7.50 (t, 1H, H-500),
7.43 (t, 2H, H-400, 600), 7.25–7.18 (m, 5H, H-50-90), 7.10 (d,
J = 8.4 Hz, 2H, H-5, 9), 6.61 (d, J = 8.4 Hz, 2H, H-6, 8), 4.63 (m, 1H,
H-2), 3.78 (m, 1H, H-20), 3.57 (s, 3H, OCH3), 3.07–2.78 ppm (m,
4H, H-3, 30); 13C NMR (100 MHz, DMSO): d 171.93, 171.89, 166.2
(C-100), 155.7 (C-7), 137.1 (C-40), 134.1 (C-200), 131.4 (C-500), 130.2
(C-5, 9), 129.2 (C-60, 80), 128.4 (ꢁ3, C-400, 600, C-4), 128.3 (C-50, 90),
127.5 (C-300, 700), 126.7 (C-70), 114.9 (C-6, 8), 54.9 (C-2), 53.8 (C-
20), 52.0 (OCH3), 36.6, 36.2 ppm; ESI–HRMS: m/z [M + Na]+ Calcd
for C26H26N2O5Na: 469.1739, Found 469.1742.
4.2.2. N-(N-500-hydroxy-benzoyl-
L-phenylalanyl)-L-phenylalanine
methyl ester (1)
(Colorless needle, yield 61.9%) mp: 151.0–153.0 °C, 1H NMR
(400 MHz, DMSO): d 9.96 (s, 1H, Ar-OH), 8.44 (d, J = 7.2 Hz, 1H,
NHCO), 8.24 (d, J = 8.0 Hz, 1H, NHCO), 7.64 (d, J = 8.4 Hz, 2H, H-
300, 700), 7.31–7.12 (m, 10H, H-5-9, 50-90), 6.75 (d, J = 8.8 Hz, 2H, H-
400, 600), 4.69 (m, 1H, H-2), 3.49 (m, 1H, H-20), 3.57 (s, 3H, OCH3),
3.06–2.88 ppm (m, 4H, H-3, 30); 13C NMR (100 MHz, DMSO): d
171.8 (C-1, 10), 165.9 (C-100), 160.2 (C-500), 139.4 (C-4), 137.0 (C-
40), 129.4 (C-300, 700), 129.17 (ꢁ2), 129.13 (ꢁ2), 128.3 (C-50, 90),
128.0 (C-5, 9), 126.6 (C-70), 126.2 (C-7), 124.7 (C-200), 114.7 (C-400,
600), 54.4 (C-2), 53.7 (C-20), 51.8 (OCH3), 36.9, 36.6 ppm; ESI–HRMS:
m/z [M + Na]+ Calcd for C25H24N2O5Na: 455.1583, Found 455.1589.
4.2.7. N-(N-400-nitro-benzoyl-
L-tyrosyl)-L-phenylalanol (6)
(Colorless needle, yield 73.0%) mp: 225.5–227.0 °C, EI-MS m/z:
463 (M+), 445, 297, 285, 206, 150 (100), 120, 107, 91, 60; 1H
NMR (400 MHz, DMSO): d 9.15 (s, 1H, Ar-OH), 8.92 (d, J = 8.0 Hz,
1H, NHCO), 8.62 (s, 1H, H-300), 8.37 (d, J = 8.0 Hz, 1H, H-500), 8.22
(d, J = 7.6 Hz, 1H, H-700), 7.94 (d, J = 8.0 Hz, 1H, NHCO), 7.76 (t, 1H,
H-600), 7.21–7.08 (m, 7H, H-50-90, H-5, 9), 6.61 (d, J = 8.0 Hz, 2H,
H-6, 8), 4.80 (t, 1H, OH), 4.64 (m, 1H, H-2), 3.89 (m, 1H, H-20),
3.33–3.25 (m, 2H, H-10), 2.96–2.62 ppm (m, 4H, H-3, 30); 13C
NMR (100 MHz, DMSO): d 170.7 (C-1), 163.9 (C-100), 155.7 (C-7),
147.6 (C-400), 139.0 (C-40), 135.6 (C-200), 133.9 (C-700), 130.1 (C-5,
9), 130.0 (C-600), 129.1 (C-60, 80), 128.2 (C-4), 128.0 (C-50, 90),
125.8 (C-70, C-500), 122.2 (C-300), 114.8 (C-6, 8), 62.2 (C-10), 55.3
(C-2), 52.5 (C-20), 36.5, 36.4 ppm; Anal. Calcd for C25H25N3O6: C
64.79, H 5.44; N 9.07, Found: C 64.55, H 5.67; N 8.91.
4.2.3. N-(N-500-methyl-benzoyl-
L-tyrosyl)-L-phenylalanol (2)
(Colorless needle, yield 31.6%) mp: 193.0–195.0 °C, 1H NMR
(400 MHz, DMSO): d 9.17 (s, 1H, ArNHCO), 8.36 (d, J = 8.4 Hz, 1H,
NHCO), 7.88 (d, J = 8.4 Hz, 1H, NHCO), 7.72 (d, J = 8.0 Hz, 2H, H-
300, 700), 7.26–7.00 (m, 9H, H-400, 600, H-5, 9, H-50-90), 6.61 (d,
J = 8.4 Hz, 2H, H-6, 8), 4.83 (t, 1H, OH), 4.58 (m, 1H, H-2), 3.88
(m, 1H, H-20), 3.36–3.25 (m, 2H, H-10), 2.93–2.62 (m, 4H, H-3, 30),
2.34 ppm (s, 3H, Ar-CH3); 13C NMR (100 MHz, DMSO): d 171.2
(C-1), 165.9 (100), 155.7 (C-7), 141.1 (500), 139.1 (C-40), 131.4 (C-
200), 130.1 (C-5, 9), 129.2 (C-60, 80), 128.7 (C-400, 600), 128.4 (C-4),
128.1 (C-50, 90), 127.5 (C-300, 700), 125.9 (C-70), 114.8 (C-6, 8), 62.2
(C-10), 55.2 (C-2), 52.5 (C-20), 36.5, 36.4, 21.0 ppm (Ar-CH3); ESI–
HRMS: m/z [M + Na]+ Calcd for C26H28N2O4Na: 455.1947, Found
455.1925.
The compounds 7–9 [7] and 10–14 [8] have been synthesized in
our Lab formally.
4.2.8. N-(N-benzoyl-6-nitro-
(15)
L
-tyrosyl)-L-phenylalanine methyl ester
4.2.4. N-(N-500-nitro-benzoyl-
L-tyrosyl)-
L-phenylalanine methyl ester
(3)
A solution of N-benzoyl-L-tyrosine (III-a) (5.7 g, 20 mmol) in
(Colorless needle, yield 60.3%) mp: 212.0–214.0 °C, EI-MS m/z:
491 (M+), 325, 285, 180, 163 (100), 147, 120, 107, 91; 1H NMR
(400 MHz, DMSO): d 9.17 (s, 1H, Ar-OH), 8.89 (d, J = 8.4 Hz, 1H,
NHCO), 8.60 (d, J = 7.2 Hz, 1H, NHCO), 8.29 (d, J = 8.4 Hz, 2H, H-
400, 600), 7.99 (d, J = 8.8 Hz, 2H, H-300, 700), 7.26–7.18 (m, 5H, H-50-
90), 7.11 (d, J = 8.0 Hz, 2H, H-5, 9), 6.61 (d, J = 8.4 Hz, 2H, H-6, 8),
4.68 (m, 1H, H-2), 4.49 (m, 1H, H-20), 3.57 (s, 3H, OCH3), 3.08–
2.78 ppm (m, 4H, H-3, 30); 13C NMR (100 MHz, DMSO): d 171.9,
171.5, 164.5 (C-100), 155.8 (C-7), 149.1 (C-500), 139.7 (C-200), 137.1
(C-40), 130.1 (C-5, 9), 129.1 (C-60, 80), 128.9 (C-300, 700), 128.3 (C-50,
90), 128.1 (C-4), 126.6 (C-70), 123.5 (C-400, 600), 114.9 (C-6, 8), 55.1
(C-2), 53.8 (C-20), 51.9 (OCH3), 36.5, 36.3 ppm; ESI–HRMS: m/z
[M + Na]+ Calcd for C26H25N3O7Na: 514.1590, Found 514.1581.
DMF (40 mL) was added dropwise to 22% HNO3 (40 mL) at 30 °C.
After stirring at 30 °C for additional 4 h, the reaction was extracted
with EtOAc (100 ml). The organic phase was washed with water,
dried (Na2SO4) and evaporated in vacuo to give the compound IV
as pale yellow waxy solid (5.63 g, 85.0%). To a solution of IV
(0.66 g, 2.0 mmol) and L-phenylalanine methyl ester hydrochloride
(0.47 g, 2.2 mmol) in CH2Cl2 (40 mL) and DMF (10 mL) under an
atmosphere of argon was successively added N-methylmorpholine
(NMM, 0.51 ml, 4.6 mmol), isobutylchloroform (IBCF, 0.27 ml,
2.14 mmol) at ꢀ5 °C, the reaction mixture was stirred at this tem-
perature for 15 min and then wormed up to room temperature and
stirred for 9 h. Then CH2Cl2 was removed and the residue was
diluted with water before it was extracted with EtOAc, the com-
bined organic phase was then successively washed with saturated
NaHCO3 and brine, dried with MgSO4, filtrated and evaporated in
vacuo. Purification by recrystallization from EtOAc afforded the
final compound 15 (0.54 g, 55%) as a yellow crystal. Mp 201.0–
202.5 °C, EI-MS m/z: 491 (M+), 473, 370, 285, 208, 192, 162, 122,
105 (100), 91, 77; 1H NMR (400 MHz, DMSO-d6): d 8.61–8.56
(2H, m, NHCO ꢁ 2), 7.91 (s, 1H, H-5), 7.76 (d, J = 8.4 Hz, 2H, H-300,
4.2.5. N-(N-500-methyl-benzoyl-
L-tyrosyl)-L-phenylalanine methyl
ester (4)
(Colorless needle, yield 65.2%) mp: 206–208 °C, EI-MS m/z: 460
(M+), 325, 254, 180, 162, 147, 136, 119(100), 107, 91; 1H NMR
(400 MHz, DMSO): d 9.20 (s, 1H, Ar-OH), 8.50 (d, J = 7.2 Hz, 1H,
NHCO), 8.40 (d, J = 8.4 Hz, 1H, NHCO), 7.70 (d, J = 6.8 Hz, 2H,