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P. Lagisetty et al. / Bioorg. Med. Chem. 18 (2010) 6109–6120
was filtered-off on a Buchner funnel, and the filtrate was concen-
trated to dryness to obtain the NHS ester as a yellow solid
(295 mg, 81% yield). Rf (10:90 methanol/chloroform) = 0.80. 1H
NMR (300 MHz, CDCl3): d 7.92, 7.88 (2s, 2H, C@CH), 7.39 (t, 4H,
Ar-H, J = 7.0), 7.27–7.10 (m, 4H, Ar-H), 4.81 (s, 2H), 4.57 (s, 2H),
2.86 (t, 2H, J = 6.7), 2.90–2.75 (m, 6H, CH2, NHS). ESI Mass calcd
for C27H22F2N2NaO6 (M+Na)+ 531.13, found 531.00.
A solution of stearoyl chloride (450 mg, 1.49 mmol) in 1,2-dichlo-
roethane was added drop-wise to the ice-cold solution of com-
pound 1. The reaction mixture was stirred at room temperature
for 16 h. After completion of the reaction, 10% potassium carbonate
solution (10 ml) was added, and stirred for 30 min. The organic
phase was separated, dried with anhydrous sodium sulfate, and
concentrated to obtain a shiny solid of 25 (373 mg, 67% yield). 1H
NMR (300 MHz, CDCl3): d 7.92, 7.89 (2s, 2H, C@CH), 7.50–7.35
(m, 4H, Ar-H), 7.30–7.14 (m, 4H, Ar-H), 4.79, 4.55 (2s, 4H), 2.44
(td, 2H, J = 7.3, 2.3), 2.09 (t, 2H, J = 7.6), 1.65 (t, 2H, J = 7.0), 1.41
(t, 2H, J = 7.3), 1.40–1.05 (m, 24H), 0.87 (t, 3H, J = 6.7, CH3). 13C
NMR (75 MHz, CDCl3): d 172.05, 133.77, 133.40, 133.48, 130.76,
130.23, 124.29, 116.39, 116.09, 115.81, 46.45, 43.48, 35.26, 33.08,
31.92, 29.69, 29.37, 28.86, 25.06, 24.21, 22.69, 14.12. ESI Mass
calcd for C37H50F2NO2 (M+H)+ 578.38, found 578.40.
3.1.4.5. Glucosamine conjugate, 4-oxo-4-[3,5-bis(2-fluoroben-
zylidene-4-piperidonylcarbonyl)-2-glucose butanamide] (22).
Glucosamine (13 mg, 0.06 mmol) was added to a solution (30 mg,
0.06 mmol) of 21 in dry pyridine (0.3 ml), and stirred at 90 °C for
3 h. The compound was eluted with (20:80 methanol/chloroform)
on a silica column to obtain 22 as a yellow solid (23 mg, 68% yield).
1H NMR (300 MHz, CDCl3): d 8.67 (br, 1H, NH), 7.73 (s, 2H, C@CH),
7.65–7.50 (m, 4H, Ar-H), 7.40–7.30 (m, 4H, Ar-H), 7.20 (d, 1H, H-1’,
J = 4.5), 5.59 (br, 1H, OH), 5.17 (t, 1H, H-2’, J = 4.3), 4.75 (s, 4H),
3.80–3.50 (m, 4H, H-30, 40, CH2), 3.15 (t, 2H, CH2, J = 5.8), 2.90–
3.1.5.3.
3-[3,5-Bis-(2-fluorobenzylidene)-4-oxo-piperidine-1-
carbonyl]-pentadec-4-enoic acid (26). Dodecenyl succinic anhy-
dride (179 mg, 0.67 mmol) and triethylamine (0.18 ml, 1.29 mmol)
were added to a solution of compound 1 (200 mg, 0.64 mmol) in
dry methylene chloride and stirred at room temperature for 2 h.
The mixture was chromatographed on a silica column, and the title
compound 26 was eluted from the column using 10% methanol/
chloroform as eluant. The compound 26 was obtained as yellow
thick syrup (352 mg, 95% yield). Rf (10:90 methanol/chloro-
form) = 0.26. 1H NMR (300 MHz, CDCl3): d 7.90–7.80 (m, 3H,
2C@CH, vinyl-H), 7.42–7.00 (m, 9H, Ar-H, vinyl-H), 5.30–5.05 (m,
4H), 5.00–4.95 (m, 2H), 4.82–7.78 (m, 2H), 4.65–4.40 (m, 4H),
2.85–2.70 (m, 2H), 2.50–2.40 (m, 2H), 2.30–2.10 (m, 4H), 2.08–
1.90 (m, 4H), 1.90–1.70 (m, 2H), 0.91 (t, 3H, J = 6.4, CH3). 13C
*
2.75 (m, 5H, H-50, 60, 600, 2 OH). ESI Mass calcd for C29H31F2N2O8
(M+H)+ 573.20, found 573.00.
3.1.4.6. 2-[3,5-Bis(2-fluorobenzylidene-4-piperidone-1-yl)-N-(4-
fluorobenzyl)acetamide] (23). Commercially available 4-fluo-
robenzylamine (500 mg, 3.99 mmol) was reacted with bromoace-
tyl bromide (380
ll, 4.39 mmol) in presence of triethylamine
(600 l, 4.39 mmol) at room temperature for 20 min. The progress
l
of the reaction was monitored by a faster moving spot in silica TLC
(60% ethyl acetate in hexanes). At the end of the reaction, the mix-
ture was filtered, and the solvent was dried to obtain 2-bromo-N-
[4-fluorobenzyl]acetamide. Potassium iodide (166 mg, 1 mmol)
and Cs2CO3 (325 mg, 1 mmol) and 2-bromo-N-(4-fluoroben-
zyl)acetamide (270 mg, 1.20 mmol) were added to the compound
1 (311 mg, 1 mmol) in DMF (2 ml). The reaction mixture was
heated at 95 °C for 60 min. The solvent was evaporated to dryness,
and the residue was dissolved in chloroform. After brine and water
wash, the organic phase was dried over anhydrous sodium sulfate,
and concentrated to obtain a crude yellow solid. The crude com-
pound was recrystallized from chloroform and hexanes to get the
title compound 23 as a yellow crystalline solid (252 mg, 53% yield).
1H NMR (300 MHz, CDCl3): 7.93 (s, 1H), 7.83 (s, 2H, C@CH), 7.75–
7.02 (m, 8H, Ar-H), 6.97 (dd, 2H, Ar-H, J = 7.2, 2.1), 6.68 (t, 2H,
Ar-H, J = 7.2), 4.19 (s, 2H, benzylic), 4.17 (s, 2H, benzylic), 3.76 (s,
4H). ESI Mass calcd for C28H23F3N2NaO2 (M+Na)+ 499.16, found
499.91.
NMR (75 MHz, CDCl3):
d 185.81, 173.27, 170.15, 161.96 (d,
J = 55.2), 159.45 (d, J = 53.7), 135.38, 134.29, 133.30, 133.10,
131.52, 130.78, 130.51, 125.33, 124.78, 124.23 (d, J = 3.1), 122.47
(d, J = 13.3), 122.22 (d, J = 14.8), 116.32 (d, J = 18.9), 116.22 (d,
J = 21.8), 115.93 (d, J = 25.7), 46.45 (d, J = 3.2), 46.48 (d, J = 3.1),
35.27,33.08, 31.92, 29.9, 29.19, 29.44, 29.16, 28.86, 25.05, 24.21,
22.67, 14.13. ESI Mass calcd for C35H41F2NNaO4 (M+Na)+ 600.29,
found 600.20.
3.1.5.4.
3-[3,5-Bis-(2-fluorobenzylidene)-4-oxo-piperidine-1-
carbonyl]-heptadec-4-enoic acid (27). Tetradecenyl succinic
anhydride (198 mg, 0.67 mmol) and triethylamine (0.18 ml,
1.29 mmol) were added to a solution of compound 1 (200 mg,
0.64 mmol) in methylene chloride. The reaction mixture was stir-
red at room temperature for 2 h. The crude compound was passed
through silica column, and using 10% methanol/chloroform as elu-
ant, compound 27 was obtained as yellow thick syrup (357 mg,
92% yield). Rf (10:90 methanol/chloroform) = 0.31. 1H NMR
(300 MHz, CDCl3): d 7.90–7.80 (m, 3H, 2C@CH, vinyl-H), 7.45–
7.00 (m, 9H, Ar-H, vinyl-H), 5.40–4.50 (m, 9H), 2.70–1.70 (m,
9H), 1.40–1.20 (m, 12H), 0.93 (t, 3H, J = 6.6, CH3). 13C NMR
(75 MHz, CDCl3): d 186.10, 174.03, 170.76, 162.6 (d, J = 51.2),
133.75, 133.55, 132.36, 130.75, 126.68, 124.22 (d, J = 9.8), 115.98
(d, J = 21.2), 44.75, 32.46, 31.90, 22.67, 14.12. ESI Mass calcd for
3.1.5. Synthesis of series E compounds
In this series we synthesized a few conjugates of compound 1
containing a long lipid chain at piperidinyl nitrogen.
3.1.5.1. 4-[3,5-Bis(2-fluorobenzylidene)-4-oxo-piperidin-1-yl]-
N-hexadecyl-4-oxo-butyramide (24). Hexadecylamine (14 mg,
0.06 mmol) was added to a solution of compound 21 (30 mg,
0.06 mmol) in dry pyridine (0.3 ml) and stirred at 90 °C for 3 h.
After completion of the reaction, the solvent was dried, and the
crude compound was eluted with (20:80 methanol/chloroform)
on a silica column to obtain compound 24 as a yellow solid
(22 mg, 59% yield). 1H NMR (300 MHz, CDCl3): d 7.89, 7.87 (2s,
2H, C@CH), 7.53–7.10 (m, 8H, Ar-H), 6.11 (t, 2H, J = 4.9), 4.75,
4.62 (2s, 4H), 3.11 (q, 2H, J = 6.6), 2.48 (t, 2H, J = 5.6), 2.36 (t, 2H,
J = 6.2), 1.87 (br, 2H), 1.71–1.64 (m, 2H), 1.40–1.08 (m, 22H), 0.85
(t, 3H, J = 6.6, CH3). ESI Mass calcd for C39H52F2N2O3 (M+H)+
635.40, found 635.20.
C
37H45F2NNaO4 (M+Na)+ 628.32, found 628.27.
3.1.5.5. 3-[3,5-Bis-(2-fluorobenzylidene)-4-oxo-piperidine-1-
carbonyl]-heneicos-4-enoic acid (28). Octadecenyl succinic
anhydride (235 mg, 0.67 mmol) and triethylamine (0.18 ml,
1.29 mmol) were added to a solution of compound 1 (200 mg,
0.64 mmol) in methylene chloride. Compound 28 was purified as
described above, and was obtained as yellow syrup (395 mg, 93%
yield). Rf (10:90 methanol/chloroform) = 0.32. 1H NMR (300 MHz,
CDCl3): d 7.88–7.82 (m, 3H, 2C@CH, vinyl-H), 7.40–7.05 (m, 9H,
Ar-H, vinyl-H,), 5.21–5.14 (m, 2H), 5.01–4.90 (m, 2H), 4.68–4.50
(m, 8H), 2.80–2.70 (m, 2H), 2.66–2.41 (m, 4H), 2.28–2.19 (m,
3.1.5.2. N-Stearoyl-3,5-bis(2-fluorobenzylidene)-4-piperidone
(25). Triethylamine (0.4 ml, 2.85 mmol) was added to a solution
of compound 1 (300 mg, 0.96 mmol) in ice-cold 1,2 dichloroethane.