5166 Liu et al.
Asian J. Chem.
cm-1): 3124, 2973, 2896, 1657, 1404, 1226, 1073, 823, 780.
Elemental analysis [Anal. calcd. (%) for C18H26O6]: C 63.89,
H 7.74; Found (%): C 63.71, H 7.32.
TABLE-1
PRODUCTS AND YIELDS FROM THE DIFFERENT
STARTING MATERIALS IN K2CO3/EtOH SYSTEM
Entry
X Groups
CH3O
Melt point (°C)
155-157
136.4
Yield (%)
98.0
2,5-Diisoamylformate hydroquinone (9):Yield: 80.1 %.
1
m.p. 48-49 °C; H NMR (400 Hz, CDCl3): δ 12.07 (s, 2H),
1
2
3
4
5
6
7
8
9
CH3CH2O
98.2
7.26 (s, 2H), 4.34-4.31 (t, 4H), 3-2.89 (m, 4H), 1.72-1.60 (m,
2H), 0.92-0.90 (d, 12 H); IR (KBr, νmax, cm-1): 3128, 2959,
2872, 1655, 1401, 1220, 1074, 822, 778. Elemental analysis
[Anal. calcd. (%) for C18H26O6]: C 63.89, H 7.74; Found (%):
C 63.53, H 7.47.
CH3CH2CH2O
(CH3)2CHO
100.4
98.3
136.2-137.1
101.8
97.0
CH3(CH2)2CH2O
CH3CH2(CH3)CHO
(CH3)2CHCH2O
CH3(CH2)3CH2O
(CH3)2CHCH2CH2O
87.9
> 200
85.8
111
86.7
104.7-105
48-49
83.6
2,5-Dicyclohexylformate hydroquinone (10): Yield:
79.2 %. m.p. 207-208 °C; 1H NMR (400 Hz, CDCl3): δ 12.24
(s, 2H), 7.34 (t, 2H), 4-3.98 (m, 2H), 2.03-1.95 (m, 8H), 1.87-
1.66 (m, 8H), 1.44-1.27 (m, 4H); IR (KBr, νmax, cm-1): 3048,
2627, 2561, 1646, 1424, 1228, 1058, 836, 749. Elemental
analysis [Anal. calcd. (%) for C20H26O6]: C 66.28, H 7.23;
Found (%): C 66.04, H 7.15.
80.1
O
10
207-208.2
79.2
[Anal. calcd. (%) for C10H10O6]: C 53.10, H 4.46; Found (%):
C 53.02, H 4.22.
2,5-Diethylformate hydroquinone (2): Yield: 98.2 %.
m.p. 136.4 °C; 1H NMR (400 Hz, CDCl3): δ 9.87 (s, 2H), 7.27
Antimicrobial activity: The antibacterial activity of the
synthesized compounds was tested against Escherichia coli
and Bacillus subtilis using MH medium (Mueller-Hinton
medium), the antifungal activity of the compounds was tested
against Candida albicans using RPMI-1640 mediun. The MICs
(minimum inhibitory concentrations) of the test compounds
were determined by a colorimetric method using the dye
MTT12,13. Suspension of the microbes prepared to contain
approximately 105 cfu/mL and applied to 96-well microplates
with serially diluted compounds in DMSO to be tested and
incubated at 37 °C for 24 h and 48 h for bacteria and fungi,
respectively.After the MICs were visually determined on each
of microtitration plates, 50 µL MTT solution was added to
each well for 4-5 h. The supernatant of each well was removed
and 100 µL of isopropanol containing 5 % 1 mol/L HCl was
added to extract the dye. The optical density (OD value) was
measured with a microplate reader at 550 nm.
(s, 2H), 4.39-4.31 (m, 4H), 1.34-1.31 (t, 6H); IR (KBr, νmax
,
cm-1): 3296, 2990, 2907, 1685, 1402, 1197, 1099, 802, 792.
Elemental analysis [Anal. calcd. (%) for C12H14O6]: C 56.68,
H 5.55; Found (%): C 56.30, H 5.41.
2,5-Dipropylformate hydroquinone (3):Yield: 98.3 %.
1
m.p. 100.4 °C; H NMR (400 Hz, CDCl3): δ 10.11 (s, 2H),
7.25 (s, 2H), 3.41-3.36 (t, 4H), 1.46-1.30 (m, 4H), 0.94-0.86
(t, 6H); IR (KBr, νmax, cm-1): 3117, 2963, 2897, 1665, 1402,
1208, 1067, 815, 780. Elemental analysis [Anal. calcd. (%)
for C14H18O6]: C 59.57, H 6.43; Found (%): C 59.13, H 6.41.
2,5-Diisopropylformate hydroquinone (4):Yield: 97 %.
m.p. 136.2-137.1 °C; 1H NMR (400 Hz, CDCl3): d 12.14 (s,
2H), 7.27 (s, 2H), 3.09-2.50 (m, 2H), 1.34-1.24 (d, 12H); IR
(KBr, νmax, cm-1): 3125, 2973, 1663, 1377, 1219, 1061, 713,
753. Elemental analysis [Anal. calcd. (%) for C14H18O6]: C
59.57, H 6.43; Found (%): C 59.04, H 6.13.
2,5-Dibutylformate hydroquinone (5): Yield: 87.9 %.
1
m.p. 101.8 °C; H NMR (400 Hz, CDCl3): δ 12.07 (s, 2H),
RESULTS AND DISCUSSION
The MICs of the compounds against three bacterias are
presented in Table-2. The compounds 2-9 showed to be inactive
against Escherichia coli and Bacillus subtilis. To the contrary,
compounds 1 and 10 exhibited antimicrobial activity against
the two bacteria strain with an MIC value of 18.9-28.6 µg/mL,
which was comparable to the positive control kanamycin and
penicillin.Although all the inhibiting activities were lower than
the positive control, the activities of compounds 1 and 10
exhibited similar antibacterial activities with commercial
antibiotics. Compounds 1-10 were also tested against Candida
albicans which they had no antifungal activity.
7.21 (s, 2H), 4.184.15 (t, 4H), 1.71-1.58 (m, 4H), 1.45-1.31 (m,
4H), 0.93-0.88 (t, 6H); IR (KBr, νmax, cm-1): 3126, 2962, 2898,
1663, 1402, 1212, 1066, 814, 799. Elemental analysis [Anal.
calcd. (%) for C16H22O6]: C 61.92, H 7.15; Found (%): C 61.84,
H 6.89.
2,5-Di-α-methylpropylformate hydroquinone (6):
Yield: 85.8 %. m.p. > 200 °C; 1H NMR (400 Hz, CDCl3): δ
12.23 (s, 2H), 7.28 (s, 2H), 2.99-2.74 (m, 2H), 1.94-1.80 (m,
4H), 1.46-1.43 (d, 6H), 1.27-1.24 (t, 6H); IR (KBr, νmax, cm-1):
3125, 2935, 2565, 1669, 1440, 1217, 1058, 849, 753.
Elemental analysis [Anal. calcd. (%) for C16H22O6]: C 61.92,
H 7.15; Found (%): C 61.90, H 7.07.
Compounds 1 and 10 showed strong antimicrobial
activities. According to structure-activity relationships, it is
assumed that the non-substitutional group phenyl ring may
play a key role. Other compounds showed no significant inhibi-
tion. This may be due to the large substituents hindering the
compounds to permeate the cell membrane. Nevertheless, the
biological activities of their potential metabolites seems to be
worth studying.
2,5-Diisobutylformate hydroquinone (7):Yield: 86.7 %.
m.p. 111 °C; 1H NMR (400 Hz, CDCl3): δ 12.07 (s, 2H), 7.29
(s, 2H), 3.97-3.95 (d, 4H), 1.98-1.91 (m, 2H), 0.99-0.88 (d,
12H); IR (KBr, νmax, cm-1): 3126, 2968, 2910, 1663, 1407,
1237, 1073, 826, 775. Elemental analysis [Anal. calcd. (%)
for C16H22O6]: C 61.92, H 7.15; Found (%): C 61.57, H 6.94.
2,5-Diamylformate hydroquinone (8): Yield: 83.6 %.
m.p. 104-105 °C; 1H NMR (400 Hz, CDCl3): δ 12.10 (s, 2H),
7.26 (s, 2H), 4.30-4.27 (t, 4H), 4.18-4.13 (m, 4H), 3.19-2.96
Conclusion
We have synthesized a series of 2,5-substituent hydro-
quinone derivatives derivatives using a successful method
(m, 4H), 1.73-1.56 (m, 4H), 1.36-1.27 (t, 6H); IR (KBr, νmax
,