Beilstein J. Org. Chem. 2017, 13, 26–32.
refluxing temperature of methanol for 6 h. After completion of The product was characterized by 1H and 13C NMR, IR, ESIMS
the reaction as shown by TLC (hexane/ethyl acetate 80:20, v/v), and HRMS spectral studies. Mp 55–56 °C; 1H NMR (500 MHz,
excess methanol was removed under reduced pressure and the CDCl3) δ 7.64 (d, J = 15.6 Hz, 1H), 7.54–7.46 (m, 5H), 6.24 (d,
product was diluted with ethyl acetate (30 mL), washed with J = 15.6 Hz, 1H), 3.66 (s, 3H), 3.56 (q, 2H), 2.73 (t, 2H), 2.58
5% aqueous NaHCO3 solution (3 × 30 mL), and dried over an- (t, 2H), 2.30 (t, 2H), 1.24–1.62 (m, 12H, CH2); 13C NMR
hydrous Na2SO4. The organic solvent was removed under (75 MHz, CDCl3) δ 174.37 (-C(O)-OCH3), 165.50
reduced pressure to afford crude methyl ester of 10-undecenoic (-NH-C(O)-), 141.25 (-NH-C(O)-CH=CH-),134.81–127.83,
acid. The product was purified by column chromatography with 120.52 (-NH-C(O)-CH=CH-), 51.47 (-C(O)-OCH3-), 38.49
basic alumina and hexane as the eluent to get 99% pure methyl (-CH2-NH-), 29.44 (-S-CH2-), 29.36 (-CH2-S-), 29.22 (-CH2-
undec-10-enoate (1) as indicated by GC. The product was CH2-S-), 29.19–24.96 (-CH2-CH2-); IR (cm−1, KBr): 2853,
analyzed by 1H NMR, 13C NMR, ESIMS, and FTIR and the 2853, 1720, 1654, 1599, 1527, 1441, 1365; ESIMS (m/z): 406
structure was confirmed by comparing the data with those re- [M + H]+, 428 [M + Na]+; HRMS (m/z): [M + H]+ calcd for
ported in the literature [14].
C23H36O3NS, 406.24104; found, 406.24077.
Synthesis of methyl 11-(2-aminoethylthio) undecanoate (2): Synthesis of methyl 11-((2-((E)-3-(4-hydroxyphenyl)acryl-
For the synthesis of compound 2, a reported protocol was fol- amido)ethyl)sulfanyl)undecanoate (3b): Similarly, methyl
lowed with slight modifications [20]. Briefly, methyl unde- 11-((2-((E)-3-(4-hydroxyphenyl)acrylamido)ethyl)sulfanyl)un-
cenoate (1, 6 g, 30.3 mmol) and ABCN (0.18 g, 3 wt % of 1) decanoate (3b) was prepared from 2 (0.6 g, 2.1 mmol) and
were dissolved in 40 mL chloroform. Then, 2-mercaptoethyl- coumaric acid (0.5 g, 3.2 mmol) in 85% yield (0.78 g) and the
amine hydrochloride (6.8 g, 60 mmol) and 40 mL of 1,4- product was characterized by 1H and 13C NMR, IR, ESIMS and
dioxane/ethanol (70:30; v/v) were added and the mixture was HRMS spectral studies. Mp 64–65 °C; 1H NMR (500 MHz,
stirred at 85 °C for 48 h. The progress of the reaction was moni- CDCl3) δ 7.57 (d, J = 15.6 Hz, 1H), 7.39 (d, J = 8.6 Hz, 1H),
tored by TLC (hexane/ethyl acetate 80:20, v/v). After maximum 6.85 (d, J = 8.6 Hz, 1H), 6.26 (d, J = 15.6 Hz, 1H), 3.67 (s, 3H),
conversion, the reaction mixture was extracted with dichloro- 3.58 (q, 2H), 2.73 (t, 2H), 2.58 (t, 2H), 2.30 (t, 2H), 1.24–1.62
methane (2 × 40 mL) and the combined organic phases were (m, 12H, CH2); 13C NMR (75 MHz, CDCl3) δ 174.71 (-C(O)-
washed with saturated K2CO3, brine and finally with water and OCH3), 166. 84 (-NH-C(O)-), 158.33, 141.51 (-NH-C(O)-
dried over anhydrous Na2SO4. This crude product mixture was CH=CH-),129.64, 128.99, 117.32 (-NH-C(O)-CH=CH-),
concentrated and purified by column chromatography with 115.98, 51.58 (-C(O)-OCH3-), 38.63 (-CH2-NH-), 34.16 (-S-
hexane/ethyl acetate (92:8, v/v) to obtain pure methyl 11-(2- CH2-), 31.89 (-CH2-S-), 31.84 (-CH2-CH2-S-), 29.69–24.96
aminoethylthio)undecanoate (2) in 89% yield (7.41 g). The (-CH2-CH2-); IR (cm−1, KBr): 3409, 2923, 2853, 1729, 1652,
purified product was characterized by 1H and 13C NMR, IR and 1595, 1519, 1452, 1373; ESIMS (m/z): 422 [M + H]+, 444
ESIMS spectral studies and the structure was confirmed by [M + Na]+; HRMS (m/z): [M + H]+ calcd for C26H36O4NS,
comparing the data with those reported in the literature [15]. 422.23596; found, 422.23491.
Synthesis of methyl 11-((2-(cinnamamido)ethyl)sulfanyl)un- Synthesis of methyl 11-((2-((E)-3-(3,4-dihydroxyphenyl)-
decanoate (3a): The amidation reaction was performed acrylamido)ethyl)sulfanyl)undecanoate (3c): Similarly,
following a reported protocol with slight modifications [21]. methyl 11-((2-((E)-3-(3,4-dihydroxyphenyl)acrylamido)-
Briefly, compound 2 (0.58 g, 2.1 mmol) and cinnamic acid ethyl)sulfanyl)undecanoate was prepared from 2 (0.6 g,
(0.4 g, 3.1 mmol) were dissolved in dichloromethane (30 mL) 2.1 mmol) and caffeic acid (0.5 g, 3.2 mmol) in 85% yield
and the mixture was stirred at 0–5 °C under a nitrogen atmo- (0.81 g) and the product was characterized by 1H and
sphere. EDC·HCl (0.4 g, 2.52 mmol) and HOBt (0.3 g, 13C NMR, IR, ESIMS and HRMS spectral studies. 1H NMR
3.1 mmol) were added and the contents were stirred at 0–5 °C (500 MHz, CDCl3) δ 7.55 (d, J = 15.6 Hz, 1H), 7.12 (d, J = 8.6
for 10 min. After the addition, the mixture was stirred for 12 h Hz, 1H), 6.95 (s, 1H) 6.87 (d, J = 8.6 Hz, 1H), 6.24 (d, J = 15.6
at rt under a nitrogen atmosphere and the progress of reaction Hz, 1H), 3.68 (s, 3H), 3.56 (q, 2H), 2.73 (t, 2H), 2.58 (t, 2H),
was monitored by TLC using the solvent system chloroform/ 2.30 (t, 2H), 1.24–1.62 (m, 12H, CH2); 13C NMR (75 MHz,
methanol (80:20, v/v). After maximum conversion, the reaction CDCl3) δ 174.74 (-C(O)-OCH3), 167. 38 (-NH-C(O)-), 146.87,
mixture was extracted with dichloromethane, washed with 144.53, 142.53 (-NH-C(O)-CH=CH-), 127.07, 121.33, 117.12
water and dried over anhydrous Na2SO4 and concentrated to (-NH-C(O)-CH=CH-), 115.46, 114.71, 51.60 (-C(O)-OCH3-),
obtain the crude product. The crude product was purified by 39.05 (-CH2-NH-), 38.88 (-S-CH2-), 38.76 (-CH2-S-), 34.16
column chromatography (chloroform/methanol 90:10, v/v) to (-CH2-CH2-S-), 29.59–24.96 (-CH2-CH2-); IR (cm−1, KBr):
obtain the thioamide of cinnamic acid in 86% yield (0.73 g). 3359, 2953, 2854, 1721, 1654, 1599, 1527, 1441, 1365; ESIMS
30