Pentasaccharides from the Seeds of Ipomoea intrapilosa
Journal of Natural Products, 2007, Vol. 70, No. 7 1157
was methylated with CH2N2 and further acetylated (Ac2O-C5H5N, 2:1)
to give a residue (64 mg) that was subjected to preparative HPLC on
a reversed-phase C18 column (7 µm, 19 × 300 mm). The elution was
isocratic with CH3CN-MeOH (95:5) using a flow rate of 9 mL/min.
The eluate with a tR of 12.5 min was again collected by heart cutting,
and the 1H and 13C NMR data for the isolated product allowed its
identification as the peracetylated derivative of operculinic acid A
methyl ester: mp 80-82 °C; [R]D -31 (c 1.0, MeOH), which was
identified by comparison of NMR data with published values.4
Esterification of the Saponification-Liberated Carboxylic Acids.
Compound 5 (30 mg) in 5% KOH-H2O (1 mL) was refluxed at 95 °C
for 45 min. The reaction mixture was acidified to pH 3.0 and extracted
with CH2Cl2 (5 mL). The organic layer was dried over anhydrous Na2-
SO4 and filtered. A solution of benzyl alcohol (10.5 mg) in CH2Cl2 (1
mL), containing dicyclohexylcarbodiimide (3 mg) and 4-dimethylami-
nopyridine (1 mg), was added to the mixture of carboxylic acids. The
reaction was stirred for 12 h at room temperature and filtered, and the
solvent was evaporated. The residue was analyzed by GC-MS: benzyl
R-methylbutyrate (tR 3.64 min) [M]+ 192 (5), 108 (19), 92 (8.0), 91
(100), 77 (10), 65 (15), 57 (16), 39 (12); benzyl trans-cinnamoate (tR
6.20 min) [M]+ 238 (14), 220 (8.6), 194 (10.5), 193 (72), 178 (8), 161
(8), 147 (8), 132, (12), 131 (100), 115 (20), 103 (52), 91 (86), 77 (41),
65 (23), 51 (24), 39 (11); and benzyl dodecanoate (tR 6.58 min) [M]+
290 (15), 272 (3), 224 (13), 199 (62), 198 (16), 181 (47), 180 (11),
163 (43), 162 (9), 143 (10), 139 (3), 125 (10), 121 (6), 108 (92), 107
(26), 105 (7), 92 (15), 91 (100), 81 (10), 67 (3), 65 (17), 56 (3), 43
(10), 39 (23). The crude mixture was purified by HPLC on a normal-
phase column (µPorasil, 10 µm, 3.9 × 300 mm; Waters) using hexane-
EtOAc (99:1, flow rate 0.6 mL/min) to give three peaks: benzyl
dodecanoate (tR 7.92 min), benzyl R-methylbutyrate (tR 8.43 min), and
benzyl cinnamoate (tR 11.22 min). The physical and spectroscopic
constants measured for the eluate with tR 8.43 min were identical in
all aspects to those previously reported14 for (S)-(+)-benzyl R-meth-
ylbutyrate: oil, [R]598 +9.3, [R]578 +9.6, [R]546 +10.9, [R]436 +17.3,
[R]365 +26 (c 1.0, CHCl3). Treatment of the mixture of carboxylic acids
obtained from intrapilosin IV (4, 6.0 mg), as described above, yielded
the (R)-(-)-benzyl R-methylbutyrate: [R]598 -9, [R]578 -9, [R]546
-10.5, [R]436 -17, [R]365 -25 (c 0.8, CHCl3). Saponification of
compounds 1, 2, and 6 afforded (S)-(+)-R-methylbutyric acid: [R]D
+10 (c 1.5, CHCl3).
Acknowledgment. This research was supported by Consejo Na-
cional de Ciencia y Tecnolog´ıa (45861-Q). G.B.H. was a visiting scholar
at UNAM with the financial support of a Fulbright-Garc´ıa Robles grant.
L.C. is grateful to Direccio´n General de Estudios de Posgrado (UNAM)
for a scholarship. Thanks are due to G. Duarte and M. Guzma´n (USAI,
Facultad de Qu´ımica, UNAM) for the recording of mass spectra. Dr.
P. Hersch (Instituto Nacional de Antropolog´ıa e Historia, Me´xico)
kindly provided ethnobotanical information.
References and Notes
(1) A medicinal plant complex consists of an assemblage of herbal drugs
that are taxonomically different at the specific, generic, and/or familial
level but that shares a common name, one or more key morphological
features, certain organoleptic characteristics, and one therapeutic
application. For an example, see: (a) Linares, E.; Bye, R. J.
Ethnopharmacol. 1987, 19, 153-183. (b) Pereda-Miranda, R.;
Fragoso-Serrano, M.; Escalante-Sa´nchez, E.; Herna´ndez-Carlos, B.;
Linares, E.; Bye, R. J. Nat. Prod. 2006, 69, 1460-1466.
(2) The Mexican term “cazahuate” is derived from the Nahuatl (“cuau-
hzahuatl”) words for tree (“quauitl”) and mange (“zahuatl”) and refers
to the uses of this medicinal plant complex to treat itching and rashes
(“zahuistle”) by rubbing the raw flowers directly on the skin.
(3) Leo´n, I.; Miro´n, G.; Alonso, D. J. Nat. Prod. 2006, 69, 896-
902.
(4) Che´rigo, L.; Pereda-Miranda, R. J. Nat. Prod. 2006, 69, 595-599.
(5) Emmart, E. W. The Badianus Manuscript (Codex Barberini, Latin
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MD, 1940; p 215.
(6) (a) Argueta Villamar, A.; Cano Asseleih, L. M.; Rodarte, M. E. Atlas
de las Plantas de la Medicina Tradicional Mexicana; Instituto
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Ort´ız, C.; Castillo-Espan˜a, P. Plantas Medicinales Utilizadas en el
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Sugar Analysis. A solution of the crude glycosidic acid (20 mg)
obtained from the saponification of the resin glycoside mixture in 4 N
HCl (10 mL) was heated at 90 °C for 2 h. The reaction mixture was
diluted with H2O (5 mL) and extracted with Et2O (30 mL). The aqueous
phase was neutralized with 1 N KOH, extracted with n-BuOH (30 mL),
and concentrated to give a colorless solid. The residue was dissolved
in CH3CN-H2O (1:1) and directly analyzed by HPLC: Waters standard
column for carbohydrate analysis (µBondapak NH2; 3.9 × 300 mm,
10 µm), using an isocratic elution of CH3CN-H2O (85:15), a flow
rate of 1 mL/min, and a sample injection of 20 µL (sample concentra-
tion: 5 mg/mL). Coelution experiments with standard carbohydrate
samples allowed the identification of rhamnose (tR ) 5.9 min), fucose
(tR ) 7.7 min), and glucose (10.1 min). Each of these eluates were
individually collected, concentrated, and dissolved in H2O. Optical
activity was recorded after stirring the solutions for 2 h at room
temperature: L-rhamnose [R]598 +8, [R]578 +8, [R]546 +9, [R]436 +15,
[R]365 +21 (c 0.1, H2O); D-fucose [R]598 +81, [R]578 +83, [R]546 +94,
[R]436 +155, [R]365 +236 (c 0.1, H2O); D-glucose [R]598 +50, [R]578
+51, [R]546 +57, [R]436 +97, [R]365 +150 (c 0.1, H2O).
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