JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
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times. Afer being concentrated to dryness, the organic residue was separated by semipre-
parative HPLC [1.0 ml/min, MeCN/0.1%HCOOH–H2O (45:55)] to yield 2-methyl-4-(3-
indolyl)-butyric acid (a), and paniculidine C (b) (each 0.3 mg) at 11.3 min and 12.7 min,
respectively. e structures of compounds a and b were identified by LC-MS (Figure S25,
Supporting Information) under the following conditions: an Agilent 1260 chromatograph
equipped with an Agilent Zorbax SB-Aq RP C18 column (4.6 × 250 mm, 5 μm); column
temperature: 35 °C; mobile phase: 0–30 min MeCN/0.1%HCOOH–H2O (10:90–100:0); flow
rate: 1.0 ml/min; UV detection wavelength: 210 nm. e molecular weights of a and b were
m/z 217 and 203, respectively. e signs of the specific optical rotation of a [[ꢀ]2D5 + 46.7
(c 0.03, MeOH)] and b [[ꢀ]25 + 53.3 (c 0.03, MeOH)] were the same as that of 6. Hence, the
absolute configuration of 2Dwas deduced as (12R, 12′R).
3.5. Preparation of the (R)- and (S)-MPA esters of 3
Compound 3 (1.0 mg) was dissolved in 350 μl of CH2Cl2, and DCC (0.8 mg), DMAP
(0.5 mg), and (R)-MPA (0.6 mg) were then added sequentially. e reaction mixture was
stirred for 16 h at room temperature. e crude products were separated by semiprepara-
tive HPLC [1.0 ml/min, MeCN/H2O (80:20)] to yield the (R)-MPA ester 3r at 6.5 min. In
a similar manner, (S)-MPA ester 3s was prepared by semipreparative HPLC [1.0 ml/min,
MeCN/H2O (80:20)] at 6.7 min, from the reaction of 3 (1.0 mg) with (S)-MPA.
(R)-MPA ester (3r): 1H NMR (CDCl3, 500 MHz): δH 7.55 (1H, d, J = 9.3 Hz, H-4′), 7.46
(1H, d, J = 10.2 Hz, H-11′), 7.43 (1H, s, H-2), 7.37 (1H, d, J = 8.7 Hz, H-5′), 7.04 (1H, d,
J = 7.8 Hz, H-4), 6.99 (1H, t, J = 7.8 Hz, H-5), 6.86 (1H, d, J = 8.7 Hz, H-6′), 6.73 (1H, d,
J = 7.8 Hz, H-6), 6.22 (1H, d, J = 9.3 Hz, H-3′), 4.89 (1H, s, H-14′), 4.64 (1H, s, H-14′), 4.12
(3H, s, OCH3-7), 4.07 (1H, m, H-13), 3.99 (3H, s, OCH3-7′), 3.93 (1H, m, H-13), 2.61 (1H,
m, H-10), 2.53 (1H, m, H-10), 1.80 (1H, m, H-11), 1.73 (1H, m, H-12), 1.67 (3H, s, H-15′),
1.62 (1H, m, H-11), 0.88 (3H, d, J = 6.6 Hz, H-14). (S)-MPA ester (3s): 1H NMR (CDCl3,
500 MHz): δH 7.53 (1H, d, J = 9.6 Hz, H-4′), 7.45 (1H, d, J = 10.2 Hz, H-11′), 7.42 (1H, s,
H-2), 7.32 (1H, d, J = 8.7 Hz, H-5′), 6.98 (1H, d, J = 7.7 Hz, H-4), 6.94 (1H, t, J = 7.7 Hz,
H-5), 6.79 (1H, d, J = 8.7 Hz, H-6′), 6.65 (1H, d, J = 7.7 Hz, H-6), 6.21 (1H, d, J = 9.6 Hz,
H-3′), 5.07 (1H, s, H-14′), 4.46 (1H, s, H-14′), 4.08 (3H, s, OCH3-7), 4.03 (1H, m, H-13),
3.92 (3H, s, OCH3-7′), 3.99 (1H, m, H-13), 2.60 (1H, m, H-10), 2.34 (1H, m, H-10), 1.80
(1H, m, H-11), 1.73 (1H, m, H-12), 1.62 (1H, m, H-11), 1.45 (3H, s, H-15′), 0.84 (3H, d,
J = 6.7 Hz, H-14).
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
is work was financially supported by National Natural Sciences Foundation of China [NSFC; grant
numbers 81473106, 81222051]; and National Key Technology R&D Program “New Drug Innovation”
of China [grant number 2012ZX09301002-002-002].