PAPER
Total Synthesis of Rhoiptelol B
ESI-MS: m/z = 383 [M + Na]+.
HRMS (ESI): m/z [M + Na]+ calcd for C20H24O6Na: 383.1470;
found: 383.1461.
4305
1H NMR (300 MHz, CDCl3): d = 7.78–7.64 (m, 6 H), 7.49–7.33 (m,
6 H), 7.30–7.23 (m, 2 H), 7.03–6.92 (m, 3 H), 6.75–6.66 (m, 3 H),
6.62–6.49 (m, 1 H), 4.71–4.61 (m, 1 H), 4.30–4.18 (m, 1 H), 3.53
(s, 3 H), 3.57–3.46 (m, 1 H), 3.45–3.33 (m, 1 H), 2.69–2.41 (m, 2
H), 2.45 (s, 3 H), 1.99–1.54 (m, 4 H), 1.07 (s, 9 H), 0.98 (s, 9 H),
0.17 (s, 6 H).
13C NMR (75 MHz, CDCl3): d = 151.4, 145.0, 144.6, 135.7, 133.4,
133.3, 133.2, 131.2, 129.7, 129.3, 129.2, 128.6, 127.5, 124.6, 123.5,
119.6, 117.3, 109.5, 75.2, 71.7, 70.5, 69.0, 55.5, 39.3, 38.5, 38.1,
26.9, 25.6, 21.6, 19.2, 18.2, –4.2.
Acknowledgment
T.P. and V.V.B.R. thank UGC and CSIR, New Delhi, respectively,
for the awards of fellowships.
ESI-MS: m/z = 907 [M + Na]+.
HRMS (ESI): m/z [M + Na]+ calcd for C49H64O9NaSSi2: 907.3707;
References
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4-{(2R,4S,6S)-4-Hydroxy-6-[(1S)-1-hydroxy-2-(4-hydroxyphe-
nyl)ethyl]tetrahydro-2H-2-pyranyl}-2-methoxyphenyl 4-Meth-
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mL round-bottom flask was dissolved in anhyd CH2Cl2 (10 mL) un-
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mixture was stirred for 30 min. After the reaction was complete
(TLC), it was diluted with Et2O (20 mL) and washed with sat. aq
NaHCO3 soln (3 × 10 mL) and brine (10 mL), and then dried over
Na2SO4. Removal of the solvent followed by purification on silica
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Yield: 0.60 g (76%).
IR (neat): 3452, 2923, 1638, 1512, 1369, 1151, 1090, 865, 771 cm–1.
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1H NMR (300 MHz, CDCl3): d = 7.76 (d, J = 8.3 Hz, 2 H), 7.30 (d,
J = 8.1 Hz, 2 H), 7.09–7.01 (m, 3 H), 6.83 (d, J = 8.1 Hz, 2 H), 6.69
(d, J = 8.3 Hz, 2 H), 4.80 (d, J = 10.3 Hz, 1 H), 4.35 (m, 1 H), 3.94–
3.83 (m, 1 H), 3.70 (dd, J = 12.4, 5.2 Hz, 1 H), 3.56 (s, 3 H), 2.88–
2.67 (m, 2 H), 2.44 (s, 3 H), 1.95–1.60 (m, 4 H).
13C NMR (75 MHz, CDCl3): d = 154.4, 151.6, 145.0, 142.8, 137.2,
133.1, 130.3, 129.6, 129.3, 128.4, 123.6, 117.7, 115.3, 110.2, 75.0,
73.6, 73.1, 64.4, 55.5, 40.2, 38.4, 29.6, 21.6.
ESI-MS: m/z = 537 [M + Na]+.
HRMS (ESI): m/z [M + Na]+ calcd for C27H30O8NaS: 537.1559;
found: 537.1577.
Rhoiptelol B (2)
To a soln of compound 19 (0.10 g, 0.17 mmol) in MeOH (5 mL)
was added K2CO3 (133 mg, 0.95 mmol) and the mixture heated at
reflux temperature for 2 h, cooled to 0 °C, acidified with 1 M HCl
until pH 2. The combined aq–organic soln was extracted with
EtOAc (3 × 5 mL), washed with brine (3 mL), dried over Na2SO4
and concentrated in vacuo. Purification by column chromatography
(EtOAc–hexane, 7:3) gave rhoiptelol B (2) as a white, amorphous
powder.
Yield: 0.052 g (80%); mp 65–67 °C; [a]D25 +86.2 (c 0.3, MeOH).
IR (KBr): 3455, 2923, 1640, 1517, 1457, 1240, 1034, 769 cm–1.
1H NMR (300 MHz, CD3OD): d = 7.05 (br s, 1 H), 7.04 (d, J = 8.4
Hz, 2 H), 6.83 (dd, J = 8.4, 2.0 Hz, 1 H), 6.75 (d, J = 8.4 Hz, 1 H),
6.68 (d, J = 8.4 Hz, 2 H), 4.69 (dd, J = 10.7, 3.2 Hz, 1 H), 4.27 (t,
J = 3.2 Hz, 1 H), 3.85 (s, 3 H), 3.80 (dt, J = 12.7, 2.9 Hz, 1 H), 3.59
(dt, J = 7.4, 3.2 Hz, 1 H), 2.85 (dd, J = 13.0, 6.6 Hz, 1 H), 2.68 (dd,
J = 13.0, 7.4 Hz, 1 H), 1.91 (dd, J = 13.3, 3.0 Hz, 1 H), 1.84 (dd,
J = 14.3, 2.9 Hz, 1 H), 1.73 (ddd, J = 13.6, 10.9, 2.8 Hz, 1 H), 1.57
(dd, J = 13.6, 2.0 Hz, 1 H).
13C NMR (75 MHz, CD3OD): d = 156.5, 148.6, 146.7, 136.0, 131.4,
131.3, 131.1, 119.6, 116.0, 115.9, 115.7, 111.0, 76.5, 75.2, 74.2,
65.5, 56.2, 41.2, 39.7, 35.1.
Synthesis 2010, No. 24, 4300–4306 © Thieme Stuttgart · New York