SCHEME 5 a
a Reagents and conditions: (a) Ac2O, pyridine, rt, 96%; (b) AIBN, n-Bu3SnH, benzene, reflux, 95%; (c) H2O2, LiOH, THF/H2O, 0 °C, 91%; (d) TFA,
TFAA, reflux, 41%; (e) AlI3, Bu4N+I-, benzene, rt, 94%; (f) AcCl/MeOH, 0 °C, 90%.
(td, J ) 4.8, 1.5 Hz, 1H), 4.75 (ddd, J ) 12.9, 7.8, 3.6 Hz, 1H),
4.61 (d, J ) 6.3 Hz, 1H), 4.15-4.26 (m, 2H), 3.91 (t, J ) 9.6 Hz,
1H), 3.79 (d, J ) 1.5 Hz, 6H), 3.55 (s, 2H), 3.26 (dd, J ) 13.2,
3.3 Hz, 1H), 3.17 (s, 1H), 2.79 (dd, J ) 13.2, 9.6 Hz, 1H), 2.14 (s,
3H), 1.74-1.79 (m, 2H), 1.27 (d, J ) 6.3 Hz, 3H); 13C NMR
(75 MHz, CDCl3) δ 171.2, 170.1, 160.7, 152.8, 136.3, 134.8, 129.4,
129.0, 127.4, 107.1, 99.2, 68.7, 65.9, 65.8, 55.2, 54.9, 49.6, 42.0,
40.9, 37.5, 20.6, 13.4; IR (KBr) 3506, 2926, 1777, 1687, 1599,
1459, 1361, 1294, 1205, 1155, 1064 cm-1; HRMS m/z calcd for
C27H33NO8S [M + Na]+ 554.1825, found 554.1820.
was quenched by water. The methanol and chloroform were distilled
out in vacuo, and the mixture was then extracted with ethyl acetate
(3 × 20 mL), washed with water, dried over Na2SO4, concentrated
in vacuo, and the residue was purified by column chromatography
on silica gel (CHCl3/EtOAc, 1:1) to give xestodecalactone B (23
25
mg, 90%) as a white solid: mp 171-173 °C dec; [R]D +19 (c
0.3, CH3OH); 1H NMR (400 MHz, DMSO-d6) δ 9.96 (s, 1H), 9.74
(s, 1H), 6.27 (s, 1H), 6.11 (s, 1H), 4.81 (d, J ) 6.4 Hz, 1H), 4.77
(d, J ) 4.8 Hz, 1H), 4.02 (s, 1H), 3.63 (d, J ) 17.6 Hz, 1H), 3.54
(d, J ) 17.6 Hz, 1H), 3.48 (t, J ) 14.8 Hz, 1H), 2.59 (dd, J )
14.8, 8.8 Hz, 1H), 1.86 (d, J ) 4.4 Hz, 1H), 1.74 (d, J ) 4.4 Hz,
1H), 1.15 (d, J ) 6.8 Hz, 3H); 13C NMR (100 MHz, DMSO-d6) δ
205.0, 169.0, 159.0, 156.8, 135.4, 119.7, 109.8, 101.2, 68.1, 64.1,
52.5, 42.0, 30.6, 19.5; IR (KBr) 3208, 1726, 1608, 1464, 1338,
1263, 1162, 1024, 849 cm-1; HRMS m/z calcd for C14H16O6 [M +
H]+ 281.1020, found 281.1024. Xestodecalactone C (25 mg, 88%)
was obtained as a white solid from 18b (32 mg, 0.1 mmol) by the
same operation for the synthesis of xestodecalactone B: mp 167-
Macrolides 17a and 17b. The acid 16a (368 mg, 1 mmol) was
dissolved in a mixture of trifluoroacetic acid (20 mL) and
trifluoroacetic acid anhydride (4 mL), and the solution was refluxed
for 30 min at 60 °C, cooled to rt, poured into an excess of sodium
hydrogen carbonate, and the product was isolated with ether. The
combined extracts were washed with water, dried (Na2SO4), and
the solvent removed. The residue was purified by column chro-
matography (hexanes/EtOAc, 4:1) to give the metabolite 17a
(144 mg, 41%) as a pale yellow foam: [R]D25 +45 (c 0.4, CHCl3);
1H NMR (300 MHz, CDCl3) δ 6.40 (d, J ) 6.3 Hz, 1H), 6.27 (d,
J ) 9.9 Hz, 1H), 5.31 (t, J ) 9.9 Hz, 1H), 5.02 (br s, 1H), 4.26 (d,
J ) 18.6 Hz, 1H), 3.84 (s, 3H), 3.82 (s, 3H), 3.42 (d, J ) 18.6 Hz,
1H), 3.29 (dd, J ) 15.3, 10.5 Hz, 1H), 3.01 (d, J ) 15.3 Hz, 1H),
2.05 (s, 3H), 1.83-1.98 (m, 2H), 1.19 (d, J ) 6.3 Hz, 3H); 13C
NMR (75 MHz, CDCl3) δ 202.9, 169.8, 168.6, 161.5, 159.0, 134.6,
123.9, 107.8, 97.1, 71.6, 71.2, 55.6, 55.4, 51.6, 42.8, 40.3, 21.3,
20.7; IR (KBr) 2939, 1735, 1603, 1459, 1425, 1334, 1237, 1157,
1093 cm-1; HRMS m/z calcd for C18H22O7 [M + H]+ 351.1444,
found 351.1438. 16b (368 mg,1 mmol) was treated with 20 mL of
trifluoroacetic acid and 4 mL of trifluoroacetic acid anhydride as
described for the synthesis of 17a to give 17b (138 mg, 39%) as a
pale yellow foam: [R]D25 +49 (c 1.15, CHCl3); 1H NMR (400 MHz,
CDCl3) δ 6.40 (d, J ) 2.0 Hz, 1H), 6.25 (s, 1H), 5.31 (t, J ) 10.4
Hz, 1H), 4.99-5.03 (m, 1H), 4.26 (d, J ) 18.8 Hz, 1H), 3.83 (s,
3H), 3.82 (s, 3H), 3.42 (d, J ) 19.2 Hz, 1H), 3.28 (dd, J ) 15.2,
11.2 Hz, 1H), 3.01 (d, J ) 15.2 Hz, 1H), 2.04 (s, 3H), 1.95 (d, J
) 13.2 Hz, 1H), 1.19 (d, J ) 6.4 Hz, 3H); 13C NMR (100 MHz,
CDCl3) δ 202.9, 169.7, 168.6, 161.6, 159.1, 134.6, 124.0, 107.8,
97.1, 71.6, 71.1, 55.6, 55.4, 51.6, 42.8, 40.3, 21.3, 20.7; IR (KBr)
25
1
169 °C dec; [R]D +24 (c 0.3, CH3OH); H NMR (400 MHz,
DMSO-d6) δ 9.91 (s, 1H), 9.72 (s, 1H), 6.27 (d, J ) 1.6 Hz, 1H),
6.09 (s, 1H), 4.76 (d, J ) 4.0 Hz, 1H), 4.72 (dd, J ) 11.2, 5.6 Hz,
1H), 3.95 (br s, 1H), 3.82 (d, J ) 18.8 Hz, 1H), 3.48 (d, J ) 18.8
Hz, 1H), 3.08 (dd, J ) 14.8, 10.4 Hz, 1H), 2.81 (d, J ) 14.8 Hz,
1H), 1.83 (d, J ) 13.6 Hz, 1H), 1.64 (dd, J ) 14.8, 11.2 Hz, 1H),
1.08 (d, J ) 6.0 Hz, 3H); 13C NMR (100 MHz, DMSO-d6) δ 204.5,
168.8, 159.1, 157.0, 134.4, 121.2, 109.2, 101.3, 70.6, 67.8, 55.3,
46.0, 20.7; IR (KBr) 3343, 2923, 1721, 1657, 1608, 1463, 1339,
1261, 1162, 1023, 832 cm-1; HRMS m/z calcd for C14H16O6 [M +
Na]+ 303.0839, found 303.0843.
Acknowledgment. We are grateful for the generous financial
support by the Special Doctorial Program Funds of the Ministry
of Education of China (20040730008), NSFC (QT program, No.
20572037), NCET-05-0879, the key grant project of Chinese
ministry of Education (No. 105169), and Gansu Science
Foundation (3ZS051-A25-004).
2938, 1734, 1680, 1603, 1459, 1337, 1236, 1158, 1093, 1058 cm-1
;
HRMS m/z calcd for C18H22O7 [M + H]+ 351.1444, found
351.1447.
Supporting Information Available: Experimental procedures
and characterization data for compounds 8-11, 12a/12b- 18a/
18b, and xestodecalactones B and C. This material is available free
Xestodecalactones B and C. A quantity of 0.2 mL of acety1
chloride was added to anhydrous methanol (5 mL) at 0 °C, and
after being stirred for 15 min at 0 °C, a solution of the compound
18a (30 mg, 0.09 mmol) in chloroform/methanol (1 mL/1 mL) was
added and the mixture was stirred at 0 °C for 12 h. The reaction
JO070159V
J. Org. Chem, Vol. 72, No. 7, 2007 2697