2608
A. D. Wadsworth et al.
PAPER
Dehydroherbarin (6)
Yield: 2.5 mg, 7.9 × 10–3 mmol (80%); bright-yellow amorphous
solid; mp 164–167 °C (Lit.4 mp not reported); [a]D19 +35.0 (c 0.14,
CHCl3); {Lit.4 [a]D27.4 +45.1 (c 0.12, CHCl3)}.
To a soln of 7,9-dimethoxy-3-methyl-1H-benzo[g]isochromen-10-
ol (8; 20 mg, 0.07 mmol) in MeCN (3.0 mL), was added salcomine
(14 mg, 0.044 mmol) and the reaction mixture was stirred at r.t. un-
der a balloon of O2 for 3 h. The reaction mixture was concentrated
in vacuo and purified by flash chromatography (silica gel; hexanes–
EtOAc, 2:1) to give the title compound 6.
Yield: 15 mg, 0.05 mmol (72%); purple solid; mp 184–186 °C (Lit.9
187.2–187.5 °C).
1H NMR (400 MHz, CDCl3): d = 2.00 (d, J = 3.2 Hz, 3 H, Me), 3.93
(s, 3 H, OMe), 3.95 (s, 3 H, OMe), 5.11 (s, 2 H, CH2), 5.83 (m, 1 H,
H-4), 6.71 (d, J = 2.4 Hz, 1 H, H-8), 7.26 (d, J = 2.4 Hz, 1 H, H-6).
IR (neat): 2962, 2928, 2854, 1658, 1640, 1592, 1454, 1336, 1321,
1278, 1087, 961, 819, 741 cm–1.
1H NMR (400 MHz, CDCl3): d = 1.38 (d, J = 6.2 Hz, 3 H, Me), 2.23
(dd, J = 19.1, 11.2 Hz, 1 H, Hax-4), 2.66 (dd, J = 19.1, 3.6 Hz, 1 H,
Heq-4), 3.57 (s, 3 H, OMe), 3.92 (s, 3 H, OMe), 3.94 (s, 3 H, OMe),
4.21 (m, 1 H, H-3), 5.54 (s, 1 H, H-1), 6.72 (d, J = 2.4 Hz, 1 H, H-
8), 7.24 (d, J = 2.4 Hz, 1 H, H-6).
13C NMR (100 MHz, CDCl3): d = 21.0 (Me), 29.0 (CH2), 55.9 (1-
OMe), 56.1 (7-OMe), 56.2 (9-OMe), 62.0 (CH, C-3), 93.7 (CH, C-
1), 103.2 (CH, C-6), 104.3 (CH, C-8), 114.2 (q, C-9a), 135.6 (q, C-
5a), 140.6 (q, C-4a), 141.0 (q, C-10a), 162.0 (q, C-9), 164.5 (q, C-
7), 180.8 (C=O), 184.9 (C=O).
The spectroscopic data were consistent with those reported in the
literature.9
(+)-Astropaquinone C (5)
MS (EI, 70 eV): m/z (%) = 341 (73) [M + Na]+, 319 (8), 309 (4), 303
To a soln of (S)-7,9-dimethoxy-3-methyl-3,4-dihydro-1H-ben-
zo[g]isochromene-5,10-dione (7;2 10 mg, 0.035 mmol) in CCl4 (8.2
mL), was added a portion of Bz2O2 (1 crystal). Bromine (105 mL,
1 M in CCl4, 0.105 mmol) was added every 30 min for 1.5 h, while
the reaction vessel was irradiated with a 60 W desk lamp and heated
to gentle reflux. The reaction mixture was concentrated to dryness
in vacuo and the crude bromides were taken up in THF (2.4 mL).
H2O (1.2 mL) was added and the reaction mixture was stirred for 0.5
(4), 287 (100).
HRMS-FAB: m/z [M + Na]+ calcd for C17H18O6Na: 341.1364;
found: 341.0987.
All collected data were in agreement with values reported in the lit-
erature.4
h before further H2O (2.0 mL) was added and the reaction was left Acknowledgment
for 1 h. The reaction mixture was diluted with CH2Cl2 (8 mL) and
Financial support from the Royal Society of New Zealand Marsden
Fund (J.S.) is gratefully acknowledged.
H2O (5 mL), the organic layer was separated and the aqueous layer
was extracted with CH2Cl2 (2 × 10 mL). The combined organic ex-
tracts were dried (MgSO4), filtered and concentrated in vacuo. The
remaining solid was taken up in THF and loaded onto a preparative
TLC plate for purification (silica gel; hexanes–EtOAc, 2:1, 1%
Et3N) to give the title compound 5.
References
(1) Singh, S. B.; Cordingley, M. G.; Ball, R. G.; Smith, J. L.;
Dombrowski, A. W.; Goetz, M. A. Tetrahedron Lett. 1991,
32, 5279.
(2) Sperry, J.; Yuen, T. Y.; Brimble, M. A. Synthesis 2009,
2561.
(3) Opatz, T.; Kolshorn, H.; Thines, E.; Anke, H. J. Nat. Prod.
2008, 71, 1973; Ascomycones A and B were reported to
show no detectable optical rotation and were thus assigned
as racemic at C1.
Yield: 9.6 mg, 0.03 mmol (91%); bright-yellow solid; mp 178–
19
181 °C (Lit.4 mp not stated); [a]D +31.1 (c 0.10; CHCl3) {Lit.4
[a]D19 +53.9 (c 0.10, CHCl3)}.
IR (neat): 3420, 2972, 2924, 2845, 1652, 1638, 1593, 1561, 1458,
1432, 1383, 1354, 1340, 1318, 1270, 1213, 1198, 1155, 1123, 1082,
1067, 1019, 967, 941, 922, 859, 843, 830, 819, 747, 713, 685, 641
cm–1.
1H NMR (300 MHz, CDCl3): d = 1.36 (d, J = 6.3 Hz, 3 H, Me), 2.18
(dd, J = 19.2, 10.8 Hz, 1 H, Hax-4), 2.69 (dd, J = 19.2, 3.3 Hz, 1 H,
Heq-4), 3.93 (s, 3 H, OMe), 3.94 (s, 3 H, OMe), 4.26 (m, 1 H, H-3),
5.99 (s, 1 H, H-1), 6.71 (d, J = 2.4 Hz, 1 H, H-8), 7.25 (d,
J = 2.4 Hz, 1 H, H-6).
13C NMR (75 MHz, CDCl3): d = 21.1 (Me), 29.1 (CH2, C-4), 56.0
(OMe), 56.5 (OMe), 62.8 (CH, C-3), 87.1 (CH, C-1), 103.6 (CH, C-
6), 104.3 (CH, C-8), 114.1 (q, C-9a), 135.8 (q, C-5a), 140.4 (q, C-
4a), 142.2 (q, C-10a), 162.1 (C-O, C-9), 164.8 (C-O, C-7), 182.0
(C=O, C-10), 184.7 (C=O, C-5).
MS (EI, 70 eV): m/z (%) = 327 (100) [M + Na]+, 287 (10), 167 (5),
118 (8).
HRMS-FAB: m/z [M + Na]+ calcd for C16H16O6Na: 327.0844;
found: 327.0848.
(4) Wang, L.; Dong, J. Y.; Song, H. C.; Shen, K. Z.; Wang, L.
M.; Sun, R.; Wang, C. R.; Gao, Y. X.; Li, G. H.; Li, L.;
Zhang, K. Q. Planta Med. 2009, 75, 1339.
(5) (a) Kadkol, M. V.; Gopalkrishnan, K. S.; Narasimhachari, N.
J. Antibiot. 1971, 24, 245. (b) Nagarajan, R.;
Narasimhachari, N.; Kadkol, M. V.; Gopalkrishnan, K. S.
J. Antibiot. 1971, 24, 249.
(6) (a) Evans, G. E.; Leeper, F. J.; Murphy, J. A.; Staunton, J.
J. Chem. Soc., Chem. Commun. 1979, 205. (b) Dodd, J. H.;
Weinreb, S. M. Tetrahedron Lett. 1979, 38, 3593.
(7) Nakata, H. Bull. Chem. Soc. Jpn. 1960, 33, 1693.
(8) Zhang, Z.; Yu, B. J. Org. Chem. 2003, 68, 6309.
(9) Kesteleyn, B.; De Kimpe, N. J. Org. Chem. 2000, 65, 640.
(10) Xu, Y. C.; Lebeau, E.; Gillard, J. W.; Attardo, G.
Tetrahedron Lett. 1993, 34, 3841.
(11) Isobe, K.; Takeda, N.; Mohri, K.; Tsuda, Y. Chem. Pharm.
All collected data were in agreement with values reported in the lit-
erature.4
Bull. 1989, 12, 3390.
(12) Harling, J. D.; Orlek, B. S. Tetrahedron 1998, 54, 14905.
(13) Chiarello, J.; Jouillé, M. Tetrahedron 1988, 44, 41.
(14) (a) Gill, M.; Donner, C. D. Tetrahedron Lett. 1999, 40,
3921. (b) Donner, C. D.; Gill, M. J. Chem. Soc., Perkin
Trans. 1 2002, 938.
(+)-Astropaquinone B (4)
To a soln of astropaquinone C (5; 3 mg, 9.86 × 10–3 mmol) in
MeOH (2 mL) was added PTSA (1 mg, 0.05 mmol) and the reaction
mixture was stirred at r.t. for 16 h. The reaction mixture was con-
centrated in vacuo and the remaining solid was taken up in THF and
loaded onto a preparative TLC plate (silica gel; hexanes–EtOAc,
2:1, 1% Et3N) to give the title compound 4.
(15) Hansen, C. A.; Frost, J. W. J. Am. Chem. Soc. 2002, 124,
5926.
Synthesis 2010, No. 15, 2604–2608 © Thieme Stuttgart · New York