LETTER
Hemitectol, Tectol, and Tecomaquinone I
2941
Pessoa, O. D. L.; Braz-Filho, R. Nat. Prod. Res. 2007, 21,
529.
(5) tert-Butyl(4-methoxynaphthalen-1-yloxy)dimethylsilane
(8)
served for 13 with those of dimer 15 confirmed the struc-
ture and cis,trans,cis relative configuration of 13.
ESI-HRMS analysis of 14 established a molecular formu-
la of C32H33O5 [M + H]+, being isomeric with 13, while
close analysis of COSY, HSQC, and HMBC data identi-
fied 14 to have the same planar skeleton as 13 (Scheme 5).
IR (ATR): 2929, 2857, 1625, 1596, 1461, 1384, 1273, 1095
cm–1. 1H NMR (400 MHz, CDCl3): δ = 8.25–8.23 (m, 2 H,
H-5, H-8), 7.60–7.56 (m, 2 H, H-6, H-7), 6.86 (d, J = 8.5 Hz,
1 H, H-3), 6.73 (d, J = 8.5 Hz, 1 H, H-2), 4.03 (s, 3 H, OCH3),
1
However, unlike the symmetrical analogue 13, the H
1.20 (s, 9 H, H-4′, H-5′, H-6′), 0.36 (s, 6 H, H-1′, H-2′). 13
NMR (100 MHz, CDCl3): δ = 149.9 (C-1), 145.2 (C-4),
128.6 (ArC), 126.6 (ArC), 125.8 (ArCH), 125.5 (ArCH),
C
NMR and 13C NMR spectra of 14 were more complex,
suggesting an unsymmetrical structure. NOESY correla-
tions were observed between the tetrahydrofuran protons
H-3 (δ = 2.74 ppm), H-4′ (δ = 4.88 ppm), H-4 (δ = 5.13
ppm), and two of the gem-dimethyl groups (δ = 1.64, 1.60
ppm) indicating these protons to be cis-related. Further
NOESY correlations were observed between H-3′ (δ =
2.10 ppm) and the remaining two methyl groups (δ = 1.17,
1.70 ppm) indicating these protons to be on the opposite
face of the molecule (Scheme 5). The structure and rela-
tive configuration of 14 agreed with the configuration re-
ported by Fraga et al.17 for their second furopyran dimer
16.
122.5 (ArCH), 122.0 (ArCH), 111.9 (C-3), 103.5 (C-2), 55.7
(OCH3), 26.0 (C-4′, C-5′, C-6′), 18.5 (C-3′), –4.2 (C-1′, C-
2′). ESI-HRMS: m/z calcd for C17H25O2Si [MH+]: 289.1618;
found: 289.1624.
(6) 4-(tert-Butyldimethylsiloxy)naphthalene-1-ol (9)
IR (ATR): 3255, 2929, 1595, 1471, 1347, 1266, 1069 cm–1.
1H NMR (400 MHz, CDCl3): δ = 8.10–8.09 (m, 2 H, H-5, H-
8), 7.50–7.47 (m, 2 H, H-6, H-7), 6.68 (s, 2 H, H-2, H-3),
1.09 (s, 9 H, H-4′, H-5′, H-6′), 0.24 (s, 6 H, H-1′, H-2′). 13
NMR (100 MHz, CDCl3): δ = 145.4 (C-1), 138.7 (C-4),
126.4 (2 × Ar-C), 125.7 (ArCH), 125.5 (ArCH), 122.7
C
(ArCH), 121.5 (ArCH), 112.0 (C-2), 108.3 (C-3), 25.9 (C-4′,
C-5′, C-6′), 18.4 (C-3′), –4.3 (C-1′, C-2′). ESI-HRMS: m/z
calcd for C16H23O2Si [MH+]: 275.1462; found: 275.1462.
(7) Lee, Y. R.; Kim, Y. M. Helv. Chim. Acta 2007, 90, 2401.
(8) tert-Butyl(2,2-dimethyl-2H-benzo[h]chromen-6-
yloxy)dimethylsilane (10)
O
O
O
O
O
O
H
H
H
H
3'
IR (ATR): 2930, 1595, 1457, 1409, 1370, 1274, 1084 cm–1.
1H NMR (400 MHz, CDCl3): δ = 8.15–8.03 (m, 2 H, H-7, H-
10), 7.43–7.40 (m, 2 H, H-8, H-9), 6.54 (s, 1 H, H-5), 6.35
(d, J = 9.7 Hz, 1 H, H-4), 5.63 (d, J = 9.7 Hz, 1 H, H-3), 1.49
(s, 6 H, H-11, H-12), 1.08 (s, 9 H, H-4′, H-5′, H-6′), 0.24 (s,
6 H, H-1′, H-2′). 13C NMR (100 MHz, CDCl3): δ = 144.8 (C-
6), 142.4 (C-10b), 129.9 (C-3), 128.3 (ArC), 126.0 (ArC),
125.5 (ArCH), 125.3 (ArCH), 122.9 (C-4), 122.5 (ArCH),
121.8 (ArCH), 115.0 (C-4a), 110.9 (C-5), 76.2 (C-2), 27.6
(C-11, C-12), 25.9 (C-4′, C-5′, C-6′), 18.4 (C-3′), –4.2 (C-1′,
C-2′). ESI-HRMS: m/z calcd for C21H29O2Si [MH+]:
341.1931; found: 341.1919.
4'
3
3
H
O
O
H
O
O
4
4
H
H
O
O
O
O
15
16
Figure 2 Furopyran dimers 15 and 16
In summary, we have successfully accomplished the first
syntheses of the natural products hemitectol (6) and tectol
(5) with the use of a silyl-protected naphthol in combina-
tion with a SEAr–cycloaddition reaction. Hemitectol (6)
was discovered to spontaneously dimerise to the natural
product tectol (5) in the presence of silica or triethyl-
amine. Future work will focus on applying this strategy to
access other related analogues.
(9) Hemitectol (6)
Dark yellow oil. IR (ATR): 3419, 2973, 1586, 1451, 1402,
1369, 1360, 1257, 1070 cm–1. 1H NMR (400 MHz, DMSO-
d6): δ = 8.03–7.96 (m, 2 H, H-7, H-10), 7.46–7.37 (m, 2 H,
H-8, H-9), 6.60 (s, 1 H, H-5), 6.43 (d, J = 9.5 Hz, 1 H, H-4),
5.75 (d, J = 9.5 Hz, 1 H, H-3), 1.42 (s, 6 H, H-11, H-12). 13
NMR (100 MHz, DMSO-d6): δ = 146.4 (C-6), 143.7 (C-
C
10b), 130.4 (C-3), 125.6 (ArCH), 125.1 (ArC), 124.9 (ArC),
124.7 (ArCH), 122.6 (C-4), 122.1 (ArCH), 121.1 (ArCH),
115.2 (C-4a), 105.9 (C-5), 75.7 (C-2), 27.1 (C-11, C-12).
ESI-HRMS: m/z calcd for C15H15O2 [MH+]: 227.1067;
found: 227.1063.
Acknowledgment
We thank Dr. Michael Schmitz and Dr. Nick Lloyd for their assi-
stance with the NMR and mass spectroscopic data and the Univer-
sity of Auckland for funding this research.
(10) Tectol (5)
White solid; 206–209 °C (lit.2 207–208 °C). IR (ATR):
3420, 2973, 1586, 1451, 1402, 1369, 1361, 1221, 1071 cm–
1. 1H NMR (400 MHz, DMSO-d6): δ = 8.17–8.08 (m, 4 H, H-
7, H-7′, H-10, H-10′), 7.52–7.44 (m, 4 H, H-8, H-8′, H-9, H-
9′), 5.78 (d, J = 9.9 Hz, 2 H, H-4, H-4′), 5.59 (d, J = 9.9 Hz,
2 H, H-3, H-3′), 1.45 (s, 6 H, H-11, H-11′), 1.43 (s, 6 H, H-
12, H-12′). 13C NMR (100 MHz, DMSO-d6): δ = 144.1 (C-
6, C-6′), 140.6 (C-10b, C-10b′), 130.0 (C-3, C-3′), 125.5
(2 × ArC), 125.4 (2 × ArCH), 125.1 (2 × ArC), 125.0
(2 × ArCH), 122.5 (2 × ArCH), 121.2 (2 × ArCH), 120.9
(C-4, C-4′), 115.9 (C-4a, C-4a′), 113.2 (C-5, C-5′), 75.2 (C-
2, C-2′), 27.0 (C-11, C-11′, C-12, C-12′). ESI-HRMS: m/z
calcd for C30H26O4Na [MNa+]: 473.1723; found: 473.1714.
References and Notes
(1) Chan, S. T. S.; Pearce, A. N.; Januario, A. H.; Page, M. J.;
Kaiser, M.; McLaughlin, R. J.; Harper, J. L.; Webb, V. L.;
Barker, D.; Copp, B. R. J. Org. Chem. 2011, 76, 9151.
(2) Sumthong, P.; Romero-González, R. R.; Verpoorte, R. J.
Wood. Chem. Tech. 2008, 28, 247.
(3) Sandermann, W.; Simatupang, M. H. Chem. Ber. 1964, 97,
588.
(4) Lemos, T. L. G.; Monte, F. J. Q.; Santos, A. K. L.; Fonseca,
A. M.; Santos, H. S.; Oliveira, M. F.; Costa, S. M. O.;
© Georg Thieme Verlag Stuttgart · New York
Synlett 2012, 23, 2939–2942