Y. Morimoto et al. / Tetrahedron Letters 42 (2001) 6307–6309
6309
C2-symmetric structure and the cis stereochemistry of
the 2,2,5-trisubstituted THF rings newly formed in 3
could be confirmed by the presence of 15 signals in the
13C NMR spectrum and NOE shown in 3, respectively.
from the polyether structure 1 are currently under
investigation in our laboratory.1
Acknowledgements
Under irradiation with visible light (589 nm, 240 W
sodium lamp) in the presence of molecular oxygen and
a minute amount of rose bengal as a sensitizer, the
trisubstituted alkene 3 underwent an ene reaction with
singlet oxygen to give the C2-symmetric photooxygena-
tion product 13 bearing only trans olefins (J=15.9 Hz
between the olefinic protons). The regioselectivities in
the photooxygenation of 3 (95% total yield; tert,tert-
hydroperoxide 13:tert,sec-hydroperoxide:sec,sec-hydro-
peroxide=ca 1:2:1) were, however, reflected only by
those observed in the known singlet oxygen reactions.¶
Finally, monoreduction of the bishydroperoxide 13 to
an alcohol was effected by 0.66 equiv. of triphenylphos-
phine to produce (−)-longilene peroxide (1),ꢀꢀ mp 135.5–
136.5°C (diisopropyl ether–hexane); [h]2D7 −44.8 (c 0.40,
CHCl3) [lit.2 mp 142–143°C; [h]2D5 −23.0 (c 0.44,
CHCl3)], in 84% yield based on 40% recovery of the
starting material 13. The spectral characteristics (1H
and 13C NMR, IR) of the synthetic 1 were identical to
those reported for the natural product.2 Thus, it has
been found that the hitherto unknown absolute
configuration of longilene peroxide is as indicated in
the structural formula 1, which possesses the same
absolute stereochemistry as glabrescol (2).
We are grateful to the SUNBOR GRANT (Suntory
Institute for Bioorganic Research), the Shorai Founda-
tion for Science and Technology, and a Grant-in-Aid
for Encouragement of JSPS Research Fellows from the
Japan Society for the Promotion of Science for finan-
cial support.
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In conclusion, we have accomplished the first asymmet-
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¶ It has been reported that trisubstituted alkenes such as 14 give a
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ꢀꢀ Compound 1: 1H NMR (400 MHz, CDCl3) l 10.67 (1H, s), 5.83
(1H, ddd, J=15.4, 8.5, 6.3 Hz), 5.78 (1H, dt, J=15.2, 7.6 Hz), 5.63
(1H, d, J=15.6 Hz), 5.45 (1H, d, J=15.6 Hz), 5.29 (1H, s), 5.07
(1H, d, J=1.7 Hz), 4.17–4.09 (2H, m), 3.73 (2H, t, J=6.6 Hz), 3.37
(1H, s), 2.20 (2H, dd, J=13.5, 7.4 Hz), 2.14–1.97 (6H, m), 1.93–1.83
(3H, m), 1.79 (1H, dd, J=13.2, 8.8 Hz), 1.56–1.41 (4H, m), 1.39
(3H, s), 1.34 (3H, s), 1.30 (6H, s), 1.22 (3H, s), 1.21 (3H, s), 1.11
(3H, s), 1.09 (3H, s); 13C NMR (100 MHz, CDCl3) l 141.1, 137.0,
125.7, 122.2, 85.7, 85.5, 85.4, 85.10, 85.08, 84.1, 81.0, 73.9, 73.7,
70.5, 41.3, 40.7, 30.1, 29.9, 29.8, 29.7, 29.5, 29.3, 26.9, 25.7, 25.2,
24.3, 24.2, 24.1, 23.6; IR (KBr) 3323, 2970, 1456, 1371, 1086, 1074
cm−1; FAB-MS m/z (relative intensity) 541 [(M+H)+, 6.0], 523 (6.0),
505 (7.0), 471 (8.0), 389 (24), 325 (53), 237 (41), 153 (39); FAB-
HRMS calcd for C30H53O8 [(M+H)+] 541.3740, found 541.3734.
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Tetrahedron Lett. 1993, 34, 6485–6488.
13. Nagawa, I.; Hata, T. Tetrahedron Lett. 1975, 1409–1412.
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