The Revised Structure of Trichodermatide A
the corresponding correlation was the opposite phase in our
case.
[
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in trichodermatide A, we investigated the transformation of
our original hexylated intermediate 16[ to Trauner’s com-
pound, which was the initially proposed structure of tricho-
dermatide A (Scheme 2). TBS protection of the α-hydroxy
ketone gave compound 17 together with a small amount of
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an inseparable diastereomer. Allylic oxidation using SeO2
and subsequent Mitsunobu reaction to invert the allylic
alcohol at C10 were followed by base treatment to afford
the allylic alcohol 20 together with an inseparable dia-
stereomer. Cobalt-catalyzed hydration of 20 gave hemi-
acetal 21, also with an inseparable diastereomer. Notably,
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pend on the proximal allylic hydroxyl group. The easily
changeable stereochemistry of hemiketal C9 would be fixed
by a plausible intramolecular hydrogen bond between OH9
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1
[8] We consider that Trauner’s compound 1 is exceptionally solid
reasonable, judging from the greater similarity of its H
probably due to the stereochemistry of its core.
NMR spectrum to 1 than 22; therefore, the generation of
diastereomer 22 was promoted by the basicity of the TBAF
treatment as in Trauner’s report.
[
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1
5
[
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sponding correlation is quite unclear.
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Conclusions
4
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In summary, we newly proposed the structure of tricho-
dermatide A as 15. This revision is supported by the X-ray
structure obtained for synthetic intermediate 13, which was
synthesized by our synthetic route for trichodermatide A.
The stereochemistry of 15 was also supported by NOESY
experiments. Finally, by converting our total synthetic inter-
mediate 16 to Trauner’s intermediate, which was based on
the originally proposed structure, the stereochemistry of
C10 was confirmed.
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Acknowledgments
1
35, 10306–10309; m) H. Shigehisa, E. Nishi, M. Fujisawa, K.
We thank Dr. Takashi Fujiwara at Saitama University for the as-
sistance with the X-ray analysis. The work was supported by JSPS
KAKENHI Grant No. 26860017 (H. S.) and 15K07872 (K. H.),
the Society of Synthetic Organic Chemistry, Takeda Pharmaceuti-
cal Company award, and the Uehara Memorial Foundation.
Hiroya, Org. Lett. 2013, 15, 5158–5161; n) T. Tokuyasu, S. Ku-
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Received: October 5, 2015
Published Online: November 9, 2015
Eur. J. Org. Chem. 2015, 7670–7673
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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