C O M M U N I C A T I O N S
Scheme 2
at rt for 6.5 days in 45% isolated yield (17:16 ) 52:48). Therefore,
the total isolated yield of 16 was 34%. Interestingly, the recently
isolated bisglaucumlides C and D have the Z-configuration at the
C4-position.6
Finally, the acetonide group in 16 was deprotected with aqueous
AcOH to afford 1 in 50% yield (Scheme 2). The spectral data of
the synthetic sample were identical to those of the natural one.2a
In summary, together with the improved synthesis of the 14-
membered diene unit 15, we have succeeded in the first total
synthesis of 1 via the intermolecular Diels-Alder reaction between
the 14-membered dienophile unit, 2, and the diene unit 15. The
absolute configuration of 1 was confirmed by this total synthesis.
Although the Diels-Alder reaction proceeded only at high tem-
perature and the diene unit bears the acetonide protecting group,
our results suggest that 1 could be biosynthesized by the inherent
reactivity of 2 and 3, possibly without the aid of an enzyme.19
Acknowledgment. We thank Professor Takenori Kusumi, The
University of Tokushima, for providing spectral copies of natural
methyl sarcophytoate and for his generous discussion. We are
grateful to Yoshiko Koyama, Hiyoshi Medicinal Chemistry Re-
search Institute, for measurement of 500 MHz NMR spectra. This
research was partially supported by a Grant-in-Aid Scientific
Research on Priority Areas 17035076 and 18032067 from MEXT,
Japan.
Supporting Information Available: Experimental procedures and
compound characterization data. This material is available free of charge
conformation because of the steric repulsion between the 38-methyl
and 33-methylene groups, whereas the C21-C34 and C35-C36
double bonds easily reside in the s-cis conformation under the given
reaction conditions. The CO2Me endo transition states are more
favorable than the CO endo transition states because both reactants
in the latter reside in a more crowded position. In order to account
for the π-face- and regioselectivities, the solution conformations
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Figure 2. Solution conformations.
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J. AM. CHEM. SOC. VOL. 129, NO. 32, 2007 9863