Month 2019
An Alternative Approach to the Synthesis of Parvistone C
stereoselective and regioselective epoxide ring-opening of
goniothalamin oxide 7 with methanol in the presence of
Lewis acid Eu (OTf)3 provided the target natural product
compound 8 (40 mg, 0.18 mmol) in methanol (1 mL)
was added Eu (OTf)3 (12.2 mg, 0.02 mmol) at room
temperature and stirred for 12 h. The methanol was
removed under vacuum, and the residue was purified by
flash column chromatography (hexane: EtOAc, 6:4) to
provide parvistone C (1b) (43 mg, 95%) as a white solid.
[α]2D5 = À219 (c 0.5, CHCl3), HRESIMS m/z 271.0936
[M + Na]+ (Calcd for C14H16O4Na, 271.0940).
1
parvistone C (1b) in 95% yield with 96:4 dr. The H-
NMR and 13C-NMR data of natural parvistone C were
well agreed with our synthetic compound 1b (Table 1).
CONCLUSIONS
The protecting group-free stereoselective total synthesis
of lactone natural product parvistone C (1b) was achieved
in simple five steps without using any protecting group
from readily available starting material trans-
cinnamaldehyde with 27% overall yield. Key
transformations of our synthetic scheme include an
asymmetric aldol reaction and asymmetric epoxidation
and regioselective epoxide ring opening.
Acknowledgments. R. K. R. thanks K L University for constant
encouragement during this research program. R. K. R. is also
grateful to GVK Biosciences for providing basic research facility.
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EXPERIMENTAL
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General.
Solvents were dried over standard drying
agents and freshly distilled prior to use. All moisture-
sensitive reactions were carried out under nitrogen.
Organic solutions were dried over anhydrous MgSO4 and
concentrated below 40°C in vacuo. All column
chromatographic separations were performed on silica gel
1
of 60–120 mesh. H-NMR and 13C-NMR spectra were
recorded in CDCl3 solvent at 300, 400, 500 MHz, and
75, 100, 125 MHz, respectively, using tetramethylsilane
as internal standard. Optical rotations were measured with
a digital polarimeter at 25°C. Mass spectra were recorded
on a mass spectrometer by electrospray ionization (ESI-
MS). High-resolution mass spectra (ESI-HRMS) were
recorded on an ESI-QTOF mass spectrometer.
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General procedure for the synthesis of (R)-6-((1R,2R)-1-
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hydroxy-2-methoxy-2-phenylethyl)-5,6-dihydro-2H-pyran-2-
one (Parvistone C) (1b).
To a stirred solution of
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet