2 research outputs found
Agarsenone, a Cadinane Sesquiterpenoid from <i>Commiphora erythraea</i>
Agarsenone (<b>1</b>), a new
cadinane sesquiterpenoid, was
isolated from the resin of <i>Commiphora erythraea.</i> The
structures of <b>1</b> and
its decomposition products agarsenolides (<b>2a</b> and <b>2b</b>) and myrrhone (<b>3</b>) were established by extensive
NMR spectroscopic analysis. The absolute configuration of <b>3</b> and the relative and absolute configurations of <b>1</b> were
assigned by comparison of experimental and calculated optical rotatory
dispersion and electronic circular dichroism spectra
Absolute Configurations of Fungal and Plant Metabolites by Chiroptical Methods. ORD, ECD, and VCD Studies on Phyllostin, Scytolide, and Oxysporone
The absolute configuration (AC) of
the bioactive metabolites phyllostin
(<b>1</b>) and scytolide (<b>2</b>), two hexahydro-1,4-benzodioxines
produced by <i>Phyllosticta cirsii</i>, and oxysporone (<b>3</b>), a dihydrofuropyranone recently isolated from a strain
of <i>Diplodia africana</i>, has been assigned by computational
analysis of their optical rotatory dispersion (ORD), electronic circular
dichroism (ECD), and vibrational circular dichroism (VCD) spectra.
Computational prediction of ORD, ECD, and VCD allowed us to assign
(3<i>S,</i>4a<i>R,</i>8<i>S,</i>8a<i>R</i>) AC to naturally occurring (−)-<b>1</b>,
while (4a<i>R,</i>8<i>S,</i>8a<i>R</i>) AC was assigned to (−)-<b>2</b> employing only ECD
and VCD, because in this case ORD analysis turned out to be unsuitable
for AC assignment. Theoretical prediction of both ORD and ECD spectra
of <b>3</b> led to assignment of (4<i>S,</i>5<i>R,</i>6<i>R</i>) AC to (+)-<b>3</b>. In this
case a satisfactory agreement between experimental and calculated
VCD spectra was obtained only after taking into account solvent effects.
This study shows that in the case of flexible and complex natural
products only a concerted application of more than a single chiroptical
technique permits unambiguous assignment of absolute configuration