The Role of Total Synthesis in Structure …
3
1 Introduction
Decanolides, sometimes referred to as nonanolides, are naturally occurring tenmembered lactones. The first compound with this general structure was isolated
from jasmine oil in 1942 [1], and later named jasmine ketolactone (1). The tenmembered lactone structure could not be assigned until 1964; this assignment was
based on IR and NMR spectroscopic investigations, but elucidation of the absolute
and relative configuration required a four-step conversion into the known (–)-methyl
jasmonate (2), and comparison with the previously published specific rotation of 2
[2] (Scheme 1).
In their 1996 landmark review on ten-membered lactone natural products [3],
Dräger et al. named the diplodialides as the first examples of decanolides, probably
because these metabolites are, like the majority of decanolides known to date (and
in contrast to jasmine ketolactone (1)), pentaketides and originate from a microbial
source, the plant pathogenic fungus Diplodia pinea [4]. Diplodia pinea is the causal
agent of the diplodia tip blight, a fungal disease that affects pines and other conifers
when exposed to stressed conditions (Plates 1 and 2).
The first three decanolides from this source were discovered in 1975 by Ishida and
Wada and named diplodialides A–C [4], and a fourth metabolite was isolated in the
following year in very small quantities and named diplodialide D [5]. The strategy
for structure elucidation of the diplodialides in the 1970s was very similar to that
employed for jasmine ketolactone (1) a decade earlier: the ten-membered lactone
structure and the (E)-configuration of the endocyclic C=C double-bond were established through a combination of IR and NMR spectroscopy. However, in contrast
to the work on jasmine ketolactone (1) ten years before, high-resolution mass spectrometry (HRMS) had entered the scene and provided valuable information for elucidating the constitution. Assignment of absolute configurations to the stereocenters at
Scheme 1 Historical elucidation of absolute and relative configuration of (–)-jasmine ketolactone
(1)
3
1 Introduction
Decanolides, sometimes referred to as nonanolides, are naturally occurring tenmembered lactones. The first compound with this general structure was isolated
from jasmine oil in 1942 [1], and later named jasmine ketolactone (1). The tenmembered lactone structure could not be assigned until 1964; this assignment was
based on IR and NMR spectroscopic investigations, but elucidation of the absolute
and relative configuration required a four-step conversion into the known (–)-methyl
jasmonate (2), and comparison with the previously published specific rotation of 2
[2] (Scheme 1).
In their 1996 landmark review on ten-membered lactone natural products [3],
Dräger et al. named the diplodialides as the first examples of decanolides, probably
because these metabolites are, like the majority of decanolides known to date (and
in contrast to jasmine ketolactone (1)), pentaketides and originate from a microbial
source, the plant pathogenic fungus Diplodia pinea [4]. Diplodia pinea is the causal
agent of the diplodia tip blight, a fungal disease that affects pines and other conifers
when exposed to stressed conditions (Plates 1 and 2).
The first three decanolides from this source were discovered in 1975 by Ishida and
Wada and named diplodialides A–C [4], and a fourth metabolite was isolated in the
following year in very small quantities and named diplodialide D [5]. The strategy
for structure elucidation of the diplodialides in the 1970s was very similar to that
employed for jasmine ketolactone (1) a decade earlier: the ten-membered lactone
structure and the (E)-configuration of the endocyclic C=C double-bond were established through a combination of IR and NMR spectroscopy. However, in contrast
to the work on jasmine ketolactone (1) ten years before, high-resolution mass spectrometry (HRMS) had entered the scene and provided valuable information for elucidating the constitution. Assignment of absolute configurations to the stereocenters at
Scheme 1 Historical elucidation of absolute and relative configuration of (–)-jasmine ketolactone
(1)