The Role of Total Synthesis in Structure …
49
future investigations into the biological role of this queen-specific volatile from S.
minutus.
4 Conclusions
Elucidating the structure of natural products is often a laborious and time-consuming
endeavor due to the minute amounts isolated from the natural source, limited stability
of the metabolites or difficult purification processes that can make it almost impossible to obtain reasonably pure samples. But even in those cases where a natural
product has been isolated in pure form, NMR spectroscopic analysis might remain
ambiguous, for example, due to high flexibility of the molecule which makes it
impossible to draw reliable conclusions from NOE experiments or from an analysis of the coupling constants. In such cases, as the examples highlighted in this
chapter hopefully illustrate, modern organic synthesis can serve as a valuable tool
in confirming or revising a structural proposal. If the amounts of material available
from the biological source are so small that NMR analysis is impossible and the
proposed structure is solely based on mass-spectrometric investigations, stereoselective synthesis even becomes an indispensable tool for providing single isomers as
reference compounds.
This chapter is not intended to be a comprehensive survey, but provides the reader
with an illustrative overview. We have highlighted the role of organic synthesis for the
structure elucidation of natural products for the example of ten-membered lactones,
but it can be safely assumed that organic synthesis plays an important role for the
structure elucidation of many other classes of natural products. A surprising result
from this compilation of examples is that in a notable number of cases the synthesisbased re-examination of a structural assignment is itself erroneous and confirms
a wrong structure proposal. For this reason, it is justified to embark on the total
synthesis of a natural product even if one or more previous syntheses exist.
Acknowledgments The contributions of our group to the field have been generously supported
by the Deutsche Forschungsgemeinschaft (DFG grant Schm1095/6). The author thanks Dr. Robert
Hanus, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague,
for helpful discussions and for providing photographs of S. minutus, Prof. Stefan Schulz and Prof.
Miguel Vences, TU Braunschweig, for providing high-resolution photographs of mantellid frogs
and the Pflanzenschutzamt Berlin for providing high-resolution photographs of Diplodia tip blight
infected pine trees.
49
future investigations into the biological role of this queen-specific volatile from S.
minutus.
4 Conclusions
Elucidating the structure of natural products is often a laborious and time-consuming
endeavor due to the minute amounts isolated from the natural source, limited stability
of the metabolites or difficult purification processes that can make it almost impossible to obtain reasonably pure samples. But even in those cases where a natural
product has been isolated in pure form, NMR spectroscopic analysis might remain
ambiguous, for example, due to high flexibility of the molecule which makes it
impossible to draw reliable conclusions from NOE experiments or from an analysis of the coupling constants. In such cases, as the examples highlighted in this
chapter hopefully illustrate, modern organic synthesis can serve as a valuable tool
in confirming or revising a structural proposal. If the amounts of material available
from the biological source are so small that NMR analysis is impossible and the
proposed structure is solely based on mass-spectrometric investigations, stereoselective synthesis even becomes an indispensable tool for providing single isomers as
reference compounds.
This chapter is not intended to be a comprehensive survey, but provides the reader
with an illustrative overview. We have highlighted the role of organic synthesis for the
structure elucidation of natural products for the example of ten-membered lactones,
but it can be safely assumed that organic synthesis plays an important role for the
structure elucidation of many other classes of natural products. A surprising result
from this compilation of examples is that in a notable number of cases the synthesisbased re-examination of a structural assignment is itself erroneous and confirms
a wrong structure proposal. For this reason, it is justified to embark on the total
synthesis of a natural product even if one or more previous syntheses exist.
Acknowledgments The contributions of our group to the field have been generously supported
by the Deutsche Forschungsgemeinschaft (DFG grant Schm1095/6). The author thanks Dr. Robert
Hanus, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague,
for helpful discussions and for providing photographs of S. minutus, Prof. Stefan Schulz and Prof.
Miguel Vences, TU Braunschweig, for providing high-resolution photographs of mantellid frogs
and the Pflanzenschutzamt Berlin for providing high-resolution photographs of Diplodia tip blight
infected pine trees.