Marine natural products: Synthetic exercises
and biological data*
E.
Winterfeldt
Institut für Organische Chemie Der Universität Hannover,
Schneiderberg 1b, D-30167 Hannover, Germany
E-mail: [email protected]
Abstract: In the first part, synthetic experiments will be
described that provide information of the structural sub units responsible
for the very powerful tumor inhibiting activity of the cephalostatins.
These are bis-steroidal pyrazines that have been isolated by Petit
and coworkers from cephalodiscus gilchristi in 1988. By comparison
of relevant compounds the D 14,15
double bond which is very characteristic of these natural products
is shown to be very important and it is also demonstrated that structural
dissymmetry in the spiroketale moiety is very crucial.
A very efficient route to introduce the D
14,15 double bond and techniques for the preparation of nonsymmetric
pyrazines are reported accordingly.
In the second part an inspection of the structures
of antibacterial compounds from agelas oroides (agelorin)
will show that very probably the halogenated spirocyclohexenone
substructure of these compounds will be the essential part in these
powerful antibiotics. An enantioselective total synthesis of this
spiro-compound will be described employing the differentiation of
the enantiotopic double bonds of spirocyclohexadieno precursors
and a series of investigations proving their remarkable biological
activity will be presented.
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