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The total
synthe
si
s of the putative
structure of the
Stemona alkaloid
stemonidine ha
s been completed. The key tran
sformation
s include a1,3-dipolar cycloaddition of a chiral nitrone derived from (
S)-prolinol and a
spirolactonization proce
ss involving the generation of the critical
stereocenter. The NMR data of the
synthetic material do not match tho
se reported for the natural product. It i
s concluded that the
structurea
ssigned to
stemonidine i
s incorrect, and it mu
st be rea
ssigned a
s stemo
spironine.