Lebsack AD,
Overman LE *,
Valentekovich RJ.
University of California, Irvine, USA
Enantioselective Total Synthesis of Shahamin K.
J. Am. Chem. Soc. 2001;
123: 4851-4852
DOI:
10.1021/ja015802o
Keywords
(+)-shahamin K - spongiane diterpenoid - Johnson–Lemieux oxidation - Prins-pinacol
cascade - Peterson olefination - Michael addition - Mukaiyama esterification
Significance
In 2001, Overman and co-workers reported the enantioselective total synthesis of ( + )-shahamin
K, a spongiane diterpenoid natural product isolated from the dorid nudibranch Chromodoris gleniei. The central cis-hydroazulene motif was installed via a Prins–pinacol cascade. Spongiane diterpenoids
have been investigated for their antimicrobial and fish antifeedant properties.
Comment
Thioacetal C was engaged in the pivotal Prins–pinacol cascade reaction by exposure to BF3·Et2O, affording ketone E in high yield. Subsequent Peterson olefination and oxidation furnished ketone G, which was then employed in a Michael addition to couple fragment H. Oxidation-state adjustment furnished keto alcohol J, which was subjected to a sequence consisting of Johnson–Lemieux oxidation, reduction,
and Mukaiyama esterification to assemble the lactone moiety, affording ( + )-shahamin
K.
