摘要：

A simple route to the sesquiterpene antibiotic pentalenolactone 3 has been established. Thus, spiroannulation of 4,4-dimethyl cyclohexanone with <IMG class=charImg title=image height=15 alt=image src="http://www.sciencedirect.com/cache/MiamiImageURL/B6THR-42G5V3K-8Y-1/0?wchp=dGLbVtz-zSkzV" width=20>-(2-iodoethyl)ether, followed by diazo transfer and Wolff rearrangement, gives acid <SPAN style="FONT-WEIGHT: bold">6</SPAN>. Homologation to the corresponding β-ketoester, followed by diazo transfer and Rh-mediated intramolecular C-H insertion, then gives ester <SPAN style="FONT-WEIGHT: bold">8</SPAN>. Reduction of <SPAN style="FONT-WEIGHT: bold">8</SPAN> followed by dehydration leads to the α,β unsaturated ester, which on exposure to CrO<SUB>3</SUB> in acetic acid is oxidized preferentially at the less hindered methylene. α-Methylenation then completes the synthesis of 1.

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