An improved route to an intermediate in podophyllotoxin synthesis
- 1 January 1980
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Chemical Communications
- No. 6,p. 262-263
- https://doi.org/10.1039/c39800000262
Abstract
Cyclopropanation of the chalcone (3) with dimethylsulphonium ethoxycarbonylmethylide affords a 1 : 1 mixture of the cyclopropanyl keto-ester epimers (4) and (5); both stannic chloride and boron trifluoride etherate in nitromethane catalyse the stereoselective cyclisation of this mixture to the tetralone (2), the known podophyllotoxin precursor, in 51% overall yield.Keywords
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