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Total Synthesis of (−)-Preussochromone D
- Kerste, Eric, Harms, Klaus, Koert, Ulrich
- Organic letters 2019 v.21 no.11 pp. 4374-4377
- aldehydes, chemical structure, diastereoselectivity, diazo compounds, oxidation, stereoselective synthesis, zinc
- An efficient, stereoselective synthesis of the natural product (−)-preussochromone D is reported. The tricyclic skeleton was assembled by a diastereoselective intramolecular aldol addition of a chromanone to an α-ketoester. Further key steps are an asymmetric 1,4-addition of diisopropenyl zinc to a chromenone and an intermolecular diastereoselective aldol addition of methyl diazoacetate to an aldehyde. The diazo group was oxidized to generate the α-ketoester while oxidative side reactions at the chromanone could be prevented by the use of a difluoromethyl ether as a protecting group.