Abstract
Tetronic acid esters and amides, which are readily available
from the corresponding tetronic acids, serve as useful starting
materials in an intra- or intermolecular [2+2]-photocycloaddition
reaction. Typical reaction conditions are irradiation at λ = 254
nm in diethyl ether or an alcohol as the solvent. The bi-, tri-
or tetracyclic products so obtained can be further utilized by ring
opening either of the lactone or the cyclobutane ring. Lactone ring
opening led to the use of a tetramide photocycloaddition product
as a conformationally restricted β-proline analogue and
to an application of a tetronate photocycloaddition product in the
total synthesis of punctaporonin C.
Key words
[2+2] cycloadditions - cyclobutanes - diastereoselectivity - heterocycles - photochemistry
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