Axially chiral bicoumarin

Asymmetric syntheses of warfarin <96TL8321> and the axially chiral bicoumarin, isokotanin A <96TL3015> have been reported. The former is based on a Rh-catalysed asymmetric hydrogenation of a 3-(a,P-unsaturated ketone) substituted coumarin, whilst the key steps of the latter are an asymmetric Ullmann coupling and a selective demethylation. The stereochemistry of the fused dihydrocoumarin resulting from Li/NHs reduction of... 

An efficient atropo-enantioselective total synthesis of the axially chiral bicoumarin (+)-isokotanin was accomplished by J. Bringmann and co-workers.The key steps in this synthetic approach were the formation of a configurationally stable seven-membered biaryl lactone by the Cannizzaro reaction of the corresponding biaryl dialdehyde followed by a kinetic resolution by atroposelective ring cleavage. 

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See also in sourсe #XX -- [ ]

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