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[reaction--see text] Dimerization of salicylaldehydes provided 6H,12H-6,12-epoxydibenzo[b, f][1,5]dioxocins in multigram quantities. Deprotonation-allylation of the benzylic acetals followed by further functionalization of the diallyl derivative and double Friedel-Crafts cyclization gave a novel preussomerin analogue which possessed the full carbon skeleton of the natural products.

Fluoroallylic alcohols are easy to synthesise by a variety of routes using one or two carbon fluorinated building blocks. Sigmatropic rearrangement then transforms these intermediates into species in which the fluorine atom (or atoms) is borne on an sp3-hybridised carbon. Alternatively, allylic alcohols can be transformed into fluorinated vinyl ether derivatives; rearrangement then affords products in which the fluorine atoms occupy a different and complementary location with respect to a carbonyl function.

Whereas the lithium enolates of acetate and propionate esters of difluoroallylic alcohols fragment rapidly, even at −78 °C, methoxy- and benzyloxy-acetates form chelated enolates which undergo smooth [3,3]-rearrangement as their silyl ketene acetals. The latent ketone function can be revealed under mild conditions (MeOH, SOCl2) to afford very highly functionalised CF2 compounds.

Whereas the lithium enolates of acetate and propionate esters of difluoroallylic alcohols fragment rapidly, even at −78 °C, methoxy- and benzyloxy-acetates form chelated enolates which undergo smooth [3,3]-rearrangement as their silyl ketene acetals. The latent ketone function can be revealed under mild conditions (MeOH, SOCl2) to afford very highly functionalised CF2 compounds.

Fluoroallylic alcohols are easy to synthesise by a variety of routes using one or two carbon fluorinated building blocks. Sigmatropic rearrangement then transforms these intermediates into species in which the fluorine atom (or atoms) is borne on an sp3-hybridised carbon. Alternatively, allylic alcohols can be transformed into fluorinated vinyl ether derivatives; rearrangement then affords products in which the fluorine atoms occupy a different and complementary location with respect to a carbonyl function.

Readily available γ,γ-difluorinated allylic alcohols obtained from trifluoroethanol were esterified efficiently. Exposure to strong base (LDA) afforded the ester enolates, in which chelation both controlled configuration and stabilised against fragmentation, which were trapped as their silyl ketene acetals. Rearrangement occurred to afford base-sensitive acid products. Esterification under mild conditions afforded the purifiable methyl esters in which the masked ketone had been released. Educts with either a benzyloxy or an allyloxy group at the α-position could be deprotected releasing the alcohols.

The first total syntheses of the title fungal metabolites preussomerins F, K and L are described and their structures confirmed thereby. The syntheses were achieved following a versatile, unified, non-biomimetic approach, which is easily extendable to prepare other known and novel members of this family. Key steps include the functionalisation of a 2-arylacetal anion, tandem one-pot Friedel–Crafts cyclisation–deprotection, regioselective substrate-directable hydrogenation and reductive-opening of epoxides.

The first total syntheses of the title fungal metabolites preussomerins F, K and L are described and their structures confirmed thereby. The syntheses were achieved following a versatile, unified, non-biomimetic approach, which is easily extendable to prepare other known and novel members of this family. Key steps include the functionalisation of a 2-arylacetal anion, tandem one-pot Friedel–Crafts cyclisation–deprotection, regioselective substrate-directable hydrogenation and reductive-opening of epoxides.

Dimerization of salicylaldehydes provided 6H,12H-6,12-epoxydibenzo[b,f][1,5]dioxocins in multigram quantities. Deprotonation−allylation of the benzylic acetals followed by further functionalization of the diallyl derivative and double Friedel−Crafts cyclization gave a novel preussomerin analogue which possessed the full carbon skeleton of the natural products.

Readily available γ,γ-difluorinated allylic alcohols obtained from trifluoroethanol were esterified efficiently. Exposure to strong base (LDA) afforded the ester enolates, in which chelation both controlled configuration and stabilised against fragmentation, which were trapped as their silyl ketene acetals. Rearrangement occurred to afford base-sensitive acid products. Esterification under mild conditions afforded the purifiable methyl esters in which the masked ketone had been released. Educts with either a benzyloxy or an allyloxy group at the α-position could be deprotected releasing the alcohols.