Roberto Antonioletti

A new route to 2-alkenyl-1,3-dicarbonyl compounds, intermediates in the synthesis of dihydrofurans

A two step synthetic strategy for obtaining 2-alkenyl-1,3-dicarbonyl compounds from the corresponding 1,3-dicarbonyl compounds is reported. The method is based on a Knoevenagel condensation and a Michael addition using a high order organocuprate procedure, and proves to be of general value. Obtained compounds are useful starting materials for the synthesis of furan derivatives.

A convenient approach to furan derivatives by I2-induced cyclisation of 2-alkenyl substituted 1,3-dicarbonyl compounds

Abstract 5-iodoalkyl-4,5-dihydrofurans 2 , 5-alkylidine-4,5-dihydrofurans 3 and 2,3,5-trisubstituted furans 4 are obtained through a simple sequence, involving, in the key-step, a regio- and stereoselective iodoenoletherification of 2-alkenyl substituted 1,3-dicarbonyl compounds 1 .

An easy approach to dihydrofurans by one-step cyclisation of 2-alkenyl substituted 1,3-dicarbonyl compounds

Abstract Dihydrofuran derivatives were obtained by a simple one-step procedure involving an easy epoxidation of 2-alkenyl-1,3-dicarbonyl compounds by dimethyldioxirane prepared in situ and a subsequent cyclisation under the same basic reaction conditions.

Antifungal Activity of Resveratrol against Botrytis cinerea Is Improved Using 2-Furyl Derivatives

The antifungal effect of three furyl compounds closely related to resveratrol, (E)-3,4,5-trimethoxy-β-(2-furyl)-styrene (1), (E)-4-methoxy-β-(2-furyl)-styrene (2) and (E)-3,5-dimethoxy-β-(2-furyl)-styrene (3) against Botrytis cinerea was analyzed. The inhibitory effect, at 100 µg ml−1 of compounds 1, 2, 3 and resveratrol on conidia germination, was determined to be about 70%, while at the same concentration pterostilbene (a dimethoxyl derivative of resveratrol) produced complete inhibition. The title compounds were more fungitoxic towards in vitro mycelial growth than resveratrol and pterostilbene. Compound 3 was the most active and a potential explanation of this feature is given using density functional theory (DFT) calculations on the demethoxylation/demethylation process. Compound 3 was further evaluated for its effects on laccase production, oxygen consumption and membrane integrity of B. cinerea. An increase of the laccase activity was observed in the presence of compound 3 and, using Sytox Green nucleic acid stain, it was demonstrated that this compound altered B. cinerea membrane. Finally, compound 3 partially affected conidia respiration.

Expedient Synthesis of Hydroxytyrosol and its Esters

Abstract An efficient and friendly method for obtaining hydroxytyrosol from tyrosol, a component of olive waste, is reported. Hydroxytyrosol also may be obtained in the form of enzymatically convertible precursors (e.g., hydroxytyrosyl acetate), thus increasing the stability of the active principle.

SELECTIVE HALOGENATION OF AROMATICS BY DIMETHYL-DIOXIRANE AND HALOGEN IONS

The oxidation of halogen anions by dimethyldioxirane (DMD) produced reactive species which led, in acidic media, to the halogenation of activated aromatic rings. The reaction can be efficiently controlled to obtain selective and mixed halogenated species.

Selective halogenation of flavanones

A mild, efficient and regioselective method for the selective halogenation of flavonoids is presented. Halogenated flavanones and flavones are considered potential benzodiazepine receptor ligands and with DMD/NaX or oxone/acetone/water/NaX systems they can be synthesised in preparative amounts.

Diastereoselective synthesis of 4,5-dihydrofurans by iodoenolcyclisation of 2-allyl-1,3-dicarbonyl compounds

Abstract A study of the stereochemical aspects of I2-induced cyclisation of 2-alkenyl-1,3-dicarbonyl compounds reveals that the iodoenolcyclisation is strictly dependent on the dicarbonyl species and the substituents in the allylic position.

Stereo- and regiocontrolled transformations of vinyloxiranes with metal halides

Abstract Simple procedures for the transformation of vinyl oxiranes to trans ,  trans -dienes and regio- and stereocontrolled unsaturated bromohydrins are reported.

Asymmetric oxidation of silyl enol ethers using chiral dioxiranes derived from α-fluoro cyclohexanones

Asymmetric oxidation of silyl enolethers derived from tetralone, 2-methyl-tetralone, propiophenone and deoxybenzoin using chiral dioxiranes generated in situ from oxone and new chiral α-fluorinated cyclohexanones or fructose-derived ketone have been studied. It was observed that tetrasubstituted silyl enolethers are poor substrates, that substitution at C8 of the fluoro-ketones has a significant effect on the enantioselectivities obtained and that the fructose-derived-ketone provides higher enantioselectivities. The absolute configuration of the major hydroxy ketones obtained can be rationalized using a spiro model proposed for epoxidation of olefins.