Gaspare Barone

Facile cleavage of carbohydrate benzyl ethers and benzylidene acetals using the NaBrO3/Na2S2O4 reagent under two-phase conditions

Benzyl ether and benzylidene acetal carbohydrate protecting groups can be selectively cleaved by reaction with sodium bromate/sodium dithionite in ethyl acetate/water. Under the mild (room temperature, short reaction time) conditions needed, a variety of other protecting functionalities such as acetyl, chloroacetyl, benzoyl, pivaloyl, tosyl, t-butyldimethylsilyl, trityl, and isopropylidene groups remain unaffected.

Efficient activation of glycosyl N-(phenyl)trifluoroacetimidate donors with ytterbium(III) triflate in the glycosylation reaction

Abstract The mild, moisture-stable and cheap catalyst Yb(OTf) 3 activates glycosyl N -(phenyl)trifluoroacetimidates in the stereoselective synthesis of 1,2- trans and 1,2- cis glycosides. A suitable choice of the reaction solvent led to good yields and stereoselectivity ratios. The protocol was successfully applied to acceptors and donors both exhibiting a wide range of reactivity.

Solid phase synthesis of oligosaccharides

Abstract An efficient and stereocontrolled solid-phase chemical synthesis of oligosaccarides using a new type of insoluble support (a copolymer of polyethylene glycol and polystyrene) is described. Several Lewis acids were tested as activators of the trichloroacetimidate 12 , used as glycosyl donor, in the dimer 13 formation.

An easy approach for the acetylation of saccharidic alcohols. Applicability for regioselective protections

Abstract Cheap 4 A molecular sieves can promote acetylation of carbohydrate hydroxyl functions with Ac2O in absence of any co-reagent. The procedure is compatible with the presence of a variety of acid labile protecting groups and can be exploited for regioselective protections.

Absolute configuration of homoisoflavanones from muscari species

Abstract The absolute configuration of homoisoflavanones isolated from Muscari species was determined by applying the chiral exciton coupling method to suitable derivatives. A negative Cotton effect in the 287–295 nm region of the CD curves of the natural compounds was shown to be indicative of 3R-configuration.

Homoisoflavanones from Muscari comosum bulbs

Abstract From the bulbs of Muscari comosum 3,9-dihydropunctatin and three novel homoisoflavanones were isolated.

3-Benzyl-4-chromanones from Muscari comosum

Abstract From the bulbs of Muscari comosum two novel 3-benzyl-4-chromanones, 7- O -methyl-3,9-dihydropunctatin and 8- O -demethyl-7- O -methyl-3,9-didropunctatin, were isolated.

Three 3-benzyl-4-chromanones from Muscari comosum

Abstract Three novel 3-benzyl-4-chromanones have been isolated from the bulbs of Muscari comosum .

Activation of disarmed 2-O-alkoxycarbonylated glycosyl trichloroacetimidates with lanthanide triflates: an efficient approach for the synthesis of 1,2-trans glycosides

Disarmed glycosyl trichloroacetimidates can be activated by Yb(OTf)3 in the synthesis of 1,2-trans glycosides involving primary and secondary acceptors. Concurrent formation of orthoester side products can be avoided by the use of alkoxycarbonyl groups for the protection of the donor 2-hydroxyl.

Efficient activation of armed glycosyl trichloroacetimidates with Sm(OTf)3 in the stereoselective glycosidation of saccharidic acceptors

Catalytic amounts of Sm(OTf)3 activate armed glycosyl trichloroacetimidates under very mild conditions. This reagent proved effective in promoting the glucosylation of saccharidic acceptors 2, 3, 4, and 5, possessing primary or secondary hydroxyls, with the model donor 1. The stereoselectivity of these glycosidations can be controlled by a suitable choice of solvent.