Synthesis of a structural analogue of the repeating unit from Streptococcus pneumoniae 19F capsular polysaccharide based on the cross-metathesis-selenocyclization reaction sequence.

Pseudo-oligosaccharides have attracted much interest as scaffolds for the synthesis of sugar mimics endowed with very similar biological properties but structurally and synthetically simpler than their natural counterparts. Herein, the synthesis of pseudo-oligosaccharides using the cross-metathesis reaction between distinct sugar-olefins followed by intramolecular selenocyclization of the obtained heterodimer as key steps is first investigated. This methodology has been then applied to the preparation of structural analogues of the trisaccharide repeating unit from Streptococcus pneumoniae 19F.

Synthesis of enantiopure 1,4-dioxanes, morpholines, and piperazines from the reaction of chiral 1,2-diols, amino alcohols, and diamines with vinyl selenones.

The reactions of readily available vinyl selenones with enantiopure 1,2-diols, N-protected-1,2-aminoalcohols, and diamines gave substituted enantiopure 1,4-dioxanes, morpholines, and piperazines, respectively, in good to excellent yields. The same procedure was extended to the synthesis of thiomorpholine, benzodiazepine, and benzoxazepine. The reactions proceeded in one pot, in the presence of base, through a simple and novel application of the Michael-initiated, ring-closure (MIRC) reactions.

Diastereoselective synthesis of hexahydro-3H-pyrrolyzin-3-ones through Pd-catalyzed carboamination.

The reaction of readily available (5R)-5-but-3-en-1-ylpyrrolidin-2-one with aryl bromides, chlorides, or triflates in the presence of Pd(2)(dba)(3), Xphos, and Cs(2)CO(3) in 1,4-dioxane at 120 degrees C affords (5R,7aR)-5-aryl hexahydropyrrolizidin-3-ones in good to high yields through a diastereoselective carboamination reaction. Aryl iodides are less successful substrates than bromides and chlorides.