Methyl-α‑d‑2-selenonyl Pent-2-enofuranoside: A Reactive Selenosugar for the Diversity Oriented Synthesis of Enantiomerically Pure Heterocycles, Carbocycles, and Isonucleosides

The construction of vinyl selenone on a furanoside led to a highly reactive synthetic intermediate methyl-α-d-2-selenonyl pent-2-enofuranoside composed of a masked aldehyde, an electron-deficient double bond along with an excellent leaving group. This new Michael acceptor on reactions with different nucleophiles afforded bicyclic azasugars, cyclopropanated carbohydrate, dihydrofuran- and dihydroisoxazole- substituted furanosides, and isonucleosides in moderate to good yields. Hydrolysis of the hemiacetal linkage of some of these modified carbohydrates afforded enantiopure aziridines, nitrocyclopropane, and dihydrofuran

1,5‑Disubstituted 1,2,3-Triazolylation at C1, C2, C3, C4, and C6 of Pyranosides: A Metal-Free Route to Triazolylated Monosaccharides and Triazole-Linked Disaccharides

A pair of easily accessible vinyl sulfones derived from styrene epoxide and monotosylated glycerol were reacted with six different azidopyranosides having an azido group at C1, C2, C3, C4, C6, and at the terminal position of an exocylic chain attached to C1. The reaction was performed mostly in water at elevated temperature without any metal catalyst to afford regioselectively 1,5-disubstituted triazolylated pyranosides in high yields. Another set of exocyclic vinyl sulfones prepared from 3-<i>O</i>-methylated- and 3-<i>O</i>-benzylated glucofuranosides as well as 3-<i>O</i>-benzylated allofuranoside were also subjected to 1,3-dipolar cycloaddition reactions with six azidopyranosides under similar reaction conditions to generate a series of 1,5-disubstituted triazole-linked disaccharides. The synthesis of all 1,5-disubstituted triazolylated monosaccharides as well as all 1,5-disubstituted triazole linked disaccharides are reported for the first time. Steric bulk around the azido and vinyl sulfone groups plays a significant role in deciding the outcome of the reactions. This powerful and practical route has the potential to be exploited for the synthesis of complex 1,5-disubstituted 1,2,3-triazolylated carbohydrates

Methyl-α‑d‑2-selenonyl Pent-2-enofuranoside: A Reactive Selenosugar for the Diversity Oriented Synthesis of Enantiomerically Pure Heterocycles, Carbocycles, and Isonucleosides

The construction of vinyl selenone on a furanoside led to a highly reactive synthetic intermediate methyl-α-d-2-selenonyl pent-2-enofuranoside composed of a masked aldehyde, an electron-deficient double bond along with an excellent leaving group. This new Michael acceptor on reactions with different nucleophiles afforded bicyclic azasugars, cyclopropanated carbohydrate, dihydrofuran- and dihydroisoxazole- substituted furanosides, and isonucleosides in moderate to good yields. Hydrolysis of the hemiacetal linkage of some of these modified carbohydrates afforded enantiopure aziridines, nitrocyclopropane, and dihydrofuran

Enantiopure 1,4,5-Trisubstituted 1,2,3-Triazoles from Carbohydrates: Applications of Organoselenium Chemistry

A wide range of stable vinyl selenone-modified furanosides has been synthesized for the first time. These 2π-partners undergo 1,3-dipolar cycloaddition reactions with a wide range of organic azides to afford enantiopure trisubstituted triazoles. Furanosyl rings opened up during triazole synthesis to generate polyfunctionalized molecules, ready to undergo further transformations. This strategy is one of the most convenient methods for the synthesis of enantiopure 1,4,5-trisubstituted 1,2,3-triazoles where the chiral components are attached to C-4 or C-5 position of triazole ring. These triazoles are formed in a regioselective manner, and several pairs of regioisomeric triazoles have also been synthesized. The approach affords densely functionalized triazoles, which are amenable to further modifications because of the presence of aldehyde and hydroxyl groups. This powerful and practical route adds to the arsenals of chemists and biologists interested in the synthesis and applications of triazoles

Regioselectivity of Vinyl Sulfone Based 1,3-Dipolar Cycloaddition Reactions with Sugar Azides by Computational and Experimental Studies

DFT (M06-L) calculations on the transition state for the 1,3-dipolar cycloadditions between substituted vinyl sulfones with sugar azide have been reported in conjunction with new experimental results, and the origin of reversal of regioselectivity has been revealed using a distortion/interaction model. This study provides the scientific justification for combining organic azides with two different types of vinyl sulfones for the preparation of 1,5-disubstituted 1,2,3-triazoles and 1,4-disubstituted triazolyl esters under metal-free conditions