Synthesis of Sugar‐Fused Isoxazoline N‐Oxides from 2‐Nitroglycals

Chemistry of 2-Nitroglycals: A One-Pot Three-Component Stereoselective Approach toward 2-C-Branched O-Galactosides

“…Schmidt et al have reported that O -nucleophiles, for stereoelectronic reasons, selectively add from the α-side to 2-nitrogalactals in the presence of a strong base, generating a nitronate ion intermediate. , This nitronate ion after protonation from the β-side provides the 2-deoxy-2-nitro-α-galactosides. Our aim was to trap the nitronate ion intermediate with a suitable carbon electrophile to generate the 2- C -branched glycosides.…”

“…2-Nitroglycals are versatile intermediates for the stereoselective synthesis of various glycosides . Besides being good Michael acceptors, they also permit (2 + 3) and (2 + 4) cycloadditions, thus permitting the preparation of a number of other useful carbohydrate derived synthons.…”

Formal [4+1] Annulation Reactions in the Synthesis of Carbocyclic and Heterocyclic Systems

“…Bromomalonate has been shown to exhibit a reactivity profile that is similar to the reactivity profile of sulfur ylide in the cyclization reaction with nitroolefins. For example, Sun, Yu, and their co-workers noted that 2-nitroglycals smoothly reacted with bromomalonate in a [4+1] annulation manner in the presence of 1.2 equiv of DBU in CH 2 Cl 2 , which resulted in the corresponding sugar-fused isoxazoline N -oxides with acceptable yields (54–98%) (Scheme ) . The resulting N -oxides can efficiently undergo the 1,3-dipolar cycloaddition with the electron-deficient alkene and alkyne dipolarophiles to form nitroso acetals that bear three fused ring systems in acceptable yields with moderate diastereoselectivities.…”

“…Inspired by Sun and Yu’s study, Liu’s group successfully extended this type of [4+1] annulation to sulfur ylides 282 . Conversely, Liu’s group determined that the reaction between the 2-nitroglycals and sulfur ylides efficiently proceeded via a [4+1] annulation/rearrangement cascade using 1-phenylthiourea as the catalyst, which resulted in isoxazolines 377 in high yields with excellent diastereoselectivities (Scheme ) .…”

Facile synthesis of carbohydrate-integrated isoxazolines through tandem [4+1] cycloaddition and rearrangement of 2-nitroglycals

“…Yu et al successfully draw on such a strategy to synthesize sugar-fused isoxazolines from 2-nitroglycals. 12 2-Nitroglycals are versatile glycosyl donors useful in the synthesis of biologically active compounds and natural products, 13 underlying their periodical employment in organic reactions. 14 By virtue of the advantages associated with 2-nitroglycals 15 and in line with our ongoing efforts to develop new methodologies employing carbohydrates, 16 we herein report a successful [4+1] cycloaddition between 2-nitroglycals and sulfur ylides to produce highly selective carbohydrateintegrated isoxazoline derivatives.…”