Stereoselective Michael addition of O-nucleophiles to carbohydrate-based nitro-olefin

Michael addition reactions of O-nucleophiles to C(3) exocyclic nitromethylene derivative of diacetone glucose are reported. The reactions with primary alcohols proceed at ambient temperature in the presence of different bases with good yields and give products with excellent diastereoselectivity. The addition of the nucleophile occurs from the β-face of the carbohydrate as shown by single crystal X-ray analysis. The reactions with secondary alcohols give low yields of products while phenolic compounds do not react. Under certain conditions, isomerization of starting material is observed.

Crystal structure of 3-de-oxy-3-nitro-methyl-1,2;5,6-di-O-iso-propyl-idene-α-d-allo-furan-ose

The title compound, C13H21NO7 {systematic name: (3aR,5S,6R,6aR)-5-[(R)-2,2-dimethyl-1,3-dioxolan-4-yl]-2,2-dimethyl-6-(nitro-meth-yl)tetra-hydro-furo[2,3-d][1,3]dioxole}, consists of a substituted 2,2-di-methyl-tetra-hydro-furo[2,3-d][1,3]dioxolane skeleton. The furan-ose ring A adopts a (o)T 4 conformation. The fused dioxolane ring B and the substituent dioxolane ring C also have twisted conformations. There are no strong hydrogen bonds in the crystal structure: only weak C-H⋯O contacts are present, which link the mol-ecules to form a three-dimensional structure.

Crystal structure of 3-O-benzyl-4(R)-C-(1-benzyl-1H-1,2,3-triazol-4-yl)-1,2-O-isopropylidene-α-D-erythrofuranose

The title compound is a substituted 2,2-di­methyl­tetra­hydro­furo[2,3-d][1,3]dioxole. The furan­ose ring adopts an envelope conformation, close to C₃-exo, as does the fused dioxolane ring. In the crystal, mol­ecules are linked by weak C—H⋯O hydrogen bonds, forming zigzag chains along [010].

The title compound, C₂₃H₂₅N₃O₄, {systematic name: 1-benzyl-4-[(3aR,5R,6R,6aR)-6-benz­yloxy-2,2-di­methyl­tetra­hydro­furo[2,3-d][1,3]dioxol-5-yl]-1H-1,2,3-triazole}, consists of a substituted 2,2-di­methyl­tetra­hydro­furo[2,3-d][1,3]dioxole. The furan­ose ring adopts an envelope conformation close to C₃-exo, where the C atom substituted by the benz­yloxy group is the flap. The fused dioxolane ring also adopts an envelope conformation, with the methyl­ene C atom as the flap. In the crystal, mol­ecules are linked by weak C—H⋯O hydrogen bonds, forming zigzag chains along [010].

Crystal structure of 3-C-(N-benzyl-oxy-carbon-yl)amino-methyl-3-de-oxy-1,2:5,6-di-O-iso-propyl-idene-α-d-allo-furan-ose

The title compound, C21H29NO7 (1) [systematic name: benzyl ({(3aR,5S,6R,6aR)-5-[(R)-2,2-dimethyl-1,3-dioxolan-4-yl]-2,2-di-methyl-tetrahydro-furo[2,3-d][1,3]dioxol-6-yl}meth-yl)carbamate], consists of a substituted 2,2-di-methyl-tetra-hydro-furo[2,3-d][1,3]dioxolane skeleton. The furan-ose ring adopts an envelope conformation close to C 3-exo, where the C atom substituted by the benzyl carbamate group is the flap. The fused dioxolane ring also adopts an envelope conformation, as does the terminal dioxolane ring, with in each case an O atom as the flap. In the crystal, mol-ecules are linked by N-H⋯O and C-H⋯O hydrogen bonds, forming chains propagating along the b-axis direction.