A concise, diversity-oriented approach for the synthesis of naturally occurring 3-amino- and 3-nitro-2,3,6-trideoxypyranose derivatives and analogues thereof from simple sugars has been developed. In addition, we investigated the synthesis of various 3-aminoglycosyl donors and their application in glycosylation reactions. These studies led to the successful synthesis of a tetrasaccharide containing four different 3-aminosugar components using ortho-alkynylbenzoate donors.

Challenges for stereoselective glycosylation of deoxy sugars are notorious in carbohydrate chemistry. We herein report a novel strategy for the construction of the less investigated β-glycosidic bonds of 3,5-trans-3-amino-2,3,6-trideoxy sugars (3,5-trans-3-ADSs), which constitute the core structure of several biologically important antibiotics. Current protocol leverages a C-3 axial sulfonamide group in 3,5-trans-3-ADSs as a hydrogen-bond (H-bond) donor and repurposes substoichiometric phosphine oxide as an exogenous nucleophilic reagent (exNu) to establish an intramolecular H-bond between the former and the derived α-oxyphosphonium ion. This pivotal interaction stabilizes the α-face-covered intermediate to inhibit the formation of the more reactive β-intermediate, thereby yielding reversed β-selectivity, which is unconventional for an exNu-mediated glycosylation system. A wide range of substrates was accommodated, and good to excellent β-selectivities were ensured by this H-bonding-assisted exNu effect. The robustness of the current strategy was further attested by the architectural modification of natural products and drugs containing 3,5-trans-3-ADSs, as well as the synthesis of a trisaccharide unit in avidinorubicin.

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The synthesis of Nd-Fe-Co-B by the reduction-diffusion process from neodymium trichloride and its magnetic properties and microstructure have been investigated by x-ray diffraction, scanning electron microscope, and magnetic analysis. According to the thermodynamic data, calcium is capable of reducing neodymium trichloride and then a Nd-Fe-Co-B aHoy is formed by thermal diffusion in the presence of iron, cobalt, and ferro-boron powders at high temperature. The reduction reaction starts at 720 ·C. Thermal diffusion commenced at 800 ·C and forming some Nd 2 Fe ,4 B phase, but the matrix Nd 2 Fe l4 B formed primarily at 860--950 0c.There are three types of phases with different compositions in the sintered Nd-Pe-Co-B RID powders. The oxygen and calcium contents were 0.2 and 0.1 wt. 0/0, respectively. The best yield of Nd-Fe-Co-B powder was up to 98%. The magnetic properties of the sintcred Nd-Fe-Co-B depended on the temperature and time of the reduction-diffusion process. The best magnetic properties obtained were Br = 12.6 kGs, He = 8 kOe, and (BII) m = 36.4 MGOe.