New potent insecticidal agent: 4′-fucosyl avermectin derivative

A 4′-fucosyl avermectin derivative was designed and synthesized. This new avermectin derivative showed excellent in vivo bioactivity against cabbage larvae when compared to commercially available avermectin B_1a. In this synthesis, thioglycosyl donors, but not trichloroacetimidates, were found compatible with sugar-macrolide synthesis under rt promotion with NIS or I₂ in N-methylpyrrolidone.     

Study of structural and electronic transport properties of Ce-doped LaMnO3

The structural and electronic transport properties of La_1−x Ce _x MnO₃ (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration up to 50% doping. The system La_0.5Ce_0.5MnO₃ also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition.     

Synthesis of saponins using partially protected glycosyl donors

[reaction: see text] A new class of glycosyl donors having unprotected 2- and 2,4-hydroxyl groups were investigated under the standard glycosylation conditions. This approach was shown to be generally effective for the synthesis of alkyl and steroidal glycosides. A natural saponin, containing 2,4-branched oligosaccharide, was prepared in 35% overall yield in four straightforward sequential reactions by taking advantage of these partially protected donors.     

Stereoselective synthesis of the alpha-glycoside of a KDO "C"-disaccharide

The reaction of tert-butyl (4,5,7, 8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2-octulopyranosyl chloride)onate donor 7 with the 6-formylgalactopyranoside acceptor 4 in the presence of SmI(2) provided only the KDO alpha-C-disaccharide 8. The bulky tert-butyl ester in the donor was used to reverse the stereochemical outcome of C-glycosylation, stereoselectively forming the alpha-"C"-disaccharide of KDO.