Highly Stereoselective Synthesis of Branched Fructooligosaccharides ABW90-1 and ABW50-1 from Achyranthes bidentata with Potent Antiosteoporosis Activities

Abstract

The branched fructooligosaccharides ABW90-1 and ABW50-1 from Achyranthes bidentata with potent antiosteoporosis activities have been synthesized for the first time. The synthetic approach highlights the following features: ( 1) 6-O-picoloyl-directed β-D-fructofuranosylation via a hydrogenbond-mediated aglycone delivery strategy for the highly stereoselective constructions of β-(2 → 6)-D-fructofuranosidic linkages and β-(2 → 1)-Dfructofuranosidic linkages in the internal positions under the reaction conditions (DBDMH, −20 °C, CH 2 Cl 2 ) and (2) the reaction conditions (DBDMH, −78 °C to −35 °C, toluene) for highly stereoselective formations of β-(2 → 1)-D-fructofuranosidic linkages in the terminal positions.