Ph<sub>3</sub>PO-Modulated Kdo Glycosidation for Stereoselective\nSynthesis of β‑Kdo-Containing Disaccharides

A Ph<sub>3</sub>PO-modulated β-selective Kdo glycosidation\napproach is developed for the stereoselective synthesis of β-Kdo\nglycosides. With the readily available per-<i>O</i>-acetylated\nKdo ynenoate as the donor, the glycosylation with a series of alcohols\nin the presence of Ph<sub>3</sub>PAuOTf and Ph<sub>3</sub>PO in toluene\nat low temperatures afforded the desired Kdo glycosides with good\nto excellent β-selectivities. Furthermore, the Ph<sub>3</sub>PO-modulated approach was effectively applied to the synthesis of\nβ-(2→4)- and β-(2→8)-linked Kdo-Kdo disaccharides\nfor further biological studies.