Using a linear assembly approach a highly differentially protected deriv. of the common GPI-anchor core structure (a-D-Manp-(1->6)-a-D-Manp-(1->2)-a-D-Manp-(1->4)-a-D-GlcNH2-(1->6)-D-myo-inositol) has been synthesized. All mannose donors were prepd. from a common mannothioglycoside precursor, and coupled to GlcN3-myo-inositol acceptor in a linear five-step glycosylation-deprotection sequence in 49% overall yield, to give the key pentasaccharide intermediate, with orthogonal temporary protecting groups at the 6'', 2'', 6', and two positions of the trimannoside motif and at the one and two positions of the inositol part. Consecutive removal of the temporary protecting groups in the trimannoside moiety followed by phosphorylation, gave a tetraphosphosphate deriv. in 60% overall yield. Removal of a camphor acetal afforded a 1,2-inositol diol, which was converted to a 1,2-cyclic phosphate using com. Me dichlorophosphate (95%). One-step deprotection using sodium in liq. ammonia afforded the target polyphosphorylated core structure (60%), which will be tested for metabolic insulin action. [on SciFinder (R)]