A Ca(2+)-mobilising Carbohydrate-based Polyphosphate: Synthesis of 2-hydroxyethyl Alpha-D-glucopyranoside 2',3,4-trisphosphate

Two routes to a glucose-based mimic of the second messenger 1D-myo-inositol 1,4,5-trisphosphate related to adenophostin A are described. Fischer glycosidation of D-glucose with allyl alcohol in the presence of a strong cation-exchange resin gave a 7:3 alpha: beta-anomeric mixture of allyl glucopyranosides (5ab) from which the pure alpha anomer 5a was isolated by crystallisation. Treatment of 5ab with 1.05 equiv of dibutyltin oxide followed by 2.1 equiv of benzoyl chloride gave allyl 2,6-di-O-benzoyl-alpha-D-glucopyranoside, which was converted in 3 steps into allyl 2,6-di-O-benzyl-3,4-O-isopropylidene-alpha-D-glucopyranoside (4). Alternatively, treatment of 5a with 2.5 equiv of dibutyltin oxide followed by benzyl bromide gave allyl 2,6-di-O-benzyl-alpha-D-glucopyranoside (9) which was also converted into 4. Compound 4 was elaborated to the phosphorylation precursor 2-hydroxyethyl 2,6-di-O-benzyl-alpha-D-glucopyranoside (12) in a convenient one-pot reaction, and 12 was phosphorylated and deblocked to afford 2-hydroxyethyl alpha-D-glucopyranoside 2',3,4-trisphosphate. The 2,6-di-O-benzyl derivative 9 was converted in high yield into 2,6-di-O-benzyl-3,4-di-O-(p-methoxybenzyl)-D-glucopyranose, a useful intermediate for the synthesis of adenophostin A and related compounds.