Synthese eines 1,2- trans -konfigurierten, äquatorialen Glycosyl-phosphonat-Analogen von D - myo -Inositol-1,4,5-trisphosphat

Galactose-derived phosphonate analogues as potential inhibitors of phosphatidylinositol biosynthesis in mycobacteria

Galactose-based phosphonate analogues of myo-inositol-1-phosphate and phosphatidylinositol have been synthesized from methyl beta-d-galactopyranoside. Michaelis-Arbuzov reaction of isopropyl diphenyl phosphite or triisopropyl phosphite with a 6-iodo-3,4-isopropylidene galactoside afforded the corresponding phosphonates. Deprotection of the diphenyl phosphonate afforded methyl beta-d-galactoside 6-phosphonate, an analogue of myo-inositol-1-phosphate. The diisopropyl esters of the diisopropyl phosphonate were selectively deprotected and the corresponding anion was coupled with 1,2-dipalmitoyl-sn-glycerol using dicyclohexylcarbodiimide. Deprotection afforded a methyl beta-d-galactoside-derived analogue of phosphatidylinositol. The galactose-derived analogues of phosphatidylinositol and myo-inositol-1-phosphate were not substrates for mycobacterial mannosyltransferases (at concentrations up to 1 mM) involved in phosphatidylinositol mannoside biosynthesis in a cell-free extract of Mycobacterium smegmatis. The galactose-derived phosphonate analogue of phosphatidylinositol was shown to be an inhibitor at 0.01 mM of PimA mannosyltransferase involved in the synthesis of phosphatidylinositol mannoside from phosphatidylinositol, and a weaker inhibitor of the next mannosyltransferase(s), which catalyzes the mannosylation of phosphatidylinositol mannoside.

Synthesis of D-Galactopyranosylphosphonic and (D-Galactopyranosylmethyl)phosphonic Acids as Intermediates of Inhibitors of Galactosyltransferases

Employing the Michaelis-Arbuzov reaction of 1-O-acetyl-2,3,4,6-tetra-O-benzyl-D-galactopyranose with triethyl phosphite and trimethylsilyl trifluoromethanesulfonate, α- and β-D-galactopyranosylphosphonic acids were prepared in 33 and 28% yields, respectively. (α-D-Galactopyranosylmethyl)phosphonic acid was synthesized by a five-step route from 2,3,4,6-tetra-O-benzyl-D-galactopyranose in 52% overall yield. When tested against bovine α-1,3- and β-1,4-galactosyltransferases, all three compounds showed, at best, very poor inhibitions. Both enzymes were inhibited more effectively by β-D-galactopyranosylphosphonic acid (IC50 = 17 mmol l-1 at 13.5 μmol l-1 of UDP-Gal for β4GalT).