DIRECT SYNTHESIS OF THE ISOSTERIC PHOSPHONO ANALOGS OF ALPHA-L-RHAMNOSE 1-PHOSPHATE AND BETA-L-FUCOSE 1-PHOSPHATE

The isosteric phosphono analogue of alpha-L-rhamnose 1-phosphate has b een stereoselectively synthesized by reaction of 2,3,5-tri-O-benzyl-L- rhamnose with tetraethyl methylenediphosphonate and sodium hydride in diglyme, followed by deprotection with iodotrimethylsilane. To synthes ize stereoselectively the isosteric phosphono analogue of beta-L-fucos e 1-phosphate, 2,3,5- tri-O-benzyl-L-fuconolactone was treated with li thiated dimethyl methylenephosphonate, and the 3,4,5-tri-O-benzyl-1,7- dideoxy-1-(phospho dimethyl)-L-galactoheptulopyranose obtained was ste reoselectively reduced with triethylsilane and boron trifluoride ether ate to afford the dimethyl (2,3,4-tri-O-benzyl-beta-L fucopyranosyl)me thanephosphonate which was finally deprotected with iodotrimethylsilan e.