Compounds of the formula I wherein R3 is CH2 R6 and R6 is a halogen preferably fluorine, chlorine, iodine and bromine may be produced by reacting 1,4-dideoxy-1,4-imino-2,3-O-isopropylidene -??-D-lyxitol with triphenyl phosphine and C(R6)4 wherein R6 is a halogen preferably fluorine, chlorine, iodine, and bromine under suitable conditions.