by incorporating the various sterilized active ingredients into a sterile vehicle which contains the basic dispersion medium and the required other ingredients from those enumerated above in the case of sterile powders for the preparation of sterile injectable solutions the preferred methods of preparation are vacuum drying and freeze drying techniques which yield a powder of the active ingredient plus any additional desired ingredient from previously sterile filtered solution thereof as used herein 34 pharmaceutically acceptable carrier 34 includes any and all solvents dispersion media coatings antibacterial and antifungal agents isotonic and absorption delaying agents and the like the use of such media and agents for pharmaceutical active substances is well known in the art except insofar as any conventional media or agent is incompatible with the active ingredient its use in the therapeutic compositions is contemplated supplementary active ingredients can also be incorporated into the compositions the invention will next be described in connection with certain non limiting specific examples which are included herein for purposes of illustration it should be clear that the examples provide general schemes which outline the basic methods for synthesizing some of the compounds of the present invention unless otherwise specified the 6 pyridyl substitutions described below encompass a generic class including for example 6 pyridylthio and 6 pyridylseleno substituted pyrimidine derivatives in one embodiment 1 benzyloxymethyl 5 ethyl 6 u03b1 pyridylthio uracil according to the present invention can be prepared from 5 ethyl 1 benzyloxymethyl uracil according to the following synthesis routes 2 4 bis o trimethylsilyl 5 ethyl uracil was made from a mixture of 5 6 g 5 ethyl uracil niedzwicki et al 1982 biochem pharm 31 1857 incorporated by reference herein and 152 mg ammonium sulfate in 20 ul of hexamethyl disalazane by heating at reflux under an inert.