is isolated and dissolved in tetrahydrofuran water 60 40 and evaporated onto silica gel which is then eluted with 80 20 2 chloroform methanol water fractions containing pure diacylated product by tlc are combined to give the title compound the product from example 8 1 23 g is hydrogenated h2 pressure 40 psi in 50 aqueous ethanol in the presence of 10 of pd c 1 0 g and 1 0 n hcl 4 ml after the reaction is shown to be complete by tlc about 1 5 hours the catalyst is filtered and washed well with water the volume is reduced in vacuo in order to cause the product to crystallize filtration and recrystallization from aqueous ethanol gives the title compound this material is prepared by hydrogenation of s 9 2 3 bis n carbobenzyloxyglycyloxy 1 propoxymethyl guanine as described for the synthesis of s 9 2 3 dialanyloxy 1 propoxymethyl guanine example 11 a mixture of 0 54 g 2 mmol of s 9 2 3 dihydroxy 1 propoxymethyl guanine 1 026 g 4 3 mmol of n carbobenzyloxy dl alanine 0 04 g anhydrous p toluenesulfonic acid and 1 755 g 5 6 mmol of n n 39 dicyclohexylcarbodiimide in dry pyridine 80 ml is stirred.