Eighteen amino acid esters of acyclovir were synthesized as potential prodrugs intended for oral administration and the hydrolytic activation of these prodrugs was shown to be catalyzed by biphenyl hydrolase; an enzyme exists in epithelial cells [25].This is corresponding to 54% of absolute acyclovir [27], after its libration by  an extensive enzymatic hydrolysis in the bloodValacyclovir hydrochloride is the L-valyl amino acid ester of the anti viral agent acyclovir [26].