[The antiviral action of threo-beta-phenylserine].

L-threo-phenylserine and esters of threo-phenylserine were the most active of a series of compounds tested against influenza A virus in tissue culture. Substitution of the beta-OH or alpha-NH(2) group abolished activity. The activity of phenylserine was reversed competitively by phenylalanine. Phenylserine did not act on free virus or on the adsorption of virus to host cells. It prevented virus growth if added during the first half of the latent period.Phenylalanine appears to be necessary for virus synthesis and can be supplied by phenylalanylglycine or glycylphenylalanine.Phenylserine had no significant activity against ectromelia infections in mice, even when the amino acid content of the livers had been depleted by starvation.