The synthesized analogs P - X - HNC ( O ) - CH 2 B [ X = CH ( OH ) CH 2 , CH ( OH ) CH 2 CH 2 , CH 2 CH ( OH ) CH 2 ] appeared inactive in antiviral assays on a wide variety of DNA and RNA viruses at concentrations up to 100 μM , while two phosphonates showed cytostatic activity towards myeloid