(Phenyl L-alaninyl) cyclic HPMPC AIDS-179775 AIDS179775 Alanine, N-[(5S)-5-[(4-amino-2-oxo-1(2H)-pyrimidinyl)methyl]-2-oxido-1,4,2-dioxaphosphorinan-2-yl]-, 2-phenylethyl ester GS 7356