Lamivudine (R)S-Oxide; 4-Amino-1-[(2R,3R,S)-2-(hydroxymethyl)-3-oxido-1,3-oxathiolan-5-yl]-2(1H)-pyrimidinone; [2R-(2α,3 β,5α)]-4-Amino-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]-2(1H)-pyrimidinoneS-Oxide; 1,3-Oxathiolane, 2(1H)-pyrimidinone Deriv.; [2R-(2α,3 β,5α)]-4-Amino-1-[2-(hydroxymethyl)-3-oxido-1,3-oxathiolan-5-yl]-2(1H)-pyrimidinone; GI 138870X