.alpha.-L-(+)-(2R,5R)-1-[2-(Hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine .alpha.-L-Oxathionyl-cytidine 1,3-Oxathiolane deriv. 139757-68-9 2(1H)-Pyrimidinone, 4-amino-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]-, (2R-trans)- AIDS-002618 AIDS002618 trans-2-Hydroxymethyl-5-(cytosin-1-yl)-1,3-oxathiolane