Abstract: A compound which exhibits antiviral activity having the formula: ##STR1## wherein; R.sub.1 is selected from the group consisting of alkyls and alkenyls containing from 8 to 22 carbon atoms;A is selected from the group consisting of O and S atoms;R.sub.2 is selected from the group consisting of alkyls and alkenyls containing from 8 to 22 carbon atoms; and theNucleoside is selected from the group consisting of 2',3'-dideoxynucleosides, 3'-azido-2',3'-dideoxynucleosides, and 2',3'-didehydro-2',3'-dideoxynucleosides.

Abstract: This invention relates to cytotoxic compounds. More particularly, this invention relates to conjugates of antitumor agents, and thiophospholipids exhibiting enhanced antitumor activity to methods for producing such compounds and to pharmaceutical compositions containing cytotoxically effective amounts of such compounds as a primary effective ingredient.

Abstract: Nucleotides of nucleosides or bases having known cytotoxic activity are reacted with steroids, preferably corticosteroids, to form corresponding cytotoxic nucleoside-corticosteroid phosphodiester analogues of the formula: ##STR1## wherein: steroid is the residue formed by removal of a hydroxyl hydrogen atom from a natural or synthetic adrenal corticosteroid containing the characteristic cyclopentanophenanthrene nucleus which is esterified to the phosphate moiety at the 21-position;sugar is a naturally occurring pentose or deoxypentose in the furanose form, preferably ribose, deoxyribose, lyxose, xylose or arabinose and especially ribose, deoxyribose or arabinose, which is esterified to the phosphate moiety at the 5'-position and covalently bonded to the heterocycle moiety at the 1'-position to form a nucleoside; andheterocycle is a purine, pyrimidine, hydrogenated pyrimidine, triazolopurine or similar nucleoside base.