Biologically relevant morpholino nucleoside thio- and dithiophosphates via an oxathiaphospholane approach

Appropriately protected morpholino nucleoside 6′-O-(2-thio)-1,3,2-oxathiaphospholanes and 6′-O-(2-thio)-1,3,2-dithiaphospholanes react with 3-hydroxypropionitrile in the presence of a strong base catalyst (DBU), yielding morpholino nucleoside 6′-O-(α-thiophosphates) and 6′-O-(α,α-dithiophosphates), respectively. The synthesized compounds exhibit low cytotoxicity toward human cells, indicating their favorable biocompatibility and potential for further biological and therapeutic applications.