Synthesis of (±)-Emtricitabine and (±)-Lamivudine by Chlorotrimethylsilane-Sodium Iodide Promoted Vorbrüggen Glycosylation

By simply adding water and sodium iodide (NaI) to chlorotrimethylsilane (TMSCl), promotion of a Vorbrüggen glycosylation en route to essential HIV drugs emtricitabine (FTC) and lamivudine (3TC) is achieved. TMSCl-NaI in wet solvent (0.1 M water) activates a 1,3-oxathiolanyl acetate donor for N-glycosylation of silylated cytosine derivatives, leading to cis ox-athiolane products with up to 95% yield and >20:1 dr. This telescoped sequence is followed by recrystallization and borohydride reduction, resulting in rapid synthesis of (±)-FTC/3TC from an achiral tartrate ester.