Four isomeric methoxy substituted DCK analogues (3-6) were asymmetrically synthesized from different starting materials. 5-Methoxy-3',4'-di-O-(-)-camphanoyl-(+)-cis-khellactone (5) exhibited extremely potent anti-HIV activity against HIV-1 replication in H9 lymphocyte cells with EC50 and therapeutic index values of 0.00038 μM and >402,632, respectively, which are better than those of DCK and AZT in this assay.