To explore the structural requirements of (+)-cis-khellactone derivatives as novel anti-HIV agents, 24 monosubstituted 3', 4'-di-O-(S)-camphanoyl-(+)-cis-khellactone (DCK) derivatives were synthesized asymmetrically. These compounds included 4 isomeric monomethoxy analogues (3-6), 4 isomeric monomethyl analogues (7-10), 4 4-alkyl/aryl-substituted analogues (11-14), and 12 4-methyl-(+)-cis-khellactone derivatives (15-26) with varying 3', 4'-substituents. These (+)-cis-khellactone derivatives were screened against HIV-1 replication in acutely infected H9 lymphocytes. The results demonstrated that the (3'R,4'R)-(+)-cis-khellactone skeleton, two (S)-(-)-camphanoyl groups at the 3'- and 4'-positions, and a methyl group on the coumarin ring, except at the 6-position, were optimal structural moieties for anti-HIV activity. 3-Methyl- (7), 4-methyl- (8), and 5-methyl- (9) 3',4'-di-O-(S)-camphanoyl-(3'R, 4'R)-(+)-cis-khellactone showed EC(50) and therapeutic index values of <5.25 x 10(-5) microM and >2.15 x 10(6), respectively, in H9 lymphocytes, which are much better than those of DCK and AZT in the same assay. Furthermore, 8 and 9 also showed potent inhibitory activity against HIV-1 replication in the CEM-SS cell line, and most monosubstituted DCK analogues were less toxic than DCK in both assays.