B. Christie Vu

Examination of halogen substituent effects on HIV-1 integrase inhibitors derived from 2,3-dihydro-6,7-dihydroxy-1H-isoindol-1-ones and 4,5-dihydroxy-1H-isoindole-1,3(2H)-diones

Using 2,3-dihydro-6,7-dihydroxy-1H-isoindol-1-one and 4,5-dihydroxy-1H-isoindole-1,3(2H)-dione based HIV-1 integrase inhibitors as display platforms, we undertook a thorough examination of the effects of modifying the halogen substituents on a key benzyl ring that is hypothesized to bind in a hydrophobic pocket of the integrase.DNA complex. Data from this study suggest that in general dihalo-substituted analogues have higher potency than monohalo-substituted compounds, but that further addition of halogens is not beneficial.

Bicyclic hydroxy-1H-pyrrolopyridine-trione containing HIV-1 integrase inhibitors.

HIV‐1 integrase (IN) is a validated therapeutic target for the treatment of AIDS. However, the emergence of resistance to raltegravir, the sole marketed FDA‐approved IN inhibitor, emphasizes the need to develop second‐generation inhibitors that retain efficacy against clinically relevant IN mutants. We report herein bicyclic hydroxy‐1H‐pyrrolopyridine‐triones as a new family of HIV‐1 integrase inhibitors that were efficiently prepared using a key ‘Pummerer cyclization deprotonation cycloaddition’ cascade of imidosulfoxides. In in vitro HIV‐1 integrase assays, the analogs showed low micromolar inhibitory potencies with selectivity for strand transfer reactions as compared with 3′‐processing inhibition. A representative inhibitor (5e) retained most of its inhibitory potency against the three major raltegravir‐resistant IN mutant enzymes, G140S/Q148H, Y143R, and N155H. In antiviral assays employing viral vectors coding these IN mutants, compound 5e was approximately 200‐ and 20‐fold less affected than raltegravir against the G140S/Q148H and Y143R mutations, respectively. Against the N155H mutation, 5e was approximately 10‐fold less affected than raltegravir. Thus, our new compounds represent a novel structural class that may be further developed to overcome resistance to raltegravir, particularly in the case of the G140S/Q148H mutations.

D-(+)-iso-Methanocarbathymidine: a High-Affinity Substrate for Herpes Simplex Virus 1 Thymidine Kinase

The stereoselective syntheses of the (+)‐D and (−)‐L enantiomers of iso‐methanocarbathymidine (iso‐MCT) was achieved through two independent linear approaches that converged on two antipodal enantiomers, common to a key precursor used in the synthesis of racemic iso‐MCT. In the study reported herein we identified (+)‐3 [D‐(+)‐iso‐MCT] as the active enantiomer that was exclusively recognized by the herpes simplex virus 1 thymidine kinase (HSV1‐tk), as was predicted by molecular modeling. For this purpose, a human osteosarcoma (HOS) cell line modified to contain and express HSV1‐tk from herpes simplex virus 1 (HSV1) was used to determine the cytotoxicity of the compounds by an assay that measures the level of ATP in the cells. The work demonstrates that changes in the substitution pattern of rigid bicyclo[3.1.0]hexane nucleosides, which, relative to normal nucleosides, appear unconventional, can lead to the spatial optimization of pharmacophores and vastly improved substrate recognition.

4′-C-Methyl-2′-Deoxyadenosine and 4′-C-Ethyl-2′-Deoxyadenosine Inhibit HIV-1 Replication

ABSTRACT It is important to develop new anti-HIV drugs that are effective against the existing drug-resistant mutants. Because the excision mechanism is an important pathway for resistance to nucleoside analogs, we are preparing analogs that retain a 3′-OH and can be extended after they are incorporated by the viral reverse transcriptase. We show that 4′-C-alkyl-deoxyadenosine (4′-C-alkyl-dA) compounds can be phosphorylated in cultured cells and can inhibit the replication of HIV-1 vectors: 4′-C-methyl- and 4′-C-ethyl-dA show both efficacy and selectivity against HIV-1. The compounds are also effective against viruses that replicate using reverse transcriptases (RTs) that carry nucleoside reverse transcriptase inhibitor resistance mutations, with the exception of the M184V mutant. Analysis of viral DNA synthesis in infected cells showed that viral DNA synthesis is blocked by the incorporation of either 4′-C-methyl- or 4′-C-ethyl-2′-deoxyadenosine. In vitro experiments with purified HIV-1 RT showed that 4′-C-methyl-2′-dATP can compete with dATP and that incorporation of the analog causes pausing in DNA synthesis. The 4′-C-ethyl compound also competes with dATP and shows a differential ability to block DNA synthesis on RNA and DNA templates. Experiments that measure the ability of the compounds to block DNA synthesis in infected cells suggest that this differential block to DNA synthesis also occurs in infected cells.

North- and south-bicyclo[3.1.0]hexene nucleosides: the effect of ring planarity on anti-HIV activity.

The syntheses of new conformationally locked North‐ and South‐bicyclo[3.1.0]hexene nucleosides is reported. The North analogues were synthesized by a convergent approach from the known (1S,2R,5R)‐5‐[(tert‐butyldiphenylsilyloxy)methyl]bicyclo[3.1.0]hex‐3‐en‐2‐ol by Mitsunobu coupling with the nucleobases. The South analogues were synthesized from their bicyclo[3.1.0]hexane nucleoside precursors by the selective protection of the primary hydroxy group, conversion of the secondary alcohol into a good leaving group, and base‐catalyzed elimination to generate the olefin. The transformation of a bicyclo[3.1.0]hexane nucleoside into a bicyclo[3.1.0]hexene nucleoside flattens the five‐membered ring of the bicyclic system and rescues anti‐HIV activity for North‐D4T, North‐D4A, and South‐D4C. The relationship between planarity and the anti/syn disposition of the nucleobase that is favored by a particular pseudosugar platform are proposed as key parameters in controlling biological activity.