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A unique prenylated bicarbazole alkaloid, clausanisumine (1), and two biogenetically related known monomer carbazole alkaloids, mukonal (2) and 3-methylcarbazole (3), were isolated from the fruits of Clausena anisum-olens. Clausanisumine (1) was an uncommon prenylated bicarbazole alkaloid, possessing an unprecedented carbon skeleton, which was composed of a simple carbazole alkaloid and a prenylated carbazole alkaloid. The chemical structure of 1 was established by a combination of comprehensive spectral methods. A plausible biosynthetic pathway of 1 was also proposed. Additionally, the potential anti-HIV activities of all isolates 1-3in vitro were evaluated. Compound 1 exhibited remarkable anti-HIV-1 reverse transcriptase effects showing an EC50 value of 18.58 nM. The discovery of the prenylated bicarbazole alkaloid from C. anisum-olens with notable anti-HIV activity would be meaningful to discovering and developing new anti-HIV drugs.

Five new [daphneodorins D–H (1, 5, and 10–12)] and seven known daphnane diterpenoids (2–4 and 6–9) were isolated from Daphne odora. The structures of the new compounds were elucidated by extensive physicochemical and spectroscopic analysis. The isolated compounds were evaluated for their anti-HIV activity against HIV-1 infection of MT4 cells. Nine daphnane diterpenoid orthoesters (1–9) showed potent anti-HIV activity with EC(50) values of 1.5–7.7 nM.

New synthetic protocol for the preparation of nucleoside 5'-(N-aryl)phosphoramidate monoesters 4 was developed. It consisted of a condensation of the corresponding nucleoside 5'-H-phosphonates with aromatic- or heteroaromatic amines promoted by diphenyl phosphorochloridate, followed by oxidation of the produced H-phosphonamidates with iodine/water. 5'-(N-Aryl)phosphoramidate monoesters derived from 3'-azido-3'-deoxythymidine (AZT) or 2',3'-dideoxyuridine (ddU) nucleosides and various aromatic and heteroaromatic amines were evaluated as potential anti-HIV drugs. It was found that these compounds act most likely as pronucleotides and that some of them have therapeutic indices superior to those of the reference AZT.

Twelve new dibenzocyclooctadiene lignans, marlignans A-L (1-12), together with 16 known compounds, were isolated from the leaves and stems of Schisandra wilsoniana. The structures of 1-12 were elucidated by spectroscopic methods including 1D- and 2D-NMR techniques. Compounds 1-12 were evaluated for their anti-HIV activities, of which compounds 3, 6, 8, and 12 showed modest activities with therapeutic index values of 13.2, 15.6, 17.6, and 16.4, respectively.

Oligodeoxyribonucleotides of sequence d(5'TGGGAG3') carrying bulky aromatic groups at the 5' end were found to exhibit potent anti-HIV activity [Hotoda, H., et al. (1998) J. Med. Chem. 41, 3655-3663 and references therein]. Structure-activity relationship investigations indicated that G-quadruplex formation, as well as the presence of large aromatic substituents at the 5'-end, were both essential for their antiviral activity. In this work, we synthesized some representative examples of the anti-HIV active Hotoda's 6-mers and analyzed the resulting G-quadruplexes by CD, DSC, and molecular modeling studies, in comparison with the unmodified oligonucleotide. In the case of the sequence carrying the 3,4-dibenzyloxybenzyl (DBB) group, identified as the best candidate for further drug optimization, we developed an alternative protocol to synthesize the 5'-DBB-thymidine phosphoramidite building block in higher yields. The thermodynamic and kinetic parameters for the association/dissociation processes of the 5'-conjugated quadruplexes, determined with respect to the unmodified one, were discussed in light of the molecular modeling studies. The aromatic groups at the 5' position of d(5'TGGGAG3') dramatically enhance both the equilibrium and the rate of formation of the quadruplex complexes. The overall stability of the investigated quadruplexes was found to correlate with the reported IC50 values, thus furnishing quantitative evidence for the hypothesis that the G-quadruplex structures are the ultimate active species, effectively responsible for the biological activity.

Quantitative structure-activity relationship (QSAR) models are useful in providing a biochemical understanding of the biological activity of natural and synthetic chemicals based solely on molecular structure. One- to three-parameter multiregression equations were generated for three different groups of flavonoids to model experimental flavonoid-induced cytotoxicity and inhibition of human immunodeficiency virus I replication in lymphocyte-infected cells, using quantum chemical and geometrical parameters derived from optimized molecular structures. Both biological properties were basically dependent on electronic parameters describing charge distribution on the two fused rings of the flavonoid molecule. Atomic charges in C3 and the carbonyl carbon as well as the dipolar moment were important electronic descriptors to define the studied biological properties of flavonoids.

L-2',3'-Didehydro-2',3'-dideoxy-3'-fluorocytidine (L-3'-Fd4C), a novel potent anti-HIV agent (EC(50) 0.03 microM in PBM cells), has been synthesized from L-xylose in 14 steps. [reaction: see text]

Przewalskin B (1), a novel diterpenoid possessing a unique skeleton, was isolated from a Chinese medicinal plant Salvia przewalskii. Its structure and relative stereochemistry were elucidated by extensive NMR analysis and a single-crystal X-ray study. A possible biosynthetic pathway for 1 was proposed. Compound 1 exhibited modest anti-HIV-1 activity with EC50 = 30 microg/mL. [structure: see text].

[structure: see text] A structurally unique hydrophobic compound, biyouyanagin A, was isolated from the MeOH extract of the leaves of Hypericum chinense L. var. salicifolium. The structure of biyouyanagin A was elucidated on the basis of spectroscopic evidence. Biyouyanagin A showed a significant activity against HIV and inhibited cytokine production.

[reaction: see text] L-2'-Fluoro-4'-thio-2',3'-unsaturated cytidine 11 was synthesized from (R)-2-fluorobutenolide 2, which was prepared from 2,3-O-isopropylidene-L-glyceraldehyde 1. The synthesized compound 11 shows potent antiviral activity against HIV-1.

A series of 5,5-disubstituted hydantoin derivatives was synthesized by alkylating 5,5-bis(mercaptomethyl)-2,4-imidazolidinedione (3) with various halomethylaromatic or halomethylheteroaromatic precursors, or by using the Buchener-Berg procedure on the required ketone. When evaluated for their ability to inhibit HIV-induced cell killing and virus production in CEM or MT-2 cells only compounds 2, 4n, 4o, and 4i demonstrated modest activity, the latter with an IC50 = 53 microM.

Tipranavir, an important antiviral agent in clinical development for the treatment of HIV, is synthesized in 15 linear steps from readily available starting materials in 25% overall yield by utilizing Pd- and Mo-catalyzed DYKAT reactions to control the quaternary and tertiary stereogenic centers, respectively.