Nanotechnology and the treatment of HIV infection

Suboptimal adherence, toxicity, drug resistance and viral reservoirs make the lifelong treatment of HIV infection challenging. The emerging field of nanotechnology may play an important role in addressing these challenges by creating drugs that possess pharmacological advantages arising out of unique phenomena that occur at the “nano” scale. At these dimensions, particles have physicochemical properties that are distinct from those of bulk materials or single molecules or atoms. In this review, basic concepts and terms in nanotechnology are defined, and examples are provided of how nanopharmaceuticals such as nanocrystals, nanocapsules, nanoparticles, solid lipid nanoparticles, nanocarriers, micelles, liposomes and dendrimers have been investigated as potential anti-HIV therapies. Such drugs may, for example, be used to optimize the pharmacological characteristics of known antiretrovirals, deliver anti-HIV nucleic acids into infected cells or achieve targeted delivery of antivirals to the immune system, brain or latent reservoirs. Also, nanopharmaceuticals themselves may possess anti-HIV activity. However several hurdles remain, including toxicity, unwanted biological interactions and the difficulty and cost of large-scale synthesis of nanopharmaceuticals.

Novel polycyclic 'cage'-1,2-diamines as potential anti-tuberculosis agents

A series of polycyclic 'cage' derivatives of N-geranyl-1,2 diamines were synthesized and screened for their anti-mycobacterial activity against H(37)Rv, multidrug resistant (MDR) and extensively drug-resistant (XDR) strains of tuberculosis. By substituting the adamantyl skeleton of SQ109 with trishomocubanyl (9), oxa-pentacycloundecyl (14, 16), pentacycloundecyl, PCU, (10, 15) and azapentacycloundecyl (22, 23), the effect of other polycyclic "cage" skeletons could be investigated. Compound 9 (trishomocubanyl moiety) proved to be the most active (MICs: 0.5-2 μg/mL) while PCU hydroxyl derivatives (15 and 23), oxa-pentacycloundecyl and azapentacycloundecyl derivatives displayed similar activity to SQ109 (MICs: 0.5-4 μg/mL) against all three strains of TB used in this study.

Interaction of beta-amyloid interactions with peptide functionalized gold nanoparticles

The physicochemical properties of gold nanoparticles (GNPs) functionalized with peptides and N-methylated peptides were studied with respect to their interaction with beta-amyloid (1-42). Peptides with sequences of CGGIGLMVG and CGGGGGIGLMVG linked with GNPs of an average diameter of 13 nm were employed for this study. The peptide-GNPs were found to be soluble and dispersed at pH 7.4 in a sodium phosphate aqueous buffer solution. The resonance spectra of each peptide coated GNP was measured in the absence and presence of beta-amyloid (1-42). The difference in the intensity of the lambda(max) of the resonance absorption bands was attributed to the interaction of the functionalized GNPs with the protein. Particles bearing the CGGGGGIGLMVG sequence exhibited the largest change in lambda(max) intensity; the prevention of fibril formation and inhibition of cytotoxicity was also examined.

(S)-Benzyl 3-phenyl-carbamoyl-1,2,3,4-tetra-hydro-isoquinoline-2-carboxyl-ate

There are two independent mol­ecules in the asymmetric unit of the title compound, C₂₄H₂₂N₂O₃. The heterocyclic ring assumes a twisted boat conformation and N—H⋯O inter­actions help to construct the three-dimensional network within the crystal packing.

Synthesis, 2D-NMR and molecular modelling studies of pentacycloundecane lactam-peptides and peptoids as potential HIV-1 wild type C-SA protease inhibitors

In this study, eight non-natural peptides and peptoids incorporating the pentacycloundecane (PCU) lactam were designed and synthesized as potential inhibitors of the wild type C-SA HIV-protease. Five of these inhibitors gave IC(50) values ranging from 0.5 up to 0.75 µM against the resistance-prone wild type C-South African HIV-protease. NMR EASY-ROESY studies enabled us to describe the secondary structure of three of these compounds in solution. The 3D structures of the selected cage peptides were also modelled in solution using QM/MM/MD simulations. Satisfactory agreement between the NMR observations and the low energy calculated structures exists. Only one of these inhibitors (11 peptoid), which showed the best IC(50)(0.5 µM), exhibited a definable 3-D structure in solution. Autodock4 and AutodockVina were used to model the potential interaction between these inhibitors and the HIV-PR. It appears that the docking results are too crude to be correlated with the relative narrow range of experimental IC(50) values (0.5-10 µM). The PCU-peptides and peptoides were several orders less toxic (145 μM for 11 and 102 μM for 11 peptoid) to human MT-4 cells than lopinavir (0.025 μM). This is the first example of a polycyclic cage framework to be employed as an HIV-PR transition state analogue inhibitor and can potentially be utilized for other diseases related proteases. [Figure: see text].

6,12,18,24-Tetra-meth-oxy-4,10,16,22-tetra-kis-[(meth-oxy-carbon-yl)meth-oxy]-2,8,14,20-tetra-kis-(2-phenyl-eth-yl)resorcin[4]arene

The title compound, C₇₆H₈₀O₁₆, is a macrocyclic structure. This novel resorcin[4]arene derivative has (meth­oxy­carbon­yl)meth­oxy ‘head’ groups on the upper rim. The compound has a C_2v ‘boat’ geometry and there are a range of C—H⋯O contacts in the crystal structure.

(S)-4-Phenyl-2-(1,2,3,4-tetrahydroisoquinolin-3-yl)-1,3-thiazole

In the title compound, C₁₈H₁₆N₂S, the N-containing ring adopts a half-chair configuration. The crystal packing features C—H⋯N contacts. There is no π–π stacking within the crystal structure.

Ethyl 4-(1,3-benzodioxol-5-yl)-6-methyl-2-sulfanylidene-1,2,3,4-tetra-hydro-pyrimidine-5-carboxyl-ate

In the title compound, C(15)H(16)N(2)O(4)S, the dihedral angles between the planes of the benzodioxole and ester groups and the plane of the six-membered tetra-hydro-pyrimidine ring are 89.5 (1) and 20.2 (1)°, respectively. Inter-molecular N-H⋯S hydrogen bonds assemble the mol-ecules into dimers, which are further connected via N-H⋯O inter-actions into chains parallel to [010]. Weak C-H⋯S and C-H⋯π inter-actions enhance the stability of the crystal structure.

(1R,3S)-N-Benzhydryl-2-benzyl-6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline-3-carbothioamide

The title compound, C₃₈H₃₆N₂O₂S, has a heterocyclic ring that assumes a half-chair conformation. The phenyl rings of neighbouring mol­ecules align forming alternating chains parallel to [100] within the crystal packing. The absolute stereochemistry of the crystal was confirmed to be R,S at the 1- and 3-positions, respectively, by proton NMR spectroscopy. A single intra­molecular N—H⋯N hydrogen bond is observed.

(S)-Methyl 3-(3,4-dimethoxyphenyl)-2-[2-(diphenylphosphanyl)benzamido]propanoate

Mol­ecules of the title compound, C₃₁H₃₀NO₅P, show a sttagered conformation about the C—C bond joining the dimeth­oxy­benzene group to the chiral centre, with the dimeth­oxy­benzene ring gauche to the amide group and anti to the ester group. In the crystal, weak inter­molecular N—H⋯O and C—H⋯O hydrogen bonds form layers parallel to (110).

4,5,6,10,11,12,16,17,18,22,23,24-Dodeca-kis-[(meth-oxy-carbon-yl)meth-oxy]-2,8,14,20-tetra-pentyl-resorcin[4]arene

The title compound, C(84)H(112)O(36), has a macrocyclic structure. It has 12 (meth-oxy-carbon-yl)meth-oxy 'head groups' in the upper rim and exhibits a flattened boat geometry. Intra-molecular C-H⋯O hydrogen bonds occur. In the crystal, inter-molecular C-H⋯O contacts occur. The 'head groups' and the pentyl 'feet' contain disordered (0.5:0.5 occupancy ratio) atoms.

1,1′-(Ethane-1,2-diyl)bis(3-phenylthiourea)

The complete molecule of the title compound, C₁₆H₁₈N₄S₂, is generated by crystallographic inversion symmetry. The dihedral angle between the phenyl ring and the thio­urea group is 52.9 (4)°. The crystal structure displays inter­molecular N—H⋯S hydrogen bonding, which generates sheets in the ab plane.

4,10,16,22-Tetra-kis(2-chloro-acet-oxy)-6,12,18,24-tetra-meth-oxy-2,8,14,20-tetra-pentyl-resorcin[4]arene

The title compound, C₆₀H₇₆Cl₄O₁₂, has a macrocyclic structure and both the upper and lower rim have disordered atoms. There are no hydrogen bonds or π–π stacking inter­actions in the crystal.

Novel linear diamine disubstituted polycyclic 'cage' derivatives as potential antimycobacterial candidates

As a part of an ongoing project to develop highly potent antituberculosis therapeutics, a series novel polycyclic 'cage' tetra-amines were synthesized and screened for in-vitro antituberculosis activities against the H(37) Rv strain of tuberculosis. Three disubstituted polycyclic moieties, namely pentacyclodecane, pentacycloundecane, and tricyclodecane, were used in this study. Compounds 5 and 7 showed similar activity to SQ109 at a MIC of 1 μm while compounds 4, 6 and 8 displayed MIC activity at 1 < MIC<10 μM against H(37) Rv strain of tuberculosis. Compounds 5, 7 and SQ109 were selected for further screening against, multi-drug resistant, (R1097) and extensively drug resistant, (X149) strains of tuberculosis. Compound 5 showed anti-TB activity of a MIC = 1 μM against multi-drug resistant strain (R1097) and <1 μM against extensively drug resistant strain (X149) while compound 7 and SQ109 showed excellent anti-TB activity against both drug-resistant strains at a MIC < 1 μM. This study demonstrates the first reported analysis of pentacyclo[5.3.0.0 ²,⁵.0³,⁹.0⁴,⁸]decane as a potential therapeutic agent.

4,6,10,12,16,18,22,24-Octa-O-methyl-2,8,14,20-tetra-pentylresorcin[4]arene

The complete molecule of the title compound, C(56)H(80)O(8), is generated by a crystallographic inversion centre. The dihedral angle between the aromatic ring and the unique half of the molecule is 81.52 (16)°. There are no π-π inter-actions in the crystal structure.

1,1'-(Propane-1,3-di-yl)bis-(3-phenyl-urea)

The title compound, C₁₇H₂₀N₄O₂, has crystallographic inversion symmetry. In the crystal structure, inter­molecular hydrogen bonding between adjacent urea groups gives rise to infinite polymeric chains diagonally across the bc plane. With a centroid–centroid distance of 3.295 (2) Å, π–π stacking is present in the crystal along the same plane.

2-[(1R,3S)-6,7-Dimeth-oxy-1-phenyl-1,2,3,4-tetra-hydro-isoquinolin-3-yl]-4-phenyl-1,3-thia-zole

In the title compound, C(26)H(24)N(2)O(2)S, the dihedral angle between the thia-zole ring and the adjacent phenyl ring is 3.02 (15)°. The N-containing six-membered ring of the tetra-hydro-isoquinoline unit adopts a half-chair conformation. The dihedral angle between the least-squares plane of the tetra-hydro-isoquinoline ring system and its nearest phenyl ring is 76.90 (13)°. No classical hydrogen bonds nor π-π inter-actions were found in the crystal structure.

N-Benzyl-5-(dimethyl-amino)-naphthalene-1-sulfonamide

The structure of the title compound, C(19)H(20)N(2)O(2)S, displays inter-molecular N-H⋯O hydrogen bonding, which generates inversion dimers. There is no π-π stacking in the crystal structure. The dihedral angle between the phenyl ring and naphthalene ring system is 59.16 (11)°.

3,3'-Diphenyl-1,1'-(butane-1,4-di-yl)dithio-urea

The asymmetric unit of the title compound, C₁₈H₂₂N₄S₂, contains one half-mol­ecule, the complete mol­ecule being generated by crystallographic inversion symmetry. The crystal structure features two inter­molecular N—H⋯S hydrogen-bonding inter­actions, the first generating an infinite chain along the b axis and the second an infinite chain along the a axis, together forming an inter­locking structure.

Total synthesis of a depsidomycin analogue by convergent solid-phase peptide synthesis and macrolactonization strategy for antitubercular activity

Depsidomycin is a cyclic heptadepsi-peptide isolated from the cultured broth of Streptomyces lavendofoliae MI951-62F2. It exhibits significant antimicrobial and immunosuppressive activity. The total synthesis of a depsidomycin analogue in which 1,2-piperazine-3-carboxylic acid was substituted with proline is described. After several trials using different strategies, the desired depsidomycin analogue was obtained via stepwise synthesis starting by the amino acid 'head' and macrolactonization under Yamaguchi conditions. The cyclic depsipeptide was evaluated to have an minimum inhibitory concentration (MIC) of 4 µg/ml against H37RV and 16 µg/ml against MDR clinical strains of MTB (MDR-MTB), while the linear precursor 8 also had MICs of 4 and 16 µg/ml for the susceptible and resistant strains, respectively.

N-(Adamantan-1-yl)-2-chloroacetamide

In the title compound, C₁₂H₁₈ClNO, which was synthesized as part of a study into potential anti­tuberculosis agents, the adamantine skeleton displays shorter than normal C—C bond lengths ranging between 1.5293 (18) and 1.5366 (15) Å. The structure also displays inter­molecular N—H⋯O hydrogen bonding, which forms an infinite chain in the a-axis direction.