Craig L. Francis

Small Molecule Inhibitors of the Ledgf Site of Human Immunodeficiency Virus Integrase Identified by Fragment Screening and Structure Based Design.

A fragment-based screen against human immunodeficiency virus type 1 (HIV) integrase led to a number of compounds that bound to the lens epithelium derived growth factor (LEDGF) binding site of the integrase catalytic core domain. We determined the crystallographic structures of complexes of the HIV integrase catalytic core domain for 10 of these compounds and quantitated the binding by surface plasmon resonance. We demonstrate that the compounds inhibit the interaction of LEDGF with HIV integrase in a proximity AlphaScreen assay, an assay for the LEDGF enhancement of HIV integrase strand transfer and in a cell based assay. The compounds identified represent a potential framework for the development of a new series of HIV integrase inhibitors that do not bind to the catalytic site of the enzyme.

Structural basis for a new mechanism of inhibition of HIV-1 integrase identified by fragment screening and structure-based design

Background: HIV-1 integrase is a clinically validated therapeutic target for the treatment of HIV-1 infection, with one approved therapeutic currently on the market. This enzyme represents an attractive target for the development of new inhibitors to HIV-1 that are effective against the current resistance mutations. Methods: A fragment-based screening method employing surface plasmon resonance and NMR was initially used to detect interactions between integrase and fragments. The binding sites of the fragments were elucidated by crystallography and the structural information used to design and synthesize improved ligands. Results: The location of binding of fragments to the catalytic core of integrase was found to be in a previously undescribed binding site, adjacent to the mobile loop. Enzyme assays confirmed that formation of enzyme–fragment complexes inhibits the catalytic activity of integrase and the structural data was utilized to further develop these fragments into more potent novel enzyme inhibitors. Conclusions: We have defined a new site in integrase as a valid region for the structure-based design of allosteric integrase inhibitors. Using a structure-based design process we have improved the activity of the initial fragments 45-fold.

N,N-Dialkyl-N´-Chlorosulfonylchloroformamidines in Heterocyclic Synthesis. II. Thiazolo-, Thiadiazolo-, and Oxadiazolo-Fused [1,2,4,6]Thiatriazine Dioxides

N,N-dialkyl-N′-chlorosulfonylchloroformamidines 1 were treated with 2-aminothiazoline, 2-aminothiazoles, 2-aminobenzothiazoles, 2-amino-1,3,4-thiadiazoles, and 2-amino-1,3,4-oxadiazoles to give a 6,7-dihydrothiazolo[3,2-b][1,2,4,6]thiatriazine dioxide 3, a 6,7-dihydrothiazolo[2,3-c][1,2,4,6]thiatriazine dioxide 4, thiazolo[3,2-b][1,2,4,6]thiatriazine dioxides 5, [1,2,4,6]thiatriazino[3,2-b]benzothiazole dioxides 7, a [1,2,4,6]thiatriazino[3,4-b]benzothiazole dioxide 8, [1,3,4]thiadiazolo[2,3-c][1,2,4,6]thiatriazine dioxides 10, [1,3,4]thiadiazolo[3,2-b][1,2,4,6]thiatriazine dioxides 11, [1,3,4]oxadiazolo[2,3-c][1,2,4,6]thiatriazine dioxides 13, and [1,3,4]thiadiazolo[3,2-b][1,2,4,6]thiatriazine dioxides 14. Compounds 3, 4, 5, 7, 8, 10, 11, 13, and 14 are derivatives of new ring systems.

Spiroheterocycles via Regioselective Cycloaddition Reactions of Nitrile Oxides with 5-Methylene-1H-pyrrol-2(5H)-ones

Substituted 5-methylene-1H-pyrrol-2(5H)-ones underwent a 1,3-dipolar cycloaddition reaction with nitrile oxides to give the corresponding spiro heterocycles. Critical to this reaction was the development of a biphasic system for base-induced dehydrohalogenation of hydroximoyl chlorides, to give nitrile oxides, in the presence of a base-sensitive dipolarophile. A substituted N-tolyl 5-methylene-1H-pyrrol-2(5H)-one exhibited atropisomerism, which in turn led to a 4:1 facial selectivity during cycloaddition.

Tris and the ready production of drug-fatty acyl conjugates

The technology described in this article utilises the common laboratory reagent tris to readily produce drug–fatty acid conjugates. Tris has structural similarities to glycerol, allowing the coupling of one to three fatty acyl groups giving compounds that mimic mono‐, di‐, and triglycerides. The symmetrical carbon atom of tris avoids structural isomerisation and enables large‐scale production without the isolation problems generally associated with glycerol derivatives. The amine group provides an ideal attachment site for drugs. Tris is readily available, inexpensive, and approved for pharmaceutical use. We prepared representative fatty acid conjugates of an analgesic (e.g., morphine), nonsteroidal anti‐inflammatory drug (e.g., indomethacin), antiviral drug (e.g., AZT), and antineoplastics (e.g., methotrexate and chlorambucil). Biological activities of these conjugates demonstrated altered properties, such as cellular uptake, delivery profiles, skin retention, and toxicity. These changes may improve the therapeutic use of some compounds. Drug Dev. Res. 46:302–308, 1999.

The Reactions of N-Substituted 2-(Dimethylallyl)aniline Compounds with Phenylselanyl Halides

Cyclization of the carbamate of 2-(dimethylallyl)aniline with phenylselanyl chloride (benzeneselenenyl chloride) gave a 1 : 1 mixture of a dihydroindole and a tetrahydroquinoline. With phenylselanyl bromide only the dihydroindole was obtained. Addition of methanol to the silica used in the procedure trapped the reaction at the non-cyclized stage forming a 3-methoxy-3-methyl-2-(phenylselanyl)butyl side chain. The sulfonamide of 2- (dimethylallyl)aniline only formed the dihydroindole with phenylselanyl chloride. The corresponding trifluoroacetamide derivative did not form any cyclized product under the same conditions. The dihydroindole could be converted into the corresponding alkene by oxidative removal of the phenylseleno group. 4-Ethoxycarbonyl-2-(3,3-dimethylallyl)aniline cyclized with mercuric nitrate to give, after a reductive workup, a 2,2-dimethyltetrahydroquinoline. The X-ray crystal structures of ethyl N-{2-[3-methoxy-3-methyl-2- (phenylselanyl)butyl]phenyl}carbamate and 2-[1-methyl-1-(phenylselanyl)ethyl]-1-[(4-methylphenyl)sulfonyl]-indoline are reported.

2-Phenylimidazo[1,2-b]pyridazine derivatives highly active against Haemonchus contortus

A series of 2-phenylimidazo[1,2-b]pyridazine derivatives were synthesized and evaluated for their in vitro anthelmintic activity against Haemonchus contortus. The most active compounds had in vitro LD(99) values of 30nM, which is comparable to that of the benchmark commercial nematocide, Ivermectin.

N,N-Dialkyl-N'-Chlorosulfonyl Chloroformamidines in Heterocyclic Synthesis. V* The Preparation of some Benzimidazo-Fused [1,2,4,6]Thiatriazine Dioxides

N,N-dialkyl-N′-chlorosulfonyl chloroformamidines 1 were treated with 2-aminobenzimidazoles 2 to give [1,2,4,6]thiatriazino[2,3-a]benzimidazole 1,1-dioxides 3 and [1,2,4,6]thiatriazino[4,3-a]benzimidazole 2,2-dioxides 4. Some N-alkyl-, N-acyl-, and N-sulfonyl-derivatives of 3 were prepared. These products are derivatives of rare heterocycles.

N,N-Dialkyl-N′-Chlorosulfonyl Chloroformamidines in Heterocyclic Synthesis. IV. 3-Dialkylamino-1,1,8-trioxo-1H-1λ6-pyrano[3,4-e][1,4,3]oxathiazines

N,N-dialkyl-N′-chlorosulfonylchloroformamidines 1 reacted regioselectively with 4-hydroxy-2-pyrone derivatives 2 to give 3-dialkylamino-1,1,8-trioxo-1H-1λ6-pyrano[3,4-e][1,4,3]oxathiazines 3. Dichloride 1b reacted regioselectively with 1,3-dimethylbarbituric acid 10 to give 3-diethylamino-5,7-dimethyl-1,1,6,8-tetraoxo-1H-1λ6-pyrimido[5,4-e][1,4,3]oxathiazine 11. The compounds 3 and 11 are derivatives of new ring systems.

Tris lipidation: a chemically flexible technology for modifying the delivery of drugs and genes.

1. One of the major challenges in the development of pharmaceuticals is their formulation with other materials to give them the desired bioavailability profile when administered into the body.