James M. Coxon

Molecular Modeling, Synthesis, and Biological Evaluation of Macrocyclic Calpain Inhibitors

The design and elaboration of a series of macrocyclic templates that exhibit a propensity to adopt a beta-strand-like peptide-backbone conformation led to potent and selective inhibitors of calpain 2. Macrocycle 1 retarded calcium-induced opacification in an ovine-lens culture assay and is a lead compound for the development of a drug for cataract treatment. Cbz=carbobenzyloxy.

Medical treatment of cataract.

The incidence of cataract continues to increase with the ageing of the population. Surgical treatment with phacoemulsification and intraocular lens implantation remains the only proven treatment. This, however, is associated with significant cost and is not readily available especially in the developing countries where the prevalence of cataract is the highest. Medical treatment of cataract is therefore a highly desired alternative. Since the last major review of medical treatment of cataract the search for an anti‐cataract agent has advanced on many fronts. Some anti‐cataract drugs, such as carnosine, have now reached clinical trials and showed encouraging results that warrant further investigation. The discovery of an effective medical treatment for cataract is likely to make global impact on eye health. The aims of this paper are to review the literature on the drug therapy of cataract and provide updates of the latest development.

Synthesis of Macrocyclic β-Strand Templates by Ring Closing Metathesis

We report the synthesis of macrocycles 1-6 via ring closing metathesis of dienes 7-12. Addition of chlorodicyclohexylborane to thermal and microwave assisted RCM of dienes 8 and 9 markedly improves the yield. The geometric isomers of macrocycles 1-3 and 5 have been assigned using X-ray crystallography and NMR.

The “cieplak effect”: Hyperconjugative interactions in diels alder reactions.

Molecular orbital calculations of the transition states for the reactions of the dienes1a-e with ethylene using the AM1 Hamiltonian show the diene CX bond length for anti addition of the dienophile is longer than the comparable length when the X-substituent is syn to the approaching dienophile. The board lengthening is consistent with hyperconjugative stabilization involving the donation of electron density from the σ-bond of the anti substituent to the forming σ*-orbital.

The mechanism of 1,3-dioxolane formation from the BF3 -catalysed reaction of epoxides with carbonyl compounds

Abstract cis- and trans-But-2-ene epoxides react with acetone in the presence of BF3-etherate to give trans- and cis-2,2,4,5-tetramethyl-1,3-dioxolanes respectively. Use of O18-labelled acetone allowed the reaction mechanism to be defined.

Reactions of epoxides—XXIV: The BF3-catalysed rearrangement of 4,5- and 5,6-epoxycholestanes

Abstract 4α,5α, 4β,5β- and 5β, 6β-Epoxycholestanes give backbone rearranged compounds on BF3-catalysed rearrangement. Solvent changes markedly affect the products of rearrangement. 4α-Hydroxycompounds arise from the 4β,5β-epoxide on BF3-catalysed rearrangement.

Intercalation of ethidium and analogues with nucleic acids: a molecular orbital study.

Semiempirical calculations suggest that the intercalation complexes of phenanthridinium cations 1-4 with G-C/C-G and 1 with A-U/U-A are stabilized by frontier orbital interactions between the LUMO of the intercalator and the HOMOs of the adjacent purine bases. The charge on the ring nitrogen of 1-4 appears to be necessary for the orbital interactions, lowering the LUMO, facilitating mixing of this orbital with the HOMOs of the adjacent purine bases to give an extended HOMO stabilizing the complex and resulting in the bathochromic shift in the electron absorption spectrum. Noncationic phenanthridine 5 shows no frontier orbital interactions in the forced intercalation complex with G-C/C-G. The results of the calculations parallel experimental T(m) values.

Novel preparation of a heptacyclic cage ether

Abstract Reduction of 6 with sodium borohydride in methanol provides a novel route to the cage ether 1 by way of the intermediate hydrazine 8 .

The synthesis of some 2,10-epoxypinanes

Abstract Several 2,3,10-oxygenated pinanes have been prepared and their stereochemistry determined.

A Macrocyclic Calpain Inhibitor Slows the Development of Inherited Cortical Cataracts in a Sheep Model

PURPOSE We used sheep with an autosomal dominant gene for cortical cataract as an animal model to evaluate novel macrocyclic calpain inhibitors with potential for the medical treatment of human cataract. METHODS The macrocyclic aldehyde, CAT811, identified previously as a calpain inhibitor that prevents calcium-induced opacification in cultured sheep lenses, was tested for its ability to protect cytoskeletal proteins from calpain proteolysis. CAT811 and its alcohol analogue, CAT505, were formulated separately into ointments, and each was applied twice daily to the right eye of sheep with early cataracts for five months. Progress of cataracts in the sheep was determined by ophthalmologic examination and comparison with a matched sample of sheep treated similarly with ointment that did not contain the active ingredient. RESULTS The novel macrocyclic aldehyde, CAT811, was able to inhibit calpain proteolysis of lens cytoskeletal proteins at micromolar concentrations. When applied topically to the eyes of sheep, CAT811 was able to slow cataract development by 27% in the initial three months of treatment (P < 0.05). Its alcohol analogue, CAT505, was not able to slow cataractogenesis significantly. CONCLUSIONS The inherited sheep cataract provides a reproducible model of cortical cataract over a time scale of several months. The data reported here, using this model, demonstrated the potential of the macrocyclic calpain inhibitor, CAT811, to act as a therapeutic for treatment of cortical cataract.