Darren J. Derksen

Preparation and Use of Cysteine Orthoesters for Solid-Supported Synthesis of Peptides

Synthesis of a chiral cysteine derivative 2 with the carboxyl protected by an acid-labile 4-methyl-2,6,7-trioxabicyclo[2.2.2]octyl (OBO) orthoester is reported. A disulfide anchoring strategy is used to link the sulfur of this OBO cysteine derivative onto modified trityl polystyrene resin for synthesis of peptides having C-terminal cysteine (Cys) residues. Fmoc-based solid phase peptide synthesis affords model tripeptides without significant epimerization. The approach is used to make the orally active analgesic crotalphine and its Cys1 diastereomer.

Synthesis and evaluation of anti-inflammatory activity of derivatives of the marine natural products fuscol and eunicol.

The octocoral-derived terpenes fuscol and eunicol are known, potent anti-inflammatory agents. While total syntheses of one of the parent natural products have been published, the economic and practical feasibility of producing commercially viable amounts of material is very low. Based on the observation that the characteristic dienol of fuscol, eunicol and related compounds is conserved in anti-inflammatory activity, this project aimed to remove the structural complexity of the substituted cyclohexane and cyclodecadiene of fuscol and eunicol, respectively. The synthesis of a small panel of structurally simpler fuscol/eunicol analogues was completed and five of the six new compounds were found to have slightly superior activity to the parent natural products.

Generation of Benzyne Species from Diphenylphosphoryl Derivatives: Simultaneous Exchange of Three Functional Groups.

Interaction of (2-diphenylphosphoryl-3-iodo-4-methoxy-phenyl) methanol with NaH in DMF at ambient temperature results in the generation of benzyne intermediates that can be trapped by furan or DMF. Trapping with DMF forms 3-(dimethylaminomethyl)-2-hydroxy-6-methoxybenzaldehyde demonstrating the simultaneous exchange of three functionalities in a single step. The presence of the alkoxy substituent adjacent to iodine is critical for high regioselectivity addition of DMF. The corresponding bromide or triflate can be used in place of the iodide with equal efficiency. This methodology was used to synthesize the reported structure of gigasol and leading to a structural reassignment of this biscoumarin natural product.

Natural-Product-Derived Transient Receptor Potential Melastatin 8 (TRPM8) Channel Modulators.

A library of novel structural hybrids of menthol and cubebol was tested for each derivatives ability to interact with the transient receptor potential subfamily melastatin member 8 (TRPM8) channel. This structure-activity relationship study revealed three potent modulators of the TRPM8 ion channel: a novel agonist (4) with an EC50 value of 11 ± 1 μM, an antagonist (15) with an IC50 value of 2 ± 1 μM, and an allosteric modulator (21) that minimized channel desensitization toward menthol. Each of these novel exocyclic olefin analogues of menthol is readily accessible by synthesis and was tested using Ca(2+) assays and electrophysiology.

Divergent Photocyclization/1,4-Sigmatropic Rearrangements for the Synthesis of Sesquiterpenoid Derivatives

Combined experimental and computational efforts have demonstrated the utility of divergent photocyclization/1,4-sigmatropic rearrangement reactions for developing a general strategy toward the synthesis of cubebane-, spiroaxane-, and guaiane-type sesquiterpenes and related analogues. The configuration of the bridgehead substituent, the choice of solvent, and the wavelength of irradiation all impact diastereoselectivity in this tandem reaction process.

Thiaporphyrin-mediated photocatalysis using red light

Penetration of light through biological tissue improves in the near-IR windows beyond 650 nm. In an effort to explore the chemical reactivity accessible using this low-energy radiation, this study reveals catalysts and reactions that are experimentally viable with red light. Thiophene-containing porphyrin compounds are capable of catalytic, photo-reductive dehalogenation on an array of α-halo ketone model substrates with low catalyst loadings (0.1 mol%), in the presence of low energy, red light (>645 nm).