A series of carboxylic acids were prepared from a propargylglycine scaffold and tested for efficacy as matrix metalloproteinase (MMP) inhibitors. Detailed SAR for the series is reported for four enzymes within the MMP family. The inhibitors were typically potent against collagenase-3 (MMP-13) and gelatinase A (MMP-2), while they spared collagenase-1 (MMP-1) and only moderately inhibited stromelysin (MMP-3). Compound 40 represents a typical inhibition profile of a compound with reasonable potency. Introduction of polar groups was required in order to generate inhibitors with acceptable water solubility, and this often resulted in a loss of potency as in compound 63. High serum protein binding proved to be a difficult hurdle with many compounds such as 48 showing >99% binding. Some compounds such as 64 displayed approximately 90% binding, but no reliable method was discovered for designing molecules with low protein binding. Finally, selected data regarding the pharmacokinetic behavior of these compounds is presented.

A fully automated high-throughput liquid-liquid extraction (LLE) methodology has been developed for preparation of biological samples using a 96-well LLE plate and a 96-channel robotic liquid handling workstation. The 96-well LLE plate is made of a 96-well filter plate filled with inert diatomaceous earth particles, allowing continuous and efficient extraction of analytes between the aqueous biological sample and the organic extraction solvent. Two carboxylic acid-based protease inhibitor compounds with high and low levels of plasma protein binding were chosen for the development and application of the automated methodology. The LLE extracts of the plasma samples of the two compounds were analyzed by high-performance liquid chromatography with electrospray (ESI) tandem mass spectrometry (LC-MS/MS). The LC-MS/MS method was developed using a rapid gradient LC separation, followed by sample introduction through an ionspray interface in the negative ion mode and tandem mass spectrometric detection with selected reaction monitoring. In the optimized LLE method, a formate buffer solution was first loaded into a 96-well filter plate packed with inert diatomaceous earth material. Then crude plasma samples and a water-immiscible organic solvent, methyl ethyl ketone, were sequentially added to the LLE plate so that LLE would occur in the interface between the two liquid phases on the surface of individual particles in each well. The organic eluate containing extracted analytes was evaporated and reconstituted for LC-MS/MS analysis. This fully automated LLE methodology avoids several disjointed steps involved in a manual or semiautomated LLE method, leading to significantly reduced sample preparation time, increased sample throughput, and clean sample extracts for improved ESI-MS/MS detection. The automated LLE methodology is universal and can be employed for sample preparation of other biological fluids. The complete bioanalytical method, based on the automated LLE and fast gradient LC-MS/MS, was validated and successfully applied to the quantitative analysis of protease inhibitors in rat plasma.

A novel series of carboxylic acids containing a substituted piperidine were synthesized and tested for inhibition of selected matrix metalloproteinases. Multiple analogues prepared based on this novel design were found to inhibit the target MMPs (MMP-2, -3, -8, -9, and -13) with unprecedented, low nanomolar potency while, at the same time, sparing MMP-1 and MMP-7. Solubility and plasma protein binding of several members of this new series of carboxylic acids were also investigated.Introduction. The matrix metalloproteinases (MMPs) are a family of zinc-containing enzymes that are capable of degrading many proteinaceous components of the extracellular matrix. 1 The enzymes have been implicated in several pathological processes including arthritis, 2,3 tumor growth and metastasis, 4 periodontal disease, 5 multiple sclerosis, 6 and congestive heart failure. 7,8 Considerable research has been devoted to the discovery of potent MMP inhibitors, which may act as potential disease modifying agents in a number of important pathologies. 9,10

Gas phase hydrogen bonding was studied via infrared spectroscopy in the following systems: methyl acetatehydrogen chloride, methyl formate-hydrogen chloride, 2-butanone-hydrogen chloride, and acetone-hydrogen chloride. The intensity of the H-Cl stretching vibration was monitored as a function of temperature, and the hydrogen bond energies and enthalpies were determined. The hydrogen bond energy for all four complexes was within 2.0 kJ mol -1 of -18.3 kJ mol -1 , indicating that the hydrogen bond energy is only minimally affected by nonlocal molecular structure. The acetone-hydrogen chloride complex was modeled by ab initio methods. The energy of formation of the complex, calculated at the MP2/6-311++G** level of theory, is -20.8 kJ mol -1 , in good agreement with the experiment.

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