Pharmaceuticals 3-phase half-lives

Sulfonic Acids. Drugs that contain sulfonic acids are quite acidic. They have high water solubility and are rapidly excreted, leading to a rather short half-life. They can also be irritating to the gastrointestinal tract during the pharmaceutical phase. 

Urethane may be released to the environment in various waste streams from its production and use in the preparation and modification of amino resins, as a solubilizer and cosolvent for pesticides and fumigants, as an intermediate in the production of pharmaceuticals, as an antineoplastic agent, and as a reagent in biochemical research. If released to the atmosphere, urethane is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase urethane will be degraded in the atmosphere by reaction with photochemically produced hydroxyl radicals with an estimated half-life of 2.2 days. If released to soil, urethane is expected to have very high mobility. Volatilization from moist soil surfaces is not expected to occur. Biodegradation of urethane in soil may be important. If released into water, urethane is not expected to adsorb to suspended solids and sediment in the water column. Volatilization from water surfaces is not expected. The potential for bioconcentration in aquatic organisms is... 

Until 1992, combinatorial libraries were almost entirely restricted to peptides and oligonucleotides, but peptides are not ideal as drugs because they have poor oral bioavail-ablity and a short half-life, so the pharmaceutical industry needed more useful libraries. Chiron experimented with N-substituted glycine peptoids (Figure 2), where the side chains are attached to the amide nitrogen,but the real breakthrough in what is usually called small-molecule chemistry came when Bunin and Ellman reported the solid-phase synthesis of a 1,4-benzodiazepine library (Figure 3). Very soon afterwards DeWitt et al. reported a similar synthesis of benzodiazepines... 

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