After separation of the organic and the aqueous layer, the amine can be recovered by addition of a strong base like NaOH or KOH to the acidic extract i.e., lidocaine synthesis. Note that amides are usually not basic enough to undergo the same protonation (pKa of conjugate acid: ~ -0.5).
Most neutral compounds cannot be converted into salts without changing their chemical nature. Many of these neutral compounds tend to react in undesired ways i.e., esters undergo hydrolysis upon contact with strong bases or strong acids. One has to keep this in mind as well when other compounds are removed. For instance, epoxides hydrolyze to form diols catalyzed by acids and bases. Ketones and aldehydes undergo condensation reactions catalyzed by both, acids and bases. Esters also hydrolyze to form carboxylic acids (or their salts) and the corresponding alcohol. In order to separate these compounds from each other, chromatographic techniques are often used, where the compounds are separated based on their different polarities (see Chromatography chapter).
Based on the discussion above the following overall separation scheme can be outlined. Which sequence is the most efficient highly depends on the target molecule. There is obviously no reason to go through the entire procedure if the compound sought after can be isolated in the first step already. Note that many of these steps are interchangeable in simple separation problems.
Organic chemistry: “Amino acid and polypeptide synthesis”. Amino acid synthesis--Gabriel synthesis; synthesis. degradation. Polypeptide synthesis-- () and () amino-protecting groups; protection of the terminus via ester formation; DCC () -activating reagent. An example of calculating and charge at a specific pH for a long polypeptide
B., Synthesis of azide-alkyne fragments for click' chemical applications; formation of oligomers from orthogonally protected trialkylsilyl-propargyl azides and propargyl alcohols.
R., Activity-Based Protein Profiling Reagents for Protein Arginine Deaminase 4 (PAD4): Synthesis and in vitro Evaluation of a Fluorescently Labeled Probe.
R.; Lober, S.; Hubner, H.; Gmeiner, P., Click chemistry on solid phase: parallel synthesis of -benzyltriazole carboxamides as super-potent G-protein coupled receptor ligands.