Alkaloid salts, solid

In spite of the difficulty in definitely characterizing alkaloids by definition, they do have a surprising number of physical and chemical properties in common. For the most part, the alkaloids are insoluble or sparingly so in water but form salts (by metathesis or addition) that are usually freely soluble. The free alkaloids are usually soluble in ether or chloroform, or other immiscible solvents, in which, however, the alkaloidal salts are insoluble. This permits the isolation and purification of the alkaloids as well as their quantitative estimation. Most of the alkaloids are crystalline solids, although a few are either amorphous (coniine, nicotine, sparteine) or liquid. It is interesting to note that the liquid alkaloids have no oxygen in their molecules. Alkaloidal salts are invariably crystalline, and their crystal form and habit are often useful in their rapid microscopical identification (Sollmann, 1944). 

Alkaloids are usually basic and combine with acids to form alkaloid salts, a property often exploited to extract them from their source. Other alkaloids occur naturally as salts of organic acids. Common salts include hydrochlorides, salicylates, sulphates, nitrates, acetates, and tartrates such as morphine acetate, cocaine hydrochloride, and strychnine nitrate. Water, alcohol, and ether solutions of alkaloids and their salts are often used to administer or carry the alkaloid, particularly for medicinal purposes. Nicotine preparations can include a variety of liquid and solid mixtures of nicotine (soluble in alcohol, chloroform, ether, and water), nicotine salts, and many other nicotine compounds (e.g., nicotine sulphate and nicotine tartrate). 

Trichloroethanoic acid, CCI3COOH. A crystalline solid which rapidly absorbs water vapour m.p. 58°C, b.p. 196-5" C. Manufactured by the action of chlorine on ethanoic acid at 160°C in the presence of red phosphorus, sulphur or iodine. It is decomposed into chloroform and carbon dioxide by boiling water. It is a much stronger acid than either the mono- or the dichloro-acids and has been used to extract alkaloids and ascorbic acid from plant and animal tissues. It is a precipitant for proteins and may be used to test for the presence of albumin in urine. The sodium salt is used as a selective weedkiller. 

Contains Nitrogen.—First test the original solid ni liquid by heating in a hard-glass tube with soda-lime (p. 2), and notice if the smell is that of ammonia (ammonia salt, amide or cyanide), an amine (amine or amino-acid) or a pyridine base (alkaloid). 

True alkaloids derive from amino acid and they share a heterocyclic ring with nitrogen. These alkaloids are highly reactive substances with biological activity even in low doses. All true alkaloids have a bitter taste and appear as a white solid, with the exception of nicotine which has a brown liquid. True alkaloids form water-soluble salts. Moreover, most of them are well-defined crystalline substances which unite with acids to form salts. True alkaloids may occur in plants (1) in the free state, (2) as salts and (3) as N-oxides. These alkaloids occur in a limited number of species and families, and are those compounds in which decarboxylated amino acids are condensed with a non-nitrogenous structural moiety. The primary precursors of true alkaloids are such amino acids as L-ornithine, L-lysine, L-phenylalanine/L-tyrosine, L-tryptophan and L-histidine . Examples of true alkaloids include such biologically active alkaloids as cocaine, quinine, dopamine, morphine and usambarensine (Figure 4). A fuller list of examples appears in Table 1. 

Alkaloids are basic in nature, and form water soluble salts with mineral acids. In fact, one or more nitrogen atoms that are present in an alkaloid, typically as 1°, 2° or 3° amines, contribute to the basicity of the alkaloid. The degree of basicity varies considerably, depending on the structure of the molecule, and presence and location of the functional groups. Most alkaloids are crystalline solids and are bitter in taste. 

Oxidation of the alkaloid lycorine (359) gives a red, hygroscopic solid which readily forms salts with mineral acids. This product, which has been assigned the betaine structure 358, has also been obtained from Ungernia minor and named ungeremine. . zss TV-methyl derivative (357 R = Me, R R = OCH2O) has also been described. ... 

SALT. A compound formed by replacement of part or all of the hydrogen of an acid by one (or more) element(s) or radrcal(s) that are essentially inorganic. Alkaloids, amines, pyridines, and other basic organic substances may be regarded as substituted ammonias in this connection. The characteristic properties of salts are the ionic lattice in the solid state and the ability to dissociate completely in solution. The halogen derivatives of hydrocarbon radicals and esters are not regarded as salts in the strict definition of the term,... 

Most of the alkaloids, with the exception of coniine and nicotine, are crystalline solids they are usually insoluble or sparingly soluble in water, but being basic they dissolve in acids forming soluble salts, from which the base is usually precipitated by dilute NaOH or Na2C03. In a few cases, e.g., morphine, the alkaloid is soluble in excess of alkali, while... 

Corey employed a cinchona alkaloid-derived ammonium salt 5 for the solid-liquid phase transfer catalyst, and attained 99% ee in the addition of a glycine-derived imine to 2-cyclohexenone (Scheme 6) [13,14]. 

In an attempt to develop a PEG-supported version of a chiral phase-transfer catalyst the Cinchona alkaloid-derived ammonium salt 15 used by Corey and Lygo in the stereoselective alkylation of amino acid precursors was immobilized on a modified PEG similar to that used in the case of 13. The behaviour of the catalyst obtained 16, however, fell short of the expectations (Danelli et al. 2003). Indeed, while this catalyst (10 mol%) showed good catalytic activity promoting the benzy-lation of the benzophenone imine derived from tert-butyl glycinate in 92% yield (solid CsOH, DCM, -78 to 23 °C, 22 h), the observed ee was only 30%. Even if this was increased to 64% by maintaining the reac-... 

Studies of different cinchona alkaloids as the chiral Bronsted bases and a metal salt showed that hydrocinchonine lh (Scheme 10.13) and AgF were the most effective combination. The scope of the [3 + 2] cydoaddition of azomethine ylides and alkenes was investigated. Selected examples are shown in Scheme 10.14. High yields and moderate enantioselectivities were obtained from a variety of a-imino esters. It was worth mentioning that most of the pyrrolidine derivatives 11 obtained from tert-butyl acrylate were solids that could be enantiomerically enriched by crystallization. 

A few years ago Cahard reported a series of studies on the use of immobilized cinchona alkaloid derivatives in asymmetric reactions with phase-transfer catalysts [17[. Two types of polymer-supported ammonium salts of cinchona alkaloids (types A and B in Scheme 8.4) were prepared from PS, and their activity was evaluated. The enantioselectivity was found to depend heavily on the alkaloid immobilized, with the type B catalysts usually giving better results than the type A catalysts. By performing the reaction in toluene at -50 °C in the presence of an excess of solid cesium hydroxide and 0.1 mol equiv of catalyst 10, benzylation of the tert-butyl glycinate-derived benzophenone imine afforded the expected (S)-product in 67% yield with 94% ee, a value very close to that observed with the nonsupported catalyst. (Scheme 8.4, Equation b) Unfortunately-and again, inexplicably-the pseudoenantiomer of 10 proved to be much less stereoselective, affording the R)-product in only 23% ee. No mention of catalyst recycling was reported [18]. 

Alkaloids are basically compound ammonias, where one or more atoms of hydrogen are replaced by various radicals. Alkaloids combine with acids to form crystalline salts without the production of water. Majorities of alkaloid exsit in solid form like atropine and they contain oxygen. Some alkaloids like lobeline or nicotine occur in liquid from and contain carbon, hydrogen, and nitrogen. 

However, for economy of production, maximum yields of alkaloids, and ease of recovery of the products, certain culture media containing relatively simple nutrient sources are preferred. For example, the media which are useful in the production of the alkaloids include an assimilable source of carbon such as glucose, sucrose, starch, molasses, dex-trins, corn steep solids, corn syrup liquor, sorbitol, mannitol, lactose, and the like. A preferred source of carbon is mannitol. Additionally, the media employed contain a source of assimilable nitrogen such as oatmeal meat extracts, peptones, amino acids and their mixtures, proteins and their hydrolysates, com steep liquor, soybean meal, peanut meal and ammonium salts of organic acids such as the citrate, acetate, malate, oxalate, succinate, tartrate and like salts. 

The free bases are soluble in lipophilic organic solvents, like chloroform. The different solubility for bases and salts is used for isolation and purification. Alkaloids are generally colourless solid materials. Some alkaloids that do not contain oxygen, like coniine, nicotine and sparteine, are liquid, and berberine and chelidonine are intensely yellow. Several alkaloids, e.g. strychnine and quinine, have a very bitter taste. Alkaloids give precipitates with heavy metals like mercury and bismuth. DragendorfPs reagent is used to show the presence of alkaloids. 

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