Ephedrine molecular structure

Ephedrine is an alkaloid, a sympathomimetic amine with molecular formula Cjo Hi5 NOi, a molecular mass of 165.2, and the stmctural name (IR, 25)-2-methylamino-l-phenylpropan-l-ol. This bitter colorless or white solid-crystal is completely soluble in water, alcohol, chloroform, ether, and glycerol. Ephedrine is also produced by chemical synthesis and there is significant documentation of commercial ephedrine production using microbial biotransformation techniques [42]. Ephedrine has a structure close to methamphetamines, and its stimulant actions are comparable to epinephrine (adrenaline), a hormone produces by the adrenal glands that enhances heart rate and constriction of blood vessels in high-stress situations. Medicinal use of ephedrine began around 3000 B.C with the Chinese from md hudng, but its isolation was first reported in 1855 and its pharmaceutical application started in 1930 [22]. Studies on ephedrine s molecular structure show that two asynunetric carbon atoms are involved in ephedrine s molecular skeleton therefore, four optically active stereoisomers forms naturally occur as follows (IR, 2S)-(—)-ephedrine, (IS, 2R)-(+)-ephedrine, (IR, 2R)-( )-pseudoephedrine, (IS, 2S)-(+)-pseudoephedrine (Fig. 27.2). 

Notably, pseudoephedrine is a diastereomer of ephedrine and considerably racemic ephedrine (dl-ephedrine) has not been found naturally, however, it is prepared synthetically and is inactive for commercial purposes. Ephedrine and pseudoephedrine are completely stable compounds under changing temperature conditions, but they are quite unstable when exposed to sunlight or in the presence of oxygen pressure [2]. The unique molecular structure of ephedrine causes its different stereoisomers to be valuable for pharmaceutical applications such as nasal decongestant, pupil dilator, bronchodilator, and central nervous system stimulant. Ephedrine is a sympathomimetic substance and the principle mechanism of ephedrine activity is its influence, by enhancing the activity of noradren-alin, on post-synaptic a- and (3-receptors in the nervous system. Stimulation of a 1-adrenergic receptors produces contraction of vascular smooth muscle. 

Figure 4.12 Molecular structures of diastereomeric salts top salt of ephedrine and a cyclic phosphoric acid middle salt of 2-phenylpropanoate and 2-phenyl-ethylammonium bottom salt of 2-phenylbutyrate and 2-phenyl-ethylammonium.

While GC/MS has traditionally been the screening method of choice for controlled substances, this approach does not provide molecular structural information and cannot be used as a principal means of identification for pseudoephedrine. GC/MS cannot distinguish pseudoephedrine from its sister compound ephedrine their GC retention times and mass spectra are essentially the same because the two compounds differ only in their stereochemistry. To achieve structural discrimination, scientists have combined infrared (IR) spectroscopy and GC/MS. The IR radiation provides structural information about the intact form of the molecules under study and is able to detect subtle variations in different structural forms. In this way, pseudoephedrine can be distinguished from ephedrine. However, while highly selective, this approach is still not as sensitive as GC/MS. 

FIGURE 5.2. Molecular structure of ephedrine, an active ingredient in the traditional Chinese medicine plant Ma Huang. 

Pseudoephedrine FIGURE 5.14. Molecular structures of ephedrine and related compounds. 

Enzyme-substrate complex, 1041 Ephedrine, structure of, 65 Epibatidine, molecular model of. 332 Epichlorohydrin, epoxy resins from, 673-674 Epimer, 303... 

Since its discovery by Pasteur in 1853,5 classical resolution by selective crystallization of diastereo-isomers, despite wide and frequent use, remains to a large degree a method of trial and error. Various attempts to rationalize classical resolutions and predict a successful combination of race-mate and resolving agent by computational approaches so far have not been crowned with remarkable success.6 Even when the crystal structures of both diastereoisomeric salts are known, molecular modeling calculations do not provide a basis for a reliable prediction. Only recently has some progress been made in the calculation of the relative thermodynamic stability of ephedrine-cyclic phosphoric acid 4 diastereoisomers,7 a diastereoisomeric salt frequently used as a model system (vide infra). 

In 6, we show mescaline, a hallucinogenic drug. The structural similarity of mescaline to the iimate drugs is apparent (in the Retouches, you can find related drugs ephedrine, pseudoephedrine, and methamphetamine). It raises thoughts about the reality of emotions, independently of their unique molecular effectors. 

The polymers were acrylate esters, the amino-alcoholic portionheing a derivative of ephedrine (XXXVI), proline (XXXVII) or quinine (XXXVIII). Their structures are shown below. The molecular weight of the polymer ranged between 5000 and 14 000 it was used... 

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