D-Ephedrine

This process is now only of historical interest. Like the fermentation of butanol and acetone it has succumbed to advances in chemistry. However, it illustrates the other important feature of microbial transformations, which is their stereoselectivity. This, together with the regioselectivity apparent in the oxidation of sorbitol, is an important argument in favour of biological catalysis. 

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Nagai s ephedrine was obtained from Ma-Huang and the same alkaloid, together with its stereoisomeride pseudoephednne ( -ephedrine), was isolated by Merck from the European species, E. helvetica C. A. Meyer. From commercial Ma-Huang Smith prepared two additional bases, 1-W-methylephedrine and nnr-d- -ephedrine. Nagai and Kanao added two more, viz., d-W-methyl- -ephedrine and Z-norephedrine, and... 

Gibson and Levin have called attention to nor-d- -ephedrine as a useful base for the resolution of externally compensated acids,... 

Pseudoephedrine hydrochloride is prepared by a Welsh rearrangement10 of -ephedrine hydrochloride with acetic anhydride followed by deacetylation with hydrochloric acid.11 -Ephedrine can be resolved from d -ephedrine with -mandelic acid.12 -Ephedrine occurs naturally in certain plants of the Ma Huang species. 

Only in this case the relative position of the additional methyl groups can exert such profound differences in the interaction with the receptor, as it is observed for these drugs in the biological system and similarly with the synthetic model. The energy-niveau of the rotamer of D-ephedrine in b) is energetically only slightly higher than of the rotamer in a)... 

Asymmetric hydrovinylation.1 The reaction of ethylene with 1,3-cyclohex-adiene catalyzed by bis(l,5-cyclooctadiene)nickel, diethylaluminum chloride, and 1 gives ( + )-(S)-3-vinyl-l-cyclohexene (2) in quantitative yield and 93% ee. Related ligands prepared from (S)-proline and D-ephedrine are less effective for asymmetric hydrovinylation. 

R)-a-Phenylalkylamines. (R)-a-Phenylethylamine (4) can be prepared in about 97% optical purity by addition of methylmagnesium bromide to the chiral hydrazone obtained from benzaldehyde and the N-amino derivative (1) of D-( —)-ephedrine followed by hydrogenolysis (equation I). Acetophenone is not a suitable starting material because it reacts with 1 to form two isomeric hydrazones. ... 

Ephedrine is a diastereoisomer of pseudoephedrine (Fig. 4 [7a]) having the erythro configuration. The enantiomeric immunogens of this compound were prepared (57) in a manner similar to that described for d-pseudoephedrine (40). Tritium-labeled d,/-ephedrine was used as the... 

Cheng JT, Liu IM, Yen ST, Juang SW, Liu TP, Chan P. Stimulatory effect of D-ephedrine on beta3 adrenoceptors in adipose tissue of rats. Auton Neurosci 2001 88(1—2) 1—5. 

According to information provided on form D, ephedrine and pseudoephedrine seizures decreased significantly in North America in 2005. The record seizures totalling 175 tons of ephedrine and pseudoephedrine reported by the United States in 2004,... 

Epinephrine (adrenaline) was one of the first hormones for which differential effects on blood pressure were reported for the two epimers in the early 20th century [58]. A reassessment of epinephrine activity was made by analyzing the effects of optical isomers of ephedrine and methylephedrine on the spontaneous beating rate of the isolated right atrium of normal and reserpinized rats by investigating direct and indirect actions on al-adrenoceptors. L-ephedrine, and to a lesser extent D-ephedrine, markedly increased the beating rate of rat right atrium [59]. 

FIGURE 26.4 Preferred conformations of D-(—)-ephedrine and of D-(—)-pseudo-ephedrine. 

The enantiomeric forms D-ephedrine and (-) pseudoephedrine do not occur in nature. Concern has been expressed about the indiscriminate use of Ephedra for its stimulant and anorectic effects (Chapter VIII). 

The salt is prepared by methylation of D-(-)-ephedrine with formaldehyde followed by quarternization with dodecyl bromide. 

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