Carbon alpha

Fig. 6.16 the use of a marker atom on the alpha-carbon in an arginine residue may lead to a significant electrostatic interaction being neglected because the distance between the marker atoms exceeds the cutoff. 

But that is not the case. What the Korean lab found out was that when this procedure is performed, the OH stabilizes on the alpha carbon. That is the carbon right next to the phenyl ring. If one has any use for it as is then that is fine. But what is most preferable is to reduce the OH to get the propenylbenzene (say isoelemicin for our example). Using the simple potassium bisulfate reduction recipe, one can get rid of the OH with no problems at all. 

With Phenylpropanolamine at hand (or ephedrine and pseudo-ephedrine) one would next need to reduce that alpha carbon OH group to get the final amine. Strike understands that the current favorite methods for doing this involve lithium and amine. HI and red P or other iodine related protocols. So when you meth heads ruin every aspect of those methods as well, what will you do then The following are a couple of OH reduction methods (Strike thinks) that have applicable use [99-100]. 

Saturated ring systems lose side chains at the alpha carbon. Upon fragmentation, two ring atoms are usually lost. 

The propensity of nitriles to release cyanide subsequent to metaboHsm is the basis of their acute toxicity. Nitriles that form tertiary radicals at their alpha carbon atoms (eg, isobutyronitrile, 2-methylbutyronitrile) are substantially more acutely lethal than nitriles that form secondary radicals at their alpha carbons (eg, butyronitrile, propionitnle). Cyanohydrins are acutely toxic because they are unstable and release cyanide quickly. Alpha-aminonitriles are also acutely toxic, presumably by analogy with cyanohydrins. 

Aldehydes can undergo an intermolecular oxidation—reduction (Canni22aro reaction) in the presence of base to produce an alcohol and a carboxyUc acid salt. Any aldehyde is capable of participating in such a reaction, however, it is more common for those containing no protons on the alpha carbon, for example... 

The carboxyl group of acids appears to deactivate the hydrogens on the alpha carbon atom toward attack by the free-radical flux in oxidation reactions. Acetic acid, therefore, is particularly inert toward further oxidation (hydrogens are both primary and deactivated) (48). For this reason, it is feasible to produce acetic acid by the oxidation of butane (in the Hquid phase), even under rather severe oxidation conditions under which most other products are further oxidized to a significant extent (22). 

AEyl chloride reacts with sodamide in Hquid ammonia to produce benzene when sodamide is in excess, hexadiene dimer is the principal product, with some trimer and tetramer (C24, six double bonds). AEylation at carbon atoms alpha to polar groups is used in the preparation of a-aEyl-substituted ketones and nittiles. Preparation of P-diketone derivatives, methionic acid derivatives, and malonic ester, cyanoacetic ester, and P-keto-ester derivatives, etc, involving substitution on an alpha carbon between two polar carbonyl groups, is particularly facEe. 

And diis meant that die chain could turn corners only at die alpha carbons.. .. I creased die paper in parallel creases dirough the alpha carbon atoms,. so that I could bend it and make die bonds to the alpha carbons, along die chain, have tetrahedral value. And then I looked to see if I could form hydrogen bonds from one part of the chain to the next. He. saw diat if he folded die. strip like a chain of paper dolls into a helix, and if he got die pitch of the screw right, hydrogen bonds could be shown to form,... 

The biologically active form of vitamin Bg is pyridoxal-5-phosphate (PEP), a coenzyme that exists under physiological conditions in two tautomeric forms (Figure 18.25). PLP participates in the catalysis of a wide variety of reactions involving amino acids, including transaminations, a- and /3-decarboxylations, /3- and ") eliminations, racemizations, and aldol reactions (Figure 18.26). Note that these reactions include cleavage of any of the bonds to the amino acid alpha carbon, as well as several bonds in the side chain. The remarkably versatile chemistry of PLP is due to its ability to... 

Nitrophenyl)ethyl Carbamate. The photolytic removal of this group occurs twice as fast as does the 2-nitrobenzyl carbamate. Additionally, substitution at the alpha carbon increases the rate of cleavage even more. 

Loss of a proton from the alpha carbon atom yields the enamine product and regenerates the acid catalyst. 

Loss of an acidic proton from the alpha carbon takes place in ihe normal way to yield an enol intermediate. 

The 20 a-amino acids shown in Table 23.3 (p. 622) are those most commonly found in natural proteins. They differ from one another in the nature of the R group attached to the alpha carbon. As you can see, R can be—... 

Alpha carbon atoms, 348 Alpha decay, 417, 443 Alpha particle, 417 scattering, 245 Aluminum boiling point, 365 compounds, 102 heat of vaporization, 365 hydration energy, 368 hydroxide, 371 ionization energies, 269, 374 metallic solid, 365 occurrence, 373 properties, 101 preparation, 238. 373 reducing agent, 367 Alums, 403 Americium... 

The silyl radicals formed in the initial scission appear to undergo further reactions, which may be complex. A possible secondary reaction is hydrogen transfer from an alpha carbon atom to give Si-H and a silicon carbon double bond (21)... 

This excellent regiocontrol was exploited by subjecting terminal alkenes and hydroxyalkynoates to ruthenium catalysis conditions to afford butenolides and pentenolides (Equation (23)).36 The Alder-ene reaction occurs preferentially to form the G-G bond at the alpha-carbon of the alkynoate. The unusually high regioselectivity is attributed to a synergistic effect derived from an enhanced coordination of the hydroxyl group to the ruthenium. 

Dialkyl substitution on the alpha-carbon also abolishes activity, the a,a-dimethyl analog of DOM, Structure 10, is inactive in a variety of assays (10). Linking the two alpha-methyls to give the cyclopropyl analog Structure 11 restores activity in a cat behavioral model (10). The difference in activity between 10 and 11 has been ascribed to the inability of 10 to adopt an antiperiplanar... 

In view of the activity of 13, but the lack of activity for the alpha-ethyl homolog of DOM, the two isomeric ring-methylated derivatives Structures 16a and 16b were recently prepared (114). Neither isomer showed significant activity, either as an agonist in the rat fundus preparation or in a mouse assay, when compared with 13. It would appear that little bulk can be tolerated near the alpha-carbon, other than a methyl or methylene. 

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