Aminoacids halogenated

The a-halogenated carboxylic adds, of which the simplest is chloro-acetic acid, are widely used in synthesis. Their conversion into hydroxy-acids (by hydrolytic elimination of the halogen) and into aminoacids (p. 275) may be mentioned here ... 

For halogenated paraffins 27> and aminoacids 28> this simple method gives a charge distribution which is useful for interpreting molecular properties related to atomic electron densities dipole moments, quadruple coupling constants, chemical shifts, etc.. . It can be also applied to the a framework of heteroaromatic molecules in connection with n-... 

While the reactions ofketenes with enantiopure alcohols usually give modest selectivities [769], the use of (ethyl lactate (isopropyl lactate (/ )-2.1 (R = Me, R = i-Pr) or (R)-pantolactone 1.16 as proton donors has allowed the highly enantioselective formation of 2-arylpropionic esters. A mild hydrolysis (AcOH/HCl or LiOH) leads to the corresponding adds, which are anti-inflammatory drugs [554,923] (Figure 4.8). This method has been extended by Durst and Koh [861, 999] to the synthesis of enantioenriched a-halogenated esters, which are precursors of aminoacids (Figure 4.8). 

Fig. 6 Chemical structures of halotane 12 and inhibitor of the human Xa factor 13. For the latter, the major contacts between the inhibitor and aminoacidic residues in the receptorial pocket of the Xa factor, which can be rationalized as O-. -Cl and S-. Cl halogen bondings, were reported. (View this art in color at WWW. dekker. com)...

Conformational equilibria of amines and aminoacids have been studied in low-temperature matrix under UV or IR irradiation." Amine-imine tautomerism and formation of a radical was observed from adenine. New studies on the aniline excited states has evidenced the role of Rydberg states. A re-examination of the Oilman reaction has demonstrated that this is an electron transfer process. The photo-cyclization of halogenated (iodine is by far to be preferred) N-ben lani-lines to phenanthridine has been studied with particular attention at the preparative value and the tolerance of alko)q, dio)q methylene and halogen substituents, to which it was found to be quite tolerant. ... 

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