Acylamino properties

X. Alkyl groups usually have relatively little effect, and for convenience alkylamino compounds are included in the foregoing discussion of amino compounds. The acylamino (X = COR) and sulfon-amido (X = SO2R) derivatives are, however, treated separately. To some extent the tautomeric composition of these compounds can be predicted from a consideration of the properties of the analogous... 

In their acidity, basicity, and the directive influence exerted on electrophilic substitution reactions in benzenoid nuclei, acylamino groups show properties which are intermediate between those of free amino and hydroxyl groups, and, therefore, it is at first surprising to find that the tautomeric behavior of acylaminopyridines closely resembles that of the aminopyridines instead of being intermediate between that of the amino- and hydroxy-pyridines. The basicities of the acylaminopyridines are, indeed, closer to those of the methoxy-pyridines than to those of the aminopyridines, the position of the tautomeric equilibrium being determined by the fact that the acyl-iminopyridones are strong bases like the iminopyridones and unlike the pyridones themselves. Thus, relative to the conversion of an... 

In the heterocyclic series, racemic 3-(fur-2-yl)alanine has been prepared from furfural using this approach. In addition, (3-(pyrid-3-yl)alanine, ° p-(quinol-3-yl)alanine, ° a p-(benzofuranyl)alanine derivative, 2-amino-3-(2,2 -bipyridi-nyl)propanoic acid, and some interesting derivatives of histidines—in particular 1-alkylhistidines with amphiphilic properties have all been synthesized using this methodology. The complete reaction sequence starting from an aldehyde and an A-acylamino acid derivative is shown in Scheme 7.150. 

There are a number of comprehensive studies reported of the reactions of a particular unsaturated oxazolone with nitrogen nucleophiles. On the other hand, unsaturated 5(4/f)-oxazolones react with a variety of amines to yield acylamino amides with interesting agrochemical properties. ... 

S. Tokuyama, H. Miya, K. Hatano, and T. Takahashi, Purification and properties of a novel enzyme, N-acylamino add racemase, from Streptomyces atratus Y-53, Appl. Microbiol. Biotechnol. 1994, 40, 835-840. 

Methods of synthesis of the phenanthridine system reported up to 1950 have been surveyed in an article by Walls.7 Since the later5 of the two reviews mentioned above did not include synthetic work and the earlier article4 dealt largely with the ring closure of 2-acylamino-biphenyls, an attempt has been made here to cover the synthetic literature from 1950 while largely restricting the discussion of properties to material not dealt with by Eisch and Gilman.5... 

The ease of amine substitution is enhanced in 7-acylamino derivatives and also depends on the leaving properties of the amide. Benzamides are more reactive than acetamides and are commonly used in the substitution reactions. 

The rifamycins have some remarkable chemical properties. Rifamycin SV can be obtained from the quinone rifamycin S by treating the latter with weak reducing agents such as ascorbic acid. It is fairly stable against oxidation by air and can form a stable sodium salt. This behaviour can be ascribed to the acylamino group in position 2. Unsubstituted naphthoquinone can only be reduced under much more drastic conditions, and once in the hydroquinone form it is very sensitive to oxidation. 

A structural feature common to all previously-described and widely-used compounds is that the acylamino substituents on C-6(7) next to the lactam carbonyl are in the j8-configuration. Bioassays reveal that the epipenicillins (94) and epicephalosporins (95) having an acylamino side-chain in the a-configuration exhibit negligible antibacterial properties [180,181]. The first example of such compounds was epihetacillin, obtained from hetacillin by treatment with triethylamine [182]. The lack of activity can be explained in accordance with the mode of action of /3-lactam antibiotics [183] in the case of the epi-derivatives the structural similarity between the terminal D-alanyl-D-alanine moiety and the antibiotic molecule no longer exists. Details will be discussed in the section on the mode of action. 

Acylamino-2-oxo-l-sulfoazetidines, several of which have been isolated from certain strains of bacteria, have attracted considerable attention due to their potent antibacterial properties. Azetidinone 44, with a 3S configuration similar to that in penicillin, possesses considerable activity against Gram-negative organisms. 

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