Pyridone group

An aminoalkyl group or a l,5-dihydroxy-4-pyridone group is the preferred substituent in the oxime for strong synergy with various cephalosporin antibiotics, particularly ceftazidime. 

Ducharme and Wuest have demonstrated that an unsymmetrical bis(2-pyridone) self-assembles as a homodimer in the solid state (Fig. 3).10 The 2-pyridone units were separated by an acetylenic spacer that allowed the molecule to adopt a syn conformation, wherein the two pyridone groups are oriented along the same side of the molecule. The molecule self-assembled via four N H -O hydrogen bonds. A symmetrical analog was also shown to form a hydrogen-bonded polymer. 

Yu et. al, found that molecules containing two 2,6-diacetamido-4-pyridone groups and a nonlinear optical chromophore will self-assemble with diimides or bis(uracil) structures, to yield polymer-like hydrogen-bonded assemblies. 

Hydrogenation over Pt in acetic acid gave a tetrahydro derivative while a similar reduction in ethanol gave a dihydro derivative in which the Zl --double bond was saturated. The fact that all three compounds had identical UV-spectra is in accord with the presence of two isolated double bonds in selagine in addition to the a-pyridone grouping. With the number and nature of its functional groups established it was apparent that selagine was tricyclic. 

Biosynthetic studies using acetate (Ac), propionate (Pr), and butyrate (Bu) revealed the polyketide nature of aurodox which has the composition Pr(Ac)g for the goldinamine skeleton C-7 to C-25 and the composition Bu(Ac) for the C-27 to C-39 carbon chain of goldinonic acid. In contrast to the methyl branch at C-8, those at C-19 and C-21 are methionine-derived as are all remaining methyl groups (52,53). The biogenetic origin of the pyridone moiety is not clear. 

Mocimycin has been chemically converted to aurodox by protection of the 4-hydroxy group at the pyridone moiety as the benzoylformate, followed by /V-methylation and hydrolytic removal of the protective group (1,55). Whereas aurodox esters are active growth promotors in animals, goldinamines that are A/-acylated by acids other than goldinonic acid, such as acetic, benzoic, or arylsulfonic acids, lack useful antimicrobial or growth-promoting activity (1). 

The same convention is used when a ring =C— is transformed to a carbonyl group, an operation that requires a hydrogen atom to be affixed to another position, as in (123) and (124). This convention does not imply added hydrogen, but only locates one whose presence is already required. Thus 2-pyridone implies C5H5NO and is a fully adequate name when it is not desired to distinguish between (123) and (124) or a mixture of the two. 

In 1931 Ing pointed out that formula (II) and (III) do not contain methyl or potential methyl groups in j ositions 6 and 8 which they occupy in cytisoline. Further, a partially reduced quinoline ought to oxidise easily to a benzenecarboxylic acid and so far the only simple oxidation, products recorded from cytisine were ammonia, oxalic acid and isovaleric acid. Distillation of cytisine with zinc dust or soda-lime yields pyrrole and pyridine, but no quinoline. On these grounds Ing suggested that cytisine should be formulated without a quinoline nucleus, and that the reactions which indicate the presence of an aromatic nucleus in the alkaloid can be accounted for by an a-pyridone ring. This a-pyridone nucleus can... 

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... 

COR group decreases the basicity of a pyridone form much... 

The name hydroxamic acid was first used by Losseii in 1869, in the case of oxalohj droxamic acid, obtained from diethyl oxalate and hydroxylamine. Where this grouping forms part of the main cyclic system, however, the compound is named as a derivative of this system. In this review, 2 and 3 would be named as 1-hydroxy-2-pyrrolidone and l-hydroxy-2-pyridone, respectively. 

Activated compounds such as 5-nitropyrimidin-2-one and 1-methyl-5-nitro-2-pyridone form the 2-chloro analogs with thionyl chloride 223b. 312b displacement of the —O—SO—Cl group. In reactions... 

A thioamide of isonicotinic acid has also shown tuberculostatic activity in the clinic. The additional substitution on the pyridine ring precludes its preparation from simple starting materials. Reaction of ethyl methyl ketone with ethyl oxalate leads to the ester-diketone, 12 (shown as its enol). Condensation of this with cyanoacetamide gives the substituted pyridone, 13, which contains both the ethyl and carboxyl groups in the desired position. The nitrile group is then excised by means of decarboxylative hydrolysis. Treatment of the pyridone (14) with phosphorus oxychloride converts that compound (after exposure to ethanol to take the acid chloride to the ester) to the chloro-pyridine, 15. The halogen is then removed by catalytic reduction (16). The ester at the 4 position is converted to the desired functionality by successive conversion to the amide (17), dehydration to the nitrile (18), and finally addition of hydrogen sulfide. There is thus obtained ethionamide (19)... 

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