Pyridine acylamino

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... 

Acyl-l //-1,2-diazepines 2 isomerize on heating above 150 C to the corresponding pyridine l-imines 67c in certain cases 1,3-diazepines arc also formed (see Section 4.1.3.2.1.1.1.). These products are accompanied by variable amounts of pyridine and 2-(acylamino)pyridines. 

Acyl-2-amino-benzimidazole werden durch Pyridin (100° 1 h) zu 2-Acylamino-benzimid-azolen umacyliert (s.a. S. 351, 3S6)447. 

Nach der gleichen Methode lassen sich l-Acylamino-2-oxo-l,2-dihydro-pyridine zu Pyri-dot2,l-b]-l,3,4-oxadiazolium-Salzen cyclisieren405. Aus l-Amino-2-oxo-l,2-dihydro-pyridin erhalt man l. B. mit Acetanhydrid und Perchlorsaure in einem Rcaktionsschritt 2-Me-thyl-(pyridio[2,1-b]-l,3,4-oxadiazolium)-perchloratM>s (47% Schmp. 193-194,5°). 

Die Synthese von racemischen a-Acylamino-carbonsaure-methylestern VI aus ali-phatischen Carbonsaure-nitrilen I und dem Carbanion von Methyl-(methylthio-methyl)-sulfoxid II verlauft iiber ein Enamino-sulfoxid III. Dieses lagert sich bei der N-Acylierung mit Carbonsaure-anhydriden/Pyridin in die Aminosaure-Derivate IV mn, die iiber die a-Acylamino-a-methylthio-carbonsaure-methylester V in die a-Acylamino-carbonsaure-methylester VI iibergefiihrt werden konnen1 ... 

The thiol group can also be found in heterocyclic compounds such as 2-mercaptobenzothiazole (9) and echinoclathrine C (10). Compound 9 was isolated from the symbiont bacterium Micrococcus sp., which was obtained from the sponge Tedania ignis [13]. The pyridine alkaloid echinoclathrine C (10) and its S-acetylated derivative, echinoclathrine B (11), were isolated from the Okinawan sponge Echinoclathria sp. [14]. The position of the hydroxyl and acylamino group on the phenyl ring in echinoclathrines (11 and 10) was recently corrected [15]. Compound 11 showed weak immunosuppressive activity in the mixed lymphocyte reaction assay with an IC50 of 9.7 pg/ml [14]. 

Tetra-0-acetyl-2-amino-2-deoxy- 3-D-glucopyranose Q.) (8) was treated with do-, tetra-, hexa-, and octadecanoyl (laur-oyl, myristoyl, palmytoyl, and stearoyl) chlorides in 2 1 chloroform-pyridine solution, to give the crystalline 1,3,4,6-tetra-0-acetyl-2-acylamino-2-deoxy- 3-D-glucopyranoses ( ) (9). In addition to the n-fatty acyl compounds , we also prepared the... 

Verwendet man zur Acylierung Carbonsaureanhydridc/Py ridi n, so besteht die Gefahr, daB das 4-Acyl-oxazolinon zum a-Acylamino-keton gespalten wird (Dakin-West-Reaktion) 96>. So liefern die 4-Acyl-oxazoli-none beim Erwarmen mit Eisessig/Pyridin (96> vgl. auch 171)) oder was-serfreier Oxalsaure in guten Ausbeuten a-Acylamino-ketone. 

The H mode of the pyrimidine ring construction assuming the stepwise formation of the N(l)-C(2) and C(2)-N(3) bonds as a result of the insertion of a component serving as the source of the C(2) atom is more often used in practice. The simplest modification involves intramolecular condensation of 3-(acylamino)thienopyri-dines produced by acylation of 3-amino-2-carbamoylthieno[2,3-Z>]pyridines or their structural analogs (1995PS83). An example is the synthesis of pyrimidothienobenzo-quinoline 98 from chloroacetamide 99. 

Treatment of aromatic carboxaldehyde (diaminomethylene)hydrazones (105) with hot acetic anhydride or benzoyl chloride affords l,4-diacyl-3-acylamino-5-ary 1-4,5-dihydro- 1H-1,2,4-traizoles (106) in 75-95% yields. In contrast, when the 4-pyridine analog of 105 was employed, the unusual hemianimal triazole derivative (107) was obtained. The structures of the novel compounds were determined by spectral methods and in several cases by x-ray structural analysis. Mechanistic considerations are discussed [95M733]. The oxazole-1,2,4-triazole (108) was prepared by cyclization of the corresponding oxazolecarbonyl-thiosemicarbazide with bicarbonate, alkylation at the sulfur and oxidation to the sulfoxide with MCPBA [95JHC1235]. 

Phenolic esters are obtained similarly. The presence of a nitro group in the aromatic nucleus and the use of pyridine as solvent facilitates the reaction. This reaction is recommended for the characterization of phenols. 2,4,5-Trichlorophenyl-, pentachlorophenyl-, 4-nitrophenyl- and thiophenyl esters of N-acylamino acids are prepared in this manner. These aromatic esters are used in the stepwise lengthening of peptides, du Vigneaud and coworkers synthesized lysine vasopressin from a nonapeptide which they prepared stepwise using the nitrophenyl ester method. Room temperature esterification of dicarboxylic acids and diphenols are also carbodiimide mediated using the 1 1 complex derived from DMAP and p-toluenesulfonic acid as catalyst Methacrylic acid is also esterified with phenols using carbodiimides and DMPA to mediate the reaction. ... 

These two compounds are superior to pyridine as catalysts for acylation of alcohols, particularly for tertiary and sterically hindered alcohols. Even axial lljS-hydroxyl groups of steroids can be acetylated in yields as high as 80%. Several useful C-acylations have been reported. The reagents catalyze the transformation of amino acids into or-acylamino ketones (equation II). They are superior to pyridine for reaction of isocyanates and carboxylic acids to form amides (equation III). 

It is also superior to pyridine as a catalyst for C-acylation, for example in the Dakin-West reaction.3 This reaction is the conversion of a-amino acids into a-acylamino ketones by reaction with acid anhydrides catalyzed by a base (usually... 

---