A N-acylated

If the ring nitrogen atom forms a secondary amine, its reaction with aryl isocyanate can yield substituted ureas and this transformation is strongly related to a N-acylation. In this respect, a publication by Saczewski and Nasal <1995APH237> should be mentioned here these authors described the transformation of 119 with a number of arylisocyanates to the urea 120 in medium to high yields (49-82%) (Scheme 17). 

The obtention of the oxadiazole cycle cannot be interpreted without assuming the formation of a N-acylated amidoxime as intermediate. 

When an acylaminomalonic acid monoester is treated with nitrous acid, the nitroso derivative XX decarboxylates into a N-acyl amidoxime which spontaneously cyclizes into an oxadiazole 33 a). 

FIGURE 7.3 Comparison of theiV-acyl moieties of iV-acylethanolamines (A), N-acyl moieties of N-acyl PEs (B), fatty acids esterified at the 1-position of phosphatidylcholine (C) and free fatty acids (D) in rat brain. Values are the means of four to six determinations. (From Sugiura, T., Kondo, S., Sukagawa, A., Tonegawa, T., Nakane, S., Yamashita, A., Ishima, Y, and Waku, K. (1996) Transacylase-mediated and phosphodiesterase-mediated synthesis of iV-arachidonoylethanolamine, an endogenous cannabinoid receptor ligand, in rat brain microsomes. Comparison with synthesis from free arachidonic acid and ethanolamine, European Journal of Biochemistry 240 53-62. With permission.)... 

Mixed anhydride method, a procedure of peptide coupling using reactive species resulting from the carboxylic moiety of a N-acylated amino acid and alkyl chlorocar-bonates (alkyl chloroformates), especially isobutyl chlorocarbonate (isobutyl chloro-formate), that readily reacts with an amino component. The nucleophilic amino component attacks the carboxy group of the amino acid component, with formation of the desired peptide derivative and release of the unstable isobutyl carbonic acid which immediately decomposes into carbon dioxide and isobutanol [J. Meienhofer, in The Peptides Analysis, Synthesis, Biology,... 

A series of A-formylated aliphatic amino acids 207 were subsequently attached to the Wang resin as shown in Scheme 4.3.1, affording 208. Dehydration of 208 provided resin-bound isocyanides 209 quantitatively as shown by H-NMR of the resin. Multicomponent condensation of resin 209 with arylglyoxals 210, primary amines and carboxylic acids afforded resin-bound a-(N-acyl-N-alkylamino)-P-ketoamides 211 that were further reacted with a large excess of NH4OAC in AcOH to give immobilised imidazoles 212. Final cleavage with 10% TFA provided imidazoles 213. 

Shin, C., K. Nanjo, M. Kato, and J. Yoshimura a,P Unsaturated Carboxylic Acid Derivatives. IX. The Cyclization of a-(N-Acyl-hydroxyamino) Acid Esters with Ammonia or Hydroxylamine. Bull. Chem. Soc. Japan 48, 2584 (1975). 

Amidrazones (s. a. N-Acyl-oxamic acid ester hydra-zones)... 

In general, in CL polymerization, an equivalent concentration of activator (A) (N-acyl lactam or N-carbamoyl lactam) and initiator (I), in terms of its functional groups, is the best compromise among polymerization rate, overall conversion, degree of polymerization, high polymer yield, and polyamide properties (see Section 4.14.10.3). 

Zhal996 Zhang, C., Moran, E.J., Woiwode, T.F., Short, K.M. and Mjalli, A.M.M., Synthesis of Tetrasubstituted Imidazoles via a-(N-Acyl-N-alkylamino)-/ -ketoamides on Wang Resin, Tetrahedron Lett., 37 (1996) 751-754. 

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