JV-acyl derivative

Addition of pyruvate to Cbz-protected D-mannosamine 194 under NeuA catalysis has furnished an JV-acyl derivative of neuraminic acid 5 from which internal reductive amination yielded an azasugar which could be further elaborated to 195, an analog of the bicyclic, indolizidine type glycosidase inhibitor castanospermine [91]. 

Dibenz[6, e]azepines conformation, 7, 499 11 H-Dibenz[f>, ejazepines oxidation, 7, 525 reduction, 7, 517 synthesis, 7, 532, 533 Dibenz[6,/ azepines JV-acyl derivatives UV spectra conformation, 7, 499 mass spectrum, 7, 501 nitroxide... 

Treatment of the JV-nitrosocyanides (283)198 or the W-nitrosoguanyl-hydrazines (284)199 with hydrogen chloride yielded the 1,2,3,4-oxatriazolium chlorides (285, X = Cl), which with aqueous sodium bicarbonate gave the meso-ionic l,2,3,4-oxatriazol-5-imines (277, R2 = H).198 Nitrosation of these compounds (277, R2 = H) gave the interesting JV-nitroso compounds (277, R2 = NO), and acylation gave the JV-acyl derivatives (277, R2 = RCO).198... 

It was recently shown29 30 that the formation of a Schiffs base is the first step of the reaction between 3-aminopropan-l-ol and an aldehyde. The action of acid chlorides, such as tosyl chloride, on the Schiffs base forms the JV-acyl derivative of tetrahydro-1,3-oxazine. 

The smooth conversion of the enol acetate (151) into an JV-acyl derivative (152) under extremely mild conditions points to the high acylating capacity of these esters. This cleavage of isoxazolium salts is also caused by other anions of carboxylic acids, and thus they can be readily converted to reactive enol esters. A very convenient and specific synthesis of peptides due to Woodward et ai.113 is based on this reaction. 

Cyanoalkyl dithiobenzoates (237) can also undergo cyclization upon treatment with strong acids this is a route to 4-amino-l,3-dithiolylium ions (236). On the other hand, treatment of (237) with acyl chlorides gives the JV-acyl derivatives (238). According to their IR spectra, they exist, at least in part, in the imidol form (65BCJ596, 63BCJ1437). 

Lithium aluminium hydride reduction can be performed on either the acid or the ester 90, or on their jV-acyl derivatives 91, in diethyl ether or tetrahydrofuran, which results in excellent yields of the corresponding amino alcohols 92 and 93, respectively (Scheme 14) [40,110,111]. 

Soon after he had discovered his synthesis of quinazolines from aminoal-dehydes, Bischler turned to the amino ketones to obtain quinazolines with alkyl or aryl substituents in the 4-position (see 1). He showed that JV-acyl derivatives of 2-aminobenzophenone, heated at 170°C with ethanolic ammonia, furnished 4-phenylquinazolines,96 and 2-aminoacetophenone behaved similarly.97 However, it was later found that such severe conditions were unnecessary, for 4-methylquinazoline was produced quantitatively from 2-formamidoacetophenone and ethanolic ammonia at 20°C in 18 hr, and 2,4-dimethylquinazoline was similarly prepared (from 2-acetamidoaceto-phenone) in 5 days.81... 

Once acylated, the amino function is rendered chemically unreactive or nonnucleophilic. However, the amino acyl function often have to be introduced in a two-step procedure acylation of the entire nucleoside followed by selective deacylation of the sugar. Further, the glycosidic linkage of the JV-acyl derivative is usually more susceptible to hydrolysis. Typical... 

In any treatment of auxiliary-based alkylations (as well as aldol additions, enolate oxidations, Mannich and Michael reactions), clearly, the carboximide enolates pioneered by the group of Evans are the center of attention. Developed in the early 1980, JV-acyl derivatives of oxazolidinones 45-47 (Scheme 4.9) became the epitomes of chiral auxiliaries [7,28] with countless applications in natural products and drug syntheses. The enantiomeric oxazolidinones (S)- and (R)-47 derived from the corresponding enantiomer of phenylalanine have the advantage that, when used for various transformations, the corresponding products have a higher tendency to crystallization and were shortly later added [29] to this collection of classics. 

Another classic in asymmetric synthesis is Oppolzer s sultam 91 [48], and various JV-acyl derivatives 92 were used - inter alia - for diastereoselective alkylations. Early attempts for enolate generation from amides 92 were plagued by competing deprotonation at carbon 10, adjacent to the sulfonyl group, but regioselective metallation at the a-carbonyl position was achieved by treatment with -butyllithium, LICA, or NaHMDS. The method is applicable not only to the sultam derived from propionic acid 92 (R = Me) but also to substituted and... 

The peracetylation of amino sugars, which exist chiefly as hydrochlorides, can occur in p5oddine °, or in dimethylformamide and pyridine with acetic anhydride. In general, mixtures of the a- and /7-anomers are obtained. Treatment with methanolic NHj leads to the JV-acyl derivatives. The high stability of the acid-amide bond permits even reductive detosylization. For selective iV-acetylation a number of methods have been developed " " . 

Within the last two decades, a number of chemical structures have been proposed as metal deactivators for polyolefins. These include carboxylic acid amides of aromatic mono- and di-carboxylic acids and JV-substituted derivatives such as NiJV -diphenyloxamide, cyclic amides such as barbituric acid, hydrazones and bishydrazones of aromatic aldehydes such as benzaldehyde and salicylaldehyde or of o-hydroxy-arylketones, hydrazides of aliphatic and aromatic mono- and di-carboxylic acids as well as JV-acylated derivatives thereof, bisacylated hydrazine derivatives, polyhydrazides, and phosphorus acid ester of a thiobisphenol. An index of trade names and suppliers of a few commercial metal deactivators is given in Appendix A3. 

---