Acyl compounds, active

N-Acylcarboxylic acid amides s. a. Diacylamines, mixed Acyl compounds, active s. Carboxylic acid esters, active Acylcyanides... 

The pharmacologically active and commercially important 5//-dibenz[/>,/]azepines 40 are available by base-catalyzed dehydrobromination of their 5-acyl- 10-bromo-l 0.11-dihydro derivatives 38,118 followed by hydrolysis of the isolable tV-acyl compounds 39 29.119-121... 

Acylation of active hydrogen compounds followed by cleavage... 

Although most acylations of active methylene compounds are base catalysed, the acylations of ketones carried out with acetic anhydride take place best in presence of BF3. Acetone is converted to acetylacetone. 

The method described here belongs to a group of recently developed procedures comprising the spontaneous intramolecular acylation of active derivatives of metalated p-hydroxy alkanoates. These compounds are available by reactions of carbonyl compounds with ester enolates prepared from S-phenyl alkanethioates6 or phenyl alkanoates,15 as well as by Reformatsky16 or Darzens17 reactions of carbonyl compounds with phenyl a-halo alkanoates. 

The described imidoylation of a-acyl radicals deserves great interest since a-acyl compounds are not only versatile building blocks but also exhibit several biological activities. ... 

Acylation of active hydrogen compounds followed by cleavage 0-109 Reduction of p-keto sulfoxides 0-110 Acylation of carboxylic acid salts followed by cleavage... 

Pantothenic acid is a component of coenzyme A, which functions in the transfer of acyl groups (Figure 28.17). Coenzyme A contains a thiol group that carries acyl compounds as activated thiol esters. Examples of such structures are succinyl CoA, fatty acyl CoA, and acetyl CoA. Pantothenic acid is also a component of fatty acid synthase (see p. 182). Eggs, liver, and yeast are the most important sources of pan tothenic acid, although the vitamin is widely distributed. Pantothenic acid deficiency is not well characterized in humans, and no RDA has been established. 

In a parallel study, Wipf and Fritch11041 have shown that also urethane-protected (Boc), and even amino acid segments, are tolerated as acyl compounds on the aziridine nitrogen. The best results were obtained with alkylcopper reagents derived from CuCN and an alkyl-lithium in the presence of boron trifluoride-diethyl ether complex. Some 6-alkylated compounds (11-15%) were isolated as well. This work was extended to a solid-phase procedure that resulted in resin-bound alkene isosteres that could immediately be used in further peptide synthesis.11051 For this purpose, the 2-nitrophenylsulfonyl (oNbs) group was used for nitrogen protection and aziridine activation. It could be readily cleaved with benzenethio-late, which was compatible with the acid-sensitive Wang linker used. 

Catalysis by phosphate buffers of various active acyl compounds (344 X = O, S), (345 X = O, S) and (346) has been examined to assess its role as a nucleophile and general base.313 In water at pH 8.5 phosphate dianion functions as both nucleophile and base towards (344 X = S) the Nu role accounts for about 80-93% of the reaction, hi D2O the process is totally nucleophilic. For (345 X = S), the Nu- role is 40-50% of the reaction and for (346) the phosphate dianion adopts an entirely nucleophilic role, while the monoanion acts as a general base. 

Amphoteric compounds such as amino acids can be resolved as acid or amine forms after deriving corresponding esters or N-acyl compounds. Racemic alcohols and amines are also resolved by use of optically active isocyanates, where the alcohols and amines are derived the corresponding diastereomeric urethanes or ureas. 

For the sake of brevity, salient aspects of key structure-activity relationships in one homologous series of twelve mono- and bis-acyl homologated spermine analogues (Fig. 12.8) will be first discussed (Miller et al., 2005). We addressed two questions in this study (i) what is the optimal hydrophobic chain length for effective anti-endotoxic activity, (ii) are symmetrical bis-acyl spermines more effective than mono-acyl compounds We found that a carbon number of 14-16 is optimal in mono-acyl spermines (Fig. 12.9) which are, in general, as potent as... 

For the first time, inverse substrates provide a general method for the specific introduction of an acyl group into the trypsin active site without recourse to cation-containing acyl compounds. The preparation of various new acyl enzymes is expected to lead to the discovery of novel features of the enzymatic reaction mechanism. In addition, any desired reporter groups might be specifically introduced into the trypsin... 

Acid halides, also called acyl halides, are activated derivatives used for the synthesis of other acyl compounds such as esters, amides, and acylbenzenes (in the Friedel-Crafts acylation). The most common acyl halides are the acid chlorides (acyl chlorides), and we will generally use acid chlorides as examples. 

Glyceraldehyde-3-phosphate dehydrogenase has an essential cysteine residue in its active site. The enzyme forms a transient acyl compound with its substrate, glyceraldehyde 3-phosphate, (a) What is the general chemical name of the compound (b) Draw its likely structure. 

Undissociated hydrogen peroxide behaves, to some extent, as a nucleophile, being about 104 times more nucleophilic than water. For example, hydrogen peroxide readily adds to carbonyl bonds giving rise to hydroxyhydroperoxides (peracetals and perketals). Such compounds are often used as polymerization initiators on account of their radical decomposition at moderate temperatures (0-0 bond homolysis). Neutral hydrogen peroxide can also react with activated acyl compounds such as anhydrides to give peroxyacids. 

This first section wiU study different regjoselective processes of several types of nucleosides depending on the lipase used. Application of biotransformations over these compounds has acquired great importance in order to prepare new derivatives with interesting pharmacological activities. Two lipases, namely, Candida antarctica type B (CALB) and Pseudomonas cepacea, free (PSL) or Pseudomonas cepacea, immobilized (PSLC), are selective towards one of the two hydroxyl groups of different 2 -deoxynucleosides. Thus, it is possible to prepare the acylated compounds in S -position with CALB [10], whereas PSL is selective towards the secondary hydroxyl group [11]. Vinyl or oxime esters can be used as acyl donors. 

C-Acylation. C-Acylation of active methylene compounds is usually conducted under basic conditions. Masamune et al. have developed a new method for conducting this reaction under neutral conditions that is patterned on the enzymic synthesis of fatty acids. The acylating reagent is the imidazolide of a carboxylic acid (1) prepared in situ. The substrate is the neutral magnesium salt of a mono ester or thioester of a malonic acid (2), prepared with magnesium ethoxide. The reaction of 2 with 1 is conducted in THF at 25-35° for 18-24 hours the yield of products (3) is generally >85%. ... 

By reaction of cationic carbonyl complexes with lithium carbanions, neutral acyl complexes are prepared. Whereas treatment of [> -CpFe(CO)3]BF4 with (a) PhLi gives the expected > -CpFe(CO)2 [C(0)Ph] in 80% yield, with (b) MeLi only traces of > -CpFe(CO)2 [C(0)Me] can be detected . This complex and other phosphane-substituted acyl compounds of the type f -CpM(CO)L[C(0)Me] [M = Fe, Ru L = CO, PPh3, P(hex)j], as well as >/ -CpMo(CO)2P(hex)3[C(0)Me] (prepared by different routes), are protonated with and alkylated with [R3 0]BF4 reversibly, yielding cationic hydroxy- and alkoxy(methyl)carbene complexes, respectively . The formation of the ( + )- and ( —)-acetyl complex / -CpFe(C0)(PPh3)[C(0)Me] from the ( + )-and ( —)-conformers of optically active > -CpFe(C0XPPh3)[C(0)0-menthyl] and MeLi occurs with inversion of configuration at the asymmetric iron atom . 

Nucleotides are important constituents not only of RNA and DNA, but also of a number of other key biomolecules. Coenzymes NAD+ and FAD, prominent in oxidation-reduction reactions, have ADP as an important constituent. The acyl-group activation compound, coenzyme A, is also derived from ATP. 

---