4-Nitrophenyl acetate Subject

Hydroxamic acids have been the subject of six papersEarlier the operation of the a-effect in the reaction ofp-nitrophenyl acetate with benzohydroxamates in aqueous MeCN was discussed." The conformational behaviour of series of mono- (105) and di-hydroxamic acids (106) in MeOH, DMSO, and chloroform and in the solid state has been examined with IR and NMR spectroscopy. X-ray crystal structure determinations of (105 X = Me, R = Me) and the monohydrate of glutarodihydroxamic acid (106 n = 3, R = H) together with ab initio MO calculations for several hydrated and non-hydrated acids have been performed. The cis-Z conformation of the hydroxamate groups is preferentially stabilized by H-bonding with water. 

The diethyl 2-[3-bis(methoxycarbonyl)methyl-4-nitrophenyl]-2-methylmalonate obtained above,(4.13 g, 9.71 mmol) was dissolved in acetic acid (40 ml). To the solution were added water (16 ml) and concentrated sulfuric acid (4 ml), and the resulting mixture was heated for 15 hours under reflux. The acetic acid was distilled off under reduced pressure. The residue was concentrated under reduced pressure after addition of toluene. The precipitated crystals were collected by filtration and washed with water to give 2.06 g of the desired compound as a pale brown crystalline product. The filtrate and washing were combined and subjected to extraction using ethyl acetate. The ethyl acetate portion was washed successively with water and an aqueous saturated sodium chloride solution, and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to leave 0.32 g of 2-(3-carboxymethyl-4-nitrophenyl)propionic acid as a yellow crystalline product. The total amount was 2.38 g (yield 96.8%). 

The transesterification of N-(j3-hydroxyethyl)ethylenediamine by p-nitro-phenyl picolinate has been shown to be subject to zinc ion catalysis by Sigman and Jorgensen 27). Their investigations indicate that reaction very probably occurs through the formation of a ternary complex in which zinc ion functions both to lower the pKa of the hydroxyethyl moiety, and to serve as a template for the reaction. The high specificity manifest in this catalytic process is emphasized by the fact that no catalysis of acyl-group transfer occurs when N-((8-hydroxy-ethyl) ethylenediamine is replaced by ethylenediamine, 1,5-diaminopentane, di-ethylenetriamineor aminoethanol. Furthermore, the reactions of the p-nitrophenyl esters of isonicotinic and acetic acids with N-((8-hydroxyethyl) ethylenediamine are not subject to zinc ion catalysis. 

Intramolecular enantiosituselectivity is exemplified by the biosynthetic formation of the mustard oil glucoside sinigrin (60) in horseradish, " the deprotonation of N-Boc-pyrrolidine (62) with sec-butyllithium (s-BuLi)/(-)-sparteine, followed by methylation, "" and, the oxidation of enol 64. Intermolecular enantiosituselective transformations are exemplified by the hydrolysis of racemic N-dodecanoylphenylalanine p-nitrophenyl esters (( )-67) in the presence of tripeptide catalyst (Z)-L-Phe-L-His-L-Leu (68) in each of the latter two cases, only one (externally) enantiotopic carbonyl reacts preferentially. It should be pointed out parenthetically, that as a result of the enantiosituselectivity in these transformations, one has, in effect, kinetic resolution of ( )-67. The electron-impact induced elimination in acetate 71, and the oxidation of 73 exemplify intramolecular diastereosituselective transformations. The epoxidation of the mixture 76/77 is an example of an intermolecular diastereosituselective process at the same time that each substrate is subject to enantiositunonselectivity of the carbonyl sub-sites. 

Thought not interionic interactions, alkaline hydrolyses of p-nitrophenyl esters (acetate, propionate, valerate, caprylate, laurate, and palmitate) were subject to the hydrophobic interactions. Addition of polycations or cationic micelles (CTABr) enhanced the reaction as shown in Figure 9 [37]. 

In addition to the approach outlined in Scheme 4, several other approaches to the synthesis of glycofuranosides have been reported during the past year. Hanessian and Banoub have used cyclic amide acetals derived from vicinal diols as the source of the aglycone in condensations with l-0-acetyl-2,3,5-tri-0-benzoyl-jS-D-ribofuranose in the presence of stannic chloride (Scheme 5). Disaccharide derivatives are obtained when the cyclic amide acetal is derived from carbohydrate vicinal diols (Scheme 6), and selective methanolysis of the formate ester exposed an hydroxy-group that can be subjected to further manipulation or glycosylation. 2,3,5-Tri-0-benzoyl-a)8-L-arabinofuranosyl bromide or chloride has been condensed with 4-nitrophenyl 2,3-di-O-acetyl-a-L-arabinofuranoside to yield, after deacylation, 4-nitrophenyl 5-O-a-L-arabinofuranosyl-a-L-arabino-furanoside, with jS-peltatin A [isolated from podophyllin Podophyllum peltatum)] in glycosidation of the phenolic 8-OH group in an attempt to reduce... 

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