Benzyl and Phenyl Esters

2 Benzyl and Phenyl Esters Benzyl acetate (also furfuryl acetate and other similar acetates) and phenyl acetate eliminate the neutral molecule ketene frequently this gives rise to the base peak. 

Of course, the m/z 43 peak (CH3C=0) and m/z 91 (QH/) peaks are prominent for benzyl acetate. 

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Perfumes, Flavors, Cosmetics, and Soap. Many naturally occurring esters in essential oils and some synthetic esters are important fragrance and flavor compounds (61,62). They are used in perfumes, flavors, cosmetics, soaps, detergents, and air fresheners. Benzyl, butyl, ethyl, methyl, and phenyl esters of benzoic acid are used as flavors, perfumes, and food preservatives. Glyceryl 4-aminobenzoate [136-44-7] and 2-ethyUiexyl 4-dimethylaminobenzoate [21245-02-3] are used in cosmetic sunscreen preparations. Alkyl esters of 4-hydroxybenzoic acid, called parabens, have been used under various names for fungus infections of the skin, and as preservatives in lotions and creams (101). Soap and cosmetic fragrances use large amounts of amyl and benzyl saHcylate. Benzyl saHcylate [118-58-1] is also used in deodorant sprays. 2-Ethylhexyl saHcylate [118-60-5] and 2-ethylhexyl 4-methoxycinnamate [5466-77-3] are used in sunscreen formulations (102). 

Bistline and Stirton compared the CMC values of ester sulfonates with cyclic ester groups [54]. The phenyl esters have higher values than benzyl and cyclohexyl esters. The influence of the structure of the ester group decreases with increasing chain length of the hydrophobic fatty acid group. The cyclic esters of a-sulfostearic acid, for example, have nearly the same CMC values. 

BENZYL, CYCLOHEXYL, AND PHENYL ESTERS OF ALPHA-SULFO FATTY ACIDS. 

Unsaturated phosphatidylinositol has been synthesized by Molotkovskii and Bergelson (1971) using an optically active glycerol derivative but a racemic myo-inositol moiety which was added from an acetylated inositol phosphate benzyl ester. Klyash-chitski et ah (1971) prepared a completely optically active dipalmitoylphosphatidylinositol. However, because they used benzyl and phenyl protecting groups their method is not suitable for unsaturated phosphatidylinositols. 

Methyl, ethyl, n-propyl, isopropyl, n-hutyl, benzyl, cyclohexyl esters of formic, acetic, oxalic, succinic, tartaric, citric, benzoic, salicylic (and other substituted benzoic acids), phthalic and cinnamic acids phenyl esters of acetic, benzoic and salicylic acids. 

By condensing the salts or the esters of either dithioformic (207) or dithiophenacetic acids with a-aminonitriles (206) 5-aminothiazoles (209), in which R] = hydrogen, benzyl and Rj = phenyl, carbethoxy, or car-bophenoxy, were obtained in fairly good yields (Scheme 108) (271). These reactions were carried out in aqueous ethereal solution at room temperature. Acyclic thioamides as intermediates in this reaction have been isolated in some cases (208). 

It yields a diphenyl-urethane, which melts at 99° to 100°, and is very useful for identification purposes. The phenyl-urethane, melting at 80° is less useful for this purpose, since its melting-point is almost identical with those of benzyl and nonyl alcohols. It combines with phthalic acid to form a phthalic acid ester, melting at 188° to 189°. 

Cyclodextrins, toroidal molecules composed of 6, 7 and 8 D-glucose units, are now commercially available at reasonable cost. They form inclusion compounds with a variety of molecules and often differentially include sulfoxide enantiomers29,30. This property has been used to partially resolve some benzyl alkyl, phenyl alkyl and p-tolyl alkyl sulfoxides. The enantiomeric purities after one inclusion process ranged from 1.1 % for t-butyl p-tolyl sulfoxide to 14.5% for benzyl r-butyl sulfoxide. Repeating the process on methyl p-tolyl sulfoxide (10) increased its enantiomeric purity from 8.1% to 11.4% four recrystallizations raised the value to 71.5%. The use of cyclodextrins in asymmetric oxidations is discussed in Section II.C.l and in the resolution of sulfmate esters in Section II.B.l. 

FIGURE 5.17 Resins and linkers for synthesis of peptides using Fmoc/tBu chemistry. The linkers are secured to supports by reaction with aminomethyl resins. A protected amino acid is anchored to the support as an ester by reaction with a hydroxyl or chloro group (italicized). The alkoxy and phenyl substituents render the benzyl esters sensitive to the cleavage reagents. 

Diethyl phenyl ethyl malonate. 1 mole of benzyl cyanide is added dropwise to a solution of 1 mole of ethyl carbonate in 2 liters of anhydrous ethanol containing 5 g of clean sodium metal. This mixture is refluxed (preferably on a steam bath) for 5 hours. It is then cooled and to it is added a cooled mixture of 40 g of sulfuric acid in 100 ml of anhydrous ethanol. This alcoholic solution is refluxed for 5 hours, cooled, neutralized with sodium ethylate (use external indicator). The mixture is evaporated to half bulk, filtered from the sodium sulphate and to it is added 1 mole of clean metallic sodium. Reflux while adding 1 mole of ethyl bromide dropwise. Heat for another 2 hours after the addition is completed. Remove the alcohol by distillation and dissolve the remaining residue in water. Extract the substance from the water with benzene and after drying, the benzene is recovered and the ester should be purified by distilling in vacuo. 

We concluded that phenoxy, benzyl, benzoyl and phenyl substituents were all members of a congeneric series of substituents to which simpler members, say fluorine or a methyl group also belonged. In other words, for these simple benzyl esters, no bridging atom was required for insecticidal activity. 

The reaction of l-alkyl-3-arylthioureas (or selenoureas) with a-halo esters in the presence of base has been claimed to produce 3-alkyl-2-aryliminothiazolidin-4-ones141-143 (and the selenium analogs).144 However, Omar145 recently reported that a l-benzyl-3-phenyl-2-thiourea, when treated with ethyl bromoacetate produced a thiazolidi-none which has the alkyl side chain on the exo nitrogen, i.e., the 3-aryl-2-benzyliminothiazolidin-4-one. 

The condensation of an aldehyde, benzyl carbamate, and triphenyl phosphite, first described by Oleksyszyn et al., 25,26 affords a direct route to a-aminoalkylphosphonates 4 that are conveniently protected for subsequent reactions (Scheme 4). Since dealkylation of the quaternary phosphonium intermediate 3 is not possible in this case, formation of the pen-tavalent product 4 presumably involves activation of the solvent and formation of phenyl acetate. This method is useful for the synthesis of aliphatic and aromatic amino acid analogues. However, monomers with more elaborate side chains are often incompatible with the reaction conditions. The free amine can be liberated by treatment with HBr/AcOH or by hydrogenolysis after removal of the phenyl esters. The phosphonate moiety can be manipulated by ready exchange of the phenyl esters in alkaline MeOH and activation as described in Section 10.10.2.1.1. Related condensations with other trivalent phosphite derivatives have been reported. 27-30 ... 

The 4 -monophosphate was also prepared from the same compound as above (Figure 5). Although the 4 -hydroxyl group in 12 has rather low reactivity, its phosphorylation could be performed with phenyl phosphate and dicyclohexylcarbodiimide (DCC) in pyridine. The reaction product was converted into the benzyl phenyl ester ( ) to facilitate purification. In contrast to the above dibenzyl ester of the glycosyl phosphate, the benzyl phenyl ester of the 4 -phosphate was stable and could be purified by silica gel column chromatography after removal of the propenyl group without decomposition. Hydrogenolytic deprotection of (first with Pd-black then with PtC>2) afforded the 4 -monophosphate 17. 

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