Other Esters

A brief review of glucosinolates and other naturally occurring O-sulphates has appeared.  

D-Glucose reacted with dodecyl chloroformate in DMF in the presence of sodium carbonate to produce a mixture of carbonates which was separated into mono-, di-, and tri-carbonates by t.l.c. on silica gel. Sucrose monoesters have been prepared in 44—85% yield from sucrose and 1-alkoxyethyl isocyanates in DMF containing triethylamine. The syntheses and properties of sucrose A (aryloxyalkaneacyl)-carbamates from sucrose and the corresponding isocyanate have been reported. As part of a study of the behaviour of the 

Meissner and R. Zielinski, Zesz. Nauk - Akad. 3con. Poznaniu, Ser. 1, 1976, 69, 122 iChem. Abs., 1978, 88, 7233d), 

The use of unsymmetrical sulphites in glycoside synthesis is mentioned in Chapter 3. Reduction of dimethylsulphamoyl esters to deoxy compounds is noted in Chapter 11. Reference to ascorbic acid sulphates and phosphates is made in Chapter 15. Phenylboronates used for disaccharide synthesis are mentioned in Chapter 3. Chapter 4 includes a mention of an alkene synthesis via a thionocarbonate. 

A wide variety of other lipid esters have been reported. Wax esters are a typical example. Although the term wax should, strictly speaking, only be used for esters of long-chain fatty acids with long-chain primary alcohols, common usage, unfortunately, often equates wax with the entire mixture of lipids of which the true waxes are but a part. Ester waxes are found in animals and plants where they form part of the water-repellent surface coating (i.e. skin surface of animals and the leaf cuticle (cf. Section 2.10)). The general formula for a simple wax is  

The preen glands of birds, in addition, contain esters of normal alcohols with mono- or multi-branched fatty acids (Odham, 1967). 

Complex waxes are compounds where either the fatty acid or the alcohol component or both has a complex structure. For example, the waxes of Mycobacterium spp. are diesters of phthiocerols (C33-C35 branched-chain diols) with mycocerosic acids (C29-C32 branched-chain acids) (Asselineau, 1966). 

Animal skin surface lipids have two types of diester waxes. In the first, a hydroxy acid has its hydroxyl group esterified to a normal fatty acid and its carboxyl group to a fatty alcohol. The second wax type consists of an alkane qj, /8-diol in which both hydroxyls are esterified with fatty acids (Nicolaides et al., 1970). 

Likewise, esters are found for vitamin alcohols such as vitamin A, the vitamin Ds and vitamin E. Examples are as follows  

The nature of ester formation between borate and D-mannitol, D-glucitol, D-fructose and D- lucose in aqueous solution at pg 6 - 12 has been elucidated using B- and C-n.m.r. spectroscopy. In order to better understand the action of a gluconate-borate eluent for elution of anions from an anion-exchange resin, the structural features of such solutions have been investigated by potentiometric titrations and C-n.m.r. spectroscopy. Reference to borate esters as transport media in a model membrane will be found in Chapter 2. 

Selective protection of a primary hydroxy group can be effected 

A one-pot synthesis of bromodeoxy carbamates has been achieved using Viehe s salt followed by treatment with lithium bromide. Thus 

An efficient and stereoselective synthesis of 3,4,6-tri-O-acetyl-ot-D-glucopyranose 1,2-exo-alkyl ortho-acetates (67) has been achieved using DMF dialkyl acetals (68) and tetrabutyl ammonium bromide on acetobromoglucose. The DMF acetal from 1,2 3,4-di-0-isopropylidene bC-D-galactopyranose (69) was also prepared and used to synthesize the mixed sugar orthoester (70). 

The synthesis of halogeno-sugars via an improved preparation of cy tc carbonates and sulphates will be found in Chapter 8 and the synthesis of glycosides using these intermediates in Chapter 2. 

The complexation of aldoses with cholesterol-derived boronic acids has been reviewed, and the changes in UV absorption and fluorescence intensity of a stilbene-type boronic acid on complexation with aldoses, especially D-fructose, have been studied with a view to their use in sugar-detection. Similar work has been carried out with diboronic acids derived from biphenyl and a -functionalized diaza-18-C-6 crown ether.A carbohydrate boronic acid derivative with liquid crystal properties referred to in Chapter 6, and further reports on boronate esters are noted in Chapter 17. 

Gimisis, G. lalongo, M. Zamboni and C. Chatgilialoglu, Tetrahedron Lett., 1995, 36, 6781. 

Pertel and V.Ya. Chirva, Khim. Prir. Soedin, 1994,177 Chem. Abstr., 1995,122, 314 948). 

Baczko, C. Nugier-Chauvin, J. Banoub, P. Thibault and D. Plusquellec, Carbohydr. Res., 1995,269,79. 

Pavel and H. Ritter, Macromol. Rapid Commun., 1995,16, 337 Chem. Abstr., 1995,123,112 557). 

Orthoacetates 70 were formed quantitatively by reaction of the corresponding diol with (MeO)3CCH2Cl or (MeO)3CCHCl2 in the presence of catalytic TsOH. 

Opening with aqueous TFA was non-selective to give 4-0-/6-0 mixtures of (monochloro)acetates and (dichloro)acetates, respectively.  

A new procedure for cleaving allyloxycarbonates using Pd(0), formed in situ from Pd(OAc)2 and trisodium tris(m-sulfophenyl)phosphine, with sodium azide as allyl scavenger, has been applied to a number of carbohydrate derivatives.  

Glycopyranosyl carbamates were obtained with almost 100% P selectivity by treatment of anomerically unprotected precursors with aryl isocyanates (e.g., 71 - 72).  

The terphenyl boronic acid 73 reacted selectively with 5-0-protected P-glyco-sides of 2-deoxy-D-ribose to form boronate esters 74.  

Glucopyranosyl xanthates of general formula (27) have been prepared by reaction of 2,3,4,6-tetra-0-acetyl-o -D-glucopyranosyl chloride with potassium alkyl xanthates o.r.d., c.d., u.v., and n.m.r. spectra of the products were examined and the effect of solvents on the Cotton effect curve was studied. The thermal decomposition of the dixanthates (28) and (29), prepared 

Satsumabayashi, Y. Nomoto, S. Satsumabayashi, and K. Numanami, Nippon Shika Daigaku Kiyo, Ippan Kyoiku-kei, 1979, 8, 99 (Chem. Abs., 1979, 91, 91 864c). 

Sulphation of lactose with pyridine-SOa complex in pyridine resulted in formation of the galactose 6-sulphate. Other oligosaccharides were alsostudied. I he glycolipids, seminolipid and cerebroside sulphate, which are sulphated on the 3-position of galactose, were not oxidized by galactose oxidase. 

Acetobromoglucose reacts with silver propionate in THF to give, via the 1,2-acetoxonium ion, a mixture of the acyl orthoester (36), the first of its type reported, and the 2,3,4,6-tetra-0-acetyl-l-0-propionyl-/ -D-glucopyranose.  

Schroder, and W. Schmidt, Angew. Chem. Internat. Ed., 1979, 18, 309. 

Coupling of sugar moieties via the primary hydroxy group to proteins has been demonstrated in the attachment of several sugar derivatives to one molecule of bovine serum albumin using 6-0-(N-bromoacetyl-sulphanilyl) groups (65) These couple to proteins through amino 

A study of hydrolysis and aminolysis of xanthate esters included the two 6-substituted glucosides (68) and (69)  

Complexes of D-raannose, D-glucose, D-xylose, and L-arabinose with boric acid have been studied by C n.m.r. spectroscopy and equilibrium data they were considered to have the sugar in the furanose 80  

Sugar nitrates have been prepared by triflate displacements with nitrate ion acetals and epoxides were unaffected, enabling nitrates (70) - (72) to be obtained. 

Reference to the stability of allyloxycarbonyl groups towards various heavy-metal reducing agents is made in Chapter 5i and to glycosylation via borate esters in Chapter 17. 

Martin-Lomas, M. Bernabe, and M. E. Chacon-Fuertes, An. Quim., 1979, 75, 718 Chem. Abstr., 1980,92,147 064). 

Reagents i, succinic anhydride-4-dimethylaminopyridine-py ii. HBr-HOAc-ACjO-CHjClj iii, Et NBr-CHjCN-mol. sieve-lutidine 

Reaction of indoles with glycosyl halides in the presence of silver oxide and molecular sieve as catalysts gave orthoamides of the type shown in (35) and indole nucleosides (see Chapter 19).  

Sulphation of sucrose with pyridine-sulphur trioxide in dimethylformamide gave the octasulphate, which gave crystalline potassium, caesium, rubidium, and ammonium salts. A new sulphated glycosphingolipid, A-acetylglucosamine 6-sulphatei8-(l 3)-Gal-i8-(l 4)-Glc-(3-(l l)-ceramide, has been isolated from 

Watanabe, K. Okui, and M. Shindo, Chem. Pharm. Bull., 1980, 28, 638. 

Russian workers have reported the synthesis of a number of benzeneboronates by the reaction of aldoses and alditols with benzeneboronic acid. Thus, glycerol gave a mixture of the 1,2- and 1,3-benzeneboronates, and D- ucose afforded the l,2 3,5-bis(benzeneboronate) (83), whose structure was deduced by spectroscopic comparison with the 3,5-benzeneboronate (84) prepared from l,2-( -isopropylidene-a-D-glucofuranose. On treatment with two molar 

Reagents i, EtOCOCi-py ii, EtOCOCl-EtjN iii, l,r Carbonyldi-imidazole-THF iv, Ac 0-py 

Murase and M. Murakami, Yamanouchi Seiyaku Kenkyu Hokoku, 1974, 2, 62 Chem. 

The orthosilicates (93) of D-glucose, D-fructose, and D-galactose were obtained in 30—40% yields by treatment of two molar equivalents of the sugar with silicon disulphide in DMF, whereas the orthosilicates (94) were obtained when four molar equivalents of the sugar were used.  

Sugar == D-glucose, D-galactose, or D-fructose W. V. Dahlhoff and R. Kdster, Anmlen, 1975, 1926. 

spectroscopy has been used to determine the position of the sulphate group in each of three isomeric methyl 3-O-methyl-a-D-mannopyranoside sulphates. The preparation of L-ascorbic acid 2-[ S]sulphate is referred to in Chapter 17.  

Several new carbonate derivatives of methyl a- and j8-D-glucopyranoside, including methyl 2- and 3-0-methoxycarbonyl-a- and -jS-o-glucopyranosides and methyl a- and jS-D-glucopyranoside 2,3-carbonates, have been obtained by standard procedures. Inhibition of yeast a-D-glucosidase by methyl 2- and 3-C -methoxycarbonyl-a-D-glucopyranoside indicated that such compounds may be valuable as active-site-directed, irreversible inhibitors for glycosidases. 

The synthesis of deoxy-sugars from thiocarbonate derivatives is noted in Chapter 13.  

2S8 Place, M.-L. Roumestant, and J. Gore, Bull. Soc. ckim. France, 1976, 169. 

6-Hexakis-O-diethylborylgalactitoI (obtained by reaction of galactitol with activated triethylborane) was converted into (85) on pyrolysis at 150 and into (86) on pyrolysis at 230 Selective deborylation of either (85) 

N-diethylammonium chloride (Viehe s salt) with sugars has been 

Only low yields were obtained by using the triphenylp osphine-DEAD method to prepare cyclic carbonates from vic-diols. A detailed study of the reaction of methyl 4.,6-0-benzylidene-c -D-glucopyranoside 2,3-carbonate with methanol in the presence of the acid ion-exchange resin showed that the benzylidene group was rapidly lost and a mixture of methyl oC-D-glucopyranoside 2- and 3-0-methoxycarbonyl derivatives formed, with the latter 

A kinetic and mechanistic investigation of the nitrosation of alcohols agd thiols includes some work on D-mannitol, sucrose, and D-glucose. 

Reduction of the cyclochlorophosphite (36) with tributyl stannane in absolute benzene for 4. days at room temperature gave the parent phosphite (37), which, on heating with sulphur for 2h in benzene at reflux yielded in 72% overall yield the thiophosphite (38). 

Peracylglycosyl bromides in dichloromethane treated with alcohols 

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Note. Methyl oxalate, unlike most other esters, hydrolyses very rapidly in aqueous solution hence it will evolve CO in the above test, owing to the formation of methanol and free oxalic acid. 

Ethyl oxalate is the only liquid ester which gives this rapid separation of the amide, which is therefore characteristic. Methyl and ethyl formate react rapidly with ammonia, but the soluble formamide does not separate methyl succinate gives crystalline succinamide after about I hour s standing, other esters only after a much longer time. The solid esters, other than methyl oxalate, are either soluble in water and remain so when treated with ammonia, or alternatively are insoluble in water and hence clearly not methyl oxalate. 

In view of the difficulty of arranging esters in a chemically logical sequence they have in the following table been arranged in order of increasing b.ps (liquid) and m.ps (solid). Other esters are given in Tables XI and XII (pp. 543-545). The values for esters of polybasic acids refer to the fully esteriiied product. 

A number of selected aromatic nitro compounds are collected in Table IV,16A, It will be noted that a few nitro aromatic esters have been included in the Table. These are given here because the nitro group may be the first functional group to be identified aromatic nitro esters should be treated as other esters and hydrolysed for final identification. 

The pyridine procedure may be apphed to the preparation of other esters they are isolated by ether extraction. The yields are generally better than by the sodium hydroxide method. 

Section 20 8 Esters are polar and have higher boiling points than alkanes of compa rable size and shape Esters don t form hydrogen bonds to other ester molecules so have lower boiling points than analogous alcohols They can form hydrogen bonds to water and so are comparable to alcohols m their solubility m water... 

Acryhc esters may be saponified, converted to other esters (particularly of higher alcohols by acid catalyzed alcohol interchange), or converted to amides by aminolysis. Transesterification is comphcated by the azeotropic behavior of lower acrylates and alcohols but is useful in preparation of higher alkyl acrylates. 

In typical processes, the gaseous effluent from the second-stage oxidation is cooled and fed to an absorber to isolate the MAA as a 20—40% aqueous solution. The MAA may then be concentrated by extraction into a suitable organic solvent such as butyl acetate, toluene, or dibutyl ketone. Azeotropic dehydration and solvent recovery, followed by fractional distillation, is used to obtain the pure product. Water, solvent, and low boiling by-products are removed in a first-stage column. The column bottoms are then fed to a second column where MAA is taken overhead. Esterification to MMA or other esters is readily achieved using acid catalysis. 

Specifically MSA has been found to be more effective than -toluenesulfonic acid and sulfuric acid in preparing dioctyl phthalate (405). A U.S. patent also discloses its use to prepare light-colored fatty esters (406). It is also important as a catalyst to prepare acrylates, methacrylates, adipates, phthalates, trimeUitates, thioglycolates, and other esters. 

Uses ndReactions. The main use for citroneUol is for use in soaps, detergents, and other household products. It is also important as an intermediate in the synthesis of other important fragrance compounds, such as citroneUyl acetate and other esters, citroneUal, hydroxycitroneUal, and menthol. 

CitroneUol is easUy esterified with acid anhydrides or carboxylic acids, catalyzed by mineral acids. The price of citroneUyl acetate [150-84-5] in 1995 was 10.45/kg (45). Other esters such as the formate and isobutyrate ate also used. 

Esters. The significant esters of citric acid are trimethyl citrate, triethyl citrate, tributyl citrate, and acetylated triethyl- and tributyl citrate. Many other esters are available but have not been used on a commercial scale. Citric acid esters are made under azeotropic conditions with a solvent, a catalyst, and the appropriate alcohol. 

Other Esters. The esterification of acetic acid with various alcohols in the vapor phase has been studied using several catalysts precipitated on pumice (67). 

AC2O, AcCl, Pyr, DMAP, 24-80°, 1-40 h, 72-95% yield. The use of DMAP increases the rate of acylation by a factor of 10. These conditions will acylate most alcohols, including tertiary alcohols. The use of DMAP (4-N,N-dimethylaminopyridine) as a catalyst to improve the rate of esterification is quite general and works for other esters as well. 

Candida cylindracea, phosphate buffer pH 7, Bu20. The 6-0-acetyl of Q -methyl peracetylglucose was selectively removed. Porcine pancreatic lipase will also hydrolyze acetyl groups from carbohydrates. These lipases are not specific for acetate since they hydrolyze other esters as well. In general selectivity is dependent on the ester and the substrate. ... 

The p-phenylbenzoate ester was prepared to protect the hydroxyl group of a prostaglandin intermediate by reaction with the benzoyl chloride (Pyr, 25°, 1 h, 97% yield). It was a more ciystalline, more readily separated derivative than 15 other esters that were investigated. It can be cleaved with K2CO3 in MeOH in the presence of a lactone. ... 

Me3SiCH2CH20H, MejSiCl, THF, reflux, 12-36 h. This method of esterification is also effective for the preparation of other esters. 

C1-3,5-(N02)C5H2N, Pyr, rt - 115°, /-BuOH. Other esters are also prepared effectively using this methodology. 

Both Methods 1 and 2 have been successfully applied to a wide range of 1,2-diesters and to a variety of other esters. The use of a high-dilution cycle permits this procedure to be applied to medium-and large-ring acyloins with good to excellent results. 

The change of mechanism with tertiary alkyl esters is valuable in synthetic methodology because it permits certain esters to be hydrolyzed very selectively. The usual situation involves the use of t-butyl esters, which can be cleaved to carboxylic acids by action of acids such as p-toluenesulfonic acid or trifluoroacetic acid under anhydrous conditions where other esters are stable. 

Benzilic and other esters of tropine and 4-tropine a-phenylvalerie, diphenylacetic, fluorene-9-earboxylie, tropic, and other esters of /3-diethylaminoethanol tropic and other "esters of y-diethyl-amino- /3-dimethylpropanol (Fromherz esters of morpholinoalkyl alcohols. ... 

Ehminations of HX to give double bonds offer considerable scope for selectivity and choice of reaction conditions. The dehydration of alcohols is the most common example of this class and may be achieved directly or through intermediate derivatives. In most cases, such derivatives are transient species formed in situ, but sometimes e.g. sulfonates, certain other esters and halides) they are isolated and characterized. Eliminations from jS-substituted ketones are very facile. The dehydration of jS-hydroxy ketones has been covered in section V. 

Mixed Claisen condensations (Section 21.3) Diethyl carbonate, diethyl oxalate, ethyl formate, and benzoate esters cannot form ester enolates but can act as acylating agents toward other ester enolates. 

AUeyl NUnites arc hydrolysed like other esters, and yield alcohol and nitric ticicl (p. 82). 

CH3COCI, CH2CI2, collidine, 91% yield. A primary acetate was formed selectively in the presence of a secondary. These conditions are suitable for a variety of other esters. ... 

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