Hydroxy acids Anhydrides

Groftflns Interest in synthetic, absorbable copolymers and their use in the production of fibers, including sutures, and drug delivery systems has been addressed in the patent and technical literature over the past fifteen yearsHowever, most investigators have focused their attention on copolymers which are derived primarily from -hydroxy acids anhydrides ... 

Ethers of benzenepentol have been obtained by Dakin oxidation of the appropriately substituted acetophenone. Thus, the oxidation of 2-hydroxy-3,4,6-ttimethoxyacetophenone and 2-hydroxy-3,4,5-ttimethoxyacetophenone with hydrogen peroxide ia the presence of alkali gives l,2-dihydroxy-3,4,6-ttimethoxybenzene and l,2-dihydroxy-3,4,5-ttimethoxybenzene, respectively further methylation of these ethers yields the pentamethyl ether of benzenepentol (mp 58—59 degC) (253). The one-step aromatization of myoinositol to produce esters of pentahydroxybenzene is achieved by treatment with carboxylic acid anhydrides ia DMSO and ia the presence of pyridine (254) (see Vitamins). 6-Alkyl- or... 

Sorbic acid anhydride [13390-06-2] can be prepared by heating the polyester of 3-hydroxy-4-hexenoic acid with sorboyl chloride [2614-88-2] or by reaction of sorbic acid with oxalyl chloride (15,16). Preparation of the esters of sorbic acid must be controlled to prevent oxidation and polymerization. The lower sorbic acid esters have a pleasant odor. 

In order to become useful dmg delivery devices, biodegradable polymers must be formable into desired shapes of appropriate size, have adequate dimensional stability and appropriate strength-loss characteristics, be completely biodegradable, and be sterilizahle (70). The polymers most often studied for biodegradable dmg delivery applications are carboxylic acid derivatives such as polyamides poly(a-hydroxy acids) such as poly(lactic acid) [26100-51-6] and poly(glycolic acid) [26124-68-5], cross-linked polyesters poly(orthoesters) poly anhydrides and poly(alkyl 2-cyanoacrylates). The relative stabiUty of hydrolytically labile linkages ia these polymers (70) is as follows ... 

The 17-hydroxy group of 2,3-epithiosteroids and the hydroxy groups of some epi-thiosugars may be acylated with acid anhydrides or chlorides without affecting the episulfide (77CPB1140). 

Copper chromite 14) and barium-promoted copper chromite (75,/7) have been used for acid reductions but very high temperatures (300 C) are required. The necessary temperature is sufficiently higher than that required foresters to permit selective reduction of half-acid esters to the hydroxy acid 23). The reverse selectivity can be achieved by reduction over H Ru4 CO)a PBu3)4 at I00-200 C and 1500-3000 psig. This homogeneous catalyst will reduce acids and anhydrides, but not esters (2). 

The reaction between acid anhydrides and diols is another convenient method of polyester synthesis. The reaction proceeds in two steps with the formation of an intermediate hydroxy acid (Scheme 2.15). 

Polyesters have been obtained in organic medium by polyesterification of hydroxy acids,328,329 hydroxy esters,330 stoichiometric mixtures of diols and diacids,331-333 diols and diesters,334-339 and diols and cyclic anhydrides.340 Lipases have also been reported to catalyze ester-ester interchanges in solution or in die bulk at moderate temperature.341 Since lipases obviously catalyze the reverse reaction (i.e., hydrolysis or alcoholysis of polyester), lipase-catalyzed polyesterifications can be regarded as equilibrium polycondensations taking place in mild conditions (Scheme 2.35). 

Acid anhydride-diol reaction, 65 Acid anhydride-epoxy reaction, 85 Acid binders, 155, 157 Acid catalysis, of PET, 548-549 Acid-catalyzed hydrolysis of nylon-6, 567-568 of nylon-6,6, 568 Acid chloride, poly(p-benzamide) synthesis from, 188-189 Acid chloride-alcohol reaction, 75-77 Acid chloride-alkali metal diphenol salt interfacial reactions, 77 Acid chloride polymerization, of polyamides, 155-157 Acid chloride-terminated polyesters, reaction with hydroxy-terminated polyethers, 89 Acid-etch tests, 245 Acid number, 94 Acidolysis, 74 of nylon-6,6, 568... 

The condensation of aromatic aldehydes with anhydrides is called the Perkin reaction When the anhydride has two a hydrogens (as shown), dehydration always occurs the P-hydroxy acid salt is never isolated. In some cases, anhydrides of the form (R2CHC0)20 have been used, and then the hydroxy compound is the product since dehydration cannot take place. The base in the Perkin reaction is nearly always the salt of the acid corresponding to the anhydride. Although the Na and K salts have been most frequently used, higher yields and shorter reaction times have been reported for the Cs salt. Besides aromatic aldehydes, their vinylogs ArCH=CHCHO also give the reaction. Otherwise, the reaction is not suitable for aliphatic aldehydes. ... 

C15H21NO5) see Gusperimus trihydrochloride 4-[hydroxy[5-[[(phenylmethoxy)carhonyl]amino]pen-tyl]amino]-4-oxobutanoic acid (C,7H24N20ft 106410-46-2) see Deferoxamine D-a-(4-hydroxyphenyl)-tx-(2-methoxycarbonyl-l-methyl-cthenylamino)acetic acid anhydride with monoethyl carbonate... 

The principles set forth above account reasonably well for the course of bifunctional condensations under ordinary conditions and for the relative difficulty of ring formation with units of less than five or more than seven members. They do not explain the formation of cyclic monomers from five-atom units to the total exclusion of linear polymers. Thus 7-hydroxy acids condense exclusively to lactones such as I, 7-amino acids give the lactams II, succinic acid yields the cyclic anhydride III, and ethylene carbonate and ethylene formal occur only in the cyclic forms IV and V. 

The interaction of tris(a-hydroxy-/3,/3,/3-trichloroethyl)phosphine with phenylboric acid anhydride in the presence of triethylamine yields resins. 

In general, 3-hydroxy-l,2,4-thiadiazoles react with hard nucleophiles (acid chlorides, sulfonyl chlorides) at the oxygen atom, whereas soft nucleophiles (isocyanates, acid anhydrides) react at the N-2 position yielding 1,2,4-thiadiazolin-3-ones. Nucleophiles react at the N-4 position of 5-hydroxy-l,2,4-thiadiazoles <1996CHEC-II(4)307>. There have been no new publications on O-linked substituents since the publication of CHEC-II(1996). 

One of the most systematic investigations into the use of organic chemical microscopy was made by Dunbar and his associates, who used a series of specific reagents to develop specific tests for various functional groups. Methods were developed for amines [24,25], carboxylic acids, anhydrides, and acid chlorides [26,27], aldehydes and ketones [28], hydroxy compounds [29], amino acids [30], and cations [31]. 

A variant that eliminates the production of water and that has proved effective for esterification of hydroxy and aromatic amino acids involves the use of thionyl chloride instead of acid. At a low temperature, the alcohol reacts with the chloride, generating methyl sulfinyl chloride, which produces the ester, probably through the mixed carboxylic acid-sulfinic acid anhydride (Figure 3.18, B). p-Toluenesulfonyl chloride added to the acid and benzyl alcohol serves the same purpose in the preparation of benzyl esters. 

Treatment of diphenacylphosphinic acid with P2Os in hot toluene leads to 4-hydroxy-2,6-diphenyl-4//-1,4-oxaphosphorin 4-oxide (54) rather than to the phosphinic acid anhydride.45... 

It may be stated at this point that the presence of a /3-hydroxy-butyrate fat in certain organisms is a matter of general biochemical importance. Usually /3-hydroxybutyric acid and the acetone bodies are derived from n-butyric acid directly. The unambiguous formation of jS-hydroxybutyric acid anhydrides from carbohydrates opens up new vistas its formation from acetaldehyde, and from pyruvic acid, through aldol intermediates can be understood without difficulty. Kirrmann s reaction, to which little attention has been paid, is at the same time an example of an oxygen shift, leading from hydroxyaldehydes to fatty acids. 

Ph, R = H) and acetic anhydride-triethylamine was initially thought to be anhydro-2,3-diphenyl-4-hydroxy-l,3-thiazolium hydroxide, CijHiiNOS (114, R = R = Ph, R = H), but later studies established that the product had the molecular formula C30H24N2O2 and the constitution 116. The synthesis of the meso-ionic l,3-thiazol-4-one (114, R = R = Ph, R = H), orange-yellow needles, m.p. 113°-115°, was successfully achieved by dehydration of the acid (115, R = R = Ph, R = H) using acetic anhydride-triethylamine for a few minutes at room temperature. The acids (115, R = NR2, R = Ph, R = H) and acid anhydrides similarly yield the corresponding meso-ionic l,3-thiazol-4-ones (114, R = NRj, R = Ph, R = H). Analogous polycylic meso-ionic l,3-thiazol-4-ones have also been prepared. ... 

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