From hydroxy acids

Shellac [124,125] is a natural resin used in very old times for varnishes and moulding compounds. The resin secreted by the lac insect, Kerriar paca, is collected by scraping the shellac-encrusted trees found in southern parts of Asia. It consists of a complex mixture of cross-linked polyesters derived from hydroxy acids, principally aleuritic acid (9,10,16-trihydroxyhexadecanoic acid). From a structural point of view, it appears that this material can be used as a crosslinking agent and/or as a monomer for developing dentrite-like polymers. The question is whether it is possible to produce this material from shellac by controlled hydrolysis. 

The carboxy-hydroxy reaction (direct esterification) is the most straightforward method of polyester synthesis. It was first reported in the 1930s by Carothers10 12 and is still a very widely used method for the synthesis of polyesters from diacids and diols (Scheme 2.12) or from hydroxy acids (Scheme 2.13). Direct... 

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 ... 

From aryl halide 110 From alcohol 156 Protection 100, 101, 144 Amino acid from hydroxy acid 40 Amphidinolide synthesis 50,94 Anatoxin synthesis 82 Aromatic ring construction 171,191 Aromatic ring substitution 10,18,19,21, 48, 54, 65,69, 104, 108, 110, 111, 120, 122,138, 149, 164, 171, 174, 175, 190,205... 

In general, dehydration means loss of water molecules from chemical substances, irrespective of their structure. Even if all cases where water is bonded in hydrate form are excluded, a number of reactions remain which also include formation of nitriles from amides, lactones from hydroxy acids etc. However, the present treatment will concentrate on the heterogeneous catalytic decomposition of alcohols in the vapour phase, which can be either olefin-forming or ether-forming reactions, and on the related dehydration of ethers to olefins. 

From hydroxy acids or acyl derivatives Camphor-10-sulfonic acid, 62 Molybdenum carbonyl, 194 Sodium iodoacetate, 149 Thiophenol, 297... 

A. C. Ibay and L. P. Tenney, Polymers from hydroxy acids and polycarboxylic acids, US Patent 5206341, assigned to Southern Research Institute, November 21,2011. 

The 2-pyridinethiol ester 12 can also be prepared from hydroxy acid and... 

In a model study for erythronolide B, White et al. [43] synthesized lactone 72 from hydroxy acid 71 via a mixed sulfonic anhydride. Thus, as shown in Scheme 23, exposure of 71 to p-toluenesulfonyl chloride and triethylamine in benzene followed by chromatography afforded 72 in 52% yield. 

Several metiiods have been devdoped recently for preparing -laotouea from hydroxy acids whether these methods are generally applicable cannot be decided at this pmnt as they have only been used in spocial cases. 

The loss of water from hydroxy acids and the formation of unsaturated acids has been met with before in connection with heta-hydroxy mono-basic acids e.g., hydraciylic acid, jS-hydroxy propionic acid, and its conversion into acrylic acid, propenoic acid (p. 172). In such cases the beta-hydioxy acid loses water from two neighboring carbon groups thereby creating a double bond. 

SchOllkopfs bislactim ethers Other chiral glycine enolates Williams s method Seebach s relay chiral units Chiral Enolates from Hydroxy Acids Seebach s relay chiral units Chiral Enolates from Evans Oxazolidinones... 

Polyesters. Direct Esterification. Polyesters can be made from hydroxy acids and from diacids and diols by direct condensation ... 

MJnsaturated acids are rarely formed from -hydroxy acids by means of dehydrating agents, which, instead, afford lactides and anhydrides or, with loss of formic acid, aldehydes. However,, / -unsaturated nitriles can be obtained from a-hydroxy nitriles (cyanohydrins) by means of thionyl chloride45 or phosphorus(v) oxide,46 and are readily hydrolysed to the corresponding <%,/ -unsaturated acids. 

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