Y-Lactones acids

CHsjOH. CHlCgHg). CH(COOH). CH. COOH COOH. CHlCgHg). CH(CHaOH). CH. COOH COOH. CH(C2Hg). CH(COOH). CH. CH OH AomoPilopic acid is very stable, and is probably therefore the y-lactonic acid of one of these three hydroxy-acids. Further, pilopic acid seems to be produced from its higher homologue by loss of carbon dioxide and oxidation of the contiguous carbon atom. Of the four y-lactonic acids derivable from these three hydroxy-acids only two (I and II) answer these conditions,... 

This type of alkynol ether hydrocyanation gives rise to a new stereospecific route to a-alkyli-dene y-lactones. Acidic hydrolysis and cyclization of some of the products obtained, as above, give a-alkylidene-y-lactones in 65-83% yield with the double-bond geometry predetermined via stereoselective hydrocyanation2T... 

Appropriate olefinic acids react wifli KHCO3,12, and KI to give iodolactones. Acids with a A4 double bond such as DHA form an iodo y-lactone acids with a AS double bond such as AA or EPA form an iodo 8-lactone (Scheme 13). There are several interesting features about these reactions ... 

Two y-lactonic acids of unknown stereochemistry were found in Lecanora rupicola 174) resp. Cladonia impexa 173). 25 from the former and 26 from the latter species. 

Chapter 4.4.5. y-Lactonic Acids. Maier et al. isolated from the lichen Pmctelia microsticta gyrophoric acid, (—)-isomuronic acid and... 

By saccharic acid is usually meant D-gluco-saccharic acid, m.p. 125-126°C, obtained by the oxidation of glucose or starch. This exists in water solution in equilibrium with its two y lactones, both of which can be obtained crystalline, though the acid itself does not crystallize readily. 

This synthesis was first carried out by VeUuz, Angew. Chem.. 1960, 72, 725. The lactone can be used instead of the y-cldoro acid, see Org. Synth. CoU.. 4, 898. Other approaches to A are outlined in J. Amer. Chem. Soc., 1947, 576, 2936 and it is probable that the... 

Epoxides provide another useful a -synthon. Nucleophilic ring opening with dianions of carboxylic acids (P.L. Creger, 1972) leads to y-hydroxy carboxylic acids or y-lactones. Addition of imidoester anions to epoxides yields y-hydroxyaldehyde derivatives after reduction (H.W. Adickes, 1969). 

P-Hydroxy acids lose water, especially in the presence of an acid catalyst, to give a,P-unsaturated acids, and frequendy P,y-unsaturated acids. P-Hydroxy acids do not form lactones readily because of the difficulty of four-membered ring formation. The simplest P-lactone, P-propiolactone, can be made from ketene and formaldehyde in the presence of methyl borate but not from P-hydroxypropionic acid. P-Propiolactone [57-57-8] is a usehil intermediate for organic synthesis but caution should be exercised when handling this lactone because it is a known carcinogen. 

Avermectins and Ivermectin. The avermectias are pentacycHc lactones isolated from fermentation products of Streptomjces avermitilis and ivermectin is a semisynthetic chemical, 22,23-dihydroavermectia (46). Ivermectin is effective in very low doses for the control of red spider mites on deciduous fmits, in baits for the control of imported fire ants, and as a parasiticide for Onchocerca volvulus in humans and for catde gmbs. These insecticides appear to function as agonists for the neuroinhibitory transmitter y-aminobutyric acid (GABA) (see Antiparasitic agents, avermectins). 

Xyhtol also is obtained by sodium borohydride reduction of D-xylonic acid y-lactone (32) and from glucose by a series of transformations through diacetone glucose (46). 

Ascorbic Acid [50-81-1] (1) is the name recognized by the lUPAC-IUB Commission on Biochemical Nomenclature for Vitamin C (1). Other names are L-ascorbic acid, L-xyloascorbic acid, and L-// fi (9-hex-2-enoic acid y-lactone. The name... 

The most significant chemical characteristic of L-ascorbic acid (1) is its oxidation to dehydro-L-ascorbic acid (L-// fi (9-2,3-hexodiulosonic acid y-lactone) (3) (Fig. 1). Vitamin C is a redox system containing at least three substances L-ascorbic acid, monodehydro-L-ascorbic acid, and dehydro-L-ascorbic acid. Dehydro-L-ascorbic acid and the intermediate product of the oxidation, the monodehydro-L-ascorbic acid free radical (2), have antiscorbutic activity equal to L-ascorbic acid. 

This synthesis was the first step toward industrial vitamin production, which began in 1936. The synthetic product was shown to have the same biological activity as the natural substance. It is reversibly oxidized in the body to dehydro-L-ascorbic acid (3) (L-// fi (9-2,3-hexodiulosonic acid y-lactone), a potent antiscorbutic agent with hiU vitamin activity. In 1937, Haworth and Szent-Gyn rgyi received the Nobel Prize for their work on vitamin C. 

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