Lactone functional groups

Several studies have been directed toward examination of the interaction of acids and bases with active carbons (I, 8, 10, 17, 18, 19). Boehm (3), Garten and Weiss (9), and Snoeyink and Weber (21) have presented reviews on the subject. Garten and Weiss (8, 9, 10) have shown that acid and alkali sorption can be related to surface functional groups which form during the preparation of the carbon. Alkali sorption occurs principally on carbons activated at temperatures near 400°C., and is attributed to the presence of phenolic and lactone functional groups on the carbon surface. Carbons which sorb acid usually are activated at temperatures near 1000°C. the acid reaction in this case is assumed to take place with chromene (benzpyran) structures on the surface. 

The serum cholesterol-lowering agent mevinolin (lovastatin) is shown here. Identify the ester and lactone functional groups of lovastatin, and for each, write the structures of the carboxylic acid and alcohol from which the ester and lactone are formed. 

Based on infrared evidence, ester groups in natural rubber were initially reported to be due to the presence of lactone functional groups. " Subsequently, C-NMR studies on deproteinized natural rubber showed that the ester groups were due to the presence of fatty acids bonded to the rubber molecule, of which 80% was saturated fatty acids and 20% unsaturated fatty acids. The fatty acids were later identified to be the acyl component of phosphoHpids hnked to the a-terminal end of the rubber molecule. The phospholipids were also postulated to be the branching point of the natural rubber molecule. The effects of these groups on natural rubber s properties have been discussed above. 

The intramolecular reaction oF allcenes with various O and N functional groups offers useful synthetic methods for heterocycles[13,14,166]. The reaction of unsaturated carboxylic acids affords lactones by either exo- or endo-cyclization depending on the positions of the double bond. The reaction of sodium salts of the 3-alkenoic acid 143 and 4-alkenoic acid 144 with Li2PdCl4 affords mostly five-membcrcd lactones in 30-40% yields[167]. Both 5-hexe-noic acid (145) and 4-hexenoic acid (146) are converted to five- or six-mem-bered lactones depending on the solvents and bases[168]. Conjugated 2,4-pentadienoic acid (147) is cyclized with Li2PdCl4 to give 2-pyrone (148) in water[i69]. 

Huonnations with DAST proceed with high chemoselectivity In general, under very mild reaction conditions usually required for the replacement of hydroxyl groups, other functional groups, including phenolic hydroxyl groups [112], remain intact This provides a method for selective conversion of hydroxy esters [95 97] (Table 6), hydroxy ketones [120, 121], hydroxy lactones [722, 123], hydroxy lactams [124] and hydroxy nitriles [725] into fluoro esters, fluoro ketones, fluoro lactones, fluoro lactams, and fluoro nitnles, respectively (equations 60-63)... 

An intramolecular reaction requires the presence of two suitably positioned functional groups, the substrate function and the reagent function, in the same molecule. The demonstration of an intramolecular process is obvious when the product is cyclic, as in this lactonization ... 

Although no small molecule gets eliminated, the reaction can be considered a condensation polymerization. Monomers suitable for polymerization by ring opening condensation normally possess two different functional groups within the ring. Examples of suitable monomers are lactams (such as caprolactam), which produce polyamides, and lactons, which produce polyesters. 

Figure 3. Schematic representation of the common functional groups that are present on carbon (a) quinone (b) phenol (c) carboxyl (d) carbonyl (e) lactone (f) hydrogen.

Radical cyclization is compatible with the presence of other functional groups. Treatment of XCH2CON(R)-C(R )=CH2 derivatives (X = Cl, Br, 1) with Ph3SnH and AIBN led to formation of a lactam via radical cyclization. " Cyclization of N-iodoethyl-5-vinyl-2-pyrrolidinone led to the corresponding bicyclic lactam, " and there are other examples of radical cyclization with molecules containing a lactam unit " or an amide unit. Radical cyclization occurs with enamines as well. Photochemical irradiation of A,A-dialIyl acrylamide leads to formation of a lactam ring, and in this case thiophenol was added to generate the phenylthio derivative. Phenylseleno N-allylamines lead to cyclic amines. co-Iodo acrylate esters cyclize to form lactones. " ... 

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