Lactone ester

The paraffin wax is oxidized by air in a liquid phase process at 110-130°C. Catalysts for this radical reaction are cobalt or manganese salts [54]. The quality of the obtained mixture of homologous carboxylic acids is impaired by numerous byproducts such as aldehydes, ketones, lactones, esters, dicarboxylic acids, and other compounds. These are formed despite a partial conversion of the paraffin and necessitate an expensive workup of the reaction product [50,55]. 

The photolysis of carboxylic acids and derivatives as lactones, esters and anhydrides can yield decarboxylated products 253>. This reaction has been utilized in the synthesis of a-lactones from cyclic diacyl peroxides 254) (2.34) and in the synthesis of [2,2]paracyclophane by bis-decarboxylation of a lactone precursor (2.35) 255). This latter product was also obtained by photoinduced desulfurization of the analogous cyclic sulfide in the presence of triethyl phosphite 256). 

A new method, reported by Pearlman (262), for the preparation of Woodward s key building block also constitutes a new synthesis of reserpine as well as deserpidine. In the key step of the synthesis an internal (2ir + 2-tt] photocycliza-tion of dienone 518 gave cyclobutane derivative 519 with the established stereochemistry. Methanolysis and subsequent peracid treatment of 520 yielded lactone ester 521. Repeated methanolysis and retroaldol fission of the cyclobutane... 

The procedure that Kuhn and Baschang99 had reported for the synthesis of NeuAc was extended by Hershberger and Binkley100 to a synthesis of KDO, as follows. Condensation of di-ter -butyl oxalacetate (85 see Scheme 25) with D-arabinose gave the epimeric mixture of lactone esters, 86 and 87, which was separated by fractional recrystallization. When 86 was heated in aqueous solution, the enol lactone, 88, was produced from 87, an enol lactone diastereomeric with 88 was obtained under these conditions. Compound 88 was converted into ammonium KDO by treatment with aqueous ammonia. 

Coumarin. The coumarin moiety is found in a number of important drugs. This is a bicyclic heterocycle containing two six-membered rings and two oxygens, one endo-cyclic, one exocyclic. Since the coumarin contains an intramolecular lactone ester, it undergoes hydrolysis to yield a carboxylic acid and a phenol. 

Many cheeses contain the same or similar compounds but at different concentrations and proportions chromatograms of some cheese varieties are shown in Figure 10.25. The principal classes of components present are aldehydes, ketones, acids, amines, lactones, esters, hydrocarbons and sulphur compounds the latter, e.g. H2S, methanethiol (CH3SH), dimethyl sulphide (H3C-S-CH3) and dimethyl disulphide (H3C-S-S-CH3), are considered to be particularly important in Cheddar cheese. The biogenesis of flavour compounds has been reviewed by Fox et al. (1993, 1996a) and Fox, Singh and McSweeney (1995). 

Notes A combination of phosphorus pentasulfide and hexamethyldisiloxane can be used to prepare thionoesters and thionolactones in comparable yields and with a simplified workup.1 A solvent-free conversion of ketones, lactones, esters and amides, to the corresponding thio analogs with Lawesson s Reagent.2 See also Belleau s and Daw ,v Reagents. 

The Diels-Alder reaction of 3-methoxyfuran with octyl vinyl ketone took place at room temperature in quantitative yield to afford exclusively the endo cycloadduct (27) (81CC221). Reduction of the carbonyl group with lithium tri-r-butoxyaluminum hydride produced a single alcohol (28). Ozonolysis of the double bond followed by Jones oxidation yielded the lactone ester (29). Hydrolysis of the ester and lead tetraacetate oxidation gave the lactone acetate. This was converted by further hydrolysis and Jones oxidation to the bis-lactone (30), a known intermediate in the synthesis of ( )-isoavenaciolide (Scheme 6). 

Ethylene oxide has also been condensed with 2-carbethoxycydo-pentanooe, 8 g-oarbethoxyoydohexanone,182 and a-carbethoxy-c mphor. 17 The primary products in these reactions undergo cleavage before they can be isolated, yielding lactone esters instead of keto-lactonea (Eqs. 872 and 873). 

Certain uneaturated fatty acids give lactone esters on treatment with peracetic acid, presumably by intramolecular attack of the carboxyl function on the initially-formed epoxide ring. Thus, 4,8-cpnxypentanoic acid generated by peracetic add oxidation of 4 pentenoie acid undergoes cleavage to give a five-membered lactone as... 

Intermediate 69 can either yield aZ (hydroxy-ester) or an E (lactone) ester. Intermediate 70 can only yield an E ester (lactone) whereas intermediate 7 can produce two esters, the hydroxy-ester having an E conformation and the lactone. Thus, primary stereoelectronic effects allow the cleavage of intermediates 69-71 to produce either the hydroxy-ester or the lactone prod-... 

If one performs the transformation in an alcohol such as methanol with Meldrum s acid 35 as the 1,3-dicarbonyl compound, an opening of the Meldrum s acid moiety after the cydoaddition to give a lactone ester is observed. Thus, reaction of aldehyde 93 with Meldrum s acid 35 and ethyl vinyl ether 88 in methanol gave 94 (Scheme 5.16) [la]. 

The starting material is a cyclic ester, a lactone. Esters undergo saponification in aqueous base to give an alcohol and a carboxylate salt. 

Related studies on meso tricyclic anhydrides were published in 1988 and 1990 by Aitken et al. [7, 8]. Their best result was achieved in the methanolysis of the tetracyclic anhydride 6 with (—)-quinine (2) as catalyst (Scheme 13.2 57% yield of the lactone ester 7 with 76% ee). The enantiomeric purity of the tricyclic lactone-ester 7 could be increased significantly (> 99% ee) by subsequent recrystallization in the presence of (—)-quinine (2). 

In addition to their direct role in cheese flavor, FFAs also act as precursors for a range of other volatile flavor compounds such as K-methyl ketones (alkan-2-ones), secondary alcohols, hydroxyacids, lactones, esters, and thioesters (Collins et al., 2003a, 2004 McSweeney, 2004). General pathways though which FFAs are catabolised are shown in Figure 8. 

Quantification of FFAs in dairy products, especially in cheese, is particularly important due to the impact of some FFAs on flavor. However, FFAs act as precursors of a wide range of flavor compounds (e.g., methyl ketones, lactones, esters and aldehydes), (Singh et al, 2003). The extent of lipolysis in cheese varies widely between varieties (Table 19.2). Typically, those cheeses with more than 3000 mg/kg have a characteristic lipolytic aroma/flavor and lipolysis plays an important role in their ripening. A major difficulty in quantifying FFAs in cheese is the distribution of FFAs of different chain length within the cheese matrix. SCFFA (C4 o—C8 0) partition mainly into the aqueous phase, whereas medium (Cio q—C14 0) and longer... 

Lipid-derived volatile compounds play an important role in the flavor of foods. These compounds contribute to the characteristic notes of many dairy flavors, but are also responsible for many off-flavors. Parliament and McGorrin (2000) reviewed those volatile compounds important in milk, cream, butter, cultured creams and cheese. The pathways involved in the degradation of milk fat have also been reviewed by McSweeney and Sousa (2000) and compounds include FFAs, methyl ketones, lactones, esters, aldehydes, primary and secondary alcohols, hydroxyacids, hydroperoxides and ketoacids. 

The Stobbe condensation was reviewed by Johnson and Daub in 1951.5 They postulated the formation of a lactonic ester as an intermediate (see Scheme 2). The base-induced elimination of the lactonic ester led to the regiospecific formation of the half-ester, which is esterified to yield compound 2. 

Ozonolysis<359) of 6,14-endo-ethenotetrahydrothebaines has afforded aromatic ring cleaved products. Tertiary alcohols (214, R = Me, R1 = alkyl R2 = Me, n-Pr or CBM), for example, gave the lactonic esters 220, which had analgesic potencies similar to that of morphine. This somewhat surprising result suggested that the aromatic pharmacophore in opioids was not an essential feature for a compound to elicit opioid-like responses. The authors(359) indicated that this could be the case if pharmacophores elsewhere in the molecule compensated for the loss of aromatic binding. 

Lactonization. Esters and lactones can be prepared using a trichlorobenzoic mixed anhydride, prepared by reaction of an acid with trichlorobenzoyl chloride. Thus the anhydride reacts with an alcohol in the presence of 4-dimethylamino-pyridine to form an ester in yields usually >90%. The same method can be used for lactonization. Nine- to thirteen-membered rings can be prepared in 35-65% yield. This method was used for synthesis of methynolide (6), a macrolide antibiotic, from a sequence shown in equation (I). 

Homoconjngate addition to cyclopropanes. Corey and Fuchs have investigated the reaction of cyclopropanes with organocopper reagents as a possible synthetic route to prostanoids. For example, the tricyclic lactone ester (1) reacts with divinylcopper-lithiura (2.0 eq.) in ether at -12° (19 hr.) to give the vinylcyclopentane lactone ester (2). Tliis product was treated directly with lithium iodide (5 eq.) in pyridine (1,615-616) at reflux for 3 hr. to give the lactone (3) in about 37% yield. 

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