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Y-Lactones carboxylic acids

Treatment of dehydrooxoheteratisine (CD) with potassium tert-butoxide in feri-butanol leads to the y-lactone carboxylic acid, characterized as its methyl ester (CDXIV) [1787 cm i, (y-lactone), 1748 cm (cyclopentanone), 1728 cm i (C02Me, 1648 cm i (S-lactam)]. Its formation by cleavage of the initial retroaldol product (CDXII) to a S-lactone carboxylic acid (CDXIII) and subsequent isomerization to the y-lactone provides decisive proof for location of the tertiary hydroxyl at a position j8 to both the cyclopentanone and S-lactone carbonyls and four carbons removed from the S-lactone ether oxygen. [Pg.112]

Reduction of anhydrides to y-lactones. Carboxylic acid anhydrides are reduced by homogeneous hydrogenation catalyzed by this ruthenium complex... [Pg.654]

On treatment with hot aqueous alkali, only hydrolysis of the lactone ring occurs. However, on treatment of 19-oxodehydroheteratisine (24) with potassium t-butoxide in t-butyl alcohol, a y-lactone carboxylic acid (28) was isolated. This product may be formed as indicated in the Scheme. The rearrangement to (28)... [Pg.235]

Acetoxylichesterinic acid (neuropogolic acid) (29), 19-acetoxy-protolichesterinic acid (30), (-)-allopertusaric acid (31) and (-)-dihydropertusaric acid (32) are y-lactone carboxylic acids with an oxygen function in the side chain from Neuropogon trachycarpus (323)... [Pg.34]

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). [Pg.63]

Chiral a-methylene-y-lactones.1 (R)-( + )-Alkyl p-tolyl sulfoxides (2), readily obtainable in almost quantitative yield from (l),2 on lithiation (LiTMP) and reaction with lithium a-bromomethylacrylate (3) are converted into a-methylene-y-sulfinyl carboxylic acids (4), which can be separated by chromatography or crystallization. Reduction of optically pure 4 provides y-tolylthio acids [(S)-5], which on methylation and treatment with potassium f-butoxide are converted into (4R)-a-methylene-y-lactones (6), with inversion of chirality. [Pg.173]

Lactones are usually prepared by treating y-hydroxy carboxylic acids, esters, or amides with acid. Preferentially hydrochloric acid is used or however,... [Pg.588]

The reactivity of achiral Ru compounds for the hydrogenation of functionalized ketones has not been extensively studied. RuCl2 P(C6H5)3 3 reduces y-keto carboxylic acid at 180 °C to the corresponding y-lactone (Eq. 2.15) [115]. Heterogeneous Ru/C catalyzes the atmospheric pressure hydrogenation of furfural in water at 25 °C [86]. Under such mild conditions, glucose is industrially converted to sorbitol (Eq. 2.16) [116]. At elevated temperature and pressure, tetramethyl-l,3-cyclobutanedione can be converted to a 98 2 diastereomer mixture of the diol (Eq. 2.17) [117]. [Pg.20]

The electrochemical rearrangement of paraconic acids (CIV) [Eq. (52)], y-carboxy-3-lactones (CVI) [Eq. (53)] [168], and /6-keto carboxylic acid ethylene acetals (CVIII) [Eq. (54)] [169,170] has been known to proceed smoothly. y-Keto carboxylic acids (CX) and acetals (CXII) undergo decarboxylative rearrangement to afford esters (CXI and XCIII) as in Eqs. (55) and (56) [171,172]. [Pg.535]

J.2 y-Lactones by in situ cycUzadon of y-hydroxy carboxylic acid intermediates... [Pg.354]

Sulfinic acids will also open lactone rings by nucleophilic addition to form sulfonyl carboxylic acids thus, the y-lactone (6) yields the y-sulfonyl carboxylic acid salt (7)... [Pg.98]

Intramolecular cyclization is a useful method for the preparation of lactones and cyclic ethers [34], The most common examples are iodolactonization and iodoetherification, the former using a carboxylic acid derivative as the nucleophile and the latter relying on a hydroxy group. Thus, butyrolactones are available from Y, -unsaturated carboxylic acid derivatives [1,35,36], while unsaturated alcohols lead to cyclic ethers [37-40], Lactones are also available from a wide variety of nucleophiles such as carbonates [41], orthoesters [42], or carbamates [43,44], which can all be used in place of a carboxylate anion [44,45],... [Pg.108]

As well as the above-described intermolecular alcoholysis of esters, the intramolecular version has been successfully utilized for the synthesis of lactones from racemic hydroxy carboxylic acid esters (25-41, 64—66) (Table 11.1-22). High selectivity in the pig pancreas lipase-catalyzed enantiomer-differentiating lactonization of y-hydroxy carboxylic acid esters with formation of butyrolactones substituted in... [Pg.545]

Lactones are usually prepared by treating y-hydroxy carboxylic acids,454 455 esters,456 "464 or amides465 466 with acid. Preferentially hydrochloric acid310-459-461-466 js usec) or however, 4-toluenesulfonic acid456-457 or sulfuric acid454 458,465 give comparable results. With aldehyde 8 lactonization also occurs, presumably via initial hydrolysis to acid 9. 5-Ethoxyfuranone 10 is isolated as a mixture of diastereomers.310 No additional ethanol needs to be added. [Pg.588]

Oxetane-2-ones are also y lactones [4]. They are prepared by cyclodehydration of y hydroxy-carboxylic acids with phenylsulfonyl chloride in pyridine ... [Pg.40]

Barnett and Sohn (12, 13, see also 14) have discovered that the iodolactoni-zation of 6,Y-unsaturated carboxylic acid salts 21 yiold, under kinetically controlled conditions, the Y-iodo-e-lactones 39 in preference to the more stable 6-iodo-Y-lactones 42- Similar results were obtained in the course of the bromolactonization reaction. Thus, here again, the formation of a four-membered ring is more facile than that of a five-membered ring. This can be rationalized on the basis of Stork s analysis, i.e. the internal opening by the carboxylate anion of the three-membered ring iodonium ion (or bromonium) 38 39 is preferred over the other mode of opening 40- 41 for stereoelectronic reason. [Pg.169]

This stereoselective alkylation has been extended to y-hydroxyl-carboxylic acid that exists as a lactone." ... [Pg.1121]

This stoichiometric chemistry has been revisited in the last few years [60,79-82] and, for instance, applied to the s)mthesis of a-methylene-y-hydroxy carboxylic acids and their derivatives (c/s-p.y-disubstituted a-methylene-y-lactones) by means of nickel-mediated sequential addition of carbon dioxide and aldehydes into terminal or internal allenes [80, 81], or exploited for the preparation of P-hydroxycarboxylic acid derivatives by 02-oxidation of the Ni-n -allyl species (5.8)... [Pg.164]

CN (7a,17a)-7-(acetylthio)-17-hydroxy-3-oxopregn-4-ene-21-carboxylic acid y-lactone... [Pg.1895]

C24H420, 114002-10-7) see Desoxycortone acetate (lip,17Z)-l 1,21 -dibydroxypregna-5,17(20)-dien-3-one cyclic 1,2-etbanediyl acetal (C2,H3404 3546-74-5) see Hydrocortisone (3P,17a)-3,17-dihydroxypregn-5-ene-21-carboxylic acid y-lactone... [Pg.2358]

No reaction was observed between NO and ketones, y-lactones, or carboxylic acids. [Pg.385]

Besides fragmentation or rearrangement, the carboxylic acid anions, formed by an enzymatic hydrolysis, can also act as nucleophiles. Kuhn and Tamm used the asymmetric hydrolysis of meso-epoxy diester 8-28 with PLE to synthesize y-lactone... [Pg.533]


See other pages where Y-Lactones carboxylic acids is mentioned: [Pg.117]    [Pg.38]    [Pg.117]    [Pg.38]    [Pg.440]    [Pg.323]    [Pg.357]    [Pg.554]    [Pg.49]    [Pg.177]    [Pg.461]    [Pg.457]    [Pg.236]    [Pg.323]    [Pg.357]    [Pg.183]    [Pg.283]    [Pg.44]    [Pg.110]    [Pg.488]    [Pg.998]    [Pg.1059]    [Pg.2358]    [Pg.711]    [Pg.386]    [Pg.303]   
See also in sourсe #XX -- [ Pg.43 , Pg.215 ]




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