Of a lactone

The p-phenylbenzoate ester was prepared to protect the hydroxyl group of a prostaglandin intermediate by reaction with the benzoyl chloride (Pyr, 25°, 1 h, 97% yield). It was a more ciystalline, more readily separated derivative than 15 other esters that were investigated. It can be cleaved with K2CO3 in MeOH in the presence of a lactone. ... 

Xanthotoxin (Methoxalen, 9-methoxyfuro[3,2-g][l]benzopyran-7-one) [298-81-7] M 216.2, m 146-148 , 148 , 148-149 . Purified by recrystn from CgH6-pet ether (b 60-80°) as silky needles, Et0H-Et20 as rhombic prisms or hot H2O as needles. It is soluble in aqueous alkali due to ring opening of a lactone but recyclises upon acidification. It has UV EtOH at 219, 249 and 300nm (log e... 

Ring opening of a lactone, e.g. of e-caprolactone with dihydroxy or trihydroxy initiators ... 

Callow, Gulland and Virden obtained evidence of the presence of four replaceable hydrogen atoms and of a lactone group, thus accounting for six out of the ten oxygen atoms required by the formula. The remaining... 

The use of an ester as an anion-stabilizing group for a lithiated epoxide was demonstrated by Eisch and Galle (Table 5.5, Entry 11). This strategy has been extended to a,P-epoxy-y-butyrolactone 191, which could be deprotonated with LDA and trapped in situ with chlorotrimethylsilane to give 192, which was used in a total synthesis of epolactaene (Scheme 5.45) [69], The use of a lactone rather than a... 

Enzyme-catalyzed stereoselective hydrolysis allows the preparation of enantio-merically enriched lactones. For instance. Pseudomonas sp. lipase (PSL) was found to be a suitable catalyst for the resolution of 5-undecalactone and 5-dodecalactone (Figure 6.20). Relactonization of the hydroxy acid represents an efficient method for the preparation of both enantiomers of a lactone [67]. 

Reactive polyesters were enzymatically synthesized. Lipase catalysis chemoselecfively induced the ring-opening polymerization of a lactone having exo-methylene group to produce a polyester having the reactive exo-methylene group in the main chain (Scheme 16). This is in contrast to the anionic... 

If a polymer formed initially by the addition of monomers to a fixed number of centers is subjected to conditions permitting interchange processes to occur, either during polymerization or subsequent thereto, the distribution will broaden. Polymerization of a lactone, for example, according to the mechanism... 

Cells of Acinetobacter sp. NCIB 9871 grown with cyclohexanol carried out enantiomeri-cally specific degradation of 5-bromo-7-fluoronorbornanone and production of a lactone with >95% enantiomeric excess (Levitt et al. 1990). 

Thus, the structure of a-lactones, as reflected in their observed TRIR spectra, is dependent both on substituents at the a-carbon and on solvent polarity, with electron-donating substituents and polar solvents favoring a zwitterionic ring-opened structure. B3LYP calculations using SCRF methods to account for solvent polarity are consistent with these experimental conclusions. 

The reaction in Entry 5 was used in the syntheses of linetin, which is an aggregation pheromone of the ambrosia beetle. In Entry 6, a transannular 5-exo cyclization occurs. Entry 7 is an example of formation of a lactone by carboxylate capture. In this case, the product was isolated as the mercurochloride. 

The hydrogenolysis proceeds usually with inversion on Pd. This ability of Pd was used for stereospecific hydrogenation of a lactone during the synthesis of a phenyl kainoid on 10% Pd(OH2)/C in AcOEt at 40°C (Scheme 4.44).214... 

Fiandanese and coworkers [103] described a new approach for the synthesis of the butenolides xerulin (6/1-207) and dihydroxerulin (6/1-208), which are of interest as potent noncytotoxic inhibitors of the biosynthesis of cholesterol (Scheme 6/1.53). The key transformation is a Pd°-catalyzed Sonogashira/addition process of 6/1-204 or 6/1-206 with (Z)-3-iodo-2-propenoic acid 6/1-205, which is followed by the formation of a lactone to give 6/1-207 and 6/1-208, respectively. 

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). 

The change with the concentration cannot be due to the reversible formation and decomposition of a lactone of the ordinary type because we get the effect with ethyl malate as well as with malic add. The change cannot be due to a reversible conversion of laevo-malic acid into dextro-malic add, because then a solution of equivalent amounts of dextro- and laevo-malic acids would become optically active on addition of salts, adds and bases. Hydrochloric add or sodium hydroxide imparts no activity to a solution of d/-malic add. The changes on adding electrolytes to a solution of dextro-malic add are equal and opposite in sign to the changes in laevo-malic acid under the same conditions. 

Ascorbic acid, which is closely related to the sugars and is no doubt derived from them in the metabolism of the cells of plants, has been shown to be identical with vitamin- C (Szent-Gyorgyi). It has the constitution of a lactone of a-keto-i-gulonic acid (W. N. Haworth, T. Reichstein) ... 

Oxazolidin-5-ones (11.110) are structurally related to oxazolidines, combining the motifs of a lactone and an O-Mannich base. These derivatives have already been discussed in Sect. 8.7.5. However, they serve here as a transition to [3,1 ]benzoxazepin-4-ones as an example of potential prodrugs. Thus, [3,l]benzoxazepin-4-one derivatives (11.111, R = H or Me, R = H, Me, Et, or Ph) were prepared from diclofenac (11.112) [137]. These prodrugs were stable for at least a few hours in simulated gastric juice, but, when administered to rats elicited an anti-inflammatory response comparable to that of diclofenac. One compound (11.111, R = Me, R = Et) was even more active than diclofenac without producing the gastric mucosal injury (ulcers) caused in all rats by diclofenac itself. Here again, there was no indication of whether the mechanism of hydrolysis is chemical or enzymatic. 

Mass spectroscopic analysis of the gas phase revealed that 53 is formed with the concomitant generation of H2. Based on the proposed catalytic cycle for silyUbrmylation (Scheme 6.12), the formation of 53 and 54 can be explained by the intervention of 55 (n=2), which plays a pivotal role in the differentiation between intramolecular nucleophilic attack of the hydroxy group and reductive elimination of 54. Thus, the addition of base is believed to accelerate the conversion of 55 to the rhodate anion 56. This notation is supported by the fact that the introduction of a strong base such as DBU is advantageous for the selective formation of a lactone framework. 

The Helquist approach to quadrone begins in the same fashion and has many close similarities to the Danishefsky effort. Importantly, however, a key element of novelty in Scheme LIII is the deplopment of a lactone annulation procedure which bypasses the regiochemical complications earlier encounter . 

By monitoring the reaction of 13 with base by CNMR spectroscopy, the 4,5-epoxy carboxylate C was observed after 5 min together with a small amount of the the final product D. The reaction was complete within about 4 h. Opening of the epoxide C to give D was most likely preceded by an intramolecular substitution by the carboxylate at C-4. This resulted in an inversion at C-4 and formation of a lactone, which was immediately opened in the basic medium. The intramolecular exo-opening rather than an endo-opening... 

Alternatively, some of the desired amino acid functionality may be contained within the nitrone fragment, as in the synthesis of homochiral allyl glycines by Katagiri et al. (151), which reveals the carboxylate by hydrolysis of a lactone in the dipole (Scheme 1.24). Here, thermolysis of nitroso Meldrum s acid (112) via a nitrosoketene intermediate 113 and reaction with 1-menthone gave the separable nitrones 114a (26%) and 114b (28%) by a [3 + 2] cycloaddition, although a... 

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