Carbon 8-lactone

Conventional ring-opening polymerization of cyclic anhydrides, carbonates, lactones, and lactides require extremely pure monomers and anhydrous conditions as well as metallic catalysts, which must be completely removed before use, particularly for medical applications. To avoid these difficult restrictions, an enzymatic polymerization may be one of the more feasible methods to obtain the polyesters. This method was first reported by two independent groups (Kobayashi [152] and Gutman [153]) who showed that lipases, enzymes capable of catalyzing the hydrolysis of fatty acid esters, can polymerize various medium-sized lactones. 

In planning the synthesis of a series of carbapyranoses in their chiral non racemic format, Zanardi and co-workers [7d] utilized the seven-carbon lactone 149, in turn prepared by elaboration of butenolide 12 (vide supra, Scheme 3). 

Macrolactonizathn with inversion. Lactonization of the optically active seco-acid 1 with P(C sH,), and DEAD followed by hydrolysis of the acetonide group gives the cyclic dilactonc colletodiol (2), formed with inversion of configuration at the hydroxyl-bearing carbon. Lactonization of 1 with 2,4,6-trichlorobenzoyl chloride and tdethylamine (9, 478-479) furnishes 6-epicolletodiol after deprotection. 

Cleavage of lactones and carbonates. Lactones and carbonates react with bromotrimethylsilane to afford bromocarboxylic acid derivatives (equation I) and bromohydrin trimethylsilyl ethers (equation II), respectively acyclic, aliphatic esters do not react with bromotrimethylsilane. lodotrimethylsilane reacts in an analogous fashion with lactones, but in reaction with ethylene carbonate the main product is 1,2-diiodoethane (equation III). The >-bromocarboxylate derivatives are converted into acid chlorides by reaction with SOCL (equation I). 

Succinimides can also be post-treated to provide additional performance properties one of the most commonly used reagents is boric acid which delivers anti wear properties to a formulation [41], Post-treatments with other maleic anhydride-containing co-polymers, such as polyoctadecene succinic anhydride, yield dispersants with enhanced viscosity credit [42], Uses of other reagents, such as carbonates, lactones, sulphur dioxide, epoxides, oxalic acid and carbon disulphide, have also been disclosed [43],... 

Contrary to the previous examples of ring-forming reactions, the case of ring opening deserves mention. In the presence of zinc in acetic acid-water solution, terpenic enone-lactones undergo a reduction of the carbon-lactonic oxygen bond (Fig. 21) When the latter is axial the conversion is completed in 2 min. 

The preparation of the octa-Q-benzoyl-aldobiononitriles of cellobiose, gentiobiose, lactose, and maltose from the unprotected oximes has been effected by treatment with benzoyl chloride in pyridine at SO C. Reaction of melibiononitrile perbenzoate with methanolic ammonia yielded the 1,1-dibenzamido-derivative (37) as the major product, isolated in 38% yield.The erythro- and threo-cyanohvdrins (38) were obtained in a 4 1 ratio from 2,3-Q-isopropylidene-D-glyceraldehyde on reaction with trimethylsilyl cyanide, and were converted to the four carbon lactone synthons (39). The chiral hexane-1,6-dinitrile (40) has been synthesized CHjOH... 

Copolymerization is the one way to synthesize polymeric materials with desired properties and functions. The cyclic carbonate monomers are successfully copolymerized with various cyclic monomers, such as cyclic carbonates, lactones with/without substituents, lactide, and cyclic phosphates. TMC was copolymerized with lactide by PPL to produce poly(lactide-co-TMC)s having carbonate contents from 0 to 100% and having molecular weights of up to 21000. The glass transition temperature (Tg) of the copolymer was dependent on the carbonate content, and the Tg values linearly decreased from 35° (polylactide) to - 8° [poly(TMC)] [47]. TMC was also copolymerized with medium to large ring-sized lactones. As an example, TMC was copolymerized with PDL in toluene by lipase CA at 70 °C to yield random copolymers [135]. All the poly(PDL-TMC)s were highly crystalline, even those with an equimolar comonomer content and close-to-random distribution. Thermal stability improves with randomization of the comonomer distribution [136]. 

Benzoxazoles s. 13, 631 Potassium carbonate Lactones from bromocarboxylic acids s. 13, 291... 

Division III. Heterocyclic compounds (Heterocyclic stem nuclei). The carbon atoms are joined in closed rings which include one or more other kinds of atoms as ring components. Anhydrides and imides of dibasic acids, as well as lactones, lactams, etc. are thus included in this division... 

A highly successful route to stereoisomers of substituted 3-cyclohexene-l-carboxylates runs via Ireland-Claisen rearrangements of silyl enolates of oj-vinyl lactones. The rearrangement proceeds stereospeaifically through the only possible boat-like transition state, in which the connecting carbon atoms come close enough (S. Danishefsky, 1980 see also section 4.8.3, M. Nakatsuka, 1990). 

Open-chain carbon skeletons (including cyclic acetals, lactones, lactams, cyclic anhydrides, etc.)... 

Cyclopentene derivatives with carboxylic acid side-chains can be stereoselectively hydroxy-lated by the iodolactonization procedure (E.J. Corey, 1969, 1970). To the trisubstituted cyclopentene described on p. 210 a large iodine cation is added stereoselectively to the less hindered -side of the 9,10 double bond. Lactone formation occurs on the intermediate iod-onium ion specifically at C-9ot. Later the iodine is reductively removed with tri-n-butyltin hydride. The cyclopentane ring now bears all oxygen and carbon substituents in the right stereochemistry, and the carbon chains can be built starting from the C-8 and C-12 substit""" ... 

The wM-diacetate 363 can be transformed into either enantiomer of the 4-substituted 2-cyclohexen-l-ol 364 via the enzymatic hydrolysis. By changing the relative reactivity of the allylic leaving groups (acetate and the more reactive carbonate), either enantiomer of 4-substituted cyclohexenyl acetate is accessible by choice. Then the enantioselective synthesis of (7 )- and (S)-5-substituted 1,3-cyclohexadienes 365 and 367 can be achieved. The Pd(II)-cat-alyzed acetoxylactonization of the diene acids affords the lactones 366 and 368 of different stereochemistry[310]. The tropane alkaloid skeletons 370 and 371 have been constructed based on this chemoselective Pd-catalyzed reactions of 6-benzyloxy-l,3-cycloheptadiene (369)[311]. 

Allylalion of the alkoxymalonitrile 231 followed by hydrolysis affords acyl cyanide, which is converted into the amide 232. Hence the reagent 231 can be used as an acyl anion equivalent[144]. Methoxy(phenylthio)acetonitrile is allylated with allylic carbonates or vinyloxiranes. After allylation. they are converted into esters or lactones. The intramolecular version using 233 has been applied to the synthesis of the macrolide 234[37]. The /i,7-unsaturated nitrile 235 is prepared by the reaction of allylic carbonate with trimethylsilyl cyanide[145]. 

Silyl enol ethers are other ketone or aldehyde enolate equivalents and react with allyl carbonate to give allyl ketones or aldehydes 13,300. The transme-tallation of the 7r-allylpalladium methoxide, formed from allyl alkyl carbonate, with the silyl enol ether 464 forms the palladium enolate 465, which undergoes reductive elimination to afford the allyl ketone or aldehyde 466. For this reaction, neither fluoride anion nor a Lewis acid is necessary for the activation of silyl enol ethers. The reaction also proceed.s with metallic Pd supported on silica by a special method[301j. The ketene silyl acetal 467 derived from esters or lactones also reacts with allyl carbonates, affording allylated esters or lactones by using dppe as a ligand[302]... 

The reaction can be applied to the synthesis of q, /3-unsaturated esters and lactones by treatment of the ketene silyl acetal 551 with an allyl carbonate in boiling MeCN[356]. The preparation of the q,, 3-unsaturated lactone 552 by this method has been used in the total synthesis of lauthisan[357]. 

The slow oxidation of primary alcohols, particularly MeOH, is utilized for the oxidation of allylic or secondary alcohols with allyl methyl carbonate without forming carbonates of the alcohols to be oxidized. Allyl methyl carbonate (564) forms 7r-allylpalladium methoxide, then exchange of the methoxide with a secondary or allylic alcohol 563 present in the reaction medium takes place to form the 7r-allylpalladium alkoxide 565, which undergoes elimination of j3-hydrogen to give the ketone or aldehyde 566. The lactol 567 was oxidized selectively with diallyl carbonate to the lactone 568 without attacking the secondary alcohol in the synthesis of echinosporin[360]. 

Alkynyl)oxiranes also react with carbon nucleophiles to afford furan derivatives. Furanes of different types are obtained depending on the structure of the substrates. 7-Methyl-2-ethynyloxirane (95) reacts with acetoacetate to give the furan 97 by the elimination of formaldehyde from the cyclized product 96. The hydroxy ester of the alkylidenefuran 98 and the corresponding lactone 99 are obtained by the reaction of i-methyl-2-(2-propynyI)oxirane[40, 42]. 

Substituted allylic alcohols are carbonylated using the o.vidizing system of PdCl2 and CuCU in the presence of HCl and oxygen at room temperature and 1 atm of CO to give the 7-lactone 16 in moderate ylelds[20]. Carbonylation of secondary and tertiary allylic alcohols catalyzed by Pd2(dba)j and dppb affords the 7-lactone 17 by selective attack of CO at the terminal carbon under fairly severe conditionsf21]. 

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