Dilactone

Reactions. Mahc acid undergoes many of the characteristic reactions of dibasic acids, monohydric alcohols, and a-hydroxycarboxyUc acids. When heated to 170—180°C, it decomposes to fumaric acid and maleic anhydride which sublimes on further heating (see Maleic anhydride, maleic acid, AND FUMARIC acid). MaUc acid forms two types of condensation products linear malomalic acids and the cycHc dilactone or maUde it does not form an anhydride. 

Heat. When heated, succinic acid loses water and forms an internal anhydride with a stable ring stmcture. Dehydration starts at 170°C and becomes rapid at 190—210°C (25). Further heating of succinic anhydride causes decarboxylation and the formation of the dilactone of gamma ketopimelic acid (26) (eq. 1). The same reaction takes place at lower temperatures in the presence of alkaU. 

Succinic anhydride is stabilized against the deteriorative effects of heat by the addition of small amounts (0.5 wt %) of boric acid (27), the presence of which also decreases the formation of the dilactone of gamma ketopimelic acid (28). Compared with argon, CO2 has an inhibiting effect on the thermal decomposition of succinic acid, whereas air has an accelerating effect (29,30). 

Syntheses of macrocyclic musks, among them lactones, dilactones, and oxalac-tones 99S1707. 

A short enandoselecdve synthesis of f- -f/f,/f -pytenophorin, a naturaUy occurring and-fun-giil 16-membered macrohde dilactone, is prepared from fS -5-nitropentan-2-ol via the Michael addidon and Nef reacdon fScheme 4.23. The choice of base Is important to get the E-alkene in the Michael addidon, for other bases give a rruxture of and Z-alkenes. The reqidslte chiriil fS -5-nitropentan-2-ol Is prepared by enandoselecdve redncdon of 5-nitropentan-2-one v/ith baker s yeast. ... 

Derivatives formed by modifying the carboxy group (salts, esters, lactones, lactams, acyl halides, amides, nitriles etc.) are named by the methods of 2-Carb-20.2. Dilactones, half-esters, amic acids etc. are named by the methods of [13, 14]. In cases of ambiguity, Iocants should be specified. 

More definitive evidence of enzymatic attack was obtained with 1 1 copolymers of e-caprolactone and 6-valerolactone crosslinked with varying amounts of a dilactone (98,99). The use of a 1 1 mixture of comonomers suppressed crystallization and, together with the crosslinks, resulted in a low-modulus elastomer. Under in vitro conditions, random hydrolytic chain cleavage, measured by the change in tensile properties, occurred throughout the bulk of the samples at a rate comparable to that experienced by the other polyesters no weight loss was observed. However, when these elastomers were implanted in rabbits, the bulk hydrolytic process was accompanied by very rapid surface erosion. Weight loss was continuous, confined to the... 

FIGURE 23 Rate of enzymatic surface erosion of a 1 1 copolymer of e-caprolactone and 6-valerolactone, crosslinked with a dilactone to form an elastomer. The effect of substitution of the e-caprolactone nucleus is also shown. (From Ref. 98). 

FIGURE 24 Rate of enz3nnatic surface erosion of e-caprolactone crosslinked with 12 mol % of the dilactone, 2,2-bis( e-caprolactone-4-yl)propane. (From Ref. 98.)... 

Molecules in real solvents can exist in one or more tautomeric forms. The use of different tautomers in calculations can lead to significant variation in the estimated log P values (Pig. 15.1). Accurate prediction of the dominant tautomer requires ah initio calculahons. Due to speed limitations such calculations are not feasible for virtual screening and prediction of large compound collections. Moreover, the interpretation of the results can also be difficult, for example, the lacton-lactim (Pig. 15. IB) is the stable form of maleic hydrazide in the gas phase but the difference between this and the dilacton form (Pig. 15.1C and D) disappears in solution... 

Fig. 15.1 Different tautomeric forms, dilactim (A), lacton-lactim (B) and dilacton (C and D), of maleic hydrazide (CAS-RN 123-33-1), log P = -0.56 (-0.84 in the BioByte StarList [10]).

Ahmed M, Rahman MT. Alimuzzaman M, Shilpi JA. Analgesic sesquiterpene dilactone from Mikania cordata. Fitoterapia 2001 72 919-921. 

Herz W, Subramaniam PS, Santhanam PS, Aota K, Hall AL. Structure elucidation of sesquiterpene dilactones from Mikania scandens (L.) Willd. J Org Chem 1970 35 1453-1464. 

Diethyl 7-oxopimelate has been prepared by saturating an ethanol solution of furylacrylic acid 3-7 or 7-oxopimelic acid dilactone 5 with hydrogen chloride. It was found as a by-product in the esterification of furylacrylic acid with ethanol in the presence of />-toluenesulfonic acid.8 This procedure is a modification of the original Marckwald process.3 4... 

Perhydropyrido[l,2-A][l,2]oxazines have been utilized as key intermediates in a stereospecific total syntheses of (—)-pumiliotoxin C and 5-< />z-pumiliotoxin C <1996J(P1)1113>, and the marine alkaloids (—)-lepadins A, B, and C and macrocyclic dilactones, (+)-azimine and (+)carpaine <20000L2955, 2001JOC3338, 2003OL3839>. In the total synthesis of the marine alkaloids ( )-fasicularin and ( )-lepadiformine, perhydro[l,2]oxazino[3,2 /]quinolines were used to control the stereochemistry <2000JA4583, 2000TL1205>. 

The formation of this analog CXI of L-ascorbic acid containing one enolic hydroxy group is therefore responsible for the reducing properties displayed by the two dilactones CIX and CX and the two ester lactones CVII and CVIII of D-glucosaccharic acid. 

The methylated analog CXV of L-ascorbic acid, 2,5-dimethyl-A4-D-glucosaccharo-3,6-lactone methyl ester has been obtained by simultaneous enolization and methylation of a number of substances. For instance it is derivable by treatment, with silver oxide and methyl iodide, of D-glucosaccharo-1,5 3,6-dilactone (CIX), D-glucosaccharo-1,4 ... 

Phenyl cyclopropenone is not capable of thermal dimerization. On treatment with Cu2+ ions, however, a well-defined tetramer is formed54, to which structure 265 of a polyene dilactone was assigned. Its generation can be rationalized via 264 with both the above dimerization types contributing in metal-catalyzed reactions. 

In a very thorough investigation of the reactions of hexaric acid lactones, and particularly dilactones, with sodium methoxide, F. Smith138,139 invariably obtained unsaturated products, at that time thought to be formed by isomerization and enolization. Hence, for alkyl D-glucofuranosidurono-6,3-lactones, also of bicyclic structure, similar reactions were believed24,25 to account for their unusual behavior in alkaline solutions. 

Transformations of Methyl 5-0-Benzyl-2-0-methyl-/3-I)-glueofuranosidurono-6,3-lae-tone (86) to Dimethyl (Z,E)-2-Methoxy-5-(phenylmethoxy)-2,4-hexadienedioatevl (87). ( Elimination employing DBU b oxidation with silver oxide-sodium hydroxide followed by diazomethane esterification c acidic glycoside cleavage, oxidation by dimethyl sulfoxide-acetic anhydride with formation of 5-0-benzyl-2-0-methyI-D-glucaro-1,4 6,3-dilactone, elimination by using DBU, followed by short treatment with diazomethane d elimination by DBU with subsequent diazomethane esterification e sodium borohydride in hexamethylphosphoric triamide 1 catalytic oxidation followed by short treatment with diazomethane " dimethyl sulfoxide-sulfur trioxide-pyridine-triethylamine.150)... 

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