Maleic acid, 2- -, methyl ester, preparation

Diels-Alder Reaction. By means of the Diels-Alder reaction a considerable number of hydrobiphenyls have been prepared,486 from which it should be possible to obtain unsymmetrical biaryls by dehydrogenation. Only a few of the adducts have been converted to the completely aromatic compounds. o-Terphenyl has been prepared from the adduct of maleic anhydride and 3,4-diphenylcyclopentadienone,436 and p-terphenyl has been obtained in practically quantitative yield from the adduct of the methyl ester of acetylenedicarboxylic acid and 1,4-diphenylbutadiene.43d... 

For the synthesis of (69), the enol ether (71) from the indanone (70) was carboxylated with COa-n-butyl-Iithium in THF at —70 C to yield (72). The methyl ester (73) was converted into (75) via the maleic anhydride adduct (74), essentially as described in earlier work. Lithium aluminium hydride reduction followed by oxidation with dicyclohexylcarbodi-imide afforded the aldehyde (76). This was condensed with excess (77) to yield a mixture of the diastereomers (78). Oxidation with chromium trioxide-pyridine in methylene dichloride gave (79), which could be converted into the diketone (80) by treatment with excess benzenesulphonylazide. The diketo-lactam (81) was prepared from (80) as described for the synthesis of the analogous intermediate used in the synthesis of napelline. Reduction of (81) with lithium tri-t butoxyaluminohydride gave the desired dihydroxy-lactam (82). Methylation of (82) with methyl iodide-sodium hydride gave (83). Reduction of this lactam to the amine (84) with lithium aluminium hydride, followed by oxidation with potassium permanganate in acetic acid, gave (69). 

Miscellaneous Reactions. Trimethylsilyldiazomethane converts acid- and base-sensitive maleic anhydride derivatives into the corresponding bis(methyl esters) (eq 70). Terminal silyl enol ethers are conveniently prepared from aldehydes by first treating the carbonyl compound with TMSC(Li)N2, followed sequentially by methanol and Rh2(OAc)4 (eq 71). The method works well with base-sensitive substrates and is superior to the attempted regioselective deprotonation/O-silylation of the corresponding methyl ketone. ... 

The monomer was synthesized into 2 step process and the preparation process is described elsewhere [88]. In brief, the reaction mixture of L-leucine, thionyl chloride (SOCI2), methanol (MeOH) at -10 °C was brought to room temperature after stirring for 15 h. After completion of reaction, methanol and excess thionyl chloride were removed by distillation under reduced pressure and the residue was crystallized from diethyl ether. After filtered and dried under vacuum, (5)-leucine methyl ester hydrochloride was obtained as a white powder which was suspended into ethyl acetate (EtOAc), and triethylamine (EtsN) was dropwise added, stirred over 10 min, and collected by suction filtration. Maleic anhydride dissolved into ethyl acetate was added into the filtrate at room temperature, stirred over 24 h. The mixture was washed by H2O, saturated brine, and dried over Na2S04, and concentrated to obtain (S)-maleamic acid-L-leucine methyl ester ((5)-MLMA) as white powder. 

Several polymers were found to fit all or most of the above criteria and were used to prepare the carrier films. Many polymers have been used for this purpose, viz., ethyl cellulose, poly(y-benzyl glutamate), poly(vinyl acetate), cellulose acetate phthalate, and the copolymer of methyl vinyl ether with maleic anhydride. In addition to the base polymers, plasticizers were often needed to impart a suitable degree of flexibility. Plasticizers, which are found to be compatible with polymeric materials include, acetylated monoglycerides, esters of phthalic acid such as dibutyl tartarate, etc. An excipient was usually incorporated into the matrix of the carrier films. The excipients used were water-soluble materials, which are capable of creating channels in the polymer matrix and facilitate diffusion of the drug. PEGs of different molecular weights were used for this purpose. 

Methoxy-2-furyl alcohols can be converted to ylidenebutenolides (93) by reaction with zinc chloride/ The corresponding cis-methyl 4-oxo-2-enoate is also formed but to a lesser extent (ca. 25% of the total yield). Further work on the preparation of ylidenebutenolides (93 R = COR ) by Wittig reactions using maleic anhydride and stabilized phosphoranes has been reported. The stereochemistries of the products have been assigned and it has been shown that the relatively unstable acid (93 R = CO2H) can be obtained via the t-butyl ester (93 R = CO2BU ). 

Side-chain polymers are usually prepared in the form of copolymers with NLO-active moieties attached on the backbone via flexible spacers such as methylene units. Examples are copolymers of methyl methacrylate and chromophore-substituted methacrylate monomers [53,61-63], poly(styrene-fy -acrylic acid ester) [54], and alternating styrene-maleic-anhydride copolymer [64], and there are many others. 

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