Trimethyl ester

J. Rebek, Jr., (1987) first developed a new synthesis of Kemp s acid and then extensively explored its application in model studies. The synthesis involves the straightforward hydrogenation (A. Steitz, 1968), esterification and methylation of inexpensive 1,3,5-benzenetricar-boxylic acid (trimesic acid 30/100 g). The methylation of the trimethyl ester with dimethyl sulfate, mediated by lithium diisopropylamide (V. J. Shiner, 1981), produced mainly the desired aff-cis-1,3,5-trimethyl isomer, which was saponified to give Kemp s acid. 

Pyrazolidine 2-AcetyI-5-(methoxycarbonyImethyI)-l-methyI-3,4,5-pyrazolidinetricarboxylic acid, trimethyl ester 79CB1719... 

H-Azepine-2-thione, hexahydro-1 -methyl- C NMR, 7, 498 <79AJC567> 4H-Azepine-2,6,7-tricarboxylic acid, trimethyl ester AG 7, 499 (72JA2770)... 

The diflorasone is reacted with orthoacetic acid trimethyl ester in the presence of toluene sulfonic acid to give diflorasone diacetate. 

Both the exchange and elimination are catalyzed by the addition of a small amount of a weak acid, such as propanoic acid. These reactions are usually conducted at the reflux temperature of the orthoester, which is about 110°C for the trimethyl ester and 140° C for the triethyl ester. Microwave heating has been used and is reported to greatly accelerate orthoester-Claisen rearrangements.232... 

Trimethyl orthoformate Orthoformic acid, trimethyl ester (8) Methane, trimethoxy- (9) (149-73-5)... 

At each stage, the location of the labelled material was followed by LSC of chromatographic fractions, with the dpm in steps (2) and (3) moving only with the fluorocitrate-containing fractions. In addition, capillary GC (30 m DB-5) was used to quantify citrate, isocitrate and fluorocitrate trimethyl esters and benzoates in each fraction. Finally, dpm were observed only in the erythro isomer of trimethyl 2-fluorocitrate benzoate. The progress of the purification is given in Table 2. Full details will be published separately(25). 

Synonyms Methyl phosphite phosphorus acid trimethyl ester TMP trimethoxyphos-phine... 

Seeds by Synthetic Tricarboxylic Acid Trimethyl Esters... 

Bromo-3,4,5-trifluorobenzene Benzene, 5-bromo-1,2,3-trifluoro- (13) (138526-69-9) Trimethyl borate Boric acid, trimethyl ester (8,9) (121-43-7)... 

The characterization of the semiquinone radical anion species of PQQ in aprotic solvents was undertaken to provide information about the electrochemistry of coenzyme PQQ and to give valuable insight into the redox function of this coenzyme in living systems <1998JA7271>. The trimethyl ester of PQQ and its 1-methylated derivative were examined in aprotic organic solvents by cyclic voltammetry, electron spin resonance (ESR), and thin-layer UV-Vis techniques. The polar solvent CH3CN was found to effectively solvate the radical anion species at the quinone moiety, where the spin is more localized, whereas the spin is delocalized into the whole molecule in the nonpolar solvent CH2CI2. 

Purified by recrystn from toluene + EtOH or H2O. It forms a 1.5 hydrate with m 216-218°, and a dihydrate at 110°. Purified also by conversion to the triethyl ester b 217-218°/10mm, 151°/lmm and distillate solidifies on cooling, m 36-37° and is hydrolysed by boiling in aq HC1. The trimethyl ester can be distd and recrystd from Et20, m 48-49°. [Newman and Lawrie JACS 76 4598 7954, Lukes and Galik Coll Czech Chem Comm 19 712 1954],... 

A famous use of electrochemical reduction of porphyrin systems is that used to convert a chlorophyll a derivative, chlorin-e6 trimethyl ester (64), into a chlorophyll b derivative, rhodin-g7 trimethyl ester (65) (71LA(749)109). Electrolysis of chlorin-e6 trimethyl ester gave the chlorin-phlorin which was photolyzed in dioxane/water to give the trans-d o (Scheme 7) this was simply transformed into rhodin-g7 trimethyl ester (65) to accomplish the first ever interconversion of a chlorophyll a series pigment into one of the companion b series. 

Pheophorbide a and pheoporphyrin a5 can be converted into chlorin ee, and chloropor-phyrin e6 (105), respectively, with alkali this transformation accomplishes rupture of the /3-keto ester function in ring f., providing compounds which are much less susceptible to degradative processes (vide infra). Methanolysis of chlorin e6 gives chlorin e trimethyl ester (64). Analogous reactions of pheophorbide b (94) give rhodin gy trimethyl ester (65), the exact analogue of chlorin in the b series. 

Several productive degradative transformations of chlorophyll a and b depend upon the ready oxidation of the ring E /3-keto ester. The so-called phase test involves aerial oxidation of the enolate anion produced by treatment of the ring e keto ester with alkali. One molecule of oxygen is consumed in this allomerization reaction to produce a hydroperoxide (111) which can fragment to give (112) after acidification, the unstable chlorin (113) is obtained, and this can be transformed into purpurin-18 (114) by evaporation, or into purpurin-7 trimethyl ester (115) by esterification with diazomethane. 

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