Methyl ester derivatives

The positions, numbers, and types of sugars on the anthocyanin molecule influence its bioaccessibility. Indeed, a recent human study reported that the acylation of anthocyaifins resulted in a sigififlcant decrease of anthocyanin recoveries in plasma and urine. In addition, anthocyanins form linkages with aromatic acids, aliphatic acids, and methyl ester derivatives, which can also affect their passage through the intestinal barrier. 

Vercellotti and associates121,126 were the first to apply the Helferich -Wedemeyer procedure127 (which uses mercury dicyanide as the acid acceptor) for the preparation of a glycosylamino acid, namely, 3-0-(2-acetamido-3,4,6-tri-0-acetyl-2-deoxy-/ -D-glucopyranosyl)-N-(2,4-di-nitrophenyl)-L-serine and -DL-threonine methyl ester derivatives (162). 

A route for the asymmetric synthesis of benzo[3]quinolizidine derivative 273 was planned, having as the key step a Dieckman cyclization of a tetrahydroisoquinoline bis-methyl ester derivative 272, prepared from (.S )-phcnylalaninc in a multistep sequence. This cyclization was achieved by treatment of 272 with lithium diisopropylamide (LDA) as a base, and was followed by hydrolysis and decarboxylation to 273 (Scheme 58). Racemization could not be completely suppressed, even though many different reaction conditions were explored <1999JPI3623>. 

Corr, L. T., Berstan, R. and Evershed, R. P. (2007a) Development of N acetyl methyl ester derivatives for the determination of 813C values of amino acids using gas chromatography combustion isotope ratio mass spectrometry. Analytical Chemistry 79, 9082 9090. 

An amine-containing surface, such as an APTS-modified glass slide (see Chapter 13, Section 2), may be modified with a long-chain NHS-salicylic acid methyl ester derivative (Lonza), which then can be converted to the SHA group for coupling to a P(D)BA-modified protein. The following protocol describes this method. 

In 1975, Brown and Charalambides (62) reported the isolation of anhydroadirubine (68), also from Adina rubescens, as a methyl ester derivative (69). 

It is usual to convert fatty acids to their methyl ester derivatives before separation by GLC, although it may be possible to analyse those with short chain lengths (two to eight carbon atoms) as the free fatty acids. Polar or non-polar stationary phases can be used and capillary (open-tubular) or SCOT columns will separate positional and geometric isomers. The cis isomers have shorter retention times than the corresponding trans isomers on a non-polar phase and visa versa on a polar phase. 

The O-methylated extract was derivatized with 99 percent C-enriched methyl iodide. The NMR spectrum of the extract showed a strong absorption at 56 ppm (relative to TMS), which can be attributed to unhindered aryl methyl ethers (67%), a smaller absorption at 60 ppm, attributable to hindered aryl methyl ethers (23%), and a resonance at 51 ppm, assignable to methyl esters derived from carboxylic acids (10%).(16) TTiese results are consistant with those of Liotta l al, who studied the alkylation of whole Illinois No. 6 coal.(12)... 

Several chiral phosphorous ligands with great structural diversity are effective for the rhodium-catalyzed hydrogenation of a-dehydroamino acid derivatives. Tab. 1.1 summarizes the asymmetric hydrogenation of (Z)-2-(acetamido)ciimamic acid, 2-(acetamido)acrylic acid, and their methyl ester derivatives. 

A) Separation of fatty acid methyl esters derived from almond oil on a BPX-5 column (12 m X 0.25 mm i.d. x 0.25 pm film). Programmed 100° (1 min) then 107min to 320°. The major peaks are shown as offscale so that the minor peaks can be seen clearly. (B) The same sample separated on a HP Stabiliwax column (15 m X 0.25 mm x 0.5 pm film). Programmed 140°... 

Application of this one/pot protocol to the preparation of enantiopure amidine (215) derived from phenylglycine led to the formation of the desired cycloadducts (71). The reaction proceeded with good stereocontrol with an endo/exo ratio in the order of 10 1. In the case of the methyl ester derived product 216 (R = Me), a single isomer was isolated. The minor exo products 217 proved to have an unexpected stereochemistry at C(7), which was consistent with the energetically disfavored anti attack of the dipolarophUe, and it was therefore assumed that the product had... 

FIGURE 9.48 GC trace of methyl ester derivatives formed from polar organics in particles collected in Tsukuba, Japan (see Table 9.19) (adapted from Yokouchi and Ambe, 1986). 

TABLE 9.19 Identification of Some of the Peaks of Polar Organic Acid Methyl Ester Derivatives Shown in Fig. 9.48 ... 

Lin et al, JACS 76, 427(1954) CA 49, 3207(1955) [Describes some Methyl ester derivs, the prepn of 1,2-Dihydro-sym-tetrazine-... 

A linear detector response was obtained in the concentration range 0.1 - 0.5 pg when increasing amounts of trimethylsilyl ether/methyl ester derivatives of the standard compounds (HVA, dehydroxyphenyl acetic acid, VMA) were assayed. 

Silver ion chromatography is a useful technique for separating geometrical isomers of fatty acids (as the methyl ester derivatives) for subsequent analysis by GC. On the other hand, a stable ion-exchange column loaded with silver ions has been developed for HPLC that has proved of value in the simplification of complex mixtures of fatty acids (FAs) of natural origin for subsequent identification by GC-MS and for separating molecular species of triacylglycerols (41). 

Representative chromatograms of fatty acid methyl esters, derived from the three species most frequently used in dietary supplements, are shown in Fig. 18. In the chromatograms, the number and types of fatty acid methyl esters appear to be the same. However, ratios of the... 

A sample (ca. 1 g) of K-crotonate was placed in a Pyrex tube (6 mm i.d. (x200 mm) and heated in a metal bath maintained at a constant temperature. The tube was evacuated through the reaction. After a given time the reaction tube was taken out of the bath and allowed to cool to room temperature. The heat-treated salt was weighed and dissolved in aqueous hydrochloric acid solution and extracted with ether. The ether extract was treated with diazomethane. The methyl ester derivatives of the products were subjected to analysis by gas chromatography using diethyl maleate as internal standard. 

Synthesis of the disaccharide J.. The reaction of the known ( 1 3) methyl ketoside-methyl ester derivative 2 ... 

The structure of the imine substrate was also optimized. Since the use of amino acid methyl ester-derived substrates was highly desirable, the only aspect of substrate... 

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