Carboxylic acid groups method

This method is widely used for the resolution of chiral amines and carboxylic acids Analogous methods based on the formation and separation of diastereomers have been developed for other functional groups the precise approach depends on the kind of chem ical reactivity associated with the functional groups present m the molecule... 

Benzothiepins synthesized by a double Knoevenagel condensation (see Section 2.1.1.2.) contain free carboxylic acid groups if the reaction product is isolated under acidic conditions. Rcesterification can be performed by two methods via formation of the acid chloride and subsequent alcoholysis, or by reaction with diazomethane, e.g. the conversion of 3-benzo-thiepin-2,4-diearboxylic acid (5, R = C02H) with thionyl chloride and methanol gives the dimethyl ester 5 (R = C02Me) in 47% yield, while the diazomethane pathway provides 60% of the dimethyl ester.65 Use of excess diazomethane leads to cycloadducts (see Section 2.2.4.). 

A methacryl-type polyester macromonomer was synthesized by lipase PF-catalyzed polymerizahon of DDL using vinyl methacrylate as terminator ( terminator method ), in which the vinyl ester terminator was present from the beginning of the reachon (Scheme 17). In using divinyl sebacate as terminator, the telechelic polyester having a carboxylic acid group at both ends was obtained. Various non-protected thiol compounds were used as inihator or terminator for the thiol end-funchonalizahon of poly(8-CL). ... 

Other Gas Reactions. Several other reactive gases or vapours were examined but found to be unsatisfactory. No ester formation ( 1745 cm"1) was found when oxidatized films were exposed to acetic acid or formic acid vapour. Alcohol/carboxylic acid reactions in the solid state have often been suggested as the source of ester products, but not substantiated (4,5). Gaseous ammonia reacted with carboxylic acid groups to give absorptions at 1550 cm"1 [-C(=0)-0 ] and 1300 cm"1 (NHi +). However, these absorptions were very broad and the method inferior to acid measurement by SF. Although N20 did not react with oxidized polyolefins, the reaction of N02 with oxi-... 

Hoare, D.G., and Koshland Jr, D.E. (1967) A method for the quantitative modification and estimation of carboxylic acid groups in proteins./. Biol. Chem. 242, 2447-2453. 

One method for preparing imidazolylstannanes is direct metalation followed by treatment with RjSnCl [21]. l-Methyl-2-tributylstannylimidazole, derived in such manner, was coupled with 3-bromobenzylphosphonate (26) to furnish heterobiaryl phosphonate 27 [22], Under the same reaction conditions, 4-bromobenzylphosphonate led to the adduct in 69% yield, whereas only 24% yield was obtained for 2-bromobenzylphosphonate. The low yield encountered for the ortho derivative may be attributed to the steric factors to which the Stille reaction has been reported to be sensitive [23]. Heterobiaryl phosphonates such as 27 are not only substrates for the Wadsworth-Homer-Emmons reaction, but also bioisosteric analogs of the carboxylic acid group. 

Figure 1.2. Scheele isolated a family of naturally occurring sour substances. Subsequently, the elemental composition of each substance was determined using Lavoisier s combustion method and later the different structures were proposed. Each member contains common structural element, a carboxylic acid group which gives each its sour taste. The two-dimensional representation of chemical structures as shown is convenient but can be misleading. Also shown is the structure of urea, the first naturally occurring substance to be made in the laboratory by Wohler (shown), who provided the first experimental challenge to the concept of vitalism.

Ring opening is common in the alkali metal and liquid ammonia reduction of furans unless an anion stabilizing group is present, so most work has been done with derivatives of furancarboxylic acids. Treatment of furan-2-carboxylic acid with lithium and ammonia at -78 °C followed by rapid addition of ammonium chloride affords 2,5-dihydrofuran-2-carboxylic acid (80%). Reductive alkylation similarly gives 2-alkyl-2,5-dihydrofuran-2-carboxylic acids. This method has been used in a synthesis of rosefuran, the intermediate dihydrofuran (66) being converted into the product (67) by oxidative decarboxylation with... 

Carboxylic acid groups can also be installed in molecules using the reaction of an organometallic compound with carbon dioxide. This is a reductive method since the carbon dioxide is reduced to a carboxylic acid by formation of a new carbon-carbon bond. Both Grignard reagents and organolithium compounds work well in this reaction. 

Figure 3 describes the preparation of A-co-undecenoyl-L-valine CSP bonded to silica gel. The carboxylic acid group of L-valine was protected by the reaction with isobutylene using the method of Roeske [47]. The formed tert-butyl ester of L-valine was precipitated from diethyl ether as the oxalate by the dropwise addition of a solution of 10% oxalic acid in absolute ethanol. The precipitate is dried and the oxalate group is removed by the reaction of sodium hydroxide. The tert-butyl ester of L-valine was treated with undecenoic acid in tetrahydrofuran (THF), which resulted in A-co-undecenoyl-L-valine methyl ester. In another step, lOmM of monochlorosilane was dissolved in 20 mL of dry pyridine and was allowed to react with /V -to - u ndccenoyl-L-valine methyl ester. 

Another possibility is to use [bis(trifluoroacetoxy)iodo]benzene (BTI) and the sodium salt of a carboxylic acid. This method does not require heating because of the good nucleofugality of the trifluoroacetoxy group. When stoichiometric quantities of reagents are used, mixed [bis(acyloxy)iodo] arenes may be obtained [26]. In order to prepare [bis(trifluoroacetoxy)iodo]benzene itself,... 

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