Interconversion of functional derivatives

Acidity of Amides, Imides, and Sulfonamides Characteristic Reactions Reaction with Water Hydrolysis Reaction with Alcohols Reactions with Ammonia and Amines Reaction of Acid Chiorides with Salts of Carboxylic Acids Interconversion of Functional Derivatives Reactions with Organometallic Compounds 18.10 Reduction... 

Pteridines carrying a polyhydroxyalkyl sidechain are valuable synthons for the synthesis of functionalized derivatives. Various 6-(l,2,3-trihydroxypropyl)pteridines (216, 217, 232) have been oxidized by periodate to the corresponding pteridine-6-carbaldehydes (218, 225, 233) which are further substrates for the interconversion into oximes (219, 220, 225, 226, 234, 235), carbonitrile (221, 228, 236), hydroxymethyl (222, 229, 237) and carboxy derivatives (223, 230, 238) as well as folic acid analogues (224, 231, 239) (Scheme 34) <90Ml 718-08). 

WeVe talked at length about the interconversions of acid derivatives, explaining the mechanism of attack of nucleophiles such as ROH, H20, and NH3 on acyl chlorides, acid anhydrides, esters, acids, and amines, with or without acid or base present. We shall now go on to talk about substitution reactions of acid derivatives that take us out of this closed company of compounds and allow us to make compounds containing functional groups at other oxidation levels such as ketones and alcohols. 

When a multistep synthesis is being undertaken with other sensitive functional groups present in the molecule, milder reagents and reaction conditions may be necessary. As a result, many alternative methods for effecting interconversion of the carboxylic acid derivatives have been developed and some of the most useful reactions are considered... 

The main first part of the review (Section HI) summarizes preparation of hydroxylamine derivatives through alkylation, arylation, and addition reaction of hydroxylamine, or its derivatives such as hydroxamic acids and A-oxysulfonamides. The second main part (Sections IV-VIII) describes methods of creation of hydroxyamino groups de novo from other functionalities. Due to easy interconversion outlined in Section II, syntheses of hydroxylamines and hydroxamic acids are considered together. For the same reason, the chapter also relates to synthesis of A-oxysulfonamides and V-oxyphosphonamides as far as these methods are of interest for the preparation of hydroxylamines. 

The two target molecules, which illustrate cyclisation reactions involving substituted 1,5-dicarbonyl compounds in the presence of appropriate reagents, are diethyl 2,6-dimethylpyridine-3,5-dicarboxylate (85) and 2,4,6-triphenylpyrylium fluoroborate (86). The latter is of specific interest since it provides a simple example to illustrate a general procedure for the conversion of pyrylium salts into pyridinium derivatives these latter compounds are important reagents for a variety of functional group interconversions (see Sections 5.5.6, p. 574, and 5.15.3, p. 768). 

Most anaerobically functioning mitochondria use endogenously produced fumarate as a terminal electron-acceptor (see before) and thus contain a FRD as the final respiratory chain complex (Behm 1991). The reduction of fumarate is the reversal of succinate oxidation, a Krebs cycle reaction catalysed by succinate dehydrogenase (SDH), also known as complex II of the electron-transport chain (Fig. 5.3). The interconversion of succinate and fumarate is readily reversible by FRD and SDH complexes in vitro. However, under standard conditions in the cell, oxidation and reduction reactions preferentially occur when electrons are transferred to an acceptor with a higher standard redox potential therefore, electrons derived from the oxidation of succinate to fumarate (E° = + 30 mV) are transferred by SDH to ubiquinone,... 

B. Functional Groups — Preparation, reactions, and interconversions of alkanes, alkenes, alkynes, dienes, alkyl halides, alcohols, ethers, epoxides, sulfides, thiols, aromatic compounds, aldehydes, ketones, carboxylic acids and their derivatives, amines... 

There are several one-carbon derivatives of folate (of different redox states) that function as one-carbon carriers in different metabolic processes. In all of these reactions, the one-carbon moiety is carried in a covalent linkage to one or both of the nitrogen atoms at the 5- and 10-positions of the pteroic acid portion of tetrahydrofolate. Six known forms of carrier are shown in Figure 27-4. Folinic acid (N -formyl FH4), also called leucovorin or citrovorum factor, is chemically stable and is used clinically to prevent or reverse the toxic effect of folate antimetabolites, such as methotrexate and pyrimethamine. The formation and interconversion of some metabolites of... 

A stereoselective synthesis of 2,3,5,6-tetra- and 2,3,4,5,6-penta-substituted piperidines was achieved from oxidative cleavage of 2-azabicyclo[2.2.2]octane Diels-Alder adducts 176 derived from dihydropyridine 177. Appropriate functional group interconversions of the amidine and ester functionalities in 176 ultimately gave densely functionalized piperidines such as 178 <05OL5773> (Scheme 51). 

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