Intermediates synthetic

The determination of the purity of intermediates in a synthetic route to a target compound is more common in pharmaceutical analysis than organic or food analysis. This is because lengthy syntheses are more common in the preparation of drugs than foods or general organic compounds. [Pg.249]

Constituents of foods are frequently natural and not synthetic. Synthesis of organic compounds for general use tend not to be as complicated. Drug synthesis is frequently lengthy since only a very specific molecular shape and charge distribution will give the desired pharmacological effect and this is often not available from a simple, easily accessible compound. [Pg.250]

The determination of the purity of drug intermediates becomes more important in the later stages of the drug development process. By this [Pg.250]

The method used for the LC determination of the purity of a bulk substance will depend on circumstances. [Pg.251]

The nature of the LC conditions adopted for such a rapid generic LC method would depend on whether the compounds were acidic, neutral or basic and whether they were hydrophilic or hydrophobic. Circumstances however, would favour the use of fast LC i.e. the use of short columns packed with 3 pm particles and operated at high flow rates. Using fast LC, efficiency is satisfactory and compounds having very large capacity factors may be eluted within reasonably short times. [Pg.251]

Review Problem 9 - Suggest a synthesis of TM 125, a commonly used synthetic intermediate called Hagemaim s ester. [Pg.40]

Revision Problem 8 TM 406 is a synthetic intermediate related to the caimabinoids, naturally occurring hallucinogenic compounds. How could it be synthesised ... [Pg.130]

The large sulfur atom is a preferred reaction site in synthetic intermediates to introduce chirality into a carbon compound. Thermal equilibrations of chiral sulfoxides are slow, and parbanions with lithium or sodium as counterions on a chiral carbon atom adjacent to a sulfoxide group maintain their chirality. The benzylic proton of chiral sulfoxides is removed stereoselectively by strong bases. The largest groups prefer the anti conformation, e.g. phenyl and oxygen in the first example, phenyl and rert-butyl in the second. Deprotonation occurs at the methylene group on the least hindered site adjacent to the unshared electron pair of the sulfur atom (R.R. Fraser, 1972 F. Montanari, 1975). [Pg.8]

The growing importance of cyclopropane derivatives (A. de Meijere, 1979), as synthetic intermediates originates in the unique, olefin-like properties of this carbocycle. Cyclopropane derivatives with one or two activating groups are easily opened (see. p. 69f.). Some of these reactions are highly regio- and stereoselective (E. Wenkert, 1970 A, B E. J. Corey, 1956 A, B, 1975 see p. 70). Many appropriately substituted cyclopropane derivatives yield 1,4-difunctional compounds under mild nucleophilic or reductive reaction conditions. Such compounds are especially useful in syntheses of cyclopentenone derivatives and of heterocycles (see also sections 1.13.3 and 4.6.4). [Pg.76]

The protecting groups are also used to solubilize synthetic intermediates in organic solvents, e.g. methylene chloride. Chromatography is then possible on a larger scale, since silica gel can be used as adsorbent. Six synthetic strategies have been developed (H. Kdster, 1979) ... [Pg.216]

Carbocations stabilized by functional groups can also effect 3-alkylalion of indoles. From a synthetic point of view the most important are jV.jV-dialkyl-methyleneiminium ions which can be generated under Mannich conditions from formaldehyde and secondary amines[13]. The products, 3-(A/,A-dialkyl-aminornethyl)indoles, are useful synthetic intermediates (see Chapter 12). [Pg.106]

CX-Aminonitriles are compounds containing both cyano and amine substituents attached to the same carbon atom. They are versatile synthetic intermediates that are used to make aminoacids, agrichemicals, chelants, radical initiators, and water-treatment chemicals. In some cases, aminonitriles produced as intermediates are not isolated, but immediately further reacted, for example by hydrolysis, as is the case in producing... [Pg.221]

Some of the 5-aiyhnethylene derivatives thus obtained are useful synthetic intermediates, as shown in Figure 1. [Pg.251]

Fig. 1. 5-Substituted hydantoins as synthetic intermediates. Equation 1 (45) equation 2 (46).

Mercuration. Mercury(II) salts react with alkyl-, alkenyl-, and arylboranes to yield organomercurials, which are usehil synthetic intermediates (263). For example, dialkyhnercury and alkyhnercury acetates can be prepared from primary trialkylboranes by treatment with mercury(II) chloride in the presence of sodium hydroxide or with mercury(II) acetate in tetrahydrofuran (3,264). Mercuration of 3 -alkylboranes is sluggish and requires prolonged heating. Alkenyl groups are transferred from boron to mercury with retention of configuration (243,265). [Pg.315]

As the most reactive and economical source of the acetoacetyl moiety, diketene is used as a valuable synthetic intermediate in the manufacture of acetoacetic acid derivatives and heterocycHc compounds which are used as intermediates in the manufacture of dyestuffs, agrochemicals, pharmaceuticals, and polymers. [Pg.480]

Fig. 14. Commercialized processes for the microbial transformation of readily available sterols to useful synthetic intermediates.

Unsaturated sugars are useful synthetic intermediates (11). The most commonly used are the so-called glycals (1,5- or 1,4-anhydroalditol-l-enes). In the presence of a Lewis-acid catalyst, 3,4,6-tri-0-acetyl-l,5-anhydro-2-deoxy-D-arabinohex-l-enitol [2873-29-2] commonly called D-glucal triacetate, adds nucleophiles in both kineticaHy controlled and thermodynamically controlled (soft bases predominately at C-3 and hard bases primarily at C-1) reactions (11,13). [Pg.482]

Chloroformates are versatile, synthetic intermediates, based on the affinity of the chlorine atoms for active hydrogen atoms. Chloroformates should be considered as intermediates for syntheses of pesticides, perfumes, dmgs, polymers, dyes, and other chemicals. Some of these products, eg, carbonates, are used as solvents, plastici2ers, or as intermediates for further synthesis. A significant use of chloroformates is for conversion to peroxydicarbonates, which serve as free-radical initiators for the polymeri2ation of vinyl chloride, ethylene, and other unsaturated monomers. The most widely used percarbonate initiators are diisopropyl peroxydicarbonate (IPP), di-2-ethyIhexylperoxydicarbonate (2-EHP), and di-j -butylperoxydicarbonate (SBP). The following Hst includes most of the commercially used percarbonates. [Pg.41]

A considerable range of products, including flavors, fragrances, agrochemicals, pharmaceuticals, and polymers, has been developed using these chemicals as either synthetic intermediates or ingredients (3). [Pg.173]

Aminomethylindoles are particularly important synthetic intermediates. 3-Dimethyl-aminomethylindole (gramine) (153) and especially its quaternary salts readily undergo displacement reactions with nucleophiles (Scheme 60). Indole-2,3-quinodimethanes, generated from 2-methylgramine as shown in Scheme 61, undergo intermolecular cycloaddition reactions with dienophiles to yield carbazole derivatives (82T2745). [Pg.71]

It is often necessary to prepare /3-lactams with particular substituents at N-1, C-3 and C-4, e.g. in the preparation of fused /3-lactams from monocyclic precursors. For reasons of space it is not possible to give an exhaustive list of the variously substituted /3-lactams available however, Table 4 summarizes the most general routes to /3-lactams bearing particular substituents at C-3 and C-4. -Substitution of azetidin-2-ones has already been dealt with cf. Section 5.09.3.2.3). N-Unsubstituted /3-lactams and protected 3-amino-/3-lactams are particularly important synthetic intermediates and methods of preparing these are discussed below. [Pg.264]

As many natural and synthetic /3-lactams bear 3-acylamino substituents, the corresponding free amines or protected forms thereof are versatile synthetic intermediates. They may be prepared in several ways, for example by deacylation of the 7-amido group in naturally occurring penicillins by enzymic or chemical means. Chemical degradation usually involves conversion of the amide to a chloroimidate followed by cleavage with aqueous alcohols (75S547 p. 560, 78T1731 p. 1753). [Pg.265]

This reaction illustrates a stereoselective preparation of (Z)-vinylic cuprates, which are very useful synthetic intermediates. They react with a variety of electrophiles such as carbon dioxide, epoxides, aldehydes, allylic halides, alkyl halides, and acetylenic halides they undergo... [Pg.7]

Structure-goal Strategy. The use of a particular structure corresponding to a potentially available starting material or synthetic intermediate as a guide for retrosynthetic search. [Pg.98]

Carbonates and carbamates are reported to be intermediate in stability and easier to prepare than xanthates. " They can conveniently be prepared directly from the alcohol in high yield and give clean conversion to olefins. Cholesta-3,5-diene, for example, can be readily obtained via the phenylcar-bamate (114) or ethylcarbonate (115) of cholesterol. Such esters appear to have been somewhat neglected as synthetic intermediates. [Pg.336]

Xenon difluoride reaction with nitro enolates provides a useful entry into a wide variety of fluonnated synthetic intermediates [91 92] (equation 52)... [Pg.161]

Oxidative reactions frequently represent a convenient preparative route to synthetic intermediates and end products This chapter includes oxidations of alkanes and cycloalkanes, alkenes and cycloalkenes, dienes, aromatic fluorocarbons, alcohols, phenols, ethers, aldehydes and ketones, carboxylic acids, nitrogen compounds, and organophosphorus, -sulfur, -selenium, -iodine, and -boron compounds... [Pg.321]

Functionalized organofluorozinc reagents have received considerable attention as synthetic intermediates for the preparation of functionalized organofluorine... [Pg.683]

Reaction is catalyzed by cyanide ion. Cyanohydrins are useful synthetic intermediates cyano group can be hydrolyzed to —CO2H or reduced to —CH2NH2. [Pg.743]

Nitrosation (Section 22.15) Nitrosation of amines occurs when sodium nitrite is added to a solution containing an amine and an acid. Primary amines yield alkyl diazonium salts. Alkyl diazonium salts are very unstable and yield carbo-cation-derived products. Aryl diazonium salts are exceedingly useful synthetic intermediates. Their reactions are described in Table 22.7. [Pg.959]

Milder bases such as Et2NFI leave some of the S-N bonds intact to yield, for example, S(NEt2)2. The value of S4N4 as a synthetic intermediate can be gauged from the representative reactions in the Scheme below " and in Table 15.22. It can be seen that these reactions embrace ... [Pg.724]

The oxetane functional unit is a rare but occurring group in natural products and appears both as end products as well as synthetic intermediates. Patemo-Buchi reactions can be used to insert oxetanes directly into biologically active compounds, as in the example... [Pg.47]

Magnus prepared tetrahydrobenzofuran 37 using a Feist-Benary reaction of ethyl 2-chloroacetoacetate (32) and functionalized 1,3-cyclohexanedione 36. Compound 37 was a key synthetic intermediate in Magnus s synthesis of linderalactone, isolinderalactone, and niolinderalactone. ... [Pg.163]

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