Regeneration from Derivatives

Reagents i, NOCl ii, AcjO iii, salts iv, RONO-base v, NaBH4 

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Manufactured fibers produced from natural organic polymers are either regenerated or derivative. A regenerated fiber is one which is formed when a natural polymer or its chemical derivative is dissolved and extmded as a continuous filament, and the chemical nature of the natural polymer is either retained or regenerated after the fiber-formation process. A derivative fiber is one which is formed when a chemical derivative of the natural polymer is prepared, dissolved, and extmded as a continuous filament, and the chemical nature of the derivative is retained after the fiber-formation process. 

Selinene is a bicyclic sesquiterpene occurring in essential oil of celery. Its presence was first indicated by Ciamician and Silber who announced the isolation of a sesquiterpene boiling at 262° to 269°, but no characteristic derivatives were prepared. Schimmel Co. examined this sesquiterpene to which they assigned the name selinene. They prepared a solid dihydrochloride melting at 72° to 74° and ha-ving a specific rotation -h 18°. The pure sesquiterpene, regenerated from the dihydrochloride by means of sodium ethylate had the following characters —... 

The same authors further studied the acid hydrolysis of the original irisin and also of the product regenerated from the acetyl derivative. They believe that the hydrolysis of irisin can be represented by the following scheme. 

Carbonyl compounds are also rapidly regenerated from the corresponding semicar-bazone and phenylhydrazone derivatives using ammonium persulfate impregnated... 

Sugar lactones react readily with hydrazine to give crystalline derivatives useful for isolation and identification (127). Thus, addition of hydrazine to a reaction mixture containing an aldonolactone facilitates isolation of the product. The lactone may be regenerated from the hydrazide by treatment with nitrous acid (128). The phenylhydrazides obtained on treatment of aldonolactones with phenylhydrazine are also useful for characterization (129,130). 

Amines are regenerated from the protecting derivatives trichloro-t-butylcarbamates by treatment with sodium 2-thienyl teUurolate." The reagent is generated in a catalytic cycle by reduction of the corresponding diteUuride with sodium borohydride. 

Ketones. The lithio derivative of ( +)-(.S )-. Y,.S -dimethyl-S-phenylsulfoxiinine (16), or its enantiomer, may be used both to resolve racemic ketones164 and to determine absolute configurations of ketones. For example, rac-19 on addition of 16 formed the diastereomeric /j-hydroxy-sulfoximines 17 and 18 which were separated. The configuration of 17 was established by an X-ray analysis. The ketones can be regenerated from the /1-hydroxysulfoximines by thermolysis. Thus, heating of 17 and 18 to 80 °C (for 12 h) furnished 19 [a precursor of (+ )-modhephen] and ent-l9165. 

The inositol phosphates are linked into a metabolic cycle (Fig. 6.5) in which they can be degraded and regenerated. Via these pathways, the cell has the ability to replenish stores of inositol phosphate derivatives, according to demand. Ptdins may be regenerated from diacylglycerol via the intermediate levels of phosphatidic acid and CDP-glycerol. 

Ami noethylation of Cellulose Derivatives and of Reaenerated Cellulose Cellulose obtained by regeneration from a cuprammonium soln of cotton(in the manner described in Rept No 2,p 14) from the Wyandotte Chem Corp gave an amorphous product contg ca 23.5% N when heated with ethyleneimine in a sealed tube at 120° in the presence of toluene. The cellulose derivatives catboxy-me thy (cellulose and hydroxyetbylcellulose (prepd in the manner described in Rept No 3, pp 14—18) gave solid products with nitrogen contents of 24.8 and 28.1% respectively, when heated with ethyleneimine in a sealed tube, in the manner described in Rept No 1,... 

The 2-deoxy function may be regenerated from the 2-halo derivatives by reduction with tributyl stannic hydride, NiC /NaBH, or hydrogen/palladium on charcoal. The latter should be carried out in the presence of base in order to quench the resulting acid. Another method following the same concept is the oxyselenation-deselenation of glycals [13] ... 

The separation (resolution) of a racemic modification into its constituent enantiomers is normally achieved by converting the enantiomers in the racemate into a pair of diastereoisomers by reaction with a pure enantiomer (Figure 10.4.). Enantiomers of acids are used for racemates of bases whilst enantiomers of bases are used for racemates of acids (Table 10.1). Neutral compounds may sometimes be resolved by conversion to an acidic or basic derivative which is suitable for diastereoisomer formation. The diastereoisomers are separated using methods based on the differences in their physical properties and the pure enantiomers are regenerated from the corresponding diastereoisomers by suitable reactions. 

In many cases, the substrate to be subjected to asymmetric conversion is coupled to the carbohydrate via the anomeric position. For the synthesis of amino compounds, the substrate is linked to the carbohydrate as a derivative of a glycosyl-amine. After completion of the asymmetric synthesis the product can be detached from the carbohydrate auxiliary by acidic hydrolysis. In most cases auxiliary and product can be separated by extraction or recrystallization techniques, and the carbohydrate auxiliary readily regenerated from its recovered detachment derivative. 

The barium or ferric salt may be precipitated, and from the former the free acid may be regenerated. Other derivatives were prepared by similar reactions.2... 

Oxidmion of ketone acetals and ethers. Ketones can be regenerated from the ethylene acetal derivatives by treatment with trityl fluoroborate in dry dichloro-methanc (Nj) at room temperature. Thus the reaction of trityl fluoroborate with cyclohexanone ethylene acetal results in cyclohexanone (80%) and triphenylmethane. The reaction thus involves hydride transfer to the triphenyl carbonium ions. Triethyl-oxonium fluoroborate can also be used but is somewhat less effective than trityl fluoroborate. 

In a few cases, alkaline hydrolysis has proved applicable to special problems. Tryptophan is not destroyed in alkali, and analysis of alkaline hydrolyzates forms the basis of one method for quantitative determination of this amino acid (e.g., Dreze, 1960). Despite the fact that tryptophan-containing peptides should be more stable in alkali than acid, partial alkaline hydrolysis has not been employed for identification of this type of peptide. Amino acids often can be regenerated by alkaline hydrolysis from derivatives obtained by the amino-terminal end-group methods. Dinitrophenyl amino acids and phenylthiohydantoin (Fraenkel-Conrat et al., 1955) as well as hydantoin (Stark and Smyth, 1963) derivatives of amino acids can be treated in this manner. 

These tetrahydrofolate derivatives serve as donors of one-carbon units in a variety of biosyntheses. Methionine is regenerated from homocysteine by transfer of the methyl group ofF -methyltetrahydrofolate, as will be discussed shortly. We shall see in Chapter 25 that some of the carhon atoms of purines are acquired from derivatives of N lO-formyltetrahydrofolate. The methyl group of thymine, a pyrimidine, comes from N, N lO-methylenetetrahydrofolate. This tetrahydrofolate derivative can also donate a one-carhon unit in an alternative synthesis of glycine that starts with CO2 and NH4 +, a reaction catalyzed by glycine synthase (called the glycine cleavage enzyme when it operates in the reverse direction). 

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