Acid hydrolytic procedure

The asymmetric alcoholytic ring opening of 4-substituted-2-phenyl-4,5-dihydro-l,3-oxazin-6-ones proved to be a efficient method for the preparation of enatiomerically pure /3-amino acid derivatives <2005AGE7466>. Treatment of 2,4-diphenyl-4,5-dihydro-l,3-oxazin-6-one 208 in the presence of the bifunctional chiral thiourea catalyst 211 resulted in formation of an enantiomerically enriched mixture of the unchanged oxazinone (iJ)-208 and allyl (4)-3-benzoyl-amino-3-phenylpropanoate 209. The resolved material (iJ)-208 and the product 209 could easily be separated by a selective hydrolytic procedure that converted oxazinone (iJ)-208 quantitatively into the insoluble iV-benzoyl /3-amino acid 210 (Scheme 37). 

We have taken advantage of the hydrolytic activity of these phage proteins for the preparation of series of saccharides of various size. Such large saccharides cannot otherwise be produced by synthetic methods or commonly used partial acid hydrolysis procedures. 

The hydrolysis of halogenopyrazines to pyrazinones has never been used much, perhaps because most halogenopyrazines are themselves made from pyrazinones. Such hydrolysis can be done under acidic or basic conditions but sometimes it seems to be more rewarding to proceed in two stages via an alkoxy intermediate. The following examples illustrate all three hydrolytic procedures ... 

The N-alkylation of amides followed by hydrolysis furnishes a good route for making secondary amines. The formyl, acetyl, and aryl-sulfonyl " derivatives of amines are best suited for alkylation (method 358). Hydrolysis is accomplished by refluxing concentrated hydrochloric acid alone or in acetic acid. N-Alkyl-formamides prepared by the addition of olefins to nitriles (method 355) are hydrolyzed with aqueous alkali. Similar hydrolytic procedures... 

The use of an appropriate hydrolytic procedure for the conversion of diethyl 2,2-diethoxyeth-ylphosphonate into diethyl 1-formylmethylphosphonate is an important step in the reaction sequence. A high concentration and a large excess of acid should be avoided to prevent hydrolysis of the acid-sensitive ester groups attached at phosphorus. The use of drastic conditions may provoke undesired side reactions, resulting in loss of the expected product. In the case of diethyl 1-fonnyhnethylphosphonate, a variety of acids have been used H2SO4, H2SO4-... 

Triethyl phosphite does not react with aldimines in EtOH. However, the addition of HCOgH (1 eq) to the (EtO)3P/aldimine mixture in EtOH induces an exothermic reaction resulting in the exclusive formation of the iminoalkylphosphonate. Undoubtedly, the 1,4-addition of triethyl phosphite is promoted by initial protonation at the nitrogen atom, which activates the double bond toward Michael addition and generates the formate anion for the dealkylation step (Michaelis-Arbuzov reaction). The dialkyl-substituted formylphosphonates are obtained by hydrolysis of the imine function with an appropriate hydrolytic procedure using either 6 M HCl or 1 M oxalic acid. The method provides a simple and convenient access to a broad range of substituted diethyl 2-formyl-alkylphosphonates in satisfactory overall yields (45-80%). ... 

The other major class of cyclic amino acid derivative used in dynamic resolution reactions is the hydantoin group. Like oxazolinones, hydantoins readily undergo racemisation under mild conditions. Systems involving a two step procedure using D-hydantoinase and a carbamoylase were reported to provide a route to D-amino acids[S2, 53). Dynamic resolution of a p-hydroxyphenyl substituted hydantoin was reported in 1987[541. Using the intact cells of Pseudomonas sp. AJ-11220, the amino acid was prepared in over 90% yield, as shown in Fig. 9-24. This hydrolytic procedure leads directly to the amino acid, and the same enantiomer of product, the D-amino acid, was obtained independently of the stereochemistry of the substrate. 

The possibility that some fraction of the ascorbic add in animal tissues is bound instead of free has continued to attract interest. It can be accepted as established that there is no bound ascorbic add in blood serum (S8). The ascorbic acid present in serum is freely dialyz-able and is not increased by various hydrolytic procedures when measured by the 2,4-dinitrophenylhydrazine method. The increases after hydrolysis reported earlier may be attributed to the production of other materials which readed with the 2,6-dichlorophenolindophenol used for titration. The possibility of bound ascorbic acid is, therefore, restricted to other tissues. 

Hydrolysis. A range of hydrolytic procedures has been employed for the release of neutral sugars from plant cell walls. A high proportion of the neutral noncellulosic polysaccharides can be hydrolyzed quantitatively using 1M H2SO4 for2.5 hat 100°C (Selvendranetal., 1979),or 2M trifluoroacetic acid for 2 h at 120°C (Albersheim et al., 1967). 

When the thermal polyamino acid is an acidic type, complete recovery of amino acids may be observed, and the hydrolytic procedure may be quite the same as for proteins. 

The lability of the sugar component of thymonucleic acid had frustrated attempts to isolate structural subunits by chemical hydrolysis however, in 1929 a gentle hydrolytic procedure using dog intestinal enzymes yielded the expected four nucleosides, and the sugar was then characterized as 2-deoxy-D-ribose. Thus, it was evident that both types of nucleic acid were polymers of nucleotides. After recognition of DNA in plant tissues and the demonstration of RNA in animal tissues, it was apparent that cells in general contained both types of nucleic acid. 

Enzymatic hydrolysis of proteins is an attractive alternative to the hydrolytic procedures and has been used to avoid destruction of tryptophan (174). A mixture of proteolytic enzymes, such as chymo-trypsin, thermolysin, papain, leucine aminopeptidase and pronase has been used (135, 192, 353). Upon completion of the enzymatic hydrolysis of the protein, the hydrolyzate is rendered free of proteolytic enzymes by precipitation and centrifugation and the extract directly analyzed with the amino acid analyzer. The method however may not be generally valid, because of the possibility of artefacts due to self-digestion of the enzymes used. 

Satisfactory alternatives to the hydrolytic procedures have been sought for many years. Methods have been tried to produce colored derivatives by exploiting the reactivity of the indole nucleus in the intact protein (135, 353). Sodium hypochlorite, ferric chloride, cupric sulfate, bromine, and sodium nitrite, usually in acid solution, have been found to produce color with tryptophan-containing proteins. Later workers have formed other colored derivatives by reaction with tryptophan-specific reagents, while still others have used the characte-... 

Step 3. The neutral components. The ethereal solution (E remaining after the acid extraction of Step 2 should contain only the neutral compounds of Solubility Groups V, VI and VII (see Table XI,5). Dry it with a little anhydrous magnesium sulphate, and distil off the ether. If a residue is obtained, neutral compounds are present in the mixture. Test a portion of this with respect to its solubility in concentrated sulphuric acid if it dissolves in the acid, pour the solution slowly and cautiously into ice water and note whether any compound is recovered. Examine the main residue for homogeneity and if it is a mixture devise procedures, based for example upon differences in volatility, solubility in inert solvents, reaction with hydrolytic and other reagents, to separate the components. 

Perhaps the most interesting finding of our synthetic studies was that the interfacial preparation of poly(iminocarbonates) is possible in spite of the pronounced hydrolytic instability of the cyanate moiety (see Illustrative Procedure 3). Hydrolysis of the chemically reactive monomer is usually a highly undesirable side reaction during interfacial polymerizations. During the preparation of nylons, for example, the hydrolysis of the acid chloride component to an inert carboxylic acid represents a wasteful loss. 

---