Retention aldehyde groups

When o- or /7-hydroxy (or amino)benzaldehyde is titrated with bromine in aqueous solution at 40-45° 2,4,6-tribromophenol or -aniline is obtained almost quantitatively the aldehyde group is not oxidized to carboxyl but replaced by bromine it is eliminated as carbon monoxide which originates from decomposition of formyl bromide that is formed as intermediate.65 At 10° and 15°, respectively, these hydroxy and amino aldehydes are, however, merely converted into the dibromo aldehydes with retention of the CHO group, e.g. ... 

Identification. The retention times on the HPLC system and the Rf-values on silica gel TLC of compounds 1 to and 1 2 to 2A agreed with those of the known carotenoids from Anacystis nidulans and Chromatium vinosum, respectively. Spectroscopic properties, molecular weights and number of hydroxyl groups, all of which are primary and/or secondary, are shown in TABLE 1. Assignments of H-NMR spectra of 2 "to 6 and 8 to 11 were made by comparison with the data of typical carotenoids. The CD spectra indicated that the absolute configuration of the hydroxyl groups at C-2 and C-3 were 2R and 3R, respectively. The position of the aldehyde group in IjO was analyzed with the EI-MS spectrum [3,4] ... 

Retention of aldehyde groups. A mixture of nonanal and 5-nonanone in methylene chloride treated with 1 eq. dimethylaluminium N-methylanilide for 15 min at —78°, and 2 eqs. methyl-lithium added product. Y 92% (5-methyl-5-nonanol containing ca 10% 2-decanol). F.e.s. 

Prim, alcohols from aldehydes Preferential reduction of aldehyde groups with retention of keto-groups... 

Biochemical and Miscellaneous.—3-Methyl-2-benzothiazolone hydrazone is incorporated quantitatively into the anticodon loop of t-RNA" from yeast. Reaction occurs by Schiff s base formation with the ribose aldehyde group remaining after excision of the base Y from the nucleotide. The reaction provides a method of chemically modifying the natural polymer, with retention of its biochemical activity." ... 

The amino group is readily dia2oti2ed in aqueous solution, and this reaction forms a basis for the assay of sulfas. Aldehydes also react to form anils, and the yellow product formed with 4-(dimethylamino)hen2a1dehyde can be used for detection in thiu-layer and paper chromatography. Chromatographic retention values have been deterrnined in a number of thiu layer systems, and have been used as an expression of the lipophilic character of sulfonamides (23). These values have corresponded well with Hansch lipophilic parameters determined in an isobutyl alcohol—water system. 

Mineralocorticoids. Aldosterone [6251-69-0] (32), the most potent natural rnineralocorticoid, also possesses a A -3-one group, an oxygen substituent at Clip, and a C17P-2-hydroxyethan-l-one side chain. In addition, the C18 of aldosterone is oxidized to an aldehyde. Mineralocorticoids, particularly aldosterone, act to retain sodium and to prevent the retention of excess potassium. Antimineral ocorticoids have been used therapeutically as diuretics and as agents that regulate blood pressure (63—65). 

The chemical composition of the produced oil was analyzed by GC-MS. The samples were prepared by diluting the bio oil in methanol in a way that the fraction of organic oil was the same in each GC-vial. The products found in the oil were grouped as aldehydes, acids, alcohols, ketones, phenols, polyaromatics and others. The most interesting groups are shown in Table 4 and Table 5, arranged according to their retention time (RT). The procedure for the GC-MS analysis has been previously reported by the authors [4],... 

Transglycosidation with retention of configuration (Chipman and Sharon, 1969) would be more difficult to explain if an open-chain carbonium ion were formed in lysozyme reactions, necessitating an equilibrium reaction with free aldehyde. It seems unlikely, however, that a cyclic carbonium ion intermediate could have a sufficiently long lifetime to react with a saccharide molecule that can bind to the enzyme only after displacement of the leaving group in a fairly aqueous environment (above discussion). Therefore, the concept of a cyclic carbonium ion also presents difficulties for interpretation and should not be accepted uncritically. 

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