Oxidation quinoline structures

Renewed examination by TLC and electrophoresis of calebassinine, another curare alkaloid, but also known to be present in S. solimoesana (Table 1.4), has now revealed that it consists of two components, the major one calebassinine 1 together with a small proportion of calebassinine 2. X-ray crystal analysis of calebassinine 1 (436) has shown it to possess the quinoline structure 46a. The suggestion has been made that it could arise through a number of oxidative transformations from 2,16-dihydroakuammicine (47) a variant on the route originally proposed has been outlined (437). Isolation of the alkaloid from S. solimoesana (325) would thus imply the occurrence of an akuammicine derivative in the plant, which has not yet been demonstrated. 

In this, the first serious and successful work on the structure of a complex alkaloid, there was naturally at first some confusion between Moquinoline and the better-known quinoline. The 6 7-dimethoxy-woquinolinecarboxylic acid was thought to be a dimethoxycinchoninic acid. It known, however, that quinoline benzylchloride on oxidation furnished formylbenzylanthranilic acid, CjH4(COOH)—N(C,H,)—CHO, whereas various papaverine alkyl halides gave what were presumed to be... 

These results indicate that quinine and quinidine differ in structure from cinchonine and cinehonidine in containing a methoxyl group in position 6 in a quinoline nucleus. The identity of the other oxidation products, meroquinenine, cincboloiponic and loiponic acids, in all foiu" cases indicates that the second half of the molecule has the same structure in all four alkaloids. Further, this second half must be joined to the quinoline nucleus at position 4 by a group capable of conversion into carboxyl. 

The structure of 1,2,3-benzoxadiazole (4.16) bears some resemblance to Wallis and Dunitz s structure (4.14, Fig. 4-1) for quinoline-8-diazonium-l-oxide, as the latter structure has a tendency towards forming a five-membered heteroaromatic ring. The two compounds are, however, different with respect to the involvement of an N(2) and an N(l) diazo atom. The 1,2,3-benzoxadiazole structure is consistent with the bands observed in the 9.45 to 12.37 eV range in the photoelectron spectrum,... 

Preparative-scale fermentation of papaveraldine, the known benzyliso-quinoline alkaloid, with Mucor ramannianus 1839 (sih) has resulted in a stereoselective reduction of the ketone group and the isolation of S-papaverinol and S-papaverinol M-oxide [56]. The structure elucidations of both metabolites were reported to be based primarily on ID and 2D NMR analyses and chemical transformations [56]. The absolute configuration of S-papaverinol has been determined using Horeau s method of asymmetric esterification [56]. The structures of the compounds are shown in Fig. 7. 

Blood protein binding of IQ was found in rats dosed intragastrally with the labelled compound. The same adducts, though in much higher yields, were found when purified rat serum albumin was exposed either to /V-hydroxy-IQ or incubated with parent IQ in the presence of a microsomal system. A tripeptide was isolated which contained lV-(cystein-S -yl)TQ-,S-oxide (sulfinamide) that easily liberated IQ on acidification. Pretreatment of albumin with p-chloromercuri ben zoale reduced covalent binding drastically61. The authors concluded that the reactant most likely to yield this structure is 2-nitroso-3-methylimidazo[4,5-/]quinoline, which is probably formed by autoxidation of /V-hydroxy-IQ. 

Pyridine, the quinoline and acridine AT-oxides readily form salts e.g. hydrochlorides (27) and picrates) which have been used for their characterization. Basic salts of the type (ArNO)2HX are also known the structure (28) is indicated for 2-picoline 1-oxide hemihydro-bromide based on IR evidence. A list of these salts has been compiled (b-71MI20500). 

Oxidation of the lipid structure in foods containing oils and fats produces carbonyl compounds which are responsible for the flavor and odor associated with rancidity (B-81MI11508) the use of a suitable antioxidant can delay this process. Several heterocyclic compounds are among the antioxidants suitable for use in food ascorbic acid (69) and certain of its derivatives and erythorbic acid. The quinoline derivative (70) is mainly used as an antioxidant in animal feed, but it can also be used to preserve the color of paprika, chili powder and ground chili. 

Figure 141. Molecular structure of PhiSn(S2CO—i-Pr((quinoline /V-oxide).

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