Brucine, oxidation

Strychnine, brucine Oxidation is performed with potassium dichromate solution This oxidizes brucine to the o-qumone which can then be separated chromatographically [17]... 

Nitrate is reduced to nitrite (by cadmium reduction reaction), which is then determined by diazotization (pH = 2.0-2.5) with sulfanilamide and coupling N-( 1 -naphthyl)-1,2-ethylendiamine hydrochloride to form an intensely pink colored azo dye (540 nm) Brucine oxidation by nitrate ion in H2S04 at 100°C to form a yellow compound (cacoteline), which is measured at 410 nm... 

Chiral 4-hydroxy-2-cyclopentenones. Both (R)- and (S)-4-hydroxy-2-cyclo-pentenones can be obtained from phenol. The first step is alkaline hypochlorite oxidation to the acid 1, which is resolved with brucine. Oxidative decarboxylation of 1 gives 2, which is partially dechlorinated and protected as the silyl ether (3). The last step to 4 is reduction with zinc-silver (S, 760) or zinc-copper. ... 

In the following groups of oxidation products it is the benzene ring which is first destroyed. Hanssen showed in 1884 that brucine, on oxidation with chromic acid, furnished an acid, later corrected... 

Hanssen s Acid, CjgHjoOiNj. 2 or IHjO. This acid, obtained by the oxidation of either strychnine or brucine and certain of their derivatives as described above, forms cubical or bipyramidal crystals, m.p. 311° (dec.), — 116-3° (HgO), and yields a dihydro-derivative, CigHjaO Nj,... 

While this work was in progress Spath and Bretschneider showed that strychnine, on oxidation with permanganate in alkaline solution, furnished W-oxalylanthranilic acid (VII), brucine yielding oxalyl-4 5-dimethoxy-anthranilic acid, the latter observation providing confirmation of the evidence previously adduced that the two methoxy-groups in brucine are in the oj Ao-position relative to each other as indicated by Lions, Perkin and Robinson. The results so far considered indicate the presence in brucine and strychnine of the complex (VIII), which can be extended to (IX) if account is taken of the readiness with which carbazole can be obtained from strychnine and brucine and certain of their derivatives by decomposition with alkali at temperatures ranging from 200° to 400°, Knowledge of the structure of the rest of the molecule is mainly due to the results of the exhaustive study by Leuchs and his pupils of the oxidation... 

Three new papers bearing on the structure of strychnine have become available too late for inclusion in this summary of recent work. Woodward, Brehm and Nelson have compared the ultra-violet absorption spectra of strychnine and Leuchs s strychnone (p.. 559) and used the results for a discussion of the relationship of the two alkaloids. Prelog and Kathriner have investigated the oxidation of strychnine, i/t-strychnine and brucine by permanganate in weakly acid solution and Bailey and Robinson from a study of the brucones have confirmed the conclusion of Woodward et al. that Leuchs s strychnone is a true indole derivative. Mention must also be made of a paper by Clemo and King on new reduction products of strychnine, of which a preliminary account has been published with a summary of the ensuing discussion. 

Two pieces of chemical evidence support the three-membered ring formulation. The bifunctional oxazirane prepared from glyoxal, tert-butylamine, and peracetic acid (6) can be obtained in two crystalline isomeric forms. According to the three-membered ring formula there should be two asymmetric carbon atoms which should allow the existence of meso and racemic forms. A partial optical resolution was carried out with 2-7i-propyl-3-methyl-3-isobutyloxazirane. Brucine was oxidized to the N-oxide with excess of the oxazirane. It was found that the unused oxazirane was optically active. 

Lewis201 postulated maltosone as the first product in the oxidation of maltose by Fehling solution, but no osone was detected when maltose was treated with Fenton s reagent.23 Oxidation of maltosone with bromine water gave 2-oxo-maltobionic acid, isolated as its brucine salt.191... 

The virtue of performing the PKR in an enantioselective manner has been extensively elaborated during the last decade. As a result, different powerful procedures were developed, spanning both auxiliary-based approaches and catalytic asymmetric reactions. For instance, the use of chiral N-oxides was reported by Kerr et al., who examined the effect of the chiral brucine N-oxide in the intermolecular PKR of propargylic alcohols and norbornadiene [59]. Under optimized conditions, ee values up to 78% at - 60 °C have been obtained (Eq. 10). Chiral sparteine N-oxides are also able to induce chirality, but the observed enantioselectivity was comparatively lower [60]. 

A solution of the alkaloid brucine in concentrated sulfuric acid was reported [4, 38, 50] to give orange-red colors with nitrate esters and nitramines, probably by oxidation ofbmcine. 

One of the conceptually appealing approaches for enantioselective PKR with cobalt-alkyne complexes is the use of chiral promoters. It is expected that a sterically biased promoter can approach to one of the two equivalent cobalts preferentially, and effect oxidation of GO to make a vacant coordination site. Early attempts were marginally successful, and there remained much room for improvement. Recently, enhanced enantioselectivity has been obtained by using a bulky amine A -oxides like brucine 7V-oxide 44 under carefully controlled conditions (Scheme... 

If 2-camphanyloxyacrylonitrile (15 R = C8H 02C00) is taken for cycloaddition, diastereoisomeric cycloadducts can be separated, and the basic system, 7-oxabicyclo-[2.2.1]hept-5-en-2-one 17, can be obtained in optically pure form [36]. Another way of obtaining enantiomeric ketones is based on crystallization of a brucine complex obtained from the corresponding cyanohydrines (see Sec. III). Ketone 17 can be converted [e.g., by cis-hydroxylation (—>18), protection of the diol system, and Baeyer-Villiger oxidation] to lactone 19, the opening of which leads to furanuronic acid 20. A new development in this field is based in cycloaddition between furan and 2-chloro- or 2-bromoacrolein in the presence of 5 mol% chiral oxazaborolidine 21 as catalyst [37],... 

Groups of reportedly photochromic systems which deserve further study include (a) disulfoxides (123,124), (b) hydrazones (125-129), (c) osazones (130-133), (d ) semicarbazones (134-143), (e) stilbene derivatives (144), (/) succinic anhydrides (145-148), and (g) various dyes (149,150). A number of individual compounds also remain unclassified as to their mechanism of photochromic activity. These include o-nitro-benzylidine isonicotinic acid hydrazide (151), 2,3-epoxy-2-ethyl-3-phenyl-1-indanone (152), p-diethyl- and p-dimethyl-aminophenyli-minocamphor (153), brucine salts of bromo- and chloro-nitromethionic acid (154), diphenacyldiphenylmethane (155,156), 2,4,4,6-tetraphenyl-1,4,-dihydropyridine (155,156), 2,4,4,6-3,5-dibenzoyltetrahydropyran (155,156), o-nitrobenzylidenedesoxybenzoin (157), p-nitrobenzylidene-desoxybenzoin (157), N-(3-pyridyl)sydnone (158,159), tetrabenzoyl-ethylene (160), and the oxidation product of 2,4,5-triphenylimidazole (161,162). 

Further illustration of the inadequacy of hypobromite oxidation for the conversion of glycosides to uronides is the work of Jackson and Hudson.79 Only a twelve percent yield of the brucine salt of methyl a-D-mannuronoside was obtained because of oxidative cleavage of the carbon chain of methyl a-D-mannopyranoside. 

Strychnos lucida R.Br. (leaves) Strychnaceae Brucine (59) Brucine (V-oxide (59) /3-Colubrine (59) Normacusine B (59) Pseudobrucine (59) Pseudostrychnine (59) Strychnine (59)... 

Strychnos lucida and Strychnos ignatii Berg, have been investigated for their alkaloid contents. Alkaloids isolated from the leaves of S. lucida include strychnine, brucine, pseudobrucine, normacusine B, /3-colubrine, pseudostrychnine, and brucine A-oxide. The alkaloids in the branches (without leaves) are the same as in the leaves except for the absence of pseudostrychnine and the addition of diaboline. In the root bark of this... 

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