Synthesis of (±) montagnetol and (±) erythrin

Manaktala, S.K.; Neelakantan, S.; Seshadri, T. R.

doi:10.1016/s0040-4020(01)82157-8

Cited by 12 publications

(11 citation statements)

References 7 publications

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“…In addition, phenylhydrazines having other functional groups in the benzene ring were brought into reaction with compound I, in particular nitro-substituted phenylhydrazines. Facile reduction of nitro group to amino could give rise to extended potentialities in subsequent synthetic transformations of usnic acid derivatives.The reactions of compound I with equimolar amounts of substituted phenylhydrazines II-VIII resulted in the formation of the corresponding fused pyrazole derivatives XI-XVII (Scheme 1), in keeping with published data for unsubstituted phenylhydrazine [5]. When the reactions were carried out with 2 equiv of phenylhydrazine II-VIII or more, the second hydrazine molecule added at the acetyl carbonyl group on C 6 with formation of hydrazones XX-XXVI, but this process was considerably slower, and in most cases the conversion of usnic acid (I) into hydrazones XX-XXVI was not complete even in the presence of a large excess of phenylhydrazine.…”

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confidence: 84%

“…In continuation of our studies on synthetic transformations of usnic acid (I), we examined its reactions with substituted phenylhydrazines. Reactions of I with phenylhydrazine [5] and methylhydrazine [6] were reported previously. These reactions occurred as nucleophilic addition at the acetyl carbonyl group on C 2 (C 11 =O), followed by heterocyclization with closure of pyrazole ring; addition of the second hydrazine molecule at the acetyl group on C 6 (C 13 =O) was not accompanied by heterocyclization, and the corresponding hydrazone was formed.…”

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confidence: 99%

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Chemical modification of usnic acid: III.* Reaction of (+)-usnic acid with substituted phenylhydrazines

et al. 2009

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confidence: 84%

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confidence: 99%

Chemical modification of usnic acid: III.* Reaction of (+)-usnic acid with substituted phenylhydrazines

et al. 2009

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“…I). Some of these (2, 3, 5 and 12) represent preferential attack of the amine function at the chelated acetyl side chain of the (3-triketone system to provide novel P,PJ-diketo enamine structures which are different from the structures proposed by earlier workers (8)(9)(10)(11). Condensation of the amine with the aromatic secondary reaction and furnishes the expected imine derivative.…”

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confidence: 91%

Studies in the usnic acid series. I. The condensation of (+)-usnic acid with aliphatic and aromatic amines

Kutney¹,

Sánchez²

1976

Can. J. Chem.

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Detailed investigations concerned with the reaction of usnic acid (1) and dihydrousnic acid (14) with a variety of aliphatic and aromatic amines are described. Extensive analyses of the characteristic spectroscopic data allow structural assignments for all the isolated products. The correctness of these assignments is established by an X-ray analysis of one of the products resulting from the reaction of usnic acid with ammonia.

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“…13 ( 1 H) and 125.76 ( 13 C) MHz. IR spectra were taken on a Vector 22 spectrometer; mass spectra (70-eV ionizing electron energy), on a DFS high resolution mass spectrometer.…”

Section: Methodsmentioning

confidence: 99%

“…lichens by the literature method [11]. The 7,9-diacetate of 1 was synthesized as before [12]; the pyrazole derivative of UA (4), as before [13]. The oxidation of UA by HNO 3 used the literature method [14].…”

Section: Methodsmentioning

confidence: 99%

Oxidation of usninic acid

et al. 2010

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Reactions of usninic acid with various oxidants were studied. The oxidation occurred at the resorcinol ring. New derivatives of usninic acid were obtained from reactions with per-acids.The isolation of plant metabolites and their chemical modification to produce novel drug candidates with high physiological activity is an active area in natural product chemistry.An interesting subject for chemical modification is usninic acid (UA) (1), the principal constituent in extracts of most lichens and a compound with a broad spectrum of biological activity. Interest in UA has been unwavering for many decades [1]. Nevertheless, reactions involving oxidation of UA or its derivatives have been little studied. Thus, cleavage of the carbon skeleton of UA in the presence of base in alcohol and aqueous alcohol was reported [2][3][4][5]. Under these conditions, different researchers have obtained complicated mixtures of products, several of which were isolated in small yields. Oxidation of UA 7,9-diacetate by KMnO 4 occurred at ring C and also gave a complicated product mixture [6]. The action of H 2 O 2 on UA was studied [7]. The reaction was carried out in pyridine and formed the 2-acetoxy derivative (83% yield).Herein we report results from the reaction of UA with various oxidants. Reactions of 1 with conc. HNO 3 and CrO 3 reagents gave complicated product mixtures that resulted apparently from extensive destruction of the substrate.On the other hand, 1 was not oxidized in the presence of oxidants such as Pb(CH 3 COO) 4 , KIO 4 , O 2 , t-BuOOH, DessMartin periodinan, H 2 O 2 in CHCl 3 (in the presence of TEBA), and SeO 2 in the presence of H 2 O 2 .The oxidation occurred at room temperature and formed two compounds if organic per-acids (MCPBA, CH 3 CO 3 H, MPPA) in CHCl 3 were used as oxidants. The products were most conveniently isolated from CH 3 CO 3 H because its decomposition product, CH 3 CO 2 H, was easily removed from the reaction mixture by washing with water. If MCPBA or MPPA were used, the products were difficult to isolate from the m-chlorobenzoic or phthalic acids, respectively, formed during the reaction because the standard work up with NaHCO 3 solution removed part of the UA oxidation products with the aqueous phase. Column chromatography over silica gel isolated 2 and 3 in yields of 41 and 27%, respectively (Scheme 1).

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Synthesis of (±) montagnetol and (±) erythrin

Cited by 12 publications

References 7 publications

Chemical modification of usnic acid: III.* Reaction of (+)-usnic acid with substituted phenylhydrazines

Chemical modification of usnic acid: III.* Reaction of (+)-usnic acid with substituted phenylhydrazines

Studies in the usnic acid series. I. The condensation of (+)-usnic acid with aliphatic and aromatic amines

Oxidation of usninic acid

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