Desmotropy in reduced plumbagins: α- and β-Dihydroplumbagins

Reviriego, Felipe; Alkorta, Ibón; Elguero, José

doi:10.1016/j.molstruc.2008.04.002

Cited by 11 publications

(7 citation statements)

References 47 publications

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“…Although not discussed in detail in this survey, there are several reports on non-heterocyclic examples of desmotropy: 2-amino-3-hydroxy-6-phenylazopyridine (not named desmotropy nor tautomeric polymorphism), acetohexamide (named tautomeric polymorphism), ortho -anthraquinones (named desmotropy), salicylideneamines (named tautomeric polymorphism), plumbagins (named desmotropy), Schiff bases (named tautomeric forms); sulfamethazine (sulfadimidine, named tautomeric polymorphism), and glybenclamide (glyburide, different names). − …”

Section: Papers Reporting Tautomeric Polymorphismmentioning

confidence: 99%

Polymorphism and Desmotropy in Heterocyclic Crystal Structures

Elguero

2011

Crystal Growth & Design

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There is some confusion about concepts such as polymorphism, tautomerism, tautomeric polymorphism, and desmotropy. This perspective review tries to clarify them by defining their boundaries. Most examples are from heterocyclic compounds and differentiate between NH/OH tautomers (fast prototropy) and CH ones (slow prototropy). In the case of “tautomeric polymorphism” and “desmotropy” it is strongly recommended to use desmotropy. The different possibilities of crystallization of tautomers are examined in the conclusion.

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Section: Papers Reporting Tautomeric Polymorphismmentioning

confidence: 99%

Polymorphism and Desmotropy in Heterocyclic Crystal Structures

Elguero

2011

Crystal Growth & Design

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“…Eventually, it was found that spirocycle 25 could be tautomerized to its desmotropic form 63 under basic conditions (i.e., K 2 CO 3 , Scheme 6 ). 44 When the latter compound was treated with PIDA in CH 2 Cl 2 /H 2 O the desired quinone 64 could be isolated in only 4% yield, along with substantial quantities of benzylic oxidation product 62 (13%) and recovered starting material (45%). A number of different oxidants (i.e., Fremy’s salt, O 2 /salcomine catalyst, PIFA) were examined in efforts to improve the efficiency of the transformation of 63 to quinone 64 , but unfortunately to no avail.…”

Section: Resultsmentioning

confidence: 99%

“…Eventually, it was found that spirocycle 25 could be tautomerized to its desmotropic form 63 under basic conditions (i.e., K 2 CO 3 , Scheme ) . When the latter compound was treated with PIDA in CH 2 Cl 2 /H 2 O the desired quinone 64 could be isolated in only 4% yield, along with substantial quantities of benzylic oxidation product 62 (13%) and recovered starting material (45%).…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis of Viridicatumtoxin B and Analogues Thereof: Strategy Evolution, Structural Revision, and Biological Evaluation

et al. 2014

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The details of the total synthesis of viridicatumtoxin B (1) are described. Initial synthetic strategies toward this intriguing tetracycline antibiotic resulted in the development of key alkylation and Lewis acid-mediated spirocyclization reactions to form the hindered EF spirojunction, as well as Michael–Dieckmann reactions to set the A and C rings. The use of an aromatic A-ring substrate, however, was found to be unsuitable for the introduction of the requisite hydroxyl groups at carbons 4a and 12a. Applying these previous tactics, we developed stepwise approaches to oxidize carbons 12a and 4a based on enol- and enolate-based oxidations, respectively, the latter of which was accomplished after systematic investigations that revealed critical reactivity patterns. The herein described synthetic strategy resulted in the total synthesis of viridicatumtoxin B (1), which, in turn, formed the basis for the revision of its originally assigned structure. The developed chemistry facilitated the synthesis of a series of viridicatumtoxin analogues, which were evaluated against Gram-positive and Gram-negative bacterial strains, including drug-resistant pathogens, revealing the first structure–activity relationships within this structural type.

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“…The mass spectra of the TMS derivatives of both dihydronaphthoquinones indicate that the diketo-tautomers (assigned to structures 5a and 6a , characterized by m/z 247) are predominant in the petroleum ether extract. In contrast, the naphthotriol-tautomers ( 7 and 8 ) were not detected in underivatized samples but may be represented by their TMS derivatives ( 7c and 8c , characterized by m/z 406; 7a and 8a ; m/z 318; 7b and 8b , m/z 319) that are less abundant (following the thermodynamic ratio of about 1:4) [ 13 ]. This corresponds well with the fact that natural dihydroplumbagin ( 5 ) isolated with chloroform from Diospyros maritima retains the same configuration (2 R ) as the corresponding position (3 R ) in isoshinanolone ( 3 ) from the same plant [ 12 ], so tautomerism and subsequent racemization may be limited in aprotic solvents.…”

Section: Discussionmentioning

confidence: 99%

Contrasting Dihydronaphthoquinone Patterns in Closely Related Drosera (Sundew) Species Enable Taxonomic Distinction and Identification

Schlauer

Hartmeyer²,

Hartmeyer³

et al. 2021

Plants

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Dihydronaphthoquinones are described as constituents of sundews (Drosera), Venus flytraps (Dionaea), and dewy pines (Drosophyllum) for the first time. As in the corresponding naphthoquinones, these reduced derivatives may occur in two regio-isomeric series distinguished by the relative position of a methyl group (at position 2 or 7 in the naphthalene skeleton), depending on the taxon. Species producing plumbagin (2-methyljuglone, 1) do commonly contain the corresponding dihydroplumbagin (5), while species containing ramentaceone (7-methyljuglone, 2) also contain dihydroramentaceone (7-methyl-β-dihydrojuglone, 6). So far, only few species containing plumbagin (1) and dihydroplumbagin (5) additionally form dihydroramentaceone (6) but not ramentaceone (2). Thus, subtle but constant differences in the chemism of closely related and morphologically similar species reliably define and distinguish taxa within D. sect. Arachnopus, which is taken to exemplify their chemotaxonomic utility. The joint presence of quinones and hydroquinones allows observations and predictions on the chemical structures and the reactions of these intriguing natural products.

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Desmotropy in reduced plumbagins: α- and β-Dihydroplumbagins

Cited by 11 publications

References 47 publications

Polymorphism and Desmotropy in Heterocyclic Crystal Structures

Polymorphism and Desmotropy in Heterocyclic Crystal Structures

Total Synthesis of Viridicatumtoxin B and Analogues Thereof: Strategy Evolution, Structural Revision, and Biological Evaluation

Contrasting Dihydronaphthoquinone Patterns in Closely Related Drosera (Sundew) Species Enable Taxonomic Distinction and Identification

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