108. The synthesis of usnic acid

Barton, D. H. R.; Deflorin, A. M.; Edwards, O. E.

doi:10.1039/jr9560000530

Cited by 106 publications

(44 citation statements)

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“…This structural assignment was further supported by the subsequent reaction of the compound with acid and acetic anhydride to generate the biaryl system 29. [148] These ideas would all be turned upside down in 1955. [148] These ideas would all be turned upside down in 1955.…”

Section: The Ramifications Of Structural Misassignmentsmentioning

confidence: 99%

Chasing Molecules That Were Never There: Misassigned Natural Products and the Role of Chemical Synthesis in Modern Structure Elucidation

2005

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Over the course of the past half century, the structural elucidation of unknown natural products has undergone a tremendous revolution. Before World War II, a chemist would have relied almost exclusively on the art of chemical synthesis, primarily in the form of degradation and derivatization reactions, to develop and test structural hypotheses in a process that often took years to complete when grams of material were available. Today, a battery of advanced spectroscopic methods, such as multidimensional NMR spectroscopy and high-resolution mass spectrometry, not to mention X-ray crystallography, exist for the expeditious assignment of structures to highly complex molecules isolated from nature in milligram or sub-milligram quantities. In fact, it could be argued that the characterization of natural products has become a routine task, one which no longer even requires a reaction flask! This Review makes the case that imaginative detective work and chemical synthesis still have important roles to play in the process of solving nature's most intriguing molecular puzzles.

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Section: The Ramifications Of Structural Misassignmentsmentioning

confidence: 99%

Chasing Molecules That Were Never There: Misassigned Natural Products and the Role of Chemical Synthesis in Modern Structure Elucidation

2005

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“…A classic and well-known example, as shown in Figure 1.4, is the synthesis of (±)-usnic acid (9) by Barton et al 22 A lichen constituent usnic acid is dissymmetric at a glance. A classic and well-known example, as shown in Figure 1.4, is the synthesis of (±)-usnic acid (9) by Barton et al 22 A lichen constituent usnic acid is dissymmetric at a glance.…”

Section: Molecular Symmetry and Synthesismentioning

confidence: 99%

Introduction—Biofunctional Molecules and Organic Synthesis

Mori

2010

Chemical Synthesis of Hormones, Pheromones and Other Bioregulators

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“…Phenylquinones are wide- spread especially among fungi; in contrast, the mainly yellow pulvic acid derivatives must be regarded as typical lichen substances. While picrorocellin (27) is evidently formed by direct condensation of two phenylalanine units, the terphenylquinones are formed by condensation of two (probably activated) phenylpyruvic acid derivatives, as has been shown for the fungal quinone volucrisporin, a meta-dihydroxyterphenylquinone 1881. The subsequent oxidative ring opening of the symmetrical terphenyls such as polyporic acid then leads to the pulvic acid derivatives with their characteristic diphenylbutadiene system, as experiments with 11 -14c]-~~-3-phenylalanine 189,901 and [14C]-polyporic acid quinone 1911 have shown.…”

Section: The Shikimic Acid Groupmentioning

confidence: 99%

“…their biosynthesis proceeds in the sequence: phosphoenolpyruvic acid + erithrytyl 4-phosphate + shikimic acid + chorismic acid + prephenic acid + cs-c3 derivatives. A diketopiperazine, picrorocellin (27), two terphenylquinones, telephoric acid (29), and polyporic acid (28), as well as nine pulvic acid derivatives (30)-(35) have so far been found in lichens (Fig. 15).…”

Section: The Shikimic Acid Groupmentioning

confidence: 99%