Pyrocene Park Pyne, Stephen
American scientist,
05/2023, Volume:
111, Issue:
3
Journal Article
Stand at Glacier Point and you'll instantly understand why it is one of North America's iconic overlooks. The great trough of Yosemite Valley in California fills the foreground below and, with almost ...gravitational pull, carries the eye eastward to the crest line of the Sierra Nevada mountains. With its sheer granite walls, waterfalls that plunge hundreds of meters, and uniquely sculpted stone monoliths (such as El Capitan and Half Dome), words such as monumental hardly do justice to the scene. It's a landscape shaped by Pleistocene ice that widened and deepened valleys, rounded exposed granite, cached boulders and soils, and scoured routes for runoff that eventually became rivers and waterfalls. Pivot south, however, and you'll see a scene as aesthetically bland as Yosemite Valley is gripping. The eye passes over it as fast as a stone skimming across a lake.
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For most of human history, fire has been a pervasive presence in human life, and so also in human thought. This essay examines the ways in which fire has functioned intellectually in Western ...civilization as mythology, as religion, as natural philosophy and as modern science. The great phase change occurred with the development of industrial combustion; fire faded from quotidian life, which also removed it from the world of informing ideas. Beginning with the discovery of oxygen, fire as an organizing concept fragmented into various subdisciplines of natural science and forestry. The Anthropocene, however, may revive the intellectual role of fire as an informing idea or at least a narrative conceit.
This article is part of the themed issue ‘The interaction of fire and mankind’.
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From a fire policy of prevention at all costs to today's restored burning, Between Two Fires is America's history channeled through the story of wildland fire management. Stephen J. Pyne tells of a ...fire revolution that began in the 1960s as simple suppression and then was replaced with more enlightened programs of fire management. It then explains the counterrevolution in the 1980s that stalled the movement, and finally describes the fire scene that has evolved since then.Pyne is uniquely qualified to tell America's fire story. The author of more than a score of books, he has told fire's history in the United States, Australia, Canada, Europe, and the Earth overall. In his earlier life, he spent fifteen seasons with the North Rim Longshots at Grand Canyon National Park.In Between Two Fires, Pyne recounts how, after the Great Fires of 1910, a policy of fire suppression spread from America's founding corps of foresters into a national policy that manifested itself as a costly all-out war on fire. After fifty years of attempted fire suppression, a revolution in thinking led to a more pluralistic strategy for fire's restoration. The revolution succeeded in displacing suppression as a sole strategy, but it has failed to fully integrate fire and land management and has fallen short of its goals.Today, the nation's backcountry and increasingly its exurban fringe are threatened by larger and more damaging burns, fire agencies are scrambling for funds, firefighters continue to die, and the country seems unable to come to grips with the fundamentals behind a rising tide of megafires. Pyne has once again constructed a history of record that will shape our next century of fire management. Between Two Fires is a story of ideas, institutions, and fires. It's America's story told through the nation's flames.
The reactions of α,β-unsaturated N-acyliminium ions, generated in situ from 4(S)-O-substitutedhydroxy-5-hydroxy-5-vinyl-N-alkylpyrrolidin-2-ones, with allylsilanes and indoles leading to the ...formation of spirocyclic heterocycles, are reported. Six single crystal X-ray structures and extensive 2D NMR experiments confirmed the structures and stereochemistries of these products. In addition, computational studies provided mechanistic insights and an understanding of the stereochemical outcomes of these reactions.
The aim of this project was to develop a synthetic protocol for the preparation of a cephamycin scaffold that would readily allow the synthesis of its analogues with variations at the C-7 amino group ...and the C-3' position. We also aimed to develop a method that avoided the use of toxic and potentially explosive diphenyldiazomethane. These aims were achieved via the synthesis of the novel α-bromo acetamide
which allowed functionalization at the α-bromo acetamide position by azide and then the introduction of a 4-phenyl-1
-1,2,3-triazol-1-yl moiety via a Cu(I)-catalysed azide-alkyne cycloaddition reaction with phenylacetylene. Palladium-catalyzed arylthioallylation reactions then allowed the introduction of 3'-arylthiol substituents. We also report for the first time the synthesis of the 4-methoxybenzyl ester of (6
,7
)-3-(acetyloxy)methyl-7-amino-7-methoxy-8-oxo-5-thia-1-azabicyclo4.2.0oct-2-ene-2-carboxylic acid and the use of diphenyl trichloroacetimidate, instead of diphenyldiazomethane, and 4-methoxybenzyl trichloroacetimidate to prepare related 4-methoxybenzyl esters. The chemistry described, and several of the synthetic intermediates reported here, are potentially valuable methods and scaffolds, respectively, for further development of β-lactam antibiotics.
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The iminosugar core of natural glyphaeaside C, originally assigned as a derivative of the piperidine natural product 1-deoxynojirimycin (DNJ), has been revised as a derivative of ...2,5-dideoxy-2,5-imino-l-mannitol (l-DMDP) by the total synthesis of its enantiomer. This revised l-DMDP-derived configuration is the first of its kind to be observed in nature. The prepared iminosugars displayed the nanomolar inhibition of bovine liver β-glucosidase and β-galactosidase.
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Four new flavonoids (1–4), a new benzyl benzoate derivative (5), five new oxepinones (6–10), and 14 known compounds (11–24) were isolated from the leaf and twig extracts of Desmos cochinchinensis. ...Their structures were established by spectroscopic methods. The structure of 1 was also confirmed by X-ray diffraction data. The absolute configurations of 3, 4, and 6–10 were determined from comparisons of their ECD spectra with those of relevant reported compounds. Compounds 1, 2, 6, 8, 10, 12–15, and 17 showed α-glucosidase inhibitory activities with IC50 values ranging from 0.2 to 4.9 μM.
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The 10 glyphaeaside alkaloids isolated from the roots of Glyphaea brevis were originally purported as piperidine-based 1-C-alkylated iminosugars, with the A-, B-, and C-type glyphaeasides bearing ...l-DFJ, DGJ, and DNJ ring configurations, respectively. Subsequent investigations have revealed glyphaeaside C as being a pyrrolidine-based iminosugar with a DMDP ring configuration via total synthesis of the revised structure. In this work, side chain diastereomers of the originally purported structure of glyphaeaside C (10) and two related α-1-C-alkylated DNJ derivatives were synthesized from a common precursor, which was prepared in turn via stereoselective Grignard addition to a protected d-glycosylamine, followed by a reductive amination–cyclization sequence. Glycosidase inhibitory activity studies revealed general structure 10 as having potent inhibition against various α-glucosidases and weak inhibition against almond β-glucosidase in agreement with similar DNJ-based iminosugars and in contrast to natural glyphaeaside C, suggesting that the (1,2-dihydroxy-3-phenyl)propyl moiety does not play a particularly vital role in the inhibitory modes of action of either compound. Furthermore, the absolute configuration of natural glyphaeaside C was proposed as that of d-DMDP, and the structures of the A- and B-type glyphaeasides were revised as 1-deoxy-DALDP and DALDP derivatives, respectively, based on interpretation of their reported NMR spectroscopic data.
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