bluuebunny/crossref_metadata_2025 huggingface dataset:
Alkaloid Synthesis: Paliurine F, Lepadiformine, and 7-Deoxypancratistatin
Authors: Taber Douglass
Published: November 2020

The sedative alkaloid paliurine F 7 is a pentapeptide bridged by an arene. Gwilherm Evano of the Université de Versailles took advantage of this in his synthesis (Angew. Chem. Int. Ed. 2007, 46, 572) of 7, although it was necessary to prepare, from serine, one of the amino acid derivatives, the protected 3-hydroxyprolinol 2. The key step in the synthesis was the Cu-catalyzed intramolecular coupling of 5 to give the macrolactam 6. Deprotection and acylation then gave paliurine F 7. Lepadiformine 14, isolated from the tunicate Clavelina lepadiformis, shows moderate cytotoxicity, and is also a K+ channel blocker. The synthesis of 14 (Angew. Chem. Int. Ed. 2007, 46, 2631) by Donald Craig of Imperial College started with the aziridine 8, prepared from the corresponding epoxide. Opening of the protected aziridine with the anion of methyl phenyl sulfone set the stage for condensation of the dianion derived from 9 with the aldehyde 10, to give, with high diastereocontrol, the amine 11. Deprotection followed by cyclization then led to the activated ether 12. While the opening of 12 with an alkyl Grignard reagent proceeded with undesired inversion at the reacting center, opening with the alkynyl Grignard delivered mainly the desired 13. Reduction followed by oxidation, epimerization and reduction then gave lepadiformine 14. The Amaryllidaceae alkaloid 7-deoxypancratistatin 21 has potent antiviral activity. A challenge in the assembly of 21 is that the ring fusion is trans, less stable than the corresponding cis diastereomer. The synthesis of 21 (J. Org. Chem. 2007, 72, 2570) by Albert Padwa of Emory University started with 17, the preparation of which by the combination 15 and 16 he had previously reported in the course of his synthesis of lycoricidine (OHL December 11, 2006). Ester 17 had the desired trans ring fusion, but with an angular ester substituent that had to be removed. While it would be expected from the mechanism that Rh-mediated decarbonylation of an aldehyde would proceed with retention of absolute configuration, and this had been confirmed experimentally, this reaction had not been applied to such a challenging substrate. In the event, the transformation proceeded smoothly, to give the desired trans 19. Dehydration and dihydroxylation of 19 led to the cyclic sulfate 20, selective SN2 opening of which delivered 7-deoxypancratistatin 21.
Stereocontrolled Alkaloid Construction: Rhazinicine (Gaunt), 9-epi-Pentazocine (Zhai and Li), Fawcettidine (Dake), Strychnine (Padwa), and Yohimbine (Jacobsen)
Authors: Taber Douglass
Published: November 2020

The power of catalytic C-H functionalization is illustrated by the elegant synthesis of rhazinicine 3 devised (Angew. Chem. Int. Ed. 2008, 47, 3004) by Matthew J. Gaunt of the University of Cambridge. The key step in the synthesis was the oxidative cyclization of 1 to 2. Although 1 has many C-H sites, the Pd catalyst selected for the α position of the pyrrole, leading, after intramolecular Heck addition and β-hydride elimination, to the alkene 2. Reduction and macrolactamization completed the synthesis of 3. Hongbin Zhai of the Shanghai Institute of Organic Chemistry and Zhong Li of East China University of Science and Technology prepared (Organic Lett. 2008, 10, 2457) the analgesic (-)-9- epi -pentazocine 8 from the amino ester 4, itself available from D-tyrosine. In the conversion of 5 to 6, the (i -PrO)2 Ti formed a ring, leading to 6 as a single diastereomer and geometric isomer. HBr then effected both deprotection of the methyl ether and cyclization, to give 7, which was carried on to 8. The Pt-catalyzed cyclization of 9 to 10 set the stage for the synthesis of ( + )-fawcettidine 15 by Gregory R. Dake of the University of British Columbia (Angew. Chem. Int. Ed. 2008, 47, 4221). This synthesis also illustrated the power of the Ramberg-Bäcklund reaction for the assembly of medium rings. The thiolate liberated from 12 readily added to the enone, to give 13. Oxidation to the sulfone followed by the Ramberg-Bäcklund reaction (halogenation, intramolecular displacement, chelotropic elimination of SO2 ) then delivered 14, which was selectively reduced, leading to 15. Albert Padwa of Emory University has developed (J. Org. Chem. 2008, 73, 3539) a general route to the Strychnos alkaloids, based on the facile cyclization of the furan 16 to the tetracyclic ketone 17. This project culminated in the synthesis of the heptacyclic strychnine 20. Eric N. Jacobsen of Harvard University has devised a family of catalysts for the enantioselective Pictet-Spengler reaction of tryptamine 21. He has now (Organic Lett. 2008, 10, 745) used this approach to prepare the triene 22 in 94 % ee.
Alkaloid Synthesis: (-)-Aurantioclavine (Stoltz), (-)-Esermethole (Nakao/Hiyama/ Ogoshi), (-)-Kainic Acid (Tomooka), Dasycarpidone (Bennasar), (-)-Cephalotaxine (Ishibashi) and Lysergic Acid (Fujii/Ohno)
Authors: Taber Douglass
Published: November 2020

Intriguing strategies have been developed for the stereocontrolled assembly of complex alkaloid structures. Brian M. Stoltz of Caltech prepared (J. Am. Chem. Soc. 2008, 130, 13745) the enantiomerically-pure alcohol precursor to the secondary amine 1 by enantioselective oxidation of the racemic alcohol. Intramolecular Mitsunobu coupling of 1 then led to (-)-Aurantioclavine 3. Yoshiaki Nakao and Tamejiro Hiyama of Kyoto University and Sensuke Ogoshi of Osaka University developed (J. Am. Chem. Soc. 2008, 130, 12874) an enantioselective Ni catalyst for the cyclization of 4 to 5. Oxidation and cyclization then delivered (-)-Esermethole 6. Although the sulfonamide 7 appears to be prochiral, in fact its two most stable conformations are bent, and enantiomers of each other, with a significant barrier for interconversion. Katsuhiko Tomooka of Kyushu University separated (Tetrahedron Lett. 2008, 49, 6327) the enantiomers of 7, then carried the enantiomercially-pure 7 on, by Pd-catalyzed Cope rearrangement, to 8 and so to (-)-Kainic Acid 9. M.-Lluïsa Bennasar of the University of Barcelona prepared (J. Org. Chem. 2008, 73, 9033) the acyl selenide 11 from the indole 10. While the radical derived from 11 might have been expected to undergo 5-exo cyclization, in the event the 6-endo mode dominated, to give Dasycarpidone 12 and its diastereomer. Hiroyuki Ishibashi of Kanazawa University showed (Organic Lett. 2008, 10, 4129) that the radical cascade cyclization of the enamine 13, derived from diethyl tartrate, proceeded with remarkable diastereocontrol, to give 14. The amide 14 was converted to (-)-Cephalotaxine 15. Nobutaka Fujii and Hiroaki Ohno, also of Kyoto University, used (Organic Lett. 2008, 10, 5239) a Pd catalyst to mediate the cascade cyclization of 16 to 17. Although 16 has two stereogenic centers, including the allene, it is the aminated stereogenic center of 17 that sets the absolute configuration of the product Lysergic Acid 18. One intermediate in the conversion of 16 to the tetracyclic 17 is the tricyclic π-allyl Pd complex. If all the material could be channeled through that pathway, there is a good chance that the chiral Trost catalyst could effectively control the absolute configuration of the aminated stereogenic center as it is formed, leading to the enantiomerically enriched product 18.
Preparation of Benzene Derivatives: The Barrett Syntheses of Dehydroaltenuene B and 15G256β
Authors: Taber Douglass
Published: November 2020

Several new methods for the direct functionalization of Ar-H have appeared. Hisao Yoshida of Nagoya University observed (Chem. Comm. 2008, 4634) that under irradiation, TiO2 in water effected meta hydroxylation of benzonitrile 1 to give the phenol 2. Anisole showed ortho selectivity, while halo and alkyl aromatics gave mixtures. Melanie S. Sanford of the University of Michigan reported (J. Am. Chem. Soc. 2008, 130, 13285) a complementary study of Pd-catalyzed ortho acetoxylation. Jin-Quan Yu of Scripps/La Jolla developed (Angew. Chem. Int. Ed. 2008, 47, 5215) a Pd-catalyzed protocol for ortho halogenation of aromatic carboxylates such as 3. A related protocol (J. Am. Chem. Soc. 2008, 130, 17676) led to ortho arylation. Trond Vidar Hansen of the University of Oslo devised (Tetrahedron Lett. 2008, 49, 4443) a one-pot procedure for the net ortho cyanation of phenols such as 5 to the salicylnitrile 6. Robin B. Bedford of the University of Bristol, Andrew J. M. Caffyn of the University of the West Indies and Sanjiv Prashar of the Universidad Rey Juan Carlos established (Chem. Comm. 2008, 990) a Rh-catalyzed protocol for ortho arylation of phenols such as 7. Laurent Désaubry of the Université Louis Pasteur observed (Tetrahedron Lett. 2008, 49, 4588) regioselective coupling of unsymmetrical difluorobenzenes such as 9 to give the ether 10. Fuk Yee Kwong of Hong Kong Polytechnic University extended (Angew. Chem. Int. Ed. 2008, 47, 6402) Pd-mediated amination to the notoriously difficult mesylates, such as 11. John F. Hartwig of the University of Illinois reported (J. Am. Chem. Soc. 2008, 130, 13848) a related method for the amination of aryl tosylates. Hong Liu of the Shanghai Institute of Materia Medica found (Organic Lett. 2008, 10, 4513) that the Fe-catalyzed amination of aryl halides such as 13 sometimes gave mixtures of regioisomers. Hideki Yorimitsu and Koichiro Oshima of Kyoto University effected (Angew. Chem. Int. Ed. 2008, 47, 5833) Ag-catalyzed Grignard cross coupling with aryl halides, converting 15 into 16. Note that silyl aromatics such as 16 are readily reduced under dissolving metal conditions to give allyl silanes.
Intermolecular and Intramolecular Diels-Alder Reactions: Platencin (Banwell), Platensimycin (Matsuo), (-)-Halenaquinone (Trauner), ( + )-Cassaine (Deslongchamps)
Authors: Taber Douglass
Published: November 2020

José Barluenga of the Universidad de Oviedo described (Organic Lett. 2008, 10, 4469) a powerful route from lithiated arenes such as 1 to the benzocyclobutane 3, the immediate precursor to the powerful o-quinone methide Diels-Alder diene. Michael E. Jung of UCLA developed (Organic Lett. 2008, 10, 3647) a triflimide catalyst for the inverse electron demand coupling of the highly substituted diene 4 with the enol ether 5 to give 6 with high diastereocontrol. Joseph M. Fox of the University of Delaware showed (J. Org. Chem. 2008, 73, 4283) that the cyclopropene carboxylate 8 was a powerful and selective dienophile. Richard P. Hsung and Kevin P. Cole of the University of Wisconsin finally (Adv. Synth. Cat. 2008, 350, 2885) reduced to practice the long-sought enantioselective Diels-Alder cycloaddition of a trisubstituted aldehyde, 11. Li Deng of Brandeis University devised (J. Am. Chem. Soc. 2008, 130, 2422) a Cinchona -derived catalyst for Diels-Alder cycloaddition to the diene 13 with high ee. Miguel Á. Sierra of the Universidad Complutense, Madrid, and Alejandra G. Suárez of the Universidad Nacional de Rosario described (Organic Lett. 2008, 10, 3389) a clever switchable chiral auxiliary 16 that favored diastereomer S-18 on thermal addition, but R-18 with EtAlCl2. New approaches to the intramolecular Diels-Alder reaction continue to be introduced. Mathias Christmann, now at the TU Dortmund, showed (Angew. Chem. Int. Ed. 2008, 47, 1450) that a secondary amine organocatalyst converted the prochiral dialdehyde 19 into the bicyclic diene 20 with high de and ee. Martin G. Banwell of the Australian National University prepared (Organic Lett. 2008, 10, 4465) the triene 21 in high ee by microbiological oxidation of iodobenzene. On warming, 21 was converted smoothly into 22, which was carried on in a formal synthesis of platencin. Jun-ichi Matsuo of Kanazawa University was able (Organic Lett. 2008, 10, 4049) to induce (neat, 180 °C) the intermolecular Diels-Alder cycloaddition of 23 with 24, delivering the cycloadduct 25 with 11:1 diastereocontrol.
Stereocontrolled Carbocyclic Construction: The Trauner Synthesis of the Shimalactones
Authors: Taber Douglass
Published: November 2020

Benjamin List of the Max Planck Institute, Mülheim devised (J. Am. Chem. Soc. 2008, 130, 6070) a chiral primary amine salt that catalyzed the enantioselective epoxidation of cyclohexenone 1 . Larger ring and alkyl-substituted enones are also epoxidized with high ee. Three- and four-membered rings are versatile intermediates for further transformation. Tsutomu Katsuki of Kyushu University developed (Angew. Chem. Int. Ed. 2008, 47, 2450) an elegant Al(salalen) catalyst for the enantioselective Simmons-Smith cyclopropanation of allylic alcohols such as 3. Kazuaki Ishihara of Nagoya University found (J. Am. Chem. Soc. 2007, 129, 8930) chiral amine salts that effected enantioselective 2+2 cycloaddition of α-acyloxyacroleins such as 5 to alkenes to give the cyclobutane 7 with high enantio- and diastereocontrol. Gideon Grogan of the University of York overexpressed (Adv. Synth. Cat. 2008, 349, 916) the enzyme 6-oxocamphor hydrolase in E. coli . The 6-OCH so prepared converted prochiral diketones such as 8 to the cyclopentane 9 in high ee. Richard P. Hsung of the University of Wisconsin found (Organic Lett. 2008, 10, 661) that the carbene produced by oxidation of the ynamide 10 cyclized to 11 with high de. Teck-Peng Loh of Nanyang Technological University extended (J. Am. Chem. Soc. 2008, 130, 7194) butane-2,3-diol directed cyclization to the preparation of the cyclopentane 15. Note that sidechain relative configuration is also controlled. We established (J. Org. Chem. 2008, 73, 3467) that the thermal ene reaction of 17 delivered the tetrasubstituted cyclopentane 18 as a single diastereomer. Tony K. M. Shing of the Chinese University of Hong Kong devised (J. Org. Chem. 2007, 72, 6610) a simple protocol for the conversion of carbohydrate-derived lactones such as 19 to the highly-substituted, enantiomerically-pure cyclohexenone 21. Hiromichi Fujioka and Yasuyuki Kita of Osaka University established (Organic Lett. 2007, 9, 5605) a chiral diol-mediated conversion of the cyclohexadiene 22 to the diastereomerically pure cyclohexenone 24. Dirk Trauner, now of the University of Munich, reported (Organic Lett. 2008, 10, 149) an elegant assembly of the neuritogenic polyketide shimalactone A 28.
Stereocontrolled Carbocyclic Construction: The Mulzer Synthesis of (-)-Penifulvin A
Authors: Taber Douglass
Published: November 2020

Tanmaya Pathak of the Indian Institute of Technology, Kharagpur devised (J. Org. Chem. 2009, 74, 2710) a preparation of enantiomerically-pure oxygenated cyclopropanes such as 3 from carbohydrate precursors. Andrei K. Yudin of the University of Toronto established (Organic Lett. 2009, 11, 1281) a route to aminated cyclobutanes such as 5 based on sigmatropic rearrangement of the β-lactam 4. Tanmaya Pathak of the Indian Institute of Technology, Kharagpur devised ( J. Org. Chem. 2009 , 74 , 2710) a preparation of enantiomerically-pure oxygenated cyclopropanes such as 3 from carbohydrate precursors. Andrei K. Yudin of the University of Toronto established (Organic Lett . 2009 , 11 , 1281) a route to aminated cyclobutanes such as 5 based on sigmatropic rearrangement of the β -lactam 4 . Stephen C. Bergmeier of Ohio University reported (Tetrahedron 2009, 65, 741) a study of the balance between five- and six-membered ring formation in the cyclization of aziridines such as 6. Professor Bergmeier also described (Tetrahedron Lett. 2009, 50, 1261) the bridging additions of enones to cyclic allyl silanes such as 8. This is particularly interesting, as 8 is easily prepared by Birch reduction of the corresponding phenyl silane. Ullrich Jahn of the Academy of Sciences of the Czech Republic observed (Chem. Eur. J. 2009, 15, 58) that the free-radical cyclization of 11 proceeded to give mainly the diastereomer 12 (~ 1:1 at the secondary allylic position). Daesung Lee of the University of Illinois at Chicago reasoned (J. Am. Chem. Soc. 2009, 131, 8413) that the stereochemical relationship between the O and the adjacent C-H of 13 was such that the C-H would be deactivated. The cyclization of the alkylidene carbene derived from 13 indeed proceeded to give 14, setting the stage for the synthesis of platensimycin. Marco A. Cufolini of the University of British Columbia found (Organic Lett . 2009, 11, 1539) an easy protocol for the generation of a nitrile oxide and subsequent dipolar cycloaddition, by oxidation of the oxime.
The Takayama Synthesis of (-)-Cernuine
Authors: Taber Douglass
Published: November 2020

(-)-Cernuine 3 falls in the subset of the Lycopodium alkaloids that feature a bicyclic aminal core. There had not been a total synthesis of this class of alkaloids until the recent (Organic Lett. 2008, 10, 1987) work of Hiromitsu Takayama of Chiba University. The key step in this synthesis was a diastereoselective intramolecular reductive amination, converting 1 to 2. As is apparent from the 3-D projection, (-)-cernuine 3 has a tricyclic trans-anti-trans aminal core, with an appended six-membered ring, both branches of which are axial on the core. While the branch that is part of the aminal could be expected to equilibrate, the other branch had to be deliberately installed. The synthesis began with (+)-citronellal 4, each enantiomer of which is commercially available in bulk. After protection and ozonolysis, the first singly-aminated stereogenic center was installed by enantioselective, and therefore diastereoselective, addition of 5 to the azodicarboxylate 6, mediated by the organocatalyst 7. Reductive cleavage of the N-N bond followed by acetal methanolysis converted 8 to 9. Ionization followed by allyl silane addition then delivered 11, having the requisite axial alkyl branch. The next two tasks were the assembly of the second of the four rings of 3, and the construction of the second single-aminated stereogenic center. The ring was assembled by deprotection of 11 followed by acylation with acryloyl chloride, to give 12. Grubbs cyclization followed by hydrogenation then led to 13. Homologation of 13 to the aldehyde 14 set the stage for condensation with the camphor-derived tertiary amine 15, following the protocol developed by Kobayashi. Sequential imine formation, aza-Cope rearrangement, and hydrolysis led to 1 in 94% de. One could envision reduction of the lactam carbonyl of 1 to an aldehyde equivalent, that would then, under acidic conditions, condense to form the desired aminal 2. This approach was, however, not successful. As an alternative, conditions were developed to convert 1 to the amidine 16. Reduction then proceeded with the expected high diastereocontrol, to give the cis 1,3-fused aminal 2. This was not isolated, but was directly acylated with acryloyl chloride, to 17.
The Overman Syntheses of Nankakurines A and B
Authors: Taber Douglass
Published: November 2020

The tetracyclic alkaloids Nankakurine A and Nankakurine B were isolated from the club moss Lycopodium hamiltonii. A preliminary study of the biological activity of Nankakurine A suggested that it could induce secretion of neurotrophic factors and promote neuronal differentiation. The key step in the first syntheses of Nankakurine A and of Nankakurine B, reported (J. Am. Chem. Soc. 2008, 130, 11297) by Larry E. Overman of the University of California, Irvine was the intriguing intramolecular aza-Prins cyclization of 1 to 2. The starting material for the synthesis was 5-methyl cyclohexenone 6, prepared from (R)-pulegone. The diene 5 was prepared from the alkyne 4, following the procedure developed by Diver. There were two issues in developing the Diels-Alder addition of the enone 4 to the diene 6. The first was the relative lack of reactivity of 4 as a dienophile. The other issue was the ready epimerization of the product ketone 9. Both of these problems were solved using the activation method devised by Gassman. Condensation of 4 with 7 in the presence of the bis-silyl ether 7 and the diene 6 at cryogenic temperatures led to the ketal 8. It is thought that the active dienophile was the cation 11. Gentle hydrolysis of the ketal 8 was effected with minimal epimerization. Reductive amination with the hydrazide 10 proceeded with high diastereocontrol, to give the precursor 1. The intramolecular aza-Prins cyclization of 1 to 2 proceeded well, though the desired tetracyclic 2 was only observed when base was included in the reaction medium. In the absence of base, tricyclic alkenes dominated. Reduction of the N-N bond of 2 proceeded smoothly with freshly prepared SmI2 . After reductive methylation, hydrogenation removed the benzyl ether, and AlH3 converted the benzamide to the benzyl amine. At low temperature, mesylation of the alcohol was apparently faster than mesylation of the secondary amine, enabling cyclization to 14. Removal of the benzyl protecting group gave Nankakurine A, which was successfully methylated to give Nankakurine B.
The Castle Synthesis of (-)-Acutumine
Authors: Taber Douglass
Published: November 2020

The complex tetracyclic alkaloid (-)-acutumine 3, isolated from the Asian vine Menispermum dauricum, shows selective T-cell toxicity. The two adjacent cyclic all-carbon quaternary centers of 3 offered a particular challenge. Steven L. Castle of Brigham Young University solved (J. Am. Chem. Soc. 2009, 131, 6674) this problem by effecting net enantioselective conjugate allylation of the enantiomerically pure substrate 1 to give 2 with high diastereocontrol. The starting coupling partners ( Organic Lett . 2006, 8, 3757; Organic Lett. 2007, 9, 4033) for the synthesis were the Weinreb amide 4, prepared over several steps from 2,3- dimethoxyphenol, and the diastereomerically- and enantiomerically-pure cyclopentenyl iodide 5, prepared by singlet oxygenation of cyclopentadiene followed by enzymatic hydrolysis. Transmetalation of 5 by the Knochel protocol, addition of the resulting organometallic to 4 and enantioselective (and therefore diastereoselective) reduction of the resulting ketone delivered the alcohol 6. Methods for installing cyclic halogenated stereogenic centers are not well developed. Exposure of the allylic alcohol to mesyl chloride gave the chloride 7 with inversion of absolute configuration. Remarkably, this chlorinated center was carried through the rest of the synthesis without being disturbed. A central step in the synthesis of 3 was the spirocyclization of 7 to 8. Initially, iodine atom abstraction generated the aryl radical. The diastereoselectivity of the radical addition to the cyclopentene was set by the adjacent silyloxy group. The α-keto radical so generated reacted with the Et3Al to give a species that was oxidized by the oxaziridine to the α-keto alcohol, again with remarkable diastereocontrol. Conjugate addition to the cyclohexenone 1 failed, so an alternative strategy was developed, diastereoselective 1,2-allylation of the ketone followed by oxy-Cope rearrangement. The stereogenic centers of 1 are remote from the cyclohexenone carbonyl, so could not be used to control the facial selectivity of the addition. Fortunately, the stoichiometric enantiomerically-pure Nakamura reagent delivered the allyl group preferentially to one face of the ketone 1, to give 9. The subsequent sigmatropic rearrangement to establish the very congested second quaternary center of 2 then proceeded with remarkable facility, at 0°C for one hour.
Hojas, Blackberries, and the Tortilla King
Authors: Broughton Chad
Published: November 2020

On a Blistering morning in July 2007, four middle-aged men, already quite drunk, stood shaded under the eaves of a long, white stucco building. The building, which was derelict, sat in the middle of Agua Dulce in semitropical northern Veracruz. Our guide, Orlinda Garcia, asked the four men where we could find an hoja (husk) processing plant. Mayor Javier Gonzalez and Treasurer José Cruz stood with us as well. Gonzalez’s sky-blue municipal office was just a few hundred feet away, on the other side of the vacant town plaza. The adjacent plaza was littered with rusty rides and empty prize booths from a traveling summer carnival that had recently ended. “This is it!” a man in a Pittsburgh Pirates cap shouted. He pointed to a concealed entrance. Part of the wavy clay tile roof was missing and had been replaced with corrugated metal sheets. Plastic bags and bottles specked the ground outside. A slick, red PRI campaign banner hung on an electric pole next to the building with a candidate’s portrait. “Fiel a ti” (Loyal to you), the banner read. The plain building stretched alongside a wide, bumpy road—deserted except for a few chickens. It did not look like the site of a profitable foreign-trade operation. A young encargada (supervisor) named Marisol greeted us from behind a black metal gate. We asked her if we could see inside the facility. “The patron is not here,” she said. “I cannot let you in.” She was apologetic but firm. In a pink blouse, capri pants, and faux gem-studded flip-flops, she appeared to be dressed more for a Saturday of shopping in Monterrey than managing an export business in this half-ghost town in far-flung Veracruz. “The boss is very particular, and he doesn’t allow people from the outside to see the operation.” Another neatly dressed young woman looked at us while she embroidered some clothing in a chair behind Marisol. She sat next to a pile of plastic bags swollen with corn husks (called hojas or totomoxtle).
Feed Forward Neural Networks
Authors: Raff Lionel , Komanduri Ranga , Hagan Martin , Bukkapatnam Satish
Published: November 2020

In this section, we want to give a brief introduction to neural networks (NNs). It is written for readers who are not familiar with neural networks but are curious about how they can be applied to practical problems in chemical reaction dynamics. The field of neural networks covers a very broad area. It is not possible to discuss all types of neural networks. Instead, we will concentrate on the most common neural network architecture, namely, the multilayer perceptron (MLP). We will describe the basics of this architecture, discuss its capabilities, and show how it has been used on several different chemical reaction dynamics problems (for introductions to other types of networks, the reader is referred to References 105-107). For the purposes of this document, we will look at neural networks as function approximators. As shown in Figure 3-1, we have some unknown function that we wish to approximate. We want to adjust the parameters of the network so that it will produce the same response as the unknown function, if the same input is applied to both systems. For our applications, the unknown function may correspond to the relationship between the atomic structure variables and the resulting potential energy and forces. The multilayer perceptron neural network is built up of simple components. We will begin with a single-input neuron, which we will then extend to multiple inputs. We will next stack these neurons together to produce layers. Finally, we will cascade the layers together to form the network. A single-input neuron is shown in Figure 3-2. The scalar input p is multiplied by the scalar weight w to form wp, one of the terms that is sent to the summer. The other input, 1, is multiplied by a bias b and then passed to the summer. The summer output n, often referred to as the net input, goes into a transfer function f, which produces the scalar neuron output a.
Potential-Energy Surfaces Using Expansion Methods and Neural Networks
Authors: Raff Lionel , Komanduri Ranga , Hagan Martin , Bukkapatnam Satish
Published: November 2020

Expansion methods have been employed for some time to represent the potentialenergy surface for molecular systems. The basic concept involved with any expansion method is to write the PES expression for an N-atom system that requires the specification of 3N-6 internal coordinates as a sum of terms each of which involves fewer than N atoms and/or fewer than (3N-6) coordinate variables. Two approaches to the implementation of this concept have been suggested. In the first approach, the focus of attention is the number of internal coordinates upon which each term in the expansion depends.
Rate Coefficients and Mechanisms for the Atmospheric Oxidation of the Ketones
Authors: Calvert Jack , Mellouki Abdelwahid , Orlando John , Pilling Michael , Wallington Timothy
Published: November 2020

Ketones are emitted directly to the atmosphere, and their sources were discussed in detail in chapter I. In the U.K. acetone and butanone comprise about 7% and 5%, respectively, of the total anthropogenic emissions of oxygenated compounds, and 1.6% and 1.1%, respectively, of the total anthropogenic emissions of nonmethane volatile organic compounds. Ketone emissions from solvents (both industrial and personal) are substantial; emissions from both gasoline- and diesel-fueled vehicles also contribute. Ketones are also formed extensively in the atmosphere in the oxidation of other compounds. Acetone, for example is formed in the OH-initiated oxidation of propane, iso-butane, iso-pentane, and neopentane and from a number of higher hydrocarbons. It is also formed in the oxidation of terpenes. The distribution, sources, and sinks of acetone in the atmosphere have been analyzed by Simpson et al. (1994). Methyl vinyl ketone is an important first generation product in the OH-initiated oxidation of isoprene. In this chapter, we discuss the rate coefficients and the mechanisms of oxidation of ketones. The classes covered include alkanones, hydroxyketones, diketones, unsaturated ketones, ketenes, cyclic ketones, ketones derived from biogenic compounds, and halogen-substituted ketones. Photolysis is a major atmospheric process for many ketones, and will be discussed in chapter IX. The major bimolecular reactions removing ketones from the atmosphere are with OH. Although less important than the OH reactions, reactions with Cl have been studied quite extensively. Other than for unsaturated ketones, reactions with NO3 and O3 are unimportant in tropospheric chemistry and have been studied little. The carbonyl group deactivates the α-position with respect to reaction with OH, but activates the β-position, and possibly more distant sites as well. The net result is that the overall rate coefficient of an alkanone generally exceeds that of the equivalent alkane. The temperature dependences of the rate coefficients can be quite complex, with acetone and possibly butanone showing a minimum in the rate coefficient at ∼250 K, while the higher alkanones show negative temperature dependences across the more limited temperature ranges that have been investigated. The most likely explanation of this behavior is the formation of a pre-reaction, hydrogen-bonded complex.
Data Structures
Authors: Manzo V. J
Published: November 2020

In this chapter, we will write a program that randomly generates diatonic pitches at a specified tempo. We will learn how to filter chromatic notes to those of a specific mode by using stored data about scales. By the end of this chapter, you will have created a patch that composes diatonic music with a simple rhythm. We will also learn about adding objects in order to expand the Max language. For this chapter, you will need to access to the companion files for this book. New words are added to the English language all the time. If you open a dictionary from the 1950s, you’re not going to find commonly used words like ringtone or spyware. There was a need to incorporate these words into the language because they serve a specific function. In the same regard, the Max programming language can also be expanded through the development of external objects created by third parties. Third party objects are often referenced in journal articles, forum posts on the Cycling ’74 website (cycling74.com), and a number of repository websites for max objects. A brief, and by no means comprehensive, list of repository websites is given at the end of this chapter. Of course, at this point, we’re still learning the Max language apart from adding external objects. So why are we discussing external objects at all? Well, the beauty of Max is that you can expand the language easily to include objects that can speed up your process. For example, in Chapter 4, we made scales and chords by following a number of steps. To speed up the process of implementing scales and chords in my own patches, I developed a set of external objects called the Modal Object Library that contains objects for quickly building chords and scales. Since you already know how to build scales and chords in Max, using these objects will speed up our process of using scales and chords in our patches instead of having to copy large chunks of objects from old patches whenever you want to implement a particular scale.
Control Interfaces Continued
Authors: Manzo V. J
Published: November 2020

In this chapter, we will look at some innovative ways to control music making as we develop musical instruments. We will look at using your computer keyboard and mouse as performance instruments as well as discuss the use of videogame controllers in your patches. Designing your own custom musical instruments is a great way to tailor the controls to the specific physical abilities of users while allowing them to focus on certain specific musical concepts like pitches, scales, and harmony/chords. 1. Click on Extras>EAMIR from the top menu to view the main menu of the EAMIR SDK 2. In the umenu labeled Examples, click the third item 3.EAMIR _ASCII_Keyboard_Control.maxpat Unlock the patch that opens and look at its basic structure. As you can see, the patch is really just 4 bpatcher objects, 3 of which refer to patches we’ve already looked at. The newest bpatcher, at the top of the patch, is basically just a patch with a key object, a select object, and some fancy graphics—all things you learned to use in Chapter 3. Lock the patch and 3. Type your full name using your computer keyboard. Note that uppercase letters and lowercase letters trigger different buttons 4. Press the number keys 1–8 as these are mapped to message boxes containing numbers used as diatonic chord functions Without the top bpatcher, your patch generates chords in any key simply by clicking the message boxes. The top bpatcher is just a control interface that maps something (keys) to something else (message boxes). 5. Ctrl+click (Mac) or right click (Windows) the top bpatcher and select Object>Open Original “EAMIR_keyboard.maxpat” from the contextual menu This patch is set to open in Presentation mode. Unlock the patch and put it in Patching view. The contents of the patch are as I described: a key object, as well as a keyup object, are connected to two gigantic sel (select) objects containing the ASCII numbers for all the available characters on the computer keyboard nothing you couldn’t already do. In fact, the most impressive part of this patch, in my opinion, is the graphical part of it.
The Canal at River’s End: Thirsty Arizona
Authors: deBuys William
Published: November 2020

“ If you run the math,” says Brad Udall, “You sort of go, wow, Arizona, they may be totally out of their Central Arizona Project water.” Udall is referring to Arizona’s unenviable position as California’s aquatic whipping boy. The two states have long fought over water, and although Arizona has won a battle or two, it has taken a beating in the war. A key result of their combat has been to make the majority of Arizona’s Colorado River water rights expressly junior to California’s. This means that during inevitable and possibly imminent periods of shortage, the people of southern California, under a strict interpretation of the law, will be able to wash their cars, water their lawns, and keep their showers streaming while the millions who live in Phoenix, Tucson, and points between watch the flow from their taps slow to a dribble. Fortunately, events are unlikely to turn out so apocalyptically. When crisis comes, emergency negotiations will produce a less black-and-white outcome, and Arizona’s groundwater reserves (some of them recharged in recent years with CAP water) will be tapped to meet priority needs—at least for a time. Nevertheless, the potential for a winner-take-all showdown between large populations highlights the vulnerability of the urban centers of the arid West in an era of climate change. Fates are hardly fixed. How the cities of the region grow and change in the years ahead will significantly determine their ability to withstand the shocks of a hotter and drier future. How well they respond to the challenges ahead will also determine the future of their states and of the entire West, for in an arid land, a modern society is obliged to be an urban society. The survival of aridland cities and the struggle to preserve their quality of life will become a matter of national concern, even obsession, and the entire world will watch their stories unfold. Arizona has always been jealous of California’s economic power, its political heft in Congress, and its early and abundant claims to Colorado River water.
Models of Music Pedagogy and Their Influences on Technology-Based Music Instruction
Authors: Dorfman Jay
Published: November 2020

Pedagogical approaches to teaching music have developed into mature curricular structures. The most prominent music pedagogies have features in common that can inform the new pedagogy of TBMI, and we should learn from the success of these approaches as we develop technology-based methods that will lead students to musical ends. In the section that follows, I will briefly summarize some of the major pedagogical approaches that are in use in today’s music classrooms. Then, I will offer lessons that we can learn from examining traditional music teaching that apply to the development of the TBMI approach. Saliba (1991) described the Orff-Schulwerk approach to music education as “pedagogy to organize elements of music for children through speaking, singing, playing, and dancing” (p. vii). This approach, which dates to early 19th-century Germany, combines basic musical elements into small forms such as songs and patterns in order to make musical material manageable for young children (Saliba, 1991). Carl Orff ’s approach to music education was based on his personal experiences and his belief that integrating music and movement was fundamental to music learning processes (Frazee & Kreuter, 1987; Frazee, 2006). Performing, listening, improvising, and analyzing music are all characteristic activities of Orff -Schulwerk music lessons. An important trait of this approach is its emphasis on children feeling musical elements (through active experience) prior to conceptualizing their understanding of the elements. Other distinguishing characteristics of the Orff pedagogy include the use of ostinati as accompaniment for singing and movement at varying levels of complexity and the use of simple instruments as a means for children’s immediate expression (Wheeler & Raebeck, 1977). Creativity is central to the original Orff-Schulwerk model of music pedagogy, as is the teacher’s role in facilitating that creativity. “[Orff ’s] instructional plan includes provisions for several kinds of original work. . . . The teacher should be prepared to help children notate their musical ideas, evaluate the music they produce, and relate their creative eff orts to the study of musical form and style” (Landis & Carder, 1990, p. 110).
The Road Runner’s Appetite
Authors: Ross Andrew
Published: November 2020

Political and business leaders know that their defects and blunders will be excused if they turn in a respectable growth performance. The quarterly or annual gains in corporate revenue or GDP are really all that matters. But when and why did these raw metrics come to surpass all other indicators of well-being? Although growth is often seen as integral to any capitalist system of accumulation, its recognition as a society’s only relevant standard of worth is largely a postwar development. For example, four-fifths of U.S. growth has occurred in the last fifty years, some part of it driven by Cold War competition to prove the superiority of a market economy. The consensus mood that developed after 1945—which historians have called “growth liberalism”—presided over an expansionist boom in the industrialized world that did not contract until the 1970s. Subsequent doctrines—the supply-side gospel of the Reagan era, the high-tech evangelism of the 1990s, and the asset ownership creed of the 2000s—were all aimed at reviving and boosting the high growth rates that managers of a consumer society had come to expect. Growthmanship spread abroad, along with the internationalization of production, and soon growth in GDP became the most important yardstick for nations, whether in the advanced or the developing world. Slowing growth rates were a cause for concern, while falling numbers were a sign that something was awry, and that close scrutiny, even intervention, from the World Bank or the International Monetary Fund was in the offing. Those who believed or behaved otherwise were not wrong; they were simply treated as dropouts from modernity. So entrenched was this orthodoxy that The Limits to Growth, the momentous 1972 Club of Rome report that concluded that current rates of industrial growth could not be sustained ecologically in the long term, was received among business and policy elites as a genuinely heretical document that had to be publicly pilloried. Subsequent surveys, drawing upon a wider range of experts and a more comprehensive collection of scientific data, amplified the 1972 warning about the ruinous impact of unrestrained growth.
Delivering the Good
Authors: Ross Andrew
Published: November 2020

Why did I choose to end this book with the Gila River Indian Community’s effort to win back its water? Because it is a parable about how democracy and its courts can not only serve but also be served by the quest for sustainability. The GRIC water settlement brought a long struggle for environmental justice to a triumphant conclusion. Delivering justice meant that a large portion of the region’s available resources would be sequestered from the growth machine. Instead of supplying a new generation of low-density tract housing, the water could now be used to produce healthy, local food for the area population, and, if nonindustrial agriculture prevailed, the result would be a double win for carbon reduction. Surely, this is how a green polity ought to act, redressing the claims of those who have been aggrieved, and doing it in a way that extends long-term benefits for all. If all responses to environmental injustice were able to follow suit, it would be a welcome model for moving forward. Even if the Gila River example is unlikely to be replicated in other places, its guiding spirit is a sound one. What if the key to sustainability lies in innovating healthy pathways out of poverty for populations at risk, rather than marketing green gizmos to those who already have many options to choose from? These are not mutually exclusive options, of course, but the lessons I took away from my research convinced me of the pressing need for clear alternatives to the eco-apartheid syndrome that afflicts Phoenix and so many other cities. Building a low-carbon economy by targeting only the LOHAS demographic (Lifestyles of Health and Sustainability, the upmarket segment of 40 million, or 20 percent of consumers, nationally) will end up doing little more than adding a green gloss to patterns of chronic inequality. Likewise, placing all of our faith in clean-tech fixes will cede too much decision making to a closed circle of experts who, regardless of their technical prowess, will have no power to prevent the uneven application of their solutions.
The Shrinking Third Pole
Authors: Colopy Cheryl
Published: November 2020

Dig Tsho is another glacial lake high in the Himalaya of Nepal. On a summer afternoon in 1985, the lake’s waters burst from their bowl of ice and rock. An inland tsunami flooded the valleys below, sweeping away potato fields, yaks, and a hydropower plant. It was a Buddhist festival day in the Sherpa village of Thamo. Thamo’s residents are descendants of families that five hundred years ago came over the mountains from nearby Tibet to settle the region known as the Khumbu, below what Westerners call Mt. Everest. People were drinking chang, laughing and having fun. At four o’clock in the afternoon one woman, standing on a ridge above the Bhote Koshi, heard a sound like the roar of an airplane, then felt the ground begin to shake. The woman yelled to the other villagers, who came down to see a wall of water approaching from upriver. Those who lived on the slope closest to the river ran into their houses, grabbed religious items—portraits of monks, statues from family chapels, and Buddhist texts—along with leather trunks holding money and family jewelry. Some ran uphill to neighbors’ houses and waited, while others carried images of Buddhist deities down to the riverbank and pointed them at the advancing flood, pleading for the river to change its course. Elderly men and women in Thamo and nearby villages believe they know what caused the flood. They say a Sherpa man was tending his yaks in the high, sparse pastures near Dig Tsho that August. The morning of the flood, a stray dog ate his bowl of curd. The herder was so angry he grabbed the dog, tied its legs so it couldn’t swim, and threw it into the lake. The act of cruelty angered a local deity, who caused a big chunk of the glacier to break off and fall into the lake. The water surged out. There were no human casualties in the Sherpa villages high in the Khumbu, but lower down the channel, along the Dudh Koshi, people drowned in the churning river.
Belji of Dhulikhel
Authors: Colopy Cheryl
Published: November 2020

I first heard of Bel Prasad Shrestha five years before I met him. An article in the Nepali Times lauded his efforts to establish a water system in the town of Dhulikhel while he was its mayor. I clipped it and set it aside. Fifteen miles from Kathmandu was a municipal utility that put Kathmandu’s to shame. I wanted to know more. Perhaps I saved Bel Prasad for last, expecting the visit to Dhulikhel to be a pleasant excursion—a hopeful encounter that would show me that the break down of urban management I saw every day in Kathmandu was not an inevitable part of development in Nepal. After all those discouraging discussions about Melamchi and about Kathmandu sewage and water supply problems, perhaps I was going to meet a Newar who had a gift for water like his ancient forebears. I went to Dhulikhel the day before May Day, 2010, when Nepal’s Maoists were planning to outdo their usual May Day celebrations with protests all over the city. They were massing their cadres in Kathmandu, ostensibly to pressure the prime minister of another party to resign. On a Friday morning I set out with my friend Ram, a Kathmandu taxi driver who was always available when I needed to venture out on a longer excursion. The shocks on his little white Maruti Suzuki were shot, as they were on most taxis in Kathmandu, but Ram was a good driver who knew all the roads and backroads. Aside from worries about being able to return to the city in the face of demonstrations and roadblocks—or perhaps the complete countrywide shutdown that the Maoists were threatening—Dhulikhel was a green and quiet escape, a fine place to wait out urban riots if any were to materialize. And I found a charming host in Bel Prasad, a unique and now elderly gentleman who had straddled the wide gulf between the rural Nepal of his childhood and the world he had seen in visits to Europe, America, and Japan.