bluuebunny/crossref_metadata_2025_split huggingface dataset:
Overcoming Difficulties in Total Synthesis of (+)-Cotylenin A
Authors: Uwamori Masahiro , Osada Ryunosuke , Sugiyama Ryoji , Nagatani Kotaro , Tezuka Haruka , Hoshino Yunosuke , Minami Atsushi , Nakada Masahisa 
Published: May 2024

AbstractThe total synthesis of the natural product cotelynin A, which exhibits promising anti-cancer activity, is urgently required, as its source, Cladosporium sp. 501-7W, has lost its proliferative ability. Herein, we report the first total synthesis of cotelynin A. Contiguous asymmetric carbons at the C8 and C9 positions in the B-ring of the aglycon moiety of cotylenin A are difficult to construct after the formation of the B-ring via pinacol coupling. The revised synthesis of the aglycon moiety involved the alkenylation of a methyl ketone to construct the B-ring; for this convergent synthesis, one fragment was prepared using our catalytic asymmetric intramolecular cyclopropanation, and the other fragment was obtained via the acyl radical cyclization of a known aldehyde, which was prepared by sharpless asymmetric epoxidation of geraniol and subsequent rearrangement. Radical generation using a copper catalyst and TBHP was effective for an acyl radical cyclization. The two prepared fragments were then assembled via Utimoto coupling. The α-hydroxyketone at the C8-C9 position was stereoselectively reduced with Me4NBH(O2CiPr)3, which was newly prepared in this study, and led to the successful construction of the C8-C9 1,2-diol. A structurally unprecedented sugar moiety was synthesized for the first time by terminating successive reversible acetalizations with an irreversible epoxide ring-opening reaction. Although the glycosylation of the synthesized fragments proceeded with difficulty owing to steric hindrance around the C9 hydroxy group of the aglycone, the desired product was successfully obtained under the reaction conditions reported by Wan et al.
Unified Total Synthesis of Madangamine Alkaloids
Authors: Sato Takaaki 
Published: May 2024

AbstractDevelopment of a unified total synthesis of madangamine alkaloids is described. The synthesis consists of three parts: (1) construction of the central ABC-ring, (2) installation of the skipped diene bearing a trisubstituted olefin, and (3) the synthesis of various D-rings from a tetracyclic ABCE-common intermediate. The ABC-tricyclic framework is successfully assembled by intramolecular allenylation. The most significant issue in this synthesis is the stereoselective installation of the skipped diene. This challenge is ultimately overcome by development of a stereodivergent approach using hydroboration of allenes and Migita-Kosugi-Stille coupling. The hydroboration is especially useful because the reaction of 1,1-disubstituted allenes with either 9-BBN or (Sia)2BH gives (E)- or (Z)-allylic alcohols, respectively. The key to the success of our unified total synthesis is macrocyclic alkylation to form a wide variety of D-rings from the tetracyclic ABCE-common intermediate. Our collective synthesis of madangamine alkaloids revealed structure–activity relationship of D-rings in their cytotoxicity against human cancer cell lines.
Total Syntheses of (+)-Aquatolide and Related Humulanolides
Authors: Ogura Akihiro , Takao Ken-ichi 
Published: May 2024

AbstractHerein, the total syntheses of (+)-aquatolide, a humulane-derived sesquiterpenoid lactone, and five other related humulanolides are described. The key reactions in these syntheses are a cascade metathesis reaction of cyclobutenecarboxylate to construct a γ-butenolide with an unsaturated aldehyde side chain, an intramolecular Nozaki–Hiyama–Takai–Kishi reaction to form an all-trans-humulene lactone skeleton, and a biosynthesis-inspired [2 + 2] photocycloaddition to provide a bridged 5/5/4/8-ring system. A cycloaddition giving a 5/4/4/7-ring system was also found. In addition, biological studies were conducted using the synthesized samples.
Complex Oligosaccharides Synthesis—Challenges and Tactics
Authors: Takahashi Daisuke , Toshima Kazunobu 
Published: May 2024

Abstract1,2-cis glycoside structures exist as constituents of biologically active natural products, pharmaceuticals, and functional materials. Therefore, there is a pressing need for the development of novel and efficient 1,2-cis-glycosylation methods to understand their specific roles and to create new lead compounds for pharmaceutical and functional materials by derivatization of these glycosides. In this context, we have developed a conceptually new glycosylation method called boron-mediated aglycon delivery (BMAD), which utilizes organoboron catalysis for simultaneously controlling the 1,2-cis stereoselectivity of the glycosidic bond formed and regioselectivity of the reaction site in the glycosyl acceptor. The method has been applied to synthesize useful glycosides including complex oligosaccharides found in pathogenic bacteria. We recently extended the BMAD method to the reaction of partially protected and unprotected glycosides for the late-stage modification of natural glycosides with interesting biological activities, and synthesized complex oligosaccharides using minimal protecting groups. Furthermore, we developed a diastereoselective desymmetric BMAD reaction of meso-diols as a new synthetic tactic for complex glycosides. Herein, we discuss the abovementioned BMAD methods and their use in the synthesis of useful glycosides.
Pursuing Step Economy in Total Synthesis of Complex Marine Macrolide Natural Products
Authors: Fuwa Haruhiko 
Published: May 2024

AbstractHere I describe our first-, second-, and third-generation synthesis of (+)-neopeltolide, which is a Jamaican marine macrolide that shows potent antiproliferative and antifungal activities. The third-generation synthesis enabled an expedient access to (+)-neopeltolide in 11 linear and 23 total steps, which is so far the shortest synthesis of this natural product. Convergent synthesis planning by taking advantage of chemoselective transformations, cross-coupling reactions, and tandem reactions was the key for increasing step economy.
Nonbiomimetic Total Synthesis of Polycyclic Alkaloids
Authors: Ohno Hiroaki , Arichi Norihito , Inuki Shinsuke 
Published: May 2024

AbstractIn nonbiomimetic natural product synthesis, there are no restrictions on the design of synthetic routes; however, the feasibility of the planned routes is often completely unknown. To discover more efficient and creative syntheses of natural products, and to identify bioactive natural product derivatives that have never been synthesized in nature, our group is engaged in the nonbiomimetic total synthesis of indole alkaloids. In this chapter, we describe our nonbiomimetic total syntheses of quinocarcin, dictyodendrins A–F, and zephycarinatines C and D, by employing alkyne-based approaches and reductive radical spirocyclization. We also describe our efforts in the identification of bioactive alkaloid derivatives.
Sequential Site-Selective Functionalization: A Strategy for Total Synthesis of Natural Glycosides
Authors: Ueda Yoshihiro , Kawabata Takeo 
Published: May 2024

AbstractTotal synthesis of several ellagitannins, strictinin (1), pterocarinin C (2), cercidinin A (3), and tellimagrandin II (19), is described. The key issues for the synthetic strategy rely on the catalyst-controlled site-selective acylation and stereoselective glycosylation with unprotected glucose. Total synthesis of punicafolin (5) with a glucose core in 1C4 (chair) conformation and macaranganin (30) with a glucose core in 5S1 (skew boat) conformation was also accomplished based on a similar unconventional retrosynthetic route. For success in the synthesis of 5 and 30, the flipping behavior of the pyranose ring from the stable 4C1 conformer to the unstable axial-rich 1C4 conformer is the key. Because no protective groups for glucose were employed throughout the synthesis of these natural glycosides, the total synthesis was achieved in extremely short overall steps.
Synthetic Study of Bio-functional Glycans
Authors: Fukase Koichi , Shimoyama Atsushi , Manabe Yoshiyuki 
Published: May 2024

AbstractThe molecular structures responsible for the immune functions of complex glycans were unraveled by synthetic studies. We focused on developing efficient methods for synthesizing glycans and conducting diverse chemical syntheses of these compounds, to identify the molecular structures responsible for activating or modulating innate immunity. Many natural glycans contain multiple active structures, potentially leading to emergent higher-order functions through their synergistic interactions. Therefore, by employing a conjugation-based approach, we successfully created immune-regulating complex glycoconjugates.
Total Synthesis of a Marine Bromotriterpenoid Isodehydrothyrsiferol
Authors: Nishikawa Keisuke , Morimoto Yoshiki 
Published: May 2024

AbstractThe thyrsiferol family natural products are marine triterpene polyethers biogenetically derived from squalene and structurally characterized by a bromine atom and some six- and five-membered ethereal rings. Their stereostructures cannot easily be determined by modern spectroscopic analysis, because there are acyclic tetrasubstituted chiral centers and the remote stereoclusters. In these cases, asymmetric total synthesis demonstrates its power. Herein, to determine the entire stereostructure of the thyrsiferol family member isodehydrothyrsiferol, isolated from the red alga Laurencia viridis, the asymmetric total synthesis has been performed. The key steps are the convergent and effective synthetic strategy using a Suzuki–Miyaura cross-coupling, a one-pot construction of the tetrahydropyranyl C ring via a stoichiometric Katsuki-Sharpless asymmetric epoxidation and 6-exo oxacyclization in situ promoted by Ti chelation, and 6-endo bromoetherification for the A ring formation. Through the enantioselective total synthesis, we have accomplished complete assignment of the entire stereostructure for isodehydrothyrsiferol and found the absolute configuration of the ABC ring system is opposite to that common to the other congeners from the same red algae. In addition, such enantiodivergency also occurred between dehydrothyrsiferol and isodehydrothyrsiferol originating from the identical red alga Laurencia viridis. There are no these findings without asymmetric total synthesis.
Utilizing the pKa Concept to Address Unfavorable Equilibrium Reactions in the Total Synthesis of Palau’amine
Authors: Ohashi Eisaku , Takeuchi Kohei , Tanino Keiji , Namba Kosuke 
Published: May 2024

AbstractHerein, we introduce the pKa concept as a strategy for proceeding with unfavorable reactions in the total synthesis of palau’amine. The cascade reaction aimed at constructing palau’amine’s ABDE tetracyclic ring core initially encountered poor reproducibility due to an unfavorable equilibrium reaction. However, the addition of 1.0 equivalent of AcOH enabled the progression of the unfavorable equilibrium reaction. In the second-generation synthesis, the improved cascade reaction to construct CDE ring core also initially did not proceed due to an unfavorable equilibrium reaction, but using Ph2NLi as a base was later found to enable the reaction to proceed smoothly. The conjugate acid of Ph2NLi proved to be a suitable acid in the unfavorable equilibrium mixture. These investigations of the cascade reactions revealed that the coexistence of an appropriate acid played an important role in allowing the unfavorable equilibrium reaction to proceed. The authors propose a general equation for proceeding with an unfavorable equilibrium reaction.
Total Synthesis of (+)-Siladenoserinol A
Authors: Yoshida Masahito , Saito Koya , Doi Takayuki 
Published: May 2024

AbstractThe total synthesis of (+)-siladenoserinol A (1) was accomplished. The bicyclic acetal core, a 6,8-dioxabicyclo[3.2.1]octane skeleton, was constructed by Au(III)-catalyzed cycloisomerization of 6,7-dihydroxy-2-alkynoate. A serinol side chain was introduced by the Julia–Kocienski olefination and the other side chain was efficiently introduced by the Horner–Wadsworth–Emmons reaction with glycerophosphocholine-containing phosphonoacetate, and selective sulfamation of the serinol moiety yielded (+)-1. The synthetic (+)-1 exhibited potent inhibitory activity against p53–Hdm2 interaction comparable to that of the natural product. In contrast, the desulfamate derivative did not show the inhibitory activity. Notably, its benzoyl analog exhibited more potent activity than (+)-1.
The Asymmetric Total Synthesis of Discorhabdin B, H, K, and Aleutianamine
Authors: Sakata Juri , Shimomura Masashi , Tokuyama Hidetoshi 
Published: May 2024

AbstractThis review article summarizes the general introduction of discorhabdin marine alkaloids and the synthetic efforts in developing congeners with a hexacyclic N, S-acetal structure, which are major constituents of discorhabdin. Our total synthesis of (+)-discorhabdin B is discussed in detail following the introduction of the biosynthetic pathway and early synthetic studies, which include the landmark first total synthesis of discorhabdin A. Furthermore, previous synthetic studies on more structurally complex congeners with C6–N15 bonds are introduced, followed by the first total synthesis of (–)-discorhabdin H and (+)-discorhabdin K, which are achieved by our research group. Finally, the isolation, structure determination, and proposed biosynthesis of the structurally intriguing congener aleutianamine are summarized. Then, the first total synthesis of aleutianamine, which involves an unprecedented reductive skeletal rearrangement of N-Ts-(+)-discorhabdin B to N-Ts-aleutianamine, is discussed.
Fluoroarene Strategy in Total Synthesis of Natural Flavonoids
Authors: Ohmori Ken , Suzuki Keisuke 
Published: May 2024

AbstractVicenin-2, a naturally occurring bis-C-glucosyl flavonoid, was synthesized by exploiting a sequential C-glycoside formation and aromatic nucleophilic substitution (SNAr reaction) of the fluoroarene derivative, i.e., 1,3,5-trifluorobenzene, converting fluorine atoms to oxygen function.
Collective Total Synthesis of Secologanin-Related Natural Products
Authors: Sakamoto Jukiya , Ishikawa Hayato 
Published: May 2024

AbstractWe have been interested in the reactivity of secologanin, which is transformed into more than 3000 natural products in nature and have been working on the bioinspired synthesis of several natural products using secologanin derivatives. In this chapter, we describe the total synthesis of secologanin using an organocatalytic reaction and the collective and divergent total synthesis of glycosylated monoterpenoid indole alkaloids and hetero-oligomeric iridoid glycosides through biogenetically inspired transformations from secologanin derivatives.
Colonial Nostalgia and Postcolonial Longings
Authors: Chow Yiu Fai , de Kloet Jeroen , Schmidt Leonie 
Published: May 2024

AbstractThis chapter continues our theoretical discussion on popular music and politics with a specific remit: its intersection with postcolonial studies and its deliberations on home, identity, and power contestations. The insertion of an inquiry over Tat Ming Pair and Hong Kong here serves two purposes. The first is, quite generally, the lack of research on music and postcoloniality in the Asian experience in English language scholarship—save for some notable exceptions music. Second, and more fundamentally, we see Tat Ming Pair and its politics as an “anomaly”—as much as the decolonisation of Hong Kong itself. Put simply, Hong Kong’s decolonisation proceeds in tandem with its renationalisation. While the former colonies in postcolonial studies became nations in their own right, Hong Kong became part of China after its sovereignty was handed from London to Beijing in 1997. Drawing primarily from the interviews with Anthony Wong and Tats Lau, Chapter 2 tracks and analyses the emergence and development of the duo in the larger geopolitical and geocultural context. Their musical engagements with a host of issues including sexual autonomy, gender equality, freedom of thoughts and speech, and Sino-Hong Kong relationships will be highlighted to prelude the more detailed analyses in the following two chapters. At the same time, Chapter 2 aims at mapping out a history of Hong Kong in its colonial entanglements with the British administration, and its postcolonial struggles with the Chinese regime. It will also seek to retell a concomitant history of Hong Kong popular music that is not dictated by the “Golden Era” logic, that is from its popularity zenith as the “global cool” to its alleged post-Handover decline or even death; rather the history we write will be informed and inspired by the vitality and complexity of Tat Ming Pair’s music and politics. Chapter 2 will converse with existing scholarship on Cantopop, as well as on Tat Ming Pair.
“It’s My Party”
Authors: Chow Yiu Fai , de Kloet Jeroen , Schmidt Leonie 
Published: May 2024

AbstractIn Hong Kong, despite its overwhelming capitalist logic, pop music makers have established a tradition of political engagement, stretching from the anxiety towards the 1997 Handover, the post-Tiananmen fury and fear, to the more recent articulations against increasing intervention of the Beijing regime. While previous chapters provide a textual analysis and explore the political engagement of Tat Ming Pair’s work—their songs, performances, and music videos—Chapter 5 will take a different approach by conducting a production analysis of Tat Ming’s 2012 and 2017 concerts. The concerts that took place in the Hong Kong Coliseum created a great buzz around the city of Hong Kong and were applauded for their political, musical, and aesthetic standards. This chapter zooms in on these concerts and asks: What considerations, negotiations, tensions, controversies, and compromises on the production side underpin the narratives and aesthetics of Tat Ming’s 2012 and 2017 concerts? As such, Chapter 5 aims to unpack the making of a political pop spectacle in a city that is struggling for its future. To do so, the chapter conducts a two-fold production analysis. First, the chapter builds on a discourse analysis of the reports that have emerged in different media platforms before, during, and after the concerts. Second, we will conduct interviews with Tatming and their close collaborators, ultimately reflecting on the tension between political motivations and commercial considerations, between engagement and entertainment. By drawing on John Corner’s (1999) levels of production, we will investigate how different makers and creative workers negotiate the tension between creating an appealing aesthetic spectacle on the one hand, while trying to convey a political message on the other hand. Our analysis distils three key discourses that we find salient and helpful in furthering our understanding of a concert production. We call them the contingent, the personal, and the calibrational. They recur in the narratives of the three producers and are interwoven through different levels of production.
1 + 1 = ?
Authors: Chow Yiu Fai , de Kloet Jeroen , Schmidt Leonie 
Published: May 2024

AbstractThis chapter concerns Tat Ming Pair’s legacy as much as the more fundamental question of how to investigate legacy in pop music studies. The chapter title is not only an admittedly self-indulgent twist of a title of Tat Ming’s song “1+4=14”; it necessitates thinking on how to discuss the legacy of music practitioners in general. Shelving the titular reference to 2+2=5, the Orwellian dystopian caution of brainwashing and thought control, we are wondering how much Tats + Ming amounts to. 1+1=? Reminded of the “bias” of legacy studies, in which the effective is highlighted—in the sense of how the “man” and/or the “music” have effected into something, the legacy, we argue to pay attention to the emotional, what we will call the affective, side of any influence and impact any music practitioners may exert. We move our gaze towards cultural intermediaries, whose affinities with Tat Ming enable numerous afterlives and cultural translations of Tat Ming’s music and life. We invited eleven people to share with us; most of them are working in popular music, and a few in related fields of music and culture at large. We will first discuss Tat Ming’s legacy in terms of effect, of how Tat Ming as music makers have effected—entailed, enabled, brought about—cultural productions in music and wider cultural scenes. Tangibly, we observed how Tat Ming effected in them the very burgeoning of an interest, a passion, and a dedication to a career in music, as well as their own music and other creative works. Intangibly, we noted how Tat Ming left a yardstick for these later generations of music makers to evaluate their own music: Tat Ming’s impact on what counts as good pop—it has to be relevant and urgent, subtle and nuanced, honest and alternative. When we investigate their legacy in affective terms, these cultural intermediaries talk even more poignantly, passionately, and personally about the way they experience Tat Ming as persons. Their narratives could have resourced so much more, but we follow three protagonists: as good mentors, as good Hong Kongers, as good human beings.
Re-Evaluation of the Earthquake Catalog for Spain Using the EMS-98 Scale for the Period 1900–1962
Authors: Fernández-Fraile J. , Mattesini Maurizio , Buforn E. 
Published: May 2024

AbstractThis study uses a systematic methodology for the re-evaluation and analysis of earthquakes in the first half of the 20th century in Spain, a period with very inhomogeneous information sources. To the best of our knowledge, these earthquakes have never been previously re-evaluated using as many information sources as the collected in this paper. The methodology used in this paper has been tested in SE Spain for further application in the rest of the Iberian Peninsula. We have collected and thoroughly revised all the seismic information and data sources available, ranging from specific reports, macroseismic questionnaires, and seismograms to newspapers and pictures. In addition, for a set of 16 earthquakes between 1900 and 1962 in the selected area, we provide EMS-98 intensities and macroseismic epicenters, except for one that is instrumental. Among the 16 earthquakes, it has only been possible to provide a depth value for eight of them. The seismic intensities have been evaluated using the intensity scale EMS-98, and the epicenters have been located with both instrumental methods (Hypocenter location) and macroseismic methods (such as Bakun, Boxer 4.0 and MEEP 2.0). Our results show that, Imax (maximum seismic intensity) values from the IGN catalogue are larger in more than the half of the revised earthquakes by between a half degree to two-and-a-half degrees, and only for Lorquí earthquake on April 25th, 1912, the Imax was smaller by half a degree. Most of the epicenters were also updated with changes between 1 and 41 km. Focal depths are less than 10 km, but this parameter has large uncertainties. The result of this study is a homogeneous seismic catalog (re-evaluated epicenters and Imax) for the period 1900–1962 that can be compared with periods prior to the 20th century.