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Published online: 3rd June, 2019

Communication | Special issue | Prepress
DOI: 10.3987/COM-19-S(F)7
A Novel Condensed Heterocyclic Quinone with a Dibezofuranobisthiadiazole Skeleton

Kazuma Sugawara, Wataru Nojo, Yusuke Ishigaki, Junko Ohkanda, and Takanori Suzuki*

*Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan

Abstract

Upon oxidation of hydroquinone fused with 1,2,5-thiadiazole by using FeCl3, a novel dibenzofurano[1,2-c:6,7-c']bis[1,2,5]thiadiazole-type quinone was obtained whereas the similar dimerization-condensation process did not occur for the pyrazine-fused hydroquinone under the similar conditions.

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Published online: 3rd June, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-19-S(F)11
Isolation of Inohanalactone, a γ-Butyrolactone, from Nocardia inohanensis IFM0092T

Natsumi Kobayashi, Yasumasa Hara, Midori A. Arai, Shoko Hara, Tohru Gonoi, Takashi Yaguchi, and Masami Ishibashi*

*Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan

Abstract

Because research on the genus Nocardia has not progressed as compared to the extensively studied genus Streptomyces, Nocardia is considered as a useful undeveloped resource for exploring natural products. In this study, a new γ-butyrolactone derivative, named inohanalactone (1), was isolated from Nocardia inohanensis IFM0092T. Inohanalactone possesses an aliphatic side chain containing 8 carbons, a vicinal diol, and a cis double bond. Inohanalactone was produced by N. inohanensis IFM0092T in the modified Czapek–Dox medium, whereas it was not produced in other media such as Nutrient broth, Waksman, and Yeast-Malt-Glucose media.

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Published online: 10th April, 2019

Communication | Special issue | Prepress
DOI: 10.3987/COM-19-S(F)2
An Efficient Enantiospecific Synthesis of Neuroactive Glutamate Analogs

Shuntaro Tsukamoto, Hiyori Itagaki, Kenji Morokuma, Kei Miyako, Yuichi Ishikawa, Ryuichi Sakai, and Masato Oikawa*

*Yokohama City University, Seto 22-2, Kanazawa-ku, Yokohama 236-0027, Japan

Abstract

Herein we report improved enantiospecific synthesis and some structure-activity relationships of our heterotricyclic artificial glutamate analogs bearing seven-membered ring for the C-ring. Starting from readily available oxanorbornene rac-3, optically pure (2R)-TKM-107, (2R)-IKM-154, and the antipodes were synthesized in total nine steps for each. Mice in vivo assay indicated that only the (2R)-enantiomer was active in both cases. Behaviors phenotypes observed in the mice assay suggested that these compounds are similar in mode of action to that of IKM-159 but with discrete potency.

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Published online: 10th April, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-19-S(F)3
Planar Chiral Phosphino[2.2]paracyclophanol-Catalyzed Highly Regio- and Stereoselective [3+2] Annulation Reaction of Morita–Baylis–Hillman Carbonates with Dicyanomethylideneoxindoles

Shinji Kitagaki,* Mayuka Tsuji, Hideki Teramoto, Naoko Takenaga, and Keisuke Yoshida

*Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan

Abstract

To demonstrate the utility of [2.2]paracyclophane as a chiral organocatalyst backbone, we examined a planar chiral pseudo-ortho-diarylphosphino[2.2]paracyclophanol, phosphino-PCP-ol, which has a spacer aryl group between the pseudo-ortho-substituted PCP-ol backbone and the diarylphosphino group. We tested this catalyst in the [3+2] annulation reaction of MoritaBaylisHillman carbonates, derived from aromatic aldehydes and methyl acrylate, with 3-(dicyanomethylidene)-2-oxindole. The catalyst produced the desired 3-spirocyclopentene-2-oxindoles in high yields, and high regio-, diastereo-, and enantioselectivities.

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Published online: 27th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)99
Diastereo–/Enantioselective Diels–Alder Synthesis of 14β-Hydroxysteroid Scaffolds: A Combined Experimental and DFT Study

Clovis Peter, Philippe Geoffroy, Takatsugu Murata, Takayuki Tonoi, Isamu Shiina,* and Michel Miesch*

*Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan

Abstract

Natural, non-natural and ent-14β-hydroxyandrostane derivatives closely related to the cardenolide and bufadienolide skeletons were readily available through highly diastereo-/enantioselective Diels–Alder reactions calling for high pressure or Lewis acid activation. Moreover, in the presence of (R)- or (S)-carvone as chiral dienophile, the Diels–Alder reaction took place under chemodivergent parallel kinetic resolution control. Based on experimental and DFT studies, reasonable mechanism insights were postulated to explain the concave/convex and endo/exo selectivities observed for the formation of the different Diels–Alder and Diels–Alder–Michael adducts.

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Published online: 25th February, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)83
Study toward an Asymmetric and Catalytic Synthesis of Koumine

David Reyes Loya, Jacques Maddaluno, and Michaël De Paolis*

*Normandie Université, UNIROUEN, INSA de Rouen, CNRS, Laboratoire COBRA (UMR 6014 & FR 3038), 76000 Rouen, France

Abstract

A synthetic study of koumine, a natural product with a densely functionalized and inspiring heterocyclic skeleton, was conducted by exploring a strategy of desymmetrization of 1,3-cyclohexanedione by an intramolecular vinylation reaction of an enolate under palladium catalysis to give a strained bridgehead 1,3-cyclohexanedione scaffold. In the course of the study, a domino ring expansion was discovered and developed.

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Published online: 25th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)82
The Effect of Lithium Ion on the Stereoselectivity of the Intramolecular Michael Addition of an N-Arylsulfoximine Anion

Aswin Garimalla, Quin Long, Christopher J. Cramer,* and Michael Harmata*

*Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, USA.

Abstract

The stereochemical outcome of the intramolecular Michael addition of a sulfoximine carbanion to a Z-configured α,β-unsaturated ester is dependent on lithium ion coordination between the oxygen on the sulfoximine and the carbonyl oxygen of the ester, based on both experimental and computational studies. Formally, this leads to a more sterically congested structure than might otherwise be preferred. Indeed, addition of HMPA, a substance capable of effective solvation of lithium cations, changes the stereochemical course of the reaction dramatically.

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Published online: 20th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)101
1,2-cis-Selective Formation of a Unique Amino-Containing Amino Glycoside by Endocyclic Cleavage Strategy

Shino Manabe* and Yukishige Ito*

*Synthetic Cellular Chemistry Laboratory, RIKEN, Hirosawa, Wako, Saitama 351-0198, Japan

Abstract

2-Acetamido-4-amino-2,4,6-trideoxy-α-D-galactopyranoside (AAT), a unique aminated sugar unit, is often found in zwitterionic polysaccharides. Stereoselective formation of the 1,2-cis linkage of these unique sugar derivatives was achieved by an anomerization reaction based on an endocyclic cleavage process.

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Published online: 20th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)95
Construction of Pinpoint-Fluorinated Benzothiophene Frameworks Using Palladium-Catalyzed Cyclization of o-(Fluorovinyl)phenyl-Substituted Thiophenes

Kohei Fuchibe, Nobushige Tsuda, Kento Shigeno, and Junji Ichikawa*

*Division of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba-shi, Ibaraki 305-8571, Japan

Abstract

o-(2,2-Difluorovinyl)phenyl- or o-(1,2,2-trifluorovinyl)phenyl-substituted thiophenes underwent palladium(II)-catalyzed Friedel–Crafts-type cyclization on the fluorovinyl moieties to construct regioselectively monofluorinated or difluorinated benzothiophene frameworks (pinpoint-fluorinated naphtho[b]thiophenes). The cyclization of less nucleophilic 2-substituted thiophenes was effectively promoted by the addition of a CuOTf complex. Cyclization was also conducted in a tandem process, which facilitated the rapid synthesis of higher-order pinpoint-fluorinated PAHs (polycyclic aromatic hydrocarbons) bearing thiophene rings. Furthermore, cyclization was applied to the corresponding furan systems, which led to pinpoint-fluorinated naphtho[b]furans.

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Published online: 18th February, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)102
Synthesis of Di(3-thienyl)benzoporphyrin

Tetsuo Okujima,* Kota Muramatsu, Shigeki Mori, Masayoshi Takase, and Hidemitsu Uno

*Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, Japan

Abstract

We have successfully synthesized 2,3-di(3-thienyl)benzo[b]porphyrin based on retro DielsAlder reaction of bicyclo[2.2.2]octadiene(BCOD)-fused porphyrin and investigated its photoisomerization reaction.

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Published online: 15th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)94
Synthesis of a Poly-Heterocyclic Tetra-Substituted Alkene via a Palladium-Catalyzed Four-Fold Domino Reaction for the Design of Polymeric Molecular Switches

Taukeer A. Khan and Lutz F. Tietze*

*Institute of Organic and Biomolecular Chemistry, University of Goettingen, Tammannstrasse 2, 37077 Goettingen, Germany

Abstract

A facile synthesis of a complex poly-heterocyclic tetrasubstituted alkene 4 with intrinsic helical chirality containing two acrylate moieties suitable for polymerization is described. Compound 4 can act as a molecular switch and was prepared via a palladium-catalyzed four-fold domino reaction including two Sonogashira reactions and two domino-carbopalladation/CH-activation reactions.

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Published online: 15th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)97
Optimized Synthesis and Solid State Investigations on the Drug Candidate Encenicline Hydrochloride

Gerhard Laus, Sandro Neuner, Ramona Metz, Thomas Müller, Volker Kahlenberg, Thomas Gelbrich, Sven Nerdinger,* Erwin Schreiner, Verena Adamer, Klaus Wurst, and Herwig Schottenberger

*Global Portfolio, Sandoz GmbH, Biochemiestrasse 10, 6250 Kundl, Austria

Abstract

For the production of drug substances a robust, scalable process delivering the active pharmaceutical ingredient (API) in excellent chemical and polymorphic purity is required. For this purpose we developed a novel imidazole-mediated one-pot procedure for the preparation of encenicline hydrochloride monohydrate, which crystallizes directly from the reaction mixture as pure non-hygroscopic polymorph (Form I). Solid state studies revealed a series of additional new physical forms for which crystal structures have been determined by single crystal X-ray diffraction.

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Published online: 14th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)100
Preparation of Tricyclic Analog as CDE Ring Model of Renieramycin Marine Natural Product by Novel Photo-Induced Transformation of 6-Methoxy-1,2,3,4-tetrahydroisoquinoline-5,8-dione

Masashi Yokoya, Shohei Takahashi, and Naoki Saito*

*Graduate School of Pharmaceutical Sciences, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo, 204-8588, Japan

Abstract

2-Acetyl-6-[(benzyloxy)methyl]-9-methoxy-8-methyl-11,11a- dihydro-2H-pyrazino[1,2-b]isoquinoline-1,4,7,10(3H,6H)-tetraone (11a) was prepared as the CDE ring model of renieramycins, and its novel photo-induced transformation was demonstrated to construct a 1,3-dioxol ring.

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Published online: 14th February, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)103
Synthesis of Furan-Fused Silole and Phosphole by One-Pot Halogen Dance/Homocoupling of Bromofurfural Derivative

Kentaro Okano,* Yuki Murase, and Atsunori Mori

*Department of Chemical Science and Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan

Abstract

Synthesis of a furan-fused silole and phosphole was achieved through a one-pot halogen dance/homocoupling of a bromofurfural derivative followed by the formation of the silole and phosphole skeleton.

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Published online: 13th February, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)87
Asymmetric Synthesis of t-Butyl 3-Alkyl-oxindole-3-carboxylates via Chiral Phosphoric Acid-Catalyzed Desymmetrization of Di-t-butyl 2-Alkyl-2-(2-aminophenyl)malonates

Kyoji Ishida, Masahiro Shimizu, Yu-suke Yamai, Itaru Natsutani, Shinichi Uesato, Yasuo Nagaoka, and Takaaki Sumiyoshi*

*Department of Life Science and Biotechnology, Faculty of Chemistry, Materials and Bioengineering, Kansai University, Yamate-cho 3-3-35, Suita, Osaka, 564-8680, Japan

Abstract

We describe the asymmetric desymmetrization of di-t-butyl 2-alkyl-2-(2-aminophenyl)malonates to prepare enantioenriched t-butyl 3-alkyl-oxindole-3-carboxylates using (S)-TRIP, a chiral phosphoric acid. Optimization study increased the enantioselectivity up to 66% ee.

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Published online: 8th February, 2019

Communication | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)77
Tripeptide-Catalyzed Asymmetric Aldol Reaction of Trifluoromethylated Aromatic Ketones with Acetone

Kazumasa Kon, Yoshihito Kohari,* and Miki Murata

*School of Earth, Energy and Environmental Engineering, Faculty of Engineering, Kitami Institute of Technology, 165 Koen-Cho, Kitami, Hokkaido 090-8507, Japan

Abstract

The development of H-Pro-Gly-Ala-OH (3d) to realize an inexpensive and simple organocatalytic system for the direct asymmetric aldol reaction of trifluoromethylated aromatic ketone 1 with acetone was achieved. The 3d-catalyzed aldol reaction of 1a1j provided various aldol adducts 4a4j with up to 81% yield and 77% ee. An investigation of the transition state via DFT calculations revealed that hydrogen bonding was important for the revelation of the enantioselectivity.

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Published online: 5th February, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)90
A Novel Route to (R)-2-(3-Chlorophenyl)propan-1-amine, a Key Intermediate for the Synthesis of Lorcaserin

Ivana Gazic Smilovic, Sven Nerdinger,* Sandro Neuner, Herwig Schottenberger, Thomas Gelbrich, and Klaus Wurst

*Global Portfolio, Sandoz GmbH, Biochemiestrasse 10, 6250 Kundl, Austria

Abstract

A new and efficient three-step synthesis of (R)-2-(3-chlorophenyl)propan-1-amine is reported, which serves as an intermediate in the synthesis of the antiobesity drug lorcaserin. The key step is a chiral resolution due to the formation of a salt with l-(-)-3-phenyllactic acid. The structure of the relevant salt phase is reported.

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Published online: 5th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)84
Synthesis of N-Heterocyclic Carbene Ligands for Site-Selective C-H Alkylation by Cooperative Nickel/Aluminum Catalysis

Shogo Okumura, Tomohiro Ebara, Kazuhiko Semba, and Yoshiaki Nakao*

*Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoudai-katsura, Nishikyo, Kyoto 615-8510, Japan

Abstract

We report synthesis of N-heterocyclic carbenes (NHCs), N,N'-bis{2,6-bis(3,5-dialkylphenyl)methy-4-methoxyphenyl}imidazol-2-ylidenes {alkyl = ethyl (L2) or n-propyl (L3)} and their applications to nickel-catalyzed C–H alkylation reactions of arenes. They showed site-selectivities and/or yields higher than NHCs used previously for the reactions.

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Published online: 4th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)86
Packing and Thin-Film Structures of 5,7,12,14-Tetra(α-alkylthienylethyl)pentacenes

Hiroki Makino, Shin Sato, Junro Yoshino, Naoto Hayashi,* and Hiroyuki Okada*

*Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan

Abstract

Four 5,7,12,14-tetra(thienylethynyl)pentacenes (2–5) bearing H, Me, C5H11, and C6H13 groups at the α-positions of the thienyl groups were synthesized. The α-alkylthienyl groups enhanced solubilities of 2–5, whereas their ultraviolet/visible spectra were virtually identical. X-Ray diffraction revealed that the packing structure of 4 and 5 were significantly different because of one methylene group in each alkyl group. The thin-film structure of 4 was amorphous, while that of 5 consisted of small crystalline needles. Neither 4 nor 5 behaved as organic field-effect transistors because of inadequate packing and thin-film structure.

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Published online: 1st February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)98
Stereospecific Ring-Expanding Skeletal Rearrangement of Isoindoline to Tetrahydroisoquinoline via a Sequential Aziridine Ring Formation/Opening

Kenichi Kobayashi,* Ryusei Endo, Yusuke Honma, Emi Kasahara, Haruka Saito, Kosaku Tanaka III, Momoko Suzuki, and Hiroshi Kogen*

*Graduate School of Pharmaceutical Sciences, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan

Abstract

A stereospecific skeletal rearrangement of isoindoline to tetrahydroisoquinoline was developed under Appel reaction conditions using a combination of PPh3 and CCl4. This reaction involves a sequential ring formation/opening of a labile aziridine and enables the construction of a quaternary carbon center, offering a highly useful method for accessing 3,3,4-trisubstituted tetrahydroisoquinolines.

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Published online: 29th January, 2019

Review | Special issue | Prepress
DOI: 10.3987/REV-18-SR(F)4
Mini-Review: Organic Catalysts in the 1,3-Dipolar Cycloaddition Reactions of Nitrile Oxides

Silvia Roscales* and Joaquín Plumet*

*Complutense University, Faculty of Chemistry, Organic Chemistry Department, Ciudad Universitaria, 28040, Madrid, Spain

Abstract

In 1961, Huisgen categorized the nitrile oxides (NOs) as a member of a broader class of 1,3-dipoles that were capable of undergoing 1,3-dipolar cycloaddition (DC) reactions. Nevertheless, the cycloaddition (CA) reactions of NOs to alkenes and alkynes are in many cases hampered by the tendency to the dimerization of the NO to the related furoxan (1,2,5-oxadiazole 2-oxide). In addition, although monosubstituted alkenes and alkynes show high regioselectivity in their cycloadditions with NOs, 1,2-disubstituted derivatives often give mixtures of regioisomers. Catalyzed NOs cycloadditions constitute in many cases an appropriate response to these problems and, in particular, the metal catalyzed cycloaddition reactions have been extensively used. However, the cost, toxicity and removal of trace amounts of the metal residues from desired products is quite costly and challenging, while crucial, especially in the pharmaceutical industry. Obviously, alternative pathways under metal-free conditions to fulfill the metal-catalyzed reactions are highly appealing. The present review is devoted to the consideration of the use of organic molecules as catalysts for 1,3-dipolar cycloaddition reactions of nitrile oxides.

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Published online: 29th January, 2019

Communication | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)93
Vicinal Functionalization of Uracil Heterocycles with Base Activation of Iodonium(III) Salts

Naoko Takenaga,* Shohei Ueda, Takumi Hayashi, Toshifumi Dohi, and Shinji Kitagaki

*Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan

Abstract

We describe a new approach for the construction of bicyclic uracil systems and vicinal functionalization by utilizing uracil-iodonium(III) salts. Our method efficiently furnishes various multi-functionalized uracil derivatives in a single step.

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Published online: 25th January, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)64
Problem of Regioselectivity in the Amination of 2-Fluoro-5-iodopyridine with Adamantylalkyl Amines

Anton S. Abel, Yury N. Kotovshchikov, Alexei D. Averin,* Olga A. Maloshitskaya, Evgenii N. Savelyev, Boris S. Orlinson, Ivan A. Novakov, and Irina P. Beletskaya

*Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1-3, 119991, Moscow, Russia

Abstract

Cu(I)-Catalyzed and catalyst-free amination of 2-fluoro-5-iodopyridine with adamantylalkyl amines possessing different steric hindrances at amino group was investigated to obtain corresponding 5-amino-2-fluoro- and 2-amino-5-iodopyridines. The competition between catalytic substitution of iodine and non-catalytic substitution of fluorine was shown to take place. The catalytic system CuI/2-(isobutyryl)cyclohexanone in DMF provided yields of 5-amino-2-fluoropyridines up to 58% with stoichiometric ratio of the reagents and up to 98% with two equiv. of amines. The non-catalytic amination of 2-fluoro-5-iodopyridine provided the yields of 2-amino-5-iodopyridines up to 97%.

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Published online: 25th January, 2019

Review | Special issue | Prepress
DOI: 10.3987/REV-18-SR(F)6
Introducing a Methyl Group into Pyridines and Quinolines: A Mini-Review

Eliezer Falb and Alfred Hassner*

*Department of Chemistry, Bar-Ilan University, Ramat-Gan 5290002, Israel

Abstract

Pyridines are ubiquitous N-heterocycles that are present in many natural products and synthetic drugs with important biological applications. Introduction into a pyridine of a methyl (Me) or an isotopically labeled methyl group at carbon can alter its biological properties. However, regioselective introduction of a Me group in high yield, and preferably in a green manner, is often quite challenging. In this mini-review, several methods, most of which are recent, are examined whereby a Me or CD3 is introduced at a specific carbon in pyridines, as well as in some quinolines.

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Published online: 22nd January, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)96
A De Novo Asymmetric Synthesis of Phomopsolide E: A Practical Conversion from Phomopsolide D

Joel M. Harris, Miaosheng Li, and George A. O'Doherty*

*Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA.

Abstract

A practical three-step synthesis of phomopsolide E has been developed from a synthetic sample of phomopsolide D in three steps at 62% yield. A de novo asymmetric synthesis of phomopsolide D was accomplished in 8 steps from an achiral dienone in 47% yield. The initial asymmetry of phomopsolide E was installed by a Sharpless asymmetric dihydroxylation, whereas, a highly diastereoselective reagent control iterative asymmetric hydrogenation reaction was used to diastereoselectively install the pyranone stereochemistry. The net synthetic effort of phomopsolide E was accomplished in a total 11 steps in 40% overall yield. The route as devised provided for the first-time access to synthetic material for biological analysis and established both the absolute and relative stereochemistry for this natural product.

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Published online: 21st January, 2019

Communication | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)92
Synthesis and Stereochemical Analysis of Dynamic Planar Chiral Nine-Membered Diallylic Amide: Significant Substituent Effect on Stereochemical Stability

Jun-ichi Hayashi, Kazuhiro Uehara, Yusuke Ano, Yuuya Kawasaki, Kazunobu Igawa, and Katsuhiko Tomooka*

*Department of Molecular and Material Sciences, Institute for Materials Chemistry and Engineering, and IRCCS, Kyushu University, Kasuga, Fukuoka 816-8580, Japan

Abstract

C4-Methyl substituted nine-membered diallylic cyclic amide 1ac was synthesized. HPLC analysis using a chiral stationary phase revealed the presence of isolable enantiomers, whose absolute stereochemistry were determined by X-ray analysis. Studies on the stereochemical stability of 1ac showed that its chirality is more labile than that of the non-substituted congener 1aa and C3-methyl substituted congener 1ab.

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Published online: 18th January, 2019

Review | Special issue | Prepress
DOI: 10.3987/REV-18-SR(F)5
Xanthates and Vinyl Esters, a Remarkably Powerful Alliance

Béatrice Quiclet-Sire and Samir Z. Zard*

*Department of Chemistry, Ecole Polytechnique, CNRS UMR 7652, 91128 Palaiseau, France

Abstract

The present brief overview highlights and discusses the synthetic potential of the degenerative radical addition of xanthates to vinyl esters. The process results in the formation of masked aldehydes bearing numerous functionalities. It allows expedient and convergent syntheses of various structures, including cyclic and open-chain enones, trifluoromethyl enones, dienes, pyrroles, dithietanones, thiophenes, hydroxytetralones, naphthalenes and naphthols.

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Published online: 15th January, 2019

Communication | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)75
α-Glucoside Formation from 2-Deoxy-2-(2,2,2-trichloroethoxycarboxamido)-α-D-glucopyranosyl Acetate Using an Activating System That Used a Combination of Ytterbium(III) Triflate and a Catalytic Boron Trifluoride Diethyl Etherate Complex

Takashi Yamanoi,* Yoshiki Oda, Akihiko Koizumi, Tsubasa Kawaguchi, Shin Yagihara, and Akihiro Yoshida

*Faculty of Pharmacy and Pharmaceutical Sciences, Josai University, 1-1 Keyakidai, Sakado, Saitama 350-0295, Japan

Abstract

This study describes the formation of α-glucoside from 3,4,6-tri-O-benzyl-2-deoxy-2-(2,2,2-trichloroethoxycarboxamido)-α-D-glucopyranosyl acetate using an activating system that used a combination of ytterbium(III) triflate and a catalytic boron trifluoride diethyl etherate complex. This glucoside formation using various types of alcohol acceptors proceeded with high α-stereoselectivity. The novel glucoside method employed in this study is a useful technique for producing 2-amino-2-deoxy-α-D-glucopyranoside derivatives because a 2,2,2-trichloroethoxycarbonyl group from an N-protecting group is easily removable.

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Published online: 8th January, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)89
Further Studies on the Gold-Catalyzed Oxidative Domino Cyclization/Cycloaddition to Give Polyfunctional Tetracycles

Tobias Groß, Korany A. Ali, Anne Jäger, and Peter Metz*

*Faculty of Chemistry and Food Chemistry, Organic Chemistry I, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany

Abstract

Enyne aldehydes and ketones with ester and ether functions in the tether between the reactive functional groups were subjected to a gold(III)-catalyzed domino process in the presence of a pyridine N-oxide as external oxygen donor. The resulting tetracyclic ketoethers were formed in high yields under mild conditions and with excellent induced diastereoselectivity for substrates featuring a stereogenic center within the enyne tether.

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Published online: 8th January, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)74
Second-Generation Synthesis of a Chiral Building Block for Oxygenated Terpenoids via a Ring-Contractive Coupling with a Secondary Alcohol

Sayuri Saito, Hiroyuki Yamakoshi, and Seiichi Nakamura*

*Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan

Abstract

A much improved second-generation synthesis of a chiral building block, developed for the syntheses of C17-oxygenated steroids/triterpenoids and C9-oxygenated labdane diterpenoids, was accomplished by exploiting a ring-contractive coupling between an α-bromo-δ-valerolactone and (R)-seudenol, wherein the use of t-BuOK as a base allowed clean conversion to the corresponding tetrahydrofuran-2-carboxylate even with a small excess of the alcohol component.

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