20445-33-4Relevant articles and documents
Synthesis and Stereochemical Revision of the C31–C67 Fragment of Amphidinol 3
Wakamiya, Yuma,Ebine, Makoto,Murayama, Mariko,Omizu, Hiroyuki,Matsumori, Nobuaki,Murata, Michio,Oishi, Tohru
, p. 6060 - 6064 (2018)
Amphidinol 3 (AM3) is a marine natural product produced by the dinoflagellate Amphidinium klebsii. Although the absolute configuration of AM3 was determined in 1999 by extensive NMR analysis and degradation of the natural product, it was a daunting task because of the presence of numerous stereogenic centers on the acyclic carbon chain and the limited availability from natural sources. Thereafter, revisions of the absolute configurations at C2 and C51 were reported in 2008 and 2013, respectively. Reported herein is the revised absolute configuration of AM3: 32S, 33R, 34S, 35S, 36S, and 38S based on the chemical synthesis of partial structures corresponding to the C31–C67 fragment of AM3 in combination with degradation of the natural product. The revised structure is unique in that both antipodal tetrahydropyran counterparts exist on a single carbon chain. The structural revision of AM3 may affect proposed structures of congeners related to the amphidinols.
A Stimuli-Responsive Macromolecular Gear: Interlocking Dynamic Helical Polymers with Foldamers
Freire, Félix,Qui?oá, Emilio,Riguera, Ricardo,Rodríguez, Rafael,Suárez-Picado, Esteban
, p. 8616 - 8622 (2020)
Herein, macromolecular gears composed of helical poly(phenylacetylenes) (PPAs) bearing short oligopeptides as pendant groups are described, in which the two structural motifs (framework and substituents) are combined. These gears are obtained by polymerization of the acetylene groups introduced at the C-terminus of short oligopeptides formed by achiral (Aib)n units (n=1–3) derivatized at the N-terminus by a single enantiomer (R or S) of α-methoxy-α-trifluoromethylphenylacetic acid (MTPA, Mosher's reagent). The chiral information of the MTPA is transmitted to the achiral Aib fragments and, through either chiral tele-induction and/or chiral harvesting mechanisms, is further transferred to the polyene backbones, which adopt preferentially P or M helical senses. Moreover, these materials also show dynamic behavior and respond to the action of external stimuli by either inverting the P/M sense and/or modifying the elongation in fully reversible processes.
Stereoselective addition of Grignard reagents to (2-methyl-5-tert-butyl)phenyl 1-thio-β-D-ribopentodialdo-1,4-furanoside derivative
Ren, Huanming,Xie, Wuchen,Xiong, Bing,Shen, Jingkang,Chen, Guohua,Chen, Yue-Lei
, p. 2290 - 2304 (2017)
Addition of a wide range of Grignard reagents to acetone protected (2-methyl-5-tert-butyl)phenyl 1-thio-β-D-ribopentodialdo-1,4-furanoside 3b produced useful 5(R)[sbnd]C-substituted products with moderate to good yields, and moderate to perfect stereoselectivities, with no need of additives. n.O.e. Analysis of 3b showed that 1-S-aryl group could contribute to the stereoselectivity of addition reaction. The stereochemistry of 4 representative 5-C-substituted ribofuranoside products was further confirmed by NMR study of corresponding Mosher esters, by chemical derivatization, or by single crystal study.
NADH Mimics on Diacetone-D-glucose: Stereoselective Biomimetic Reduction of Benzoylformate and Interpretation of Chirality Transfer Deduced by Molecular Orbital Approach
Toyooka Yumiko,Matsuzawa, Toshihiro,Eguchi, Tadashi,Kakinuma, Katsumi
, p. 6459 - 6474 (1995)
We have prepared novel NADH mimics, in which the 1,4-dihydronicotinamide structure is connected to the diacetone-D-glucose molecule via its C-1 nitrogen, e.g. compound 1a, and 1b, and through the amide bond, e.g. compound 2-6, and analyzed their ability to stereoselective reduction of methyl benzoylformate.Although NADH mimics 1-3 and 6 turned out to be less effective in chirality transfer toward methyl benzoylformate, much higher chirality transfer was observed in the reactions with the compounds (4 and 5) possesing free hydroxyl groups at 5',6'-position of furanose.Importance of an additional intramolecular coordinating substitutent to bivalent metal ion has been demonstrated in enhancing the stereoselectivity in the reduction of benzoylformate with such NADH mimics.To materialize these observation, transition-states of the hydride transfer from 1-methyl-1,4-dihydronicotinamide to methyl benzoylformate in the presence of magnesium (II) ion were calculated by semi-empirical molecular orbital method, MNDO-PM3.Also discussed in this paper is a general chirality transfer mechanism deduced from the theoretical transition-state modeling.
Antiprotozoal activities of heterocyclic-substituted xanthones from the marine-derived fungus Chaetomium sp.
Pontius, Alexander,Krick, Anja,Kehraus, Stefan,Brun, Reto,Koenig, Gabriele M.
, p. 1579 - 1584 (2008)
Investigations of the marine-derived fungus Chaetomium sp. led to the isolation of the new natural products chaetoxanthones A, B, and C (1-3). Compounds 1 and 2 are substituted with a dioxane/tetrahydropyran moiety rarely found in natural products. Compound 3 was identified as a chlorinated xanthone substituted with a tetrahydropyran ring. The configurational analysis of these compounds employed CD spectroscopy, modified Mosher's method, and selective NOE gradient measurements. Compound 2 showed selective activity against Plasmodium falciparum with an IC50 value of 0.5 μg/mL without being cytotoxic toward cultured eukaryotic cells. Compound 3 displayed a moderate activity against Trypanosoma cruzi with an IC50 value of 1.5 μg/mL.
Novel synthesis of purine acyclonucleosides possessing a chiral 9-hydroxyalkyl group by sugar modification of 9-D-ribitylpurines
Hirota, Kosaku,Monguchi, Yasunari,Sajiki, Hironao,Sako, Magoichi,Kitade, Yukio
, p. 941 - 946 (1998)
A novel approach to the synthesis of purine acyclonucleosides having chiral carbons in the N9-hydroxyalkyl chain was achieved by using 9-(2,3-O-isopropylidene-D-ribityl)purines 1, which are readily prepared from commercially available purine nucleosides. 9-[(2S,3.R)-2,3,4-Trihydroxybutyl]purines 4a and 4b, 9-[(2S,3S)-2,3,4-trihydroxybutyl]purines 6a and 6b, L-eritadenine 8, and its analogue 11 are conveniently synthesized via key intermediates, (2S,3S)-2,3-isopropylidenedioxy-4-(purin-9-yl)butanals 2 prepared by NaIO4 oxidation of diols 1.
Chemical Synthesis of the (1R,2S) and (1S,2R) Arene Oxide Metabolites of Acridine
Boyd, Derek R.,Dorrity, Michael R. J.,Hamilton, Lynne,Malone, John F.,Smith, Allison
, p. 2711 - 2714 (1994)
Enantiopure samples of (+)-(1R,2S) and (-)-(1S,2R)-1,2-epoxy-1,2-dihydroacridine 4 have been obtained from the corresponding trans-2-bromo-1,2,3,4-tetrahydroacridin-1-ol MTPA esters 7a and b.Absolute configurations were deduced by stereochemical correlation to (+)-(1R,2R)-trans-2-bromo-1-(2-methoxy-2-phenyl-2-trifluoroacetoxy)-1,2,3,4-acridine 7a which was unequivocally assigned by X-ray crystal structure analysis. (-)-(1R,2R)-trans-1,2-Dihydroacridine-1,2-diol 2 was obtained by alkaline hydrolysis of (+)-(1R,2S)-acridine 1,2-oxide 4.
Diterpenoids and Bisnorditerpenoids from Blumea aromatica
Shen, Chien-Chang,Wei, Wen-Chi,Lin, Lie-Chwen
, p. 3181 - 3185 (2019)
Three new labdane-type diterpenoids, 6α-O-isovalerylnidorellol (1), (12S)-blumdane (2), and (12R)-epiblumdane (3), and three new bisnorditerpenoids, 6α-O-(3-methyl-2-butenoyl)sterebin A (5), 6α-O-angeloylsterebin A (6), and 6α-O-isovalerylsterebin A (7), plus 17 known compounds were isolated from Blumea aromatica. Their structures of the new compounds were proposed by detailed spectroscopic analysis. The absolute configuration at C-12 of blumdane (2) was determined by the modified Mosher's method. The anti-inflammatory and anti-immunosuppressive effects of these isolated compounds were assessed. Compounds 9, 16, and 23 (at 40 μM) showed a slight suppression of TNF-α production, but no or little effect on the expression of PD-L1 in granulocytic myeloid-derived suppressor cells was observed for all test compounds.
Computer-aided design of chiral ligands. Part III. A novel ligand for asymmetric allylation designed using computational techniques.
Kozlowski, Marisa C,Waters, Stephen P,Skudlarek, Jason W,Evans, Catherine A
, p. 4391 - 4393 (2002)
[reaction: see text] Computer-aided design protocols to identify new chiral ligands for reactions proceeding through well-defined transition states are outlined. Ligand families are discovered via computational screening of large structural databases such as the Cambridge Structural Database. Using this method, a novel cis-decalin ligand has been identified as a chiral auxiliary for the allylboration of aldehydes. Synthesis, resolution, and evaluation revealed that this new auxiliary provided the aldehyde facial approach upon which the design was predicated.
STEREOCHEMISTRY OF THE SPIROBIFLAVONOID GENKWANOL B FROM DAPHNE GENKWA
Baba, Kimiye,Taniguchi, Masahiko,Ohishi, Hirofumi,Kozawa, Mitsugi
, p. 221 - 223 (1993)
The absolute configuration of genkwanol B isolated from Daphne genkwa was studied and assigned as C-2(R), C-3(S), C-8(S), C-2"(S) and C-3"(R) by modified Mosher's method and the X-ray analysis of a pentamethyl ether acetate.Key Word Index - Daphne genkwa; Thymelaeaceae; spirobiflavonoid; genkwanol B; stereochemistry; X-ray analysis; modified Mosher's method.
Absolute configuration of myrobotinol, new fused-hexacyclic alkaloid skeleton from Myrioneuron nutans
Van, Cuong Pham,Jossang, Akino,Sevenet, Thierry,Van, Hung Nguyen,Bodo, Bernard
, p. 9826 - 9829 (2007)
(Chemical Equation Presented) Myrobotinol (1) was isolated from the leaves of Myrioneuron nutans (Rubiaceae) and its structure determined from spectral data, including mass spectrometry and 2D NMR. This compound presents a new hexacyclic alkaloid skeleton including a 1,3-oxazine and aminal functionality. The absolute configuration of myrobotinol was established by using Mosher's method. A plausible biosynthetic pathway starting from L-lysine via Δ-piperideine was proposed for this hexacyclic alkaloid.
Synthesis, Absolute Configurations, and Biological Activities of Floral Scent Compounds from Night-Blooming Araceae
Stamm, Patrick,Etl, Florian,Maia, Artur Campos D.,D?tterl, Stefan,Schulz, Stefan
, p. 5245 - 5254 (2021/04/12)
The uncommon jasmone derivatives dehydrojasmone, isojasmol, and isojasmyl acetate, floral scent compounds from night-blooming Araceae, were synthesized in a scalable synthesis employing conjugate addition with a selenoacetal as the key step. The stereoselective strategy with subsequent enzymatic kinetic resolution allowed determining the absolute configuration of the natural compounds by GC on a chiral phase. The homoterpene (E)-4,8-dimethyl-1,3,7-nonatrien-5-yl acetate, another uncommon scent compound, was obtained by α-regioselective aldehyde prenylation. The biological activities of dehydrojasmone and isojasmol were investigated in field assays, showing that these unique volatiles are able to selectively attract specific cyclocephaline scarab beetle pollinators.
N-Ammonium Ylide Mediators for Electrochemical C-H Oxidation
Saito, Masato,Kawamata, Yu,Meanwell, Michael,Navratil, Rafael,Chiodi, Debora,Carlson, Ethan,Hu, Pengfei,Chen, Longrui,Udyavara, Sagar,Kingston, Cian,Tanwar, Mayank,Tyagi, Sameer,McKillican, Bruce P.,Gichinga, Moses G.,Schmidt, Michael A.,Eastgate, Martin D.,Lamberto, Massimiliano,He, Chi,Tang, Tianhua,Malapit, Christian A.,Sigman, Matthew S.,Minteer, Shelley D.,Neurock, Matthew,Baran, Phil S.
supporting information, p. 7859 - 7867 (2021/05/26)
The site-specific oxidation of strong C(sp3)-H bonds is of uncontested utility in organic synthesis. From simplifying access to metabolites and late-stage diversification of lead compounds to truncating retrosynthetic plans, there is a growing need for new reagents and methods for achieving such a transformation in both academic and industrial circles. One main drawback of current chemical reagents is the lack of diversity with regard to structure and reactivity that prevents a combinatorial approach for rapid screening to be employed. In that regard, directed evolution still holds the greatest promise for achieving complex C-H oxidations in a variety of complex settings. Herein we present a rationally designed platform that provides a step toward this challenge using N-ammonium ylides as electrochemically driven oxidants for site-specific, chemoselective C(sp3)-H oxidation. By taking a first-principles approach guided by computation, these new mediators were identified and rapidly expanded into a library using ubiquitous building blocks and trivial synthesis techniques. The ylide-based approach to C-H oxidation exhibits tunable selectivity that is often exclusive to this class of oxidants and can be applied to real-world problems in the agricultural and pharmaceutical sectors.
