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.
Structure and natural occurrence of stereoisomers of the fumonisin B series mycotoxins
Gelderblom, Wentzel C. A.,Sewram, Vikash,Shephard, Gordon S.,Snijman, Petra W.,Tenza, Kenny,Van Der Westhuizen, Liana,Vleggaar, Robert
, p. 4388 - 4394 (2007)
1H and 13C NMR spectroscopy of both fumonisin B 3 and B4, as well as high-performance liquid chromatography (HPLC) analysis of samples of fumonisin B3 used as standards, showed in each case the presence of two stereoisomers, which could not be separated by preparative chromatography. The 2,3-anti relative configuration for the two minor stereoisomers of fumonisin B3 and B4 was deduced from the NMR data, and their 2S,3R absolute configurations were established by application of Mosher's method using the fumonisin B3 sample. Samples of fumonisin B3 and B 4 can contain between 10 and 40% of fumonisin B compounds of the 3-epi series. The 3-epi-FB3, determined by HPLC with fluorescence detection of the o-phthaldialdehyde derivative and confirmed by liquid chromatography-tandem mass spectrometry, was found to occur naturally in a range of maize samples at levels much lower than FB3 (20%). The identification of members of the 3-epi-fumonisin B series provides insight into the order and selectivity of steps in fumonisin biosynthesis.
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.
Synthesis and duplex-stabilizing properties of fluorinated N-methanocarbathymidine analogues locked in the C3'-endo conformation
Jung, Michael E.,Dwight, Timothy A.,Vigant, Frederic,stergaard, Michael E.,Swayze, Eric E.,Seth, Punit P.
, p. 9893 - 9897,5 (2014)
The efficient synthesis, antiviral activity, and duplex-stabilizing properties of both isomers of the 2'-fluoro analogue of Northern methanocarbathymidine (N-MCT), 2 and 3, are reported. We show that 2'-F incorporation on the N-MCT scaffold has a strong stabilizing effect on duplex thermal stability.
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.
Hispidospermidin, a novel phospholipase C inhibitor produced by Chaetosphaeronema hispidulum (Cda) Moesz NR 7127: II - Isolation, characterization and structural elucidation
Ohtsuka,Itezono,Nakayama,Sakai,Shimma,Yokose,Seto
, p. 6 - 15 (1994)
Hispidospermidin (1) is a novel phospholipase C inhibitor produced by Chaetosphaeronema hispidulum (Cda) Moesz NR 7127. Its structure (C25H47N3O) has been elucidated as a cage compound with a trimethylspermidine side chain based on various NMR studies, including 1H-1H COSY, 13C-1H COSY, HOHAHA, HMBC, COLOC and long range J C-H resolved 2D spectroscopy. The absolute configuration of 1 has been elucidated by modified MOSHER's method on the (R)- and (S)-MTPA amides of a derivative of 1.
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.
On the specificity of reactions catalysed by the antibody H11
Khalaf, Abedawn I.,Linaza, Sabin,Pitt, Andrew R.,Stimson, William H.,Suckling, Colin J.
, p. 489 - 495 (2000)
The substrate specificity and the stereochemical course of the reactions catalysed by the antibody H11 (which was raised to a protein conjugated derivative of the adduct of 1-acetoxy-buta-1,3-diene 1) have been investigated. The antibody shows high selectivity for acetoxybutadiene which it hydrolyses to the corresponding dienol, the major diene component of the cycloaddition reactions observed. However, it tolerates a range of N- alkylmaleimides. The stereochemical course of cycloaddition is shown to produce a significant enantiomeric excess of the 3aR, 4S, 7aR-endo- diastereoisomer by analysis with Mosher's ester derivatives. This study also revealed that H11 is capable of slowly catalysing the hydrolysis of N- alkylmaleimide substrates. The implications for the mechanism of action of H11 are discussed. (C) 2000 Elsevier Science Ltd.
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.
