- Degradation of lignin with aqueous ammonium-based ionic liquid solutions under milder conditions
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This study investigates the performance of two aqueous ionic liquids (ILs), dimethylbutylammonium acetate ([DMBA][Ac]) and dimethylbutylammonium butanoate ([DMBA][B]), solutions for depolymerizing alkali lignin into valuable phenolic compounds. The favorable operation conditions, including reaction temperature and reaction time, are explored. The extent of depolymerization of the lignin is evaluated by analysis with gel permeation chromatography (GPC). The results show that the average molecular weights of the depolymerized lignin samples can be reduced by as high as 93.8% and 86.8% after treating with the aqueous [DMBA][Ac] and [DMBA][B], respectively. Moreover, the aromatic chemical species in the depolymerized solutions are identified by using gas chromatography?mass spectrophotometry (GC-MS). The confirmation of the chemical species is further made by using a series of spectroscopic techniques, such as FT-IR, and 1H NMR and 13C NMR spectroscopy. Promising results have been achieved for the depolymerization of the lignin into valuable chemicals by using the proposed green media, aqueous solutions of ionic liquids [DMBA][Ac] and [DMBA][B], under milder conditions.
- Gupta, Bhupender S.,Lee, Ming-Jer,Tolesa, Leta Deressa
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p. 3357 - 3365
(2019/02/25)
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- Four new norlignan glycoside isomers from the twigs of Cephalotaxus oliveri Mast.
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Four novel isomers of norlignan glycoside were isolated from Cephalotaxus oliveri Mast. Their structures were elucidated as 3S-4″-O-β-D-glucopyranosylnyasol 1, 3S-4′-O-β-D-glucopyranosylnyasol 2, 3S-4″-O-β-D-glucopyranosylhinokiresinol 3, 3S-4′-O-β-D-gluc
- Meng, Fan-Cheng,Liu, Hui,Huang, Xiao-Jun,Chang, Yu,Ren, Dai,Lin, Li-Gen,Zeng, Qing-Qian,Zhang, Qing-Wen
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p. 1686 - 1689
(2017/11/24)
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- Practical Synthesis of (±)-Nyasol
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A practical total synthesis of racemic nyasol (7) was explored. The α-hydroxyketo compound 3 was prepared from commercially available starting materials in two steps. Chelation-controlled reduction of the α-hydroxyketo compound 3 with Zn(BH4)s
- Fang, Yuanying,Park, Haeil
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p. 137 - 142
(2015/10/20)
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- A broadly applicable NHC-Cu-catalyzed approach for efficient, site-, and enantioselective coupling of readily accessible (pinacolato)alkenylboron compounds to allylic phosphates and applications to natural product synthesis
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A set of protocols for catalytic enantioselective allylic substitution (EAS) reactions that allow for additions of alkenyl units to readily accessible allylic electrophiles is disclosed. Transformations afford 1,4-dienes that contain a tertiary carbon stereogenic site and are promoted by 1.0-5.0 mol % of a copper complex of an N-heterocyclic carbene (NHC). Aryl- as well as alkyl-substituted electrophiles bearing a di- or trisubstituted alkene may be employed. Reactions can involve a variety of robust alkenyl-(pinacolatoboron) [alkenyl-B(pin)] compounds that can be either purchased or prepared by various efficient, site-, and/or stereoselective catalytic reactions, such as cross-metathesis or proto-boryl additions to terminal alkynes. Vinyl-, E-, or Z-disubstituted alkenyl-, 1,1-disubstituted alkenyl-, acyclic, or heterocyclic trisubstituted alkenyl groups may be added in up to >98% yield, >98:2 SN2′:SN2, and 99:1 enantiomeric ratio (er). NHC-Cu-catalyzed EAS with alkenyl-B(pin) reagents containing a conjugated carboxylic ester or aldehyde group proceed to provide the desired 1,4-diene products in good yield and with high enantioselectivity despite the presence of a sensitive stereogenic tertiary carbon center that could be considered prone to epimerization. In most instances, the alternative approach of utilizing an alkenylmetal reagent (e.g., an Al-based species) represents an incompatible option. The utility of the approach is illustrated through applications to enantioselective synthesis of natural products such as santolina alcohol, semburin, nyasol, heliespirone A, and heliannuol E.
- Gao, Fang,Carr, James L.,Hoveyda, Amir H.
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supporting information
p. 2149 - 2161
(2014/03/21)
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- Iridium-catalyzed enantioselective allylic vinylation
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The first example of Ir-catalyzed asymmetric substitution reaction with vinyl trifluoroborates is described. The direct reaction between branched, racemic allylic alcohols and potassium alkenyltrifluoroborates proceeded with high site selectivity and exce
- Hamilton, James Y.,Sarlah, David,Carreira, Erick M.
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supporting information
p. 994 - 997
(2013/04/10)
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- Synthesis of norlignans and in vitro inhibitory activity of antigen-induced degranulation
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The synthesis and biological evaluation of a series of novel norlignans are described. Norlignans were evaluated for their inhibitory activity on the release of β-hexosaminidase, a marker of degranulation, from RBL-2H3 cells induced by the IgE-antigen com
- Park, Eonjeong,Yang, Yoon Jung,Kim, Aejin,Kwak, Jong Hwan,Jung, Young Hoon,Kang, Se Chan,Kim, In Su
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p. 3653 - 3655
(2012/07/16)
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- Subunit composition of hinokiresinol synthase controls enantiomeric selectivity in hinokiresinol formation
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Asparagus officinalis hinokiresinol synthase (HRS) is composed of two subunits, HRSα and HRSβ. Individually, each subunit forms (E)-hinokiresinol (EHR) from 4-coumaryl 4-coumarate, whereas a mixture of both subunits forms (Z)-hinokiresinol (ZHR) from the same substrate. In this study, we analyzed the enantiomeric compositions of ZHR and EHR formed after incubation of 4-coumaryl 4-coumarate with recombinant subunit proteins, recHRSα and/or recHRSβ, and with naturally occurring A. officinalis ZHR. The enantiomeric composition of ZHR formed by the mixture of recHRSα and recHRSβ was (+)-100% enantiomer excess (e.e.), identical to that of A. officinalis ZHR. In contrast, the enantiomeric compositions of EHR formed by recHRSα and recHRSβ, individually, were (-)-20.6 and (-)-9.0% e.e., respectively. These results clearly demonstrate that the subunit composition of A. officinalis HRS controls not only cis/trans isomerism but also enantioselectivity in hinokiresinol formation. The Royal Society of Chemistry.
- Yamamura, Masaomi,Suzuki, Shiro,Hattori, Takefumi,Umezawa, Toshiaki
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experimental part
p. 1106 - 1110
(2010/06/20)
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- Stereoisomerically pure trisubstituted vinylaluminum reagents and their utility in Copper-Catalyzed enantioselective synthesis of 1,4-Dienes containing Z or e alkenes
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"Chemical Equation Presented" The desired isomer of a chiral 1,4-diene containing an E or Z double bond can be accessed readily by a regio- and stereoselective hydroalumination of silyl-substituted alkynes and subsequent enantioselective copper-catalyzed
- Akiyama, Katsuhiro,Gao, Fang,Hoveyda, Amir H.
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supporting information; experimental part
p. 419 - 423
(2010/04/05)
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- Nyasol and Analogs Thereof for the Treatment of Estrogen Receptor Beta-Mediated Diseases
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Estrogenic compositions comprising nyasol and analogs thereof are provided. Also provided are methods of using said extracts to achieve an estrogenic effect, especially in a human, e.g. a female human. In some embodiments, the methods include treatment of
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Page/Page column 19
(2009/12/27)
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- Structure and absolute configuration of nyasol and hinokiresinol via synthesis and vibrational circular dichroism spectroscopy
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The absolute configuration of the norlignan (+)-nyasol was determined to be S by comparison of the experimental vibrational circular dichroism data with first-principle calculations taking into account the eight lowest energy conformations. The established absolute configuration of (+)-nyasol enables establishment of the absolute configuration of (-)-hinokiresinol, which is concluded to be S. A total synthesis and resolution of hinokiresinol has been performed to resolve the conflicting reports of the coupling constant of the vinylic protons of the disubstituted double bond in this molecule. Racemic hinokiresinol was resolved. Both enantiomers possess the same antiplasmodial activity.
- Lassen, Peter R.,Skytte, Dorthe Mondrup,Hemmingsen, Lars,Nielsen, Simon Feldbaek,Freedman, Teresa B.,Nafie, Laurence A.,Christensen, S. Brogger
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p. 1603 - 1609
(2008/09/17)
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- NYASIDE, A NEW TRIGLYCOSIDE FROM Hypoxis nyasica BAK
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From the rhizomes of Hypoxis nyasica a new triglycoside, (Z)-1-(4'-O-β-D-glucopyranosyl)-phenyl-3-(4''-(O-β-D-apiosyl 1IV->6''')-O-β-D-glucopyranosyl>phenyl-1,4-pentadiene, named nyaside, was isolated and its structure elucidated by chemical and spectroscopic methods.
- Galeffi, Corrado,Vicente, Yolanda de,Nicoletti, Marcello,Marini-Bettolo, Giovanni Battista
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p. 565 - 568
(2007/10/02)
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