Rune Nygaard Monrad

Technical University of Denmark, Copenhagen, Capital Region, Denmark

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Publications (6)14.32 Total impact

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    ABSTRACT: Lignin-carbohydrate complexes (LCCs) are believed to influence the recalcitrance of lignocellulosic plant material preventing optimal utilization of biomass in e.g. forestry, feed and biofuel applications. The recently emerged carbohydrate esterase (CE) 15 family of glucuronoyl esterases (GEs) has been proposed to degrade ester LCC bonds between glucuronic acids in xylans and lignin alcohols thereby potentially improving delignification of lignocellulosic biomass when applied in conjunction with other cellulases, hemicellulases and oxidoreductases. Herein, we report the synthesis of four new GE model substrates comprising α- and ɣ-arylalkyl esters representative of the lignin part of naturally occurring ester LCCs as well as the cloning and purification of a novel GE from Cerrena unicolor (CuGE). Together with a known GE from Schizophyllum commune (ScGE), CuGE was biochemically characterized by means of Michaelis-Menten kinetics with respect to substrate specificity using the synthesized compounds. For both enzymes, a strong preference for 4-O-methyl glucuronoyl esters rather than unsubstituted glucuronoyl esters was observed. Moreover, we found that α-arylalkyl esters of methyl α-D-glucuronic acid are more easily cleaved by GEs than their corresponding ɣ-arylalkyl esters. Furthermore, our results suggest a preference of CuGE for glucuronoyl esters of bulky alcohols supporting the suggested biological action of GEs on LCCs. The synthesis of relevant GE model substrates presented here may provide a valuable tool for the screening, selection and development of industrially relevant GEs for delignification of biomass. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Biotechnology and bioengineering. 11/2014;
  • Rune Nygaard Monrad, Robert Madsen
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    ABSTRACT: A straightforward synthesis of substituted quinolines is described by cyclocondensation of anilines with 1,3-diols. The reaction proceeds in mesitylene solution with catalytic amounts of RuCl(3)·xH(2)O, PBu(3) and MgBr(2)·OEt(2). The transformation does not require any stoichiometric additives and only produces water and dihydrogen as byproducts. Anilines containing methyl, methoxy and chloro substituents as well as naphthylamines were shown to participate in the heterocyclisation. In the 1,3-diol a substituent was allowed in the 1- or the 2-position giving rise to 2- and 3-substituted quinolines, respectively. The best results were obtained with 2-alkyl substituted 1,3-diols to afford 3-alkylquinolines. The mechanism is believed to involve dehydrogenation of the 1,3-diol to the 3-hydroxyaldehyde which eliminates water to the corresponding α,β-unsaturated aldehyde. The latter then reacts with anilines in a similar fashion as observed in the Doebner-von Miller quinoline synthesis.
    Organic & Biomolecular Chemistry 05/2011; 9(2):610-5. · 3.57 Impact Factor
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    Rune Nygaard Monrad, Robert Madsen
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    ABSTRACT: Recent advances in the cleavage and formation of C–C bonds at the anomeric center of carbohydrates are reviewed. Both chemical and enzymatic transformations are covered with particular emphasis on aldol condensations, radical reactions, and organometallic transformations. The report contains 230 references. Figure optionsView in workspace
    ChemInform 01/2011; 67(46):8825-8850.
  • Rune Nygaard Monrad, Charlotte Bressen Pipper, Robert Madsen
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    ABSTRACT: A synthesis of the nortropane alkaloid calystegine A3 is described from D-glucose. The key step employs a zinc-mediated tandem reaction where a benzyl-protected methyl 6-iodo glucoside is fragmented to give an unsaturated aldehyde, which is then transformed into the corresponding benzylimine and allylated in the same pot. The functionalized nona-1,8-diene, thus obtained, is converted into the seven-membered carbon skeleton in calystegine A3 by ring-closing olefin metathesis. Subsequent deoxygenation by the Barton–McCombie protocol, hydroboration and oxidative workup followed by hydrogenolysis affords calystegine A3. The synthesis uses a total of 13 steps from glucose and confirms the absolute configuration of the natural product.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
    Annalen der Chemie und Pharmacie 05/2009; 2009(20):3387 - 3395. · 3.10 Impact Factor
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    ABSTRACT: A concise synthetic route is described for the synthesis of gabosine A and N. The key step uses a zinc-mediated tandem reaction where methyl 5-deoxy-5-iodo-2,3-O-isopropylidene-β-D-ribofuranoside is fragmented to give an unsaturated aldehyde which is allylated in the same pot with 3-benzoyloxy-2-methylallyl bromide. The functionalized octa-1,7-diene, thus obtained, is converted into the six-membered gabosine skeleton by ring-closing olefin metathesis. Subsequent protective group manipulations and oxidation gives rise to gabosine N in a total of 8 steps from ribose while the synthesis of gabosine A employs an additional step for inverting a secondary hydroxy group. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
    Annalen der Chemie und Pharmacie 12/2008; 2009(3):396 - 402. · 3.10 Impact Factor
  • Rune Nygaard Monrad, Robert Madsen
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    ABSTRACT: A catalytic procedure is described for decarbonylation of unprotected aldoses to afford alditols with one less carbon atom. The reaction is performed with the rhodium complex Rh(dppp)2Cl in a refluxing diglyme-DMA solution. A slightly improved catalyst turnover is observed when a catalytic amount of pyridine is added. Under these conditions most hexoses and pentoses undergo decarbonylation into the corresponding pentitols and tetrols in isolated yields around 70%. The reaction has been applied as the key transformation in a five-step synthesis of L-threose from D-glucose.
    The Journal of Organic Chemistry 01/2008; 72(25):9782-5. · 4.56 Impact Factor