@article{KleinpeterSzatmariLazaretal.2009, author = {Kleinpeter, Erich and Szatm{\´a}ri, Istv{\´a}n and L{\´a}z{\´a}r, L{\´a}szl{\´o} and Koch, Andreas and Heydenreich, Matthias and Fulop, Ferenc}, title = {Visualization and quantification of anisotropic effects on the 1H NMR spectra of 1,3-oxazino[4,3- alpha]isoquinolines - indirect estimates of steric compression}, issn = {0040-4020}, doi = {10.1016/j.tet.2009.07.038}, year = {2009}, abstract = {The anisotropic effects of the phenyl, alpha- and beta-naphthyl moieties in four series of 1,3-oxazino[4,3- a]isoquinolines on the H-1 chemical shifts of the isoquinoline protons were calculated by employing the Nucleus Independent Chemical Shift (NICS) concept and Visualized as anisotropic cones by a through-space NMR shielding grid. The signs and extents of these spatial effects on the H-1 chemical shifts of the isoquinoline protons were compared with the experimental H-1 NMR spectra. The differences between the experimental delta (H-1)/ppm values and the calculated anisotropic effects of the aromatic moieties are discussed in terms of the steric compression that occurs in the Compounds studied.}, language = {en} } @article{SzatmariHeydenreichKochetal.2013, author = {Szatmari, Istvan and Heydenreich, Matthias and Koch, Andreas and Fulop, Ferenc and Kleinpeter, Erich}, title = {Unexpected isomerization of new naphth[1,3]oxazino[2,3-a] isoquinolines in solution, studied by dynamic NMR and supported by theoretical DFT computations}, series = {Tetrahedron}, volume = {69}, journal = {Tetrahedron}, number = {35}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2013.06.094}, pages = {7455 -- 7465}, year = {2013}, abstract = {Through the reactions of 1-aminomethyl-2-naphthol and substituted 1-aminobenzyl-2-naphthols with 3,4-dihydroisoquinoline or 6,7-dimethoxy-3,4-dihydroisoquinoline under microwave conditions, naphth[1,2-e][1,3]oxazino[2,3-a]-isoquinoline derivatives were prepared in good yields. The latter reaction was extended by using 2-aminoarylmethyl-1-naphthols, leading to isomeric naphth-[2,1-e][1,3]oxazino[2,3-a] isoquinolines. Beside the detailed NMR spectroscopic and theoretical study of both stereochemistry and dynamic behaviour of these new conformational flexible heterocyclic ring systems an unexpected dynamic process between two diastereomers was observed in solution, studied by variable temperature H-1 NMR spectroscopy and the mechanism proved by theoretical DFT computations.}, language = {en} } @article{YenesewKiplagatDereseetal.2006, author = {Yenesew, Abiy and Kiplagat, John T. and Derese, Solomon and Midiwo, Jacob O. and Kabaru, Jacques M. and Heydenreich, Matthias and Peter, Martin G.}, title = {Two unusual rotenoid derivatives, 7a-O-methyl-12a-hydroxydeguelol and spiro-13-homo-13-oxaelliptone, from the seeds of Derris trifoliata}, doi = {10.1016/j.phytochem.2006.01.002}, year = {2006}, abstract = {The crude methanol extract of the seeds of Derris trifoliata showed potent and dose dependent larvicidal activity against the 2nd instar larvae of Aedes aegypti. From this extract two unusual rotenoid derivatives, a rotenoloid (named 7a-O-methyl-12a-hydroxydeguelol) and a spirohomooxarotenoid (named spiro-13-homo-13-oxaelliptone), were isolated and characterised. In addition a rare natural chromanone (6,7-dimethoxy-4-chromanone) and the known rotenoids rotenone, tephrosin and dehydrodeguelin were identified. The structures were assigned on the basis of spectroscopic evidence. The larvicidal activity of the crude extract is mainly due to rotenone. (c) 2006 Elsevier Ltd. All rights reserved}, language = {en} } @article{YenesewIrunguDereseetal.2003, author = {Yenesew, Abiy and Irungu, Beatrice and Derese, Solomon and Midiwo, Jacob O. and Heydenreich, Matthias and Peter, Martin G.}, title = {Two prenylated flavonoids from the stem bark of Erythrina burttii}, year = {2003}, abstract = {From the stem bark of Erythrina burttii, a new isoflavone, 5,2',4'-trihydroxy-7-methoxy-6-(3- methylbut-2-enyl)isoflavone (trivial name, 7-O-methylluteone) and a new flavanone, 5,7-dihydroxy-4'-methoxy- 3'-(3-methylbutadienyl)-5'-(3-methylbut-2-enyl)flavanone (trivial name, burttinonedehydrate) along with three known isoflavonoids (8-prenylluteone, 3-O-methylcalopocarpin and genistein) were isolated. The structures were detd. on the basis of spectroscopic evidence.}, language = {en} } @article{YenesewMidiwoMeisneretal.1998, author = {Yenesew, Abiy and Midiwo, Jacob O. and Meisner, M. and Heydenreich, Matthias and Peter, Martin G.}, title = {Two prenylated flavanones from stem bark of erythrina burttii}, year = {1998}, language = {en} } @article{OmoleMoshiHeydenreichetal.2019, author = {Omole, Ruth Anyango and Moshi, Mainen Julius and Heydenreich, Matthias and Malebo, Hamisi Masanja and Gathirwa, Jeremiah Waweru and Ochieng, Sharon Alice and Omosa, Leonida Kerubo and Midiwo, Jacob Ogweno}, title = {Two lignans derivatives and two fusicoccane diterpenoids from the whole plant of Hypoestes verticillaris (L.F.) Sol. Ex roem. \& schult}, series = {Phytochemistry letters}, volume = {30}, journal = {Phytochemistry letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1874-3900}, doi = {10.1016/j.phytol.2019.02.019}, pages = {194 -- 200}, year = {2019}, abstract = {Bioassay-guided screening of Hypoestes verticillaris whole plant CH2Cl2: MeOH (1:1) extract for anti-plasmodial activity yielded four new compounds: two lignans 2, 6-dimethoxysavinin (1), 2,6-dimethoxy-(7E)-7,8-dehydroheliobuphthalmin (2); and two fusicoccane diterpenoids: 11(12)-epoxyhypoestenone (3) and 3(11)-epoxyhypoestenone (4). The chemical structures were determined using various spectroscopic techniques: UV-vis, IR, CD, 1D, 2D and MS. Two fractions (RAO-43B and RAO-43D) and the isolated compounds were tested for activity against CQ susceptible (D6) and resistant (W2) Plasmodium falciparum parasite strains, in vitro and the IC50 values determined. While the whole extract and some resultant fractions displayed moderate activity, the isolated compounds exhibited mild anti-plasmodial activity against the both strains ranging from IC50 value of 328 mu M in 1 to 93 mu M in 3 against W2 strain.}, language = {en} } @article{YenesewMidiwoHeydenreichetal.2000, author = {Yenesew, Abiy and Midiwo, Jacob O. and Heydenreich, Matthias and Schanzenbach, Dirk and Peter, Martin G.}, title = {Two Isoflavanones from the Stem Bark of Erythrina sacleuxii}, year = {2000}, abstract = {From the stem bark of Erythrina sacleuxii two new isoflavanones, (R)-5,7-dihydroxy-2',4',5'- trimethoxyisoflavanone (trivial name, (R)-2,3-dihydro-7-demethylrobustigenin) and (R)-5-hydroxy- 2',4',5'-trimethoxy-2'',2''- dimethylpyrano[5'',6'':6,7]isoflavanone (trivial name, (R)-saclenone) were isolated. In addition the known compounds shinpterocarpin, 2,3-dehydrokievitone, abyssinone V, abyssinone V-4'-methyl ether, erythrinasinate and 4'-O-methylsigmoidin B were isolated. The structures were determined on the basis of spectroscopic evidence.}, language = {en} } @article{PazHeydenreichSchmidtetal.2018, author = {Paz, Cristian and Heydenreich, Matthias and Schmidt, Bernd and Vadra, Nahir and Baggio, Ricardo}, title = {Three new dihydro-beta-agarofuran sesquiterpenes from the seeds of Maytenus boaria}, series = {Acta Crystallographica Section C}, volume = {74}, journal = {Acta Crystallographica Section C}, publisher = {International Union of Crystallography}, address = {Chester}, issn = {2053-2296}, doi = {10.1107/S2053229618005429}, pages = {564 -- 570}, year = {2018}, abstract = {As part of a project studying the secondary metabolites extracted from the Chilean flora, we report herein three new beta-agarofuran sesquiterpenes, namely (1S,4S,5S,6R,7R,8R,9R,10S)-6-acetoxy-4,9-dihydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b] oxepine-5,10-diylbis(furan-3-carboxylate), C27H32O11, (II), (1S,4S,5S,6R,7R,9S,10S)-6-acetoxy-9-hydroxy-2,2,5a, 9-tetramethyloctahydro-2H-3,9a-methanobenzo[ b] oxepine-5,10-diyl bis(furan-3-carboxylate), C27H32O10, (III), and (1S,4S,5S,6R,7R,9S,10S)-6-acetoxy-10-(benzoyloxy)-9-hydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]oxepin-5-yl furan-3-carboxylate, C29H34O9, (IV), obtained from the seeds of Maytenus boaria and closely associated with a recently published relative [Paz et al. (2017). Acta Cryst. C73, 451-457]. In the (isomorphic) structures of (II) and (III), the central decalin system is esterified with an acetate group at site 1 and furoate groups at sites 6 and 9, and differ at site 8, with an OH group in (II) and no substituent in (III). This position is also unsubstituted in (IV), with site 6 being occupied by a benzoate group. The chirality of the skeletons is described as 1S, 4S, 5S, 6R, 7R, 8R, 9R, 10S in (II) and 1S, 4S, 5S, 6R, 7R, 9S, 10S in (III) and (IV), matching the chirality suggested by NMR studies. This difference in the chirality sequence among the title structures (in spite of the fact that the three skeletons are absolutely isostructural) is due to the differences in the environment of site 8, i.e. OH in (II) and H in (III) and (IV). This diversity in substitution, in turn, is responsible for the differences in the hydrogen-bonding schemes, which is discussed.}, language = {en} } @article{YenesewMidiwoGuchuetal.2002, author = {Yenesew, Abiy and Midiwo, Jacob O. and Guchu, S. M. and Heydenreich, Matthias and Peter, Martin G.}, title = {Three iosoflav-3-enes and a 2-arylbenzofuran from the root bark of Erythrina burttii}, year = {2002}, abstract = {From the root bark of Erythrina burttii three new isoflav-3-enes, 7,4'-dihydroxy-2'-methoxy-6- (1'',1''-dimethylallyl)isoflav-3-ene (trivial name, burttinol-A), 4'-hydroxy-2'- methoxy-(2'',2''-dimethylpyrano[5'',6'':8,7]isoflav-3-ene (trivial name, burttinol-B), 7,4'-dihydroxy-2'-methoxy-8-(3'',3''-dimethylallyl)isoflav-3-ene (trivial name, burttinol-C), and a new 2-arylbenzofuran, 6,4'-dihydroxy-2'-methoxy-5- (1'',1''-dimethylallyl)-2-arylbenzofuran (trivial name, burttinol-D) were isolated. In addition, the known compounds, abyssinone V-4'-methyl ether, bidwillol A, calopocarpin, erybraedin A, erythrabyssin II, isobavachalcone, phaseollidin and phaseollin were identified. The structures were determined on the basis of spectroscopic evidence.}, language = {en} } @article{WanjohiYenesewMidiwoetal.2005, author = {Wanjohi, John M. and Yenesew, Abiy and Midiwo, Jacob O. and Heydenreich, Matthias and Peter, Martin G. and Dreyer, M. and Reichert, M. and Bringmann, Gerhard}, title = {Three dimeric anthracene derivatives from the fruits of Bulbine abyssinica}, issn = {0040-4020}, year = {2005}, abstract = {From the fruits of Bulbine abyssinica three new dimeric anthracene derivatives, (P)-8,9,1',8'- tetrahydroxy-3,3'-dimethyl[10,7'-bianthracene]-1,4,9',10'- tetraone (trivial name abyquinone A), (10R)-1,4,8,1',8-pentahydroxy-3,3'-dimethyl-[10,7'-bianthracene]9,9',10' (10H)-trione (trivial name abyquinone B), and (10R)-3,4'-dihydro-1,4,8,3',8',9'-hexahydroxy-3,3'- dimethyl-[10,7'-biant hracene]9,1'(10H,2'H)-dione (trivial name abyquinone Q were isolated. Despite their structural differences, these three compounds are connected to each other by the apparently biomimetic conversion of abyquinone C (a preanthraquinonylanthrone with two stereogenic centers) into B (an anthraquinonylanthrone with one stereogenic center) and finally into A (an axially chiral bianthraquinone) under mild conditions, involving a highly efficient center-to-axis chirality transfer. In addition, the known anthraquinones islandicin and chrysophanol were identified. The structures were determined on the basis of spectroscopical evidences, chemical transformations, and quantum chemical CD calculations. (C) 2005 Elsevier Ltd. All rights reserved}, language = {en} } @article{AtilawDuffyHeydenreichetal.2017, author = {Atilaw, Yoseph and Duffy, Sandra and Heydenreich, Matthias and Muiva-Mutisya, Lois and Avery, Vicky M. and Erdelyi, Mate and Yenesew, Abiy}, title = {Three Chalconoids and a Pterocarpene from the Roots of Tephrosia aequilata}, series = {Molecules}, volume = {22}, journal = {Molecules}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {1420-3049}, doi = {10.3390/molecules22020318}, pages = {11}, year = {2017}, abstract = {In our search for new antiplasmodial agents, the CH2Cl2/CH3OH (1:1) extract of the roots of Tephrosia aequilata was investigated, and observed to cause 100\% mortality of the chloroquine-sensitive (3D7) strain of Plasmodium falciparum at a 10 mg/mL concentration. From this extract three new chalconoids, E-2,6-dimethoxy-3,4-(2,2-dimethyl)pyranoretrochalcone (1, aequichalcone A), Z-2,6-dimethoxy-3,4-(2,2-dimethyl)pyranoretrochalcone (2, aequichalcone B), 4-ethoxy-3-hydroxypraecansone B (3, aequichalcone C) and a new pterocarpene, 3,4:8,9-dimethylenedioxy-6a,11a-pterocarpene (4), along with seven known compounds were isolated. The purified compounds were characterized by NMR spectroscopic and mass spectrometric analyses. Compound 1 slowly converts into 2 in solution, and thus the latter may have been enriched, or formed, during the extraction and separation process. The isomeric compounds 1 and 2 were both observed in the crude extract. Some of the isolated constituents showed good to moderate antiplasmodial activity against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum.}, language = {en} } @article{KruseHeydenreichEngstetal.2005, author = {Kruse, Hans-Peter and Heydenreich, Matthias and Engst, W. and Schilde, Uwe and Kroll, J{\"u}rgen}, title = {The identification of 1,3-oxazolidine-2-thiones and 1,3-thiazolidine-2-thiones from the reaction of glucose with benzyl isothiocyanate}, issn = {0008-6215}, year = {2005}, abstract = {The structure of interaction products resulting from the reaction of unmodified glucose with benzyl isothiocyanate is reported. Prior to their identification, the main products of this reaction were isolated using solid- phase extraction (SPE) as well as preparative HPLC. They were then identified by NMR and MS as 3-benzyl-4-hydroxy-5-(D- arabino-1,2,3,4-tetrahydroxybutyl)- 1,3-oxazolidine-2-thione, 3-benzyl-4-hydroxy-4-hydroxymethyl-5-(D-erythro-1,2,3- trihydroxypropyl)- 1,3-oxazolidine-2-thione, N-benzyl-(D-gluco-4,5-dihydroxy-6-hydroxymethyl-tetrahydropyrano)[2,3-b] oxazolidine-2-thione and 3-benzyl-4-(N-benzyl amino)-5-(D-arabino-1,2,3,4-tetrahydroxybutyl)-1,3-thiazolidine-2-thione . The identity of the last compound was secured by X-ray crystal structure data. (C) 2004 Elsevier Ltd. All rights reserved}, language = {en} } @article{HoldtMuellerPotteretal.2006, author = {Holdt, Hans-J{\"u}rgen and M{\"u}ller, Holger and Potter, Matthias and Kelling, Alexandra and Schilde, Uwe and Starke, Ines and Heydenreich, Matthias and Kleinpeter, Erich}, title = {The first sandwich complex with an octa(thioether) coordination sphere : Bis(maleonitrile-tetrathia-12-crown- 4)silver(I)}, issn = {1434-1948}, doi = {10.1002/ejic.200501109}, year = {2006}, abstract = {The new tetrathiacrown ethers maleonitrile-tetrathia-12-crown-4 (mn12S(4)) and maleonitrile-tetrathia-13-crown- 4 (mn13S(4)) have been prepared and characterised by X-ray crystallographic analysis. These crown ethers form 2:1, 3:2 and 1: 1 complexes with AgY (Y = BF4, PF6). The crystal structures of [Ag(mn12S(4))(2)]BF4 (3a), [Ag(mn13S(4))(2)]BF4 (4a) and [Ag-2(mn13S(4))(3)](PF6)(2) (6b) have been determined. Compound 3a contains the centrosymmetric sandwich complex cation [Ag(mn12S(4))(2)](+) where each mn12S(4) ligand is coordinated to the Ag centre in an endo manner through all four S atoms. The 2:1 complex [Ag(mn12S(4))(2)](+) is the first sandwich complex with a tetrathiacrown ether and the first complex with an octa(thioether) coordination sphere. The crystal structure of compound 4a also reveals a 2:1 complex. This complex, [Ag(mnl3S(4))(2)](+), exhibits a half-sandwich structure. One mn13S(4) ligand coordinates to Ag+ by all four S donor atoms and the other 13S(4) crown by only one S atom. Compound 6b contains a dinuclear Ag complex. The Ag complexes 3a,b-8a,b were also studied by electrospray ionisation mass spectrometry. Collision-induced dissociation (CID) was used to compare the relative stability of 2:1 complexes [AgL2]+ and 1:1 complexes [AgL](+) (L = mn12S(4), mn13S(4)). The C-13 NMR chemical shifts of 2:1 and 1:1 Ag complexes and their corresponding free ligands were also estimated and compared. The free energy of the barrier of ring inversion (Delta G(double dagger)) for [Ag(mn12S(4))(2)](+) was determined to be 64 kJmol(-1).}, language = {en} } @article{JumaAkalaEyaseetal.2011, author = {Juma, Wanyama P. and Akala, Hoseah M. and Eyase, Fredrick L. and Muiva, Lois M. and Heydenreich, Matthias and Okalebo, Faith A. and Gitu, Peter M. and Peter, Martin G. and Walsh, Douglas S. and Imbuga, Mabel and Yenesew, Abiy}, title = {Terpurinflavone an antiplasmodial flavone from the stem of Tephrosia Purpurea}, series = {Phytochemistry letters}, volume = {4}, journal = {Phytochemistry letters}, number = {2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1874-3900}, doi = {10.1016/j.phytol.2011.02.010}, pages = {176 -- 178}, year = {2011}, abstract = {The stem extract of Tephrosia purpurea showed antiplasmodial activity against the D6 (chloroquine-sensitive) and W2 (chloroquine-resistant) strains of Plasmodium falciparum with IC(50) values of 10.47 +/- 2.22 mu g/ml and 12.06 +/- 2.54 mu g/ml, respectively. A new prenylated flavone, named terpurinflavone, along with the known compounds lanceolatin A, (-)-semiglabrin and lanceolatin B have been isolated from this extract. The new compound, terpurinflavone, showed the highest antiplasmodial activity with IC(50) values of 3.12 +/- 0.28 mu M (D6) and 6.26 +/- 2.66 mu M (W2). The structures were determined on the basis of spectroscopic evidence.}, language = {en} } @article{BartaSzatmariFueloepetal.2016, author = {Barta, Petra and Szatmari, Istvan and Fueloep, Ferenc and Heydenreich, Matthias and Koch, Andreas and Kleinpeter, Erich}, title = {Synthesis and stereochemistry of new naphth[1,3]oxazino[3,2-a] benzazepine and naphth[1,3]oxazino[3,2-e]thienopyridine derivatives}, series = {Tetrahedron}, volume = {72}, journal = {Tetrahedron}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2016.03.058}, pages = {2402 -- 2410}, year = {2016}, abstract = {Through the reactions of 1- or 2-naphthol and 4,5-dihydro-3H-benz[c]azepine or 6,7-dihydrothieno[3,2-c]pyridine, new aminonaphthol derivatives were prepared. The syntheses were extended by using N-containing naphthol analogues such as 5-hydroxyisoquinoline and 6-hydroxyquinoline. The ring closures of the novel bifunctional compounds were also achieved, resulting in new naphth[2,1-e][1,3]oxazines, naphth[1,2-e][1,3]oxazines, isoquinolino[5,6-e][1,3]oxazines and quinolino[5,6-e][1,3]oxazines. H-1 NMR spectra of the target heterocycles 16, 20 and 21 were sufficiently resolved to indentify the present stereochemistry; therefore, beside computed structures, spatial experimental (dipolar coupling-NOE) and computed (ring current effect of the naphthyl moiety-TSNMRS) NMR studies were employed. The studied heterocycles exist exclusively as S(14b),R(N), R(14b),S(N), and S(16b)S(N) isomers, respectively. The flexible moieties of the studied compounds prefer. (C) 2016 Elsevier Ltd. All rights reserved.}, language = {en} } @article{KleinpeterHeydenreichKochetal.2012, author = {Kleinpeter, Erich and Heydenreich, Matthias and Koch, Andreas and Linker, Torsten}, title = {Synthesis and NMR spectroscopic conformational analysis of esters of 4-hydroxy-cyclohexanone-the more polar the molecule the more stable the axial conformer}, issn = {0040-4020}, year = {2012}, abstract = {The esters of 4-hydroxy-cyclohexanone and a series of carboxylic acids R-COOH with R of different electronic and steric influence (R=Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, sec-Bu, t-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, and CBr3) were synthesized and the conformational equilibria studied by 1H and 13C NMR spectroscopy at 103 K and at 295 K, respectively. The geometry of optimized structures of the axial/equatorial chair conformers was computed at the ab initio MO and DFT levels of theory. Only one preferred conformation was obtained for the axial and the equatorial conformer as well. When comparing the conformational equilibria of the cyclohexanone esters with those of the corresponding cyclohexyl esters a certain polarity contribution of the cyclohexanone framework was revealed, which is independent of the substituent effects and increases the stability of the axial conformers by a constant amount.}, language = {en} } @article{KleinpeterHeydenreichKochetal.2012, author = {Kleinpeter, Erich and Heydenreich, Matthias and Koch, Andreas and Linker, Torsten}, title = {Synthesis and NMR spectroscopic conformational analysis of esters of 4-hydroxy-cyclohexanone-the more polar the molecule the more stable the axial conformer}, series = {Tetrahedron}, volume = {68}, journal = {Tetrahedron}, number = {10}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2012.01.022}, pages = {2363 -- 2373}, year = {2012}, abstract = {The esters of 4-hydroxy-cyclohexanone and a series of carboxylic acids R-COOH with R of different electronic and steric influence (R=Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, sec-Bu, t-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, and CBr3) were synthesized and the conformational equilibria studied by H-1 and C-13 NMR spectroscopy at 103 K and at 295 K, respectively. The geometry of optimized structures of the axial 'equatorial chair conformers was computed at the ab initio MO and DFT levels of theory. Only one preferred conformation was obtained for the axial and the equatorial conformer as well. When comparing the conformational equilibria of the cyclohexanone esters with those of the corresponding cyclohexyl esters a certain polarity contribution of the cyclohexanone framework was revealed, which is independent of the substituent effects and increases the stability of the axial conformers by a constant amount.}, language = {en} } @article{SchusterKochHeydenreichetal.2008, author = {Schuster, Ildik{\´o} and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Forr{\´o}, Enik{\"o} and L{\´a}z{\´a}r, L{\´a}szl{\´o} and Sillanp{\"a}{\"a}, Reijo and Fulop, Ferenc}, title = {Synthesis and Conformational Analysis of Tetrahydroisoquinoline-Fused 1,3,2-Oxazaphospholidines and 1,2,3- Oxathiazolidines}, year = {2008}, abstract = {The cyclizations of tetrahydroisoquinoline 1,2-amino alcohols with phenylphosphonic dichloride, bis(2- chloroethyl)phosphoramidic dichloride, thionyl chloride and sulfuryl chloride were utilized to synthesize 1,5,6,10b- tetrahydro-1,3,2-oxazaphospholo[4,3-a]isoquinolines (2, 3), 1,5,10,10a-tetrahydro-1,3,2-oxazaphospholo[3,4- b]isoquinolines (8, 9), 1,5,6,10b-tetrahydro-1,2,3-oxathiazolo[4,3-a]isoquinolines (4-6) anda 1,5,10,10a-tetrahydro- 1,2,3-oxathiazolo[3,4-b]isoquinoline (11), which are the first representatives of these ring systems. NMR spectroscopic analysis revealed the existence of conformational equilibria that are fast on the NMR timescale. Theoretical DFT calculations pointed to the participation of generally two preferred conformers in the conformational equilibria; the positions of the equilibria were indicated by the experimental NMR spectroscopic parameters, and they are in good agreement with the theoretically calculated energy differences of the participating conformers. For two compounds, which could be not isolated (10, 12), both the preferred conformers and the stereochemistry could be concluded from the DFT calculation results.}, language = {en} } @article{CsuetoertoekiSzatmariKochetal.2011, author = {Cs{\"u}t{\"o}rt{\"o}ki, Ren{\´a}ta and Szatm{\´a}ri, Istv{\´a}n and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Fulop, Ferenc}, title = {Synthesis and conformational analysis of new naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives}, issn = {0040-4020}, year = {2011}, language = {en} } @article{CsuetoertoekiSzatmariKochetal.2011, author = {Csuetoertoeki, Renata and Szatmari, Istvan and Koch, Andreas and Heydenreich, Matthias and Kleinpeter, Erich and Fueloep, Ferenc}, title = {Synthesis and conformational analysis of new naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives}, series = {Tetrahedron}, volume = {67}, journal = {Tetrahedron}, number = {44}, publisher = {Elsevier}, address = {Oxford}, issn = {0040-4020}, doi = {10.1016/j.tet.2011.08.074}, pages = {8564 -- 8571}, year = {2011}, abstract = {A new highly functionalized aminonaphthol derivative, 1-(amino(2-aminophenyl)methyl)-2-naphthol (4), was synthesized by the reaction of 2-naphthol, 2-nitrobenzaldehyde and tert-butyl carbamate or benzyl carbamate, followed by reduction and/or removal of the protecting group. The aminonaphthol derivative thus obtained was converted in ring-closure reactions with formaldehyde. benzaldehyde and/or phosgene to the corresponding naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives. The conformational analysis of some derivatives by NMR spectroscopy and accompanying molecular modelling are also reported.}, language = {en} }