bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymmetric Diels‐Alder Reaction of 1‐Methoxybuta‐1,3‐diene with (2R)‐N‐Glyoxyloylbornane‐10,2‐sultam
Authors: Bauer Tomasz , Chapuis Christian , Kozak Janusz , Jurczak Janusz 
Published: December 2004

AbstractStarting from sultam 1, the chiral dienophile (2R)‐N‐glyoxyloylbornane‐10,2‐sultam (4) was readily prepared. Non‐catalyzed atmospheric‐ and high‐pressure as well as [Eu(fod)3]‐promoted [4 + 2] cycloadditions of 1‐methoxy‐buta‐1,3‐diene (5) to chiral dienophile 4, leading with high asymmetric induction to 6‐methoxy‐3,6‐dihydro‐2H‐pyran‐2‐yl derivatives 6–9, are described. The extent and direction of asymmetric induction in these reactions were established by 1H‐NMR analysis and chemical correlation, respectively. Stereochemical models for both non‐catalyzed and [Eu(fod)3]‐promoted reactions are proposed.
8‐Substituted Xanthines as Phosphodiesterase Inhibitors: Conformation‐Dependent Lipophilicity and Structure‐Activity Relationships
Authors: Walther Bernard , Carrupt Pierre‐Alain , El Tayar Nabil , Testa Bernard 
Published: December 2004

AbstractThe 8‐substituted xanthines 1–21 (including compound S 9795), caffeine (22), and the three isomeric dimethyl‐xanthines 23–25 (see Table 1), were examined for their lipophilic behaviour using a reversed‐phase HPLC technique. A number of flexible compounds showed a smaller‐than‐expected lipophilicity which based on conformational and tautomeric calculations were ascribed to the predominance of folded forms. A QSAR analysis of the phosphodiesterase‐inhibitory potency of several compounds showed favourable factors to be a low lipophilicity and the absence of a substituent on the N7 position.
Herstellung von substituierten 2‐Aminooxazol‐4‐carbonitrilen
Authors: Pascual Alfons 
Published: December 2004

Preparation of Substituted 2‐Aminooxazole‐4‐carbonitrilesDuring our synthetic programme to convert 4‐isoxazolylthioureas 3 into the corresponding carbodiimides 5, a side reaction leading to the hitherto unknown 2‐aminooxazole‐4‐carbonitriles 6 was observed. By selecting appropriate reaction conditions, it was possible to improve the yields of the carbodiimides 5 as well as of the novel oxazole‐carbonitriles 6 at will, thus allowing the synthesis of 6 to be conducted in very good yields. To overcome the difficulty of isolating unstable carbodiimides, the synthesis of 6 is best carried out in a one‐pot procedure. A limited mechanistic study showed that the formation of 6 proceeds via 5 as the only intermediate. The stability of the NCN bonds against base attack (depending strongly on both sterical hindrance and electronic‐density factors) forms the only limitation of this new synthetic pathway to oxazole‐4‐carbonitriles.
5,10:8,9‐Disecosteroids (= Steroklastanes): A new type of modified steroids
Authors: Lorenc Ljubrinka , Bondarenko Lidija , Pavlović Vlada , Fuhrer Hermann , Rihs Grety , Kalvoda Jaroslav , Mihailović Mihailo Lj. 
Published: December 2004

AbstractThermolysis of steroidal 5α, 8α‐ peroxides of type 3a‐d generates as major products the corresponding diseco compounds containing a 14‐membered ring instead of the standard A‐B‐C‐ring skeleton. Depending on the reaction conditions, either the primary products of type 9 or the α, β‐unsaturated ketones of type 4, formed by subsequent elimination of AcOH, are isolated. The latter, configurationally uniform compounds undergo epoxidation of the C(9)=C(10) bond followed by a Baeyer‐Villiger oxidation to give, as final products, the 15‐membered cyclic epoxyenol lactones of type 20 and 21. The structures of the various products were determined by 1H‐ and 13C‐NMR spectroscopy. The conformations of the 14‐ and 15‐membered rings were established by X‐ray structure analyses of 7 and 21a. A reaction mechanism for the above transformations is discussed.
Site‐Specific, Oxidative Addition of CC Bonds by ‘Anchored’ bare Fe(I) cations prior to CH bond activation. Preliminary communication
Authors: Karrass Sigurd , Schwarz Helmut 
Published: December 2004

AbstractEvidence is presented for the first time that ‘naked’ Fe+ ions, complexed to the NH2 group of primary amines, are capable of intramolecularly activating CC bonds in a highly specific mode without preceding CH activation.
New Triterpenoid N‐Acetylglycosides with Molluscicidal Activity from Tetrapleura tetraptera TAUB
Authors: Maillard Marc , Hostettmann Kurt , Adewunmi Clement O. 
Published: December 2004

AbstractActivity‐guided fractionation of the MeOH extract of the fruits of Tetrapleura tetraptera TAUB. (Mimosaceae) afforded 4 saponins 1–4, which exhibited strong molluscicidal properties against the schistosomiasis‐transmitting snails Biomphalaria glabrata. Chemical, enzymatic, and spectral methods (DCI‐MS, 1H‐NMR, 13C‐NMR) showed that they were N‐acetylglycosides of oleanolic acid and of echinocystic acid. Apart from saponin 1 (aridanin), previously isolated from this plant, glycosides 2–4 are new naturally occurring compounds.
Synthèse d'une sonde biotinylée à bras clivable allongé pour l'isolement des récepteurs de l'angiotensine II
Authors: Seyer René , Aumelas André , Marie Jacky , Claude Bonnafous Jean , Jard Serge 
Published: December 2004

Synthesis of a Biotinylated Probe with an Extended Cleavable Arm for Angiotensin II Receptors PurificationWe have synthesized a new biotinylated probe for angiotensin II receptors studies: biotinyl‐NH(CH2)2SS(CH2)2CO‐Gly‐ϵ Ahx‐[Ala1, Phe(4N3)8]angiotensin II (5). This molecule can be photoactivated through an arylazido group. 1H‐NMR studies suggest that it adopts an extended conformation which should allow a simultaneous recognition of both streptavidin and hormone receptor. It has a good affinity for receptors (Kd = 1 nM) and hence is a promising tool in their detection (autoradiography, gold‐, ferritin‐, enzyme‐, or fluorescent streptavidin derivatives) and separation (cell sorting, affinity chromatography). It can be monoiodinated (°6) at its tyrosine residue without a significant loss of affinity. Its extended cleavable arm allows an easy recovery of the ‘probe‐receptor’ complex from streptavidin. An HPLC monitoring of the synthesis is described, particularly of the segment coupling 1 + 2 in presence of (benzotriazol‐1‐yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP). This method can be used as well for synthesis of the D‐Phe8 derivative that has antagonist properties.
Pteridines. Part XLII. Synthesis and properties of 8‐substituted 2,4‐dithiolumazines
Authors: Hübsch Walter , Jibril Ibrahim , Huttner Gottfried , Pfleiderer Wolfgang 
Published: December 2004

AbstractCondensation reactions of the 5‐amino‐6‐(subst. amino)‐2,4‐dithiouracils 12 and 13 with diacetyl or benzil led to the 6,7,8‐trisubstituted 2,4‐dithiolumazines 14–16. Methylation of these compounds affected both thio functions forming various types of 2,4‐bis(methylthio)lumazine derivatives depending on the nature of the substituents at C(7) and N(8). The 6,7,8‐trimethyl‐2,4‐dithiolumazine (14) was converted into 7,8‐dihydro‐6,8‐dimethyl–7‐methylidene‐2,4‐bis(methylthio)pteridine (17), whereas the 8‐methyl‐6,7‐diphenyl‐(15) and the 8‐(2‐hydroxyethyl)‐6,7‐diphenyl‐2,4‐dithiolumazine (16) yielded the corresponding covalent inter‐ or intramolecular 7,8‐adducts 18–21. The unusual structures were proven by spectroscopic means and those of the alcohol adducts 20 and 21, furthermore, confirmed by X‐ray analysis.
Apparent Failure of the Wharton Rearrangement in a Tricyclo[7.1.1.02,7]undecane
Authors: Thomas Alan F. , Di Giorgio Roberto , Guntern Olivier 
Published: December 2004

AbstractThe Wharton rearrangement of 2,3‐epoxytricyclo[7.1.1.02,7]undecan‐3‐one, a sterically hindered system, which should have led to an allyl alcohol with the OH group at a bridgehead, gave instead the allylically rearranged alcohol. The desired hydroxy compound was prepared by the Barton modification of the Wharton rearrangement: borohydride reduction to the epoxy alcohols, reaction with N, N′‐thiocarbonylbisimidazole, and treatment with Bu3SnH. The bridgehead alcohol (and other 2‐oxygenated tricyclo[7.1.1.02,7]undecanes) readily rearranged under acidic or thermal conditions.
Synthesis and Biological Evaluation of 14‐Alkoxymorphinans Part 4 opioid agonists and partial opioid agonists in a series of N‐(cyclobutylmethyl)‐14‐methoxymorphinan‐6‐ones
Authors: Schmidhammer Helmut , Burkard Willy P. , Eggstein‐Aeppli Lislott 
Published: December 2004

AbstractThe N‐(cyclobutylmethyl)morphinans 12, 19, 20, 21, 27, and 29 and the N‐(2‐cyanoethyl) analogue 33 were prepared from different precursors. Pharmacological evaluation (e.g. opioid receptor binding assays, acetic‐acid writhing test, hot‐plate assay) points to a partial opioid agonism of compounds 12, 27, 29, and 33, and to full opioid agonism of compounds 19–21.
Synthèse énantiospécifique du (−)‐(1R, 3R, 5S)‐diméthyl‐1,3‐dioxa‐2,9‐bicyclo[3.3.1]nonane
Authors: Masoni Claudio , Deschenaux Pierre‐François , Kallimopoulos Thomas , Jacot‐Guillarmod André 
Published: December 2004

Enantiospecific Synthesis of (−)‐(1R, 3R, 5S)‐1,3‐Dimethyl‐2,9‐dioxabicyclo[3.3.1]nonaneThe isomer (−)‐(1R, 3R, 5S)‐endo‐1,3‐dimethyl‐2,9‐dioxabicyclo[3.3.1]nonane ((1R, 3R, 5S)‐8) has been synthesized from (−)‐(3R)‐methyl 3‐hydroxybutanoate. The key intermediate (3R, 5R)‐5 is proved to be a useful synthon for EPC syntheses.
Interaction between the buffer Tris and the eu(III) ion: Luminescence and potentiometric investigation
Authors: Pfefferlé Jean‐Marc , Bünzli Jean‐Claude G. 
Published: December 2004

AbstractThe interaction between the buffer 2‐amino‐2‐(hydroxymethyl)propane‐1,3‐diol (Tris) and the Eu(III) ion has been studied by luminescence spectroscopy in D2O. Emission and excitation spectra (5D0←7F0 transition) indicate an interaction with both [TrisH]+ and neutral Tris species. The former is weak and probably of the outer‐sphere type. The latter is of inner‐sphere type and corresponds to the formation of the [Eu(Tris)]3+ species (estimated logK1 = 2.3 ± 0.3). Buffer Tris is also demonstrated to prevent the formation of an Eu‐hydroxo species in the pD range of 7–8. Potentiometric measurements in H2O allowed a more precise calculation of the stability constant: logK1 = 2.44 ± 0.07. Comparison with the data for aliphatic amines and other metal ions lead to the conclusion that the Eu/Tris interaction is mainly achieved through the amino group. 1H‐NMR spectra in presence of Tb(III) ions confirmed both this assumption and the presence of a weak interaction with TrisH+. Quantitative determinations of association constants between lanthanide ions and macromolecules of biological interest performed in presence of Tris should, therefore, be corrected for the Eu/Tris interaction.
Synthesis of(+)‐(2S, 6S)‐trans‐α‐Irone and of(‐)‐(2S, 6S)‐trans‐γ‐Irone
Authors: Helmlinger Daniel , Fráter Georg 
Published: December 2004

AbstractA 3:1 mixture of (+)‐(2S, 6S)‐trans‐α‐irone ((+)‐1) and (−)‐(2S, 6S)‐trans‐γ‐irone (−)‐2) has been synthesized with ca. 70% e. e. by the ene reaction of (−)‐(S)‐3 and but‐3‐yn‐2‐one.
Tricarbonyl‐chromium complexes of benzannelated cycloproparenes
Authors: Müller Paul , Bernardinelli Gérald , Jacquier Yvan , Ricca Alessandra 
Published: December 2004

AbstractReaction of 1H‐cyclopropa [b]naphthalene (1a) or 1H‐cyclopropa[b]anthracene (10a) with tris(acetonitrile)tricarbonylchromium affords cyclobutanaphthalenone and cyclobutaanthracenone 2 and 11, respectively. In contrast, the bis‐silylated Cycloproparenes 1b and 10b undergo complexation at the terminal benzene ring and lead to the arene‐tricarbonylchromium complexes 4b and 12, respectively. Desifylation of 4b to 4a is effected by t‐BuOK.
Deaminocolchinyl Methyl Ether: Synthesis from 2,3,4,4′‐Tetramethoxybiphenyl‐2‐carbaldehyde. Comparison of antitubulin effects of deaminocolchinyl methyl ether and dehydro analogs
Authors: Boyé Olivier , Itoh Yoshikuni , Brossi Arnold 
Published: December 2004

AbstractSynthesis of deaminocolchinyl methyl ether 9 was achieved from tetramethoxy‐substituted biphenyl‐2‐carb‐aldehyde 12 via tricyclic ketone 20 and 5,6‐didehydro congener 11. Compound 9 was identical in every respect with material prepared from colchicine via 6,7‐didehydro congener 10. Measuring inhibition of tubulin polymerization in vitro showed compounds 4, 5, and 9–11 of the alloseries of colchicinoids to be particularly potent inhibitors.
Substituenteneffekte auf die NMR‐Spektren von Pentafulvenen. (13C, 13C)‐NMR‐Kopplungskonstanten (1J(C, C))
Authors: Bircher Hansruedi , Neuenschwander Markus 
Published: December 2004

Substituent Effects on NMR Spectra of Pentafulvenes. 13C, 13C‐NMR Coupling Constants (1J(C, C))1H‐ and 13C‐NMR spectra of 6‐monosubstituted pentafulvenes 1–8 have been analysed, and 1J(C, C) coupling constants have been determined from ID‐inadequate spectra of 13C satellites. It turns out that 13C,13C coupling constants of the ring C‐atoms, and especially J(1,2)/J(3,4) and J(2,3), reflect the extent of π delocalisation in the fulvene ring. With increasing electron‐donating capacity of the substituent R, J(1,2)/J(3,4) values are decreasing, while J(2,3) (and J(1,5)/J(4,5) as well) are increasing, and linear correlations of Hammett substituent constants σ+ and 1J(C,C) values are obtained.
Synthese und NMR‐spektroskopische Charakterisierung neuer Adenin‐ und 6‐Thioxopurincarboxamidine
Authors: Ried Walter , Woithe Heinz 
Published: December 2004

Synthesis and NMR‐Spectroscopic Characterization of New Adenine‐ and 6‐ThioxopurinecarboxamidinesAdenine (1) or 1H‐purine‐6(7H)‐thione (4) react with carboximidoyl chlorides 2 to yield the adenine‐9‐carboxamidines 3 or the 6,7‐dihydro‐6‐thioxo‐1H‐purine‐7‐carboxamidines 5 and 6,9‐dihydro‐6‐thioxo‐1H‐purine‐9‐carboxamidine 6 a, respectively. The structures of the compounds were determined by 1H‐ and 13C‐NMR spectroscopy.
Interaction between Oxygen Lone‐Pair Orbitals of Ether and α,β‐Unsaturated Ketone Functions in 3,5,6‐Trimethylidene‐7‐oxabicyclo[2.2.1]heptan‐2‐one and 3,6‐Dimethylidene‐7‐oxabicyclo[2.2.1]heptane‐2,5‐dione: A PE‐Spectroscopic Investigation
Authors: Röser Karl , Carrupt Pierre‐Alain , Vogel Pierre , Honegger Evi , Heilbronner Edgar 
Published: December 2004

AbstractControlled ozonolysis of 2,3,5,6‐tetramethylidene‐7‐oxabicyclo[2.2.1]heptane (1) afforded 3,5,6‐trimethylidene‐7‐oxabicyclo[2.2.1]heptan‐2‐one (2). Ozonolysis of 2 gave a 1:1 mixture of 3,5‐dimethylidene‐7‐oxa‐bicyclo[2.2.1]heptane‐2,6‐dione (3) and 3,6‐dimethylidene‐7‐oxabicyclo[2.2.1]heptane‐2,5‐dione (4). The He(Iα) photoelectron (PE) spectra of 2 and 4 have been recorded. Comparison with the PE data of related systems, and with the result of ab initio STO‐3G calculations, confirm the existence of significant through‐bond interactions between the oxygen lone‐pair orbitals n(CO) of the carbonyl functions and n(O) of the O(7) ether bridge.
Solution Structure of [Me‐L‐Leu7]Didemnin B Determined by NMR Spectroscopy and Refined by MD Calculation
Authors: Kessler Horst , Mronga Siggi , Will Martin , Schmidt Ulrich 
Published: December 2004

AbstractSeveral homo‐ and heteronuclear two‐dimensional NMR techniques were used to assign all H‐ and C‐resonances of the two conformers A and B of [7‐(N‐methyl‐L‐leucine)]didemnin B. Didemnine is a biologically highly active cytostaticum and immunosuppressivum. The assignment of the aliphatic C‐atoms were done by the inverse H,C‐COSY with TOCSY transfer which connects complete proton spin systems and represents them on C‐atoms. The structure of both conformers (A and B) in (D6)DMSO solution was derived from homo‐ and heteronuclear couplings (J), temperature dependencies of NH protons, and NOE effects. Distances determined from the latter were used for refinements by restrained MD calculations using the GROMOS program. The solution structure of [Me‐L‐Leu7]didemnin B (A and B) was compared to that of didemnin B. The backbone structure of the macrocyclic ring and of the linear side‐chain moiety are very similar in conformer A and didemnin B, though the Ist1‐Hip2 region of the ring is slightly ex tended in conformer A. This may be caused by the influence of the Me‐L‐Leu7 residue in A and may be responsible for its reduced biological activity in comparison to didemnin B. The more weakly populated conformer B exhibits a βVI turn in the linear side‐chain moiety.
Synthesis and Properties of Acyclic and Cryptate Europium(III) Complexes Incorporating the 3,3′‐Biisoquinoline 2,2′‐Dioxide Unit
Authors: Lehn Jean‐Marie , Pietraszkiewicz Marek , Karpiuk Jerzy 
Published: December 2004

AbstractThe lithium and europium(III) cryptates of a macrobicyclic ligand 1 incorporating the 3,3′‐biisoquinoline 2,2′‐dioxide 2 have been prepared. The Eu(III) complex [Eu(2)2]Cl3 has also been obtained. These Eu(III) complexes present characteristic 1H‐NMR spectra containing markedly shifted resonances. They are strongly luminescent; the emission spectra, quantum yields, and lifetimes have been determined.
Approaches to the Synthesis of Cytochalasans Part9. A versatile concept leading to all structural types of cytochalasans
Authors: Ackermann Jean , Matthes Michael , Tamm Christoph 
Published: December 2004

AbstractStarting from D‐glutamic acid (5), the bicyclic compounds 4a and 4b were synthesized via 17 (Schemes 1 and 2). The reaction leading to 4g and 4h with LiCuPh2 was not successful. But treatment of the N‐protected model lactams 19, 21, and 22 with Li2Cu(CN)Ph2 gave the amino ketones 24, 26, and 27, respectively (Scheme 3). The desired compound 23 was obtained from 20. Conversion of the unprotected lactams 28, 31, and 32 gave the phenyl derivative 34 in excellent yields. Ester 35 was transformed to the α ‐amino‐γ‐ oxo‐acid derivative 36. This conversion opens a novel access to this type of compounds.
Metal Complexes with Macrocyclic Ligands. Part XXXI. Protonation studies and complexation properties of tetraazamacrocyclic methylenephosphonates with earth‐alkali ions
Authors: Delgado Rita , Siegfried Liselotte C. , Kaden Thomas A. 
Published: December 2004

AbstractThe three ligands 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetrakis(methylenephosphonic acid) (1), 1,4,7,11‐tetraazacyclotridecane‐1,4,7,11‐tetrakis(methylenephosphonic acid) (2), and 1,4,8,11‐tetraazacyclotetradecane‐1,4,8,1 1‐tetrakis(methylenephosphonic acid) (3) have been synthesized by condensation of the corresponding macrocycles with formaldehyde and phosphorous acid. The protonation and stability constants with the earth‐alkali ions have been determined at 25° and I = 0.1 M (Me4)N(NO3) by potentiometric titrations. Because of the high values of the first two protonation constants, 1H‐NMR measurements were necessary to determine them. Titrations in different supporting electrolytes (NaNO3, KNO3, RbNO3, CsNO3, and Me4N(NO3)) show that their choice is of paramount importance, as the above ligands can form complexes with alkali‐metal ions. The potentiometric results for the earth‐alkali ions show that beside mononuclear complexes of different degrees of protonation ([MLHn], n = 0–4), also binuclear species are formed ([M2LHm], m = 0–2). It is interesting that 1 with the smallest macrocyclic ring has the greatest tendency to form binuclear complexes, which are so stable that they partially prevent the formation of the corresponding mononuclear species. For [ML], [MLH], [M2L], and [M2LH], the stability sequence is Mg2+ < Ca2+ > Sr2+ > Ba2+, whereas for [MLH2], [MLH3], and [MLH4], the stability steadily decreases from Mg2+ to Ba2+.
Synthese cyclischer Depsipeptide durch direkte Amid‐Cyclisierung: 12gliedrige Depsipeptide mit alternierender Sequenz von α‐Hydroxy‐ und α‐Aminosäuren
Authors: Obrecht Daniel , Heimgartner Heinz 
Published: December 2004

Synthesis of Cyclic Depsipeptides via Direct Amide Cyclization: Cyclic Depsipeptides with 12‐Ring Atoms and Alternating Sequence of α‐Hydroxy and α‐Amino AddsThe reaction of 3‐(dimethylamino)‐2,2‐dimethyl‐2H‐azirine (1; R1 = R2 = R3 = R4 = Me) with α‐hydroxy‐carboxylic acids, followed by selective hydrolysis of the terminal dimethylamide group yields the dipeptide analogues 15a and 18b (Schemes 3 and 4). After protection of the OH group (→ 16a and 19, resp.), coupling with the C‐terminus‐protected derivatives 14 and 18a, respectively, by a modified 1,1′‐carbonyldiimidazole procedure followed by hydrolysis gives the linear depsipeptides 17c and 20, respectively. Treatment with HCl gas in toluene at 100° leads to the cyclic depsipeptides 21 and 22 in very good yield. The two model reactions show that the ‘azirine/oxazolone‐method’, combined with the ‘direct amide cyclization’, is a versatile procedure for the synthesis of cyclic depsipeptides containing α,α‐disubstituted α‐amino acids.
Synthesis of Putative Intermediates on the Monensin Biosynthetic Pathway and Incorporation Experiments with the Monensin‐Producing Organism
Authors: Holmes Duncan S. , Sherringham John A. , Dyer Ulrich C. , Russell Simon T. , Robinson John A. 
Published: December 2004

AbstractAs a direct test of the Cane‐Westley hypothesis concerning the mode of assembly of ether rings in the polyether class of ionophore antibiotics, we describe experiments culminating in the synthesis of three putative intermediates on the monensin biosynthetic pathway and incorporation experiments with these materials and the monensin‐producing organism Streptomyces cinnamonensis. The putative intermediates synthesised include the trienes [21‐3H]‐7 and [13‐3H]‐10, and the diene [9‐3H]‐11. The results of the incorporation experiments conducted with whole cell cultures suggest that [13‐3H]‐10 and [21‐3H]‐7 are unable to cross the intact cell membrane of S. cinnamonensis, whereas diene [9‐3H]‐11 can gain entry to the cellular interior, but is then degraded efficiently, most likely by a pathway closely related to β‐oxidation, without being specifically incorporated into the antibiotic.
Design and Synthesis of Novel Opiate Antagonists with LH‐Stimulating Properties
Authors: Revesz Laszlo , Siegel Richard A. , Buescher Hans‐Heinz , Marko Magda , Maurer Richard , Meigel Harald 
Published: December 2004

AbstractOpiate antagonists stimulate the release of LH and might, therefore, contribute to an innovative therapy for the treatment of numerous clinical syndromes characterized by hypofunction of the HHG axis. The purpose of this work was to design and synthesize pure opiate antagonists useful for this therapy. Me, Et, Pr, and PhCH2 groups were introduced at the crucial 14β‐position of morphines and morphinans via a hetero‐Diels‐Alder key step starting from thebaine derivative 1 and tested for opiate antagonism and LH‐stimulating activity. Me‐, Et‐, and Pr‐substituted compounds 11a–c were stronger antagonists than naltrexone, whereas Pr and PhCH2 substituents in 11c, 11d, 9d, 9d3, 9d4, and 9d5 led to orally active LH stimulators. Based on our finding that the μ‐antagonists 12 and 11b5 showed no LH stimulation, we conclude that a combination of both μ‐and χ‐antagonism is necessary for potent LH stimulation.
Stereoselectivity and Chiral Recognition in the Electron‐Transfer Reaction between Spinach Ferredoxin and Optically Active Cobalt(III) Complexes
Authors: Bernauer Klaus , Monzione Michel , Schürmann Peter , Viette Véronique 
Published: December 2004

AbstractThe kinetics of the electron transfer between reduced spinach [2Fe‐2S]‐ferredoxin and the optically active complexes [Co((R,R)‐ or (S,S)‐alamp)py]+ (I), [Co((R,R)‐ or (S,S)‐promp)H2O]+ (IIa), and [Co((R,R)‐ or (S,S)‐promp)py]+ (IIb) have been investigated. The reactions are stereoselective, and for I and IIa, the Stereoselectivity strongly depends on temperature due to large differences in the activation enthalpy between enantiomeric reagents. Isokinetic behaviour is observed between enantiomers, the ΔΔH values being largely compensated by the ΔΔS values. The compensation behaviour is explained by the combination of stereochemical interactions and desolvation processes on formation of the precursor complex or the transition state.