bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contribution à la phytochimie du genre Gentiana. XXII. Identification de nouveaux O‐glucosides de la mangiférine dans Gentiana asclepiadeaL.
Authors: Goetz Michel , Jacot‐Guillarmod André 
Published: December 2004

Phytochemistry of genus Gentiana. XXII. Identification of new O‐glucosides of mangiferin in Gentiana asclepiadea L.Two new O‐glucosides of mangiferin (mangiferin‐7‐O‐β‐D‐glucoside (1) and mangiferin‐6‐O‐β‐D‐glucoside (2)) have been isolated from the leaves of Gentiana asclepiadea L. This is the first full structure elucidation of naturally occurring O‐glucosides of C‐glucosylxanthones. The known C‐glucosylflavone, saponarin (5) was also identified.
Studies on Debenzylation and Photolysis of 1‐Benzyl‐ and 1‐(β‐Phenethyl)‐1,2,3,4‐tetrahydroisoquinolines
Authors: Govindachari T. R. , Nagarajan K. , Rajeswari S. , Suguna H. , Pai B. R. 
Published: December 2004

AbstractDebenzylation of 1‐(3‐benzyloxybenzyl)‐1,2,3,4‐tetrahydroisoquinolines 1, 6, 7 with hydrochloric acid and ethanol gave the corresponding phenolic isoquinolines 2, 8, 9 and tetrahydroprotoberberines 4, 12, 13. Compounds 2, 8, 9 on photolysis also gave, besides the expected noraporphines 3, 10, 11, the tetrahydroprotoberberines 4, 12, 13 [1–4] (Schemes 1 and 2). 6‐Benzyloxy‐1‐(5‐benzyloxy‐2‐bromo‐benzyl)‐1,2,3,4‐tetrahydroisoquinoline (27a) containing no methoxy or methylenedioxy groups either in ring A or C does not give protoberberine during debenzylation; but 28, the debenzylation product of 27a, on photolysis gives both the noraporphine 29 and the tetrahydroprotoberberine 30 (Scheme 6), proving that during debenzylation of 1‐(3‐benzyloxybenzyl)‐1,2,3,4‐tetrahydroisoquinolines containing additional methoxy or methylenedioxy groups, the necessary formaldehyde comes from the latter groups. During photolysis both the methoxy groups (methylenedioxy groups) and the C(3) atom of the tetrahydroisoquinoline moiety provide the formaldehyde. Veratrole under debenzylation and photolytic conditions and tetrahydroisoquinoline under the latter condition also give rise to formaldehyde (Schemes 8 and 10).The novel bromohomoprotoberberine 43 along with 42 was formed during debenzylation of the 1‐phenethyl‐1,2,3,4‐tetrahydroisoquinoline 41. Photolysis of 42 yielded the novel nor‐homoaporphine 44, in addition to 43; the latter was debrominated to give the homoberbine 45.
Polymergebundene Cinchonaalkaloide als Katalysatoren in der Michael Reaktion
Authors: Hermann Kurt , Wynberg Hans 
Published: December 2004

Polymer Bound Cinchona Alkaloids as Catalysts in the Michael ReactionThree insoluble chiral polymers (6, 7 and 8) were prepared by functionalization of copoly(styrene −2% divinyl benzene) followed by reaction with quinine (9) or dihydrocupreine (10). Their utility as catalysts in the reaction between methyl indane‐1‐one‐2‐carboxylate (13) and 3‐butene‐2‐one (14) was studied. Table 1 (runs 2–6 and 8) shows that the Michael‐adduct 15 was formed in good chemical but low optical yields, independent of the chiral polymer used. These results are compared with those of the Michael reactions in the presence of the monomeric bases quinine (9), O‐acetyl‐quinine (11) and eucipine (12) (runs 1, 7 and 9).
Totalsynthese von (+)‐D‐Homoöstron‐3‐methyläther
Authors: Gutzwiller Jürg , Meier Werner , Fürst Andor 
Published: December 2004

Total Synthesis of (+)‐D‐Homoestrone 3‐methyl etherA novel total synthesis of (+)‐D‐homoestrone 3‐methyl ether (21) is described starting from (S)‐8a‐methyl‐3,4,8,8a‐tetrahydro‐2H, 7H‐naphthalene‐1,6‐dione (1) as a chiral synthon for the rings C and D. The key step involves alkylation of the derived 3 with m‐methoxyphenacyl bromide (4) as an AB‐building block to give the dioxo‐secosteroid 5. Hydrogenation of 5 affords the trans‐decalone 11. As by‐products the epimeric cis‐decalones 12 and 13 were characterized. Cyclization of 11 leads under kinetic control predominantly to the Δ9(11)‐tetraene 14. Catalytic hydrogenation of 14 and subsequent modification in ring D give the title compound 21. It was found that 14 and also the derived Δ8‐isomer 15a add hydrogen from the α‐face of the molecule to an extent of about 80%. The 8α‐D‐homoestrone derivatives 20a and 23 as well as the 9β‐isomers 19a and 22 were characterized.
Der Metabolismus des Retinoids Ro 10‐9359. Isolierung und Identifizierung der Hauptmetaboliten aus Plasma, Urin und Faeces des Menschen sowie aus der Galle der Ratte Synthese von drei Urinmetaboliten
Authors: Hänni Ralph , Bigler Felix , Vetter Walter , Englert Gerhard , Loeliger Peter 
Published: December 2004

The Metabolism of the Retinoid Ro 10‐9359. Isolation and Identification of the Major Metabolites in Human Plasma, Urine and Feces Synthesis of Three Urinary MetabolitesAfter oral administration of therapeutic doses of the 3H‐labelled aromatic retinoic acid analog (retinoid) Ro 10‐9359 (ethyl all‐trans‐9‐(4‐methoxy‐2,3,6‐trimethyl‐phenyl)‐3,7‐dimethyl‐2,4,6,8‐nonatetraenoate) to humans 75 and 15% of the 3H‐dose were excreted within the first five days in the feces and the urine, respectively. Using chromatographic procedures including high pressure liquid chromatography 18 metabolites could be isolated from human urine. Their structures were elucidated by mass spectrometry and FT–1H‐NMR. spectroscopy. In these urinary metabolites the tetraene side chain of the parent compound Ro 10‐9359 is shortened. The radioactivity of the identified urinary metabolites accounted for about 11% of the dose. Three urinary metabolites were synthesized. The main part of the radioactivity excreted within the first five days in the feces consisted of unchanged drug (60% of the dose). A smaller (amount 15% of the dose) could not be identified. The unchanged drug and a major metabolite, the corresponding acid, were found in human plasma.In an experiment with bile‐duct cannulated rats the radioactively labelled retinoid Ro 10‐9359 was injected intravenously. About 70% of the 3H‐dose was excreted in the bile, within the first 48 hours. The whole radioactivity of the rat bile consisted of polar metabolites. No unchanged drug could be found. After enzymatic hydrolysis of the bile conjugates three metabolites were isolated. The main metabolite (49% of the i.v. dose) was a conjugate of the corresponding acid of the parent drug, already found as free compound in human plasma. The other bile metabolites (9 and 7% of the i.v. dose) had an intact side chain, too.An enterohepatic recycling of the bile metabolites was observed in the rat.
The Influence of Fasting on the Synthesis of Cholesterol, Squalene, Fatty Acids, and Ubiquinones in Liver, Small Intestine, and Kidney of Rats in vivo
Authors: Oswald  , Wiss Verena 
Published: December 2004

Abstract
The existence of a regulating site of the cholesterol synthetic pathway in rat liver located after the squalene formation is shown by a comparison of the incorporation of labelled acetate and mevalonate in vivo over a period from 7.5 minutes to several hours under fasting and non fasting conditions. The existence of such a regulating site becomes also evident by the influence of fasting on the incorporation of labelled squalene into the cholesterol of the liver.
It is assumed that enzymes acting between acetylcoenzyme A and mevalonate, e.g. the HMG‐coenzyme‐A reductase regulate the flux of substrate in direction squalene with the tendency to keep it constant. Such an assumption is in agreement with the observed minor influence of fasting on the squalene and ubiquinone synthesis.
It could be shown, that the cholesterol synthesis in the kidneys is regulated by the same mechanism as in liver, whereas such a regulation could be excluded in the small intestine.
Structure d'alcaloïdes indoliques doubles d'un type nouveau
Authors: Kunesch Nicole , Rolland Yves , Poisson Jacques , Majumder P. L. , (Née Raychaudhuri) R. Majumder , Chatterjee A. , Agwada Vincent C. , Naranjo Jorge , Hesse Manfred , Schmid Hans 
Published: December 2004

The Structure of bis‐indoline alkaloids of a novel typeThe structure of folicangine 4, a bis‐indoline alkaloid from the leaves of Voacanga africana, is obtained by correlation with voafolidine 3a and isovoafolidine 3b. It requires an ether bridge between the two parts of the molecule, as in subsessiline (amataine 5a). Subsessiline‐lactone, from the leaves of Voacanga thouarsii has structure 5b proved by correlation with 5a. The CD. curves of double‐indole alkaloids of vobtusine type are given (Table 3).
Intramolecular Stacking in Ternary Complexes Containing Uridine 5′‐Triphosphate, 2,2′‐Bipyridyl, and a Divalent Metal Ion
Authors: Fukuda Yutaka , Mitchell Paul R. , Sigel Helmut 
Published: December 2004

AbstractThe stability constants of the ternary complexes containing UTP, 2,2′‐bipyridyl (bipy), and Co2+, Ni2+, Cu2+, or Zn2+ (M2+) have been determined by potentiometric titrations (Table 1). Changes in stability are quantified by Δlog KM = log K–log K. For the Co2+, Ni2+, Cu2+, and Zn2+ systems Δlog KM is 0.10, −0.13, 0.36, and 0.15, respectively. All these ternary complexes are considerably more stable than would be expected on statistical grounds; indeed, for Co2+, Cu2+, and Zn2+, UTP4− binds more tightly to M (bipy)2+ than to M2+. An UV. difference spectroscopic study suggests that stacked adducts between bipyridyl and the pyrimidine moiety of uridine are formed. 1H‐NMR. studies of the bipy/uridine, bipy/UTP, and bipy/UTP/Zn2+ systems (Figs. 1 and 2) confirm the presence of stacking in the binary adducts and in the ternary complex. There is also evidence for the existence of the stacked protonated complex, Zn(bipy) (HUTP)−, with the proton at the γ‐phosphate group. The acidity constant of this ternary complex has been measured (Fig. 3). The observed stability enhancement of stacked adducts by the formation of a metal ion bridge is discussed (Fig. 4) and biological implications are indicated.
Tris (methylidene)‐cyclopropane (“[3]Radialene”) Part 1. Enthalpy of formation and strain energy
Authors: Bally Thomas , Baumgärtel Helmut , Büchler Ulrich , Haselbach Edwin , Lohr Wolfgang , Maier John P. , Vogt Jürgen 
Published: December 2004

AbstractThe enthalpy of formation of tris(methylidene)‐cyclopropane (“[3]radialene”, 1) has been determined as ΔH = 396 ± 12 kJ mol−1 from three fragmentation reactions of its molecular ion 1+ formed from 1 by photoionisation using synchrotron radiation. Comparative electron impact measurements using conventional mass spectrometry were also performed. A treatment of the latter data is described which leads to satisfactory agreement with the photoionization data. The experimental value of ΔH(1) is compared with various theoretical estimates. The strain energy of 1 is calculated to be 226.3 kJ mol−1. Linear extrapolation of this quantity from the increase of strain in passing from cyclopropane to methylidenecyclopropane yields 282.4 kJ mol−1. The discrepancy between these values, already predicted by Dewar and Baird ten years ago from theoretical calculations, is discussed on the basis of maximum overlap considerations. The enthalpy of formation of bis(methylidene)cyclopropane is predicted to be ΔH= 309 kJ mol−1.
Copper Catalysed Oxygenation of Bis (2‐pyridyl) methane and 6‐Methyl‐bis (2‐pyridyl)methane to the Corresponding Ketones
Authors: Urbach Fred L. , Knopp Ursula , Zuberbühler Andreas D. 
Published: December 2004

AbstractThe ligands (L) bis (2‐pyridyl) methane (BPM) and 6‐methyl‐bis (2‐pyridyl)methane (MBPM) form the three complexes CuL2+, CuL, and Cu2L2H with Cu2+. Stability constants are log K1 = 6.23 ± 0.06, log K2 = 4.83 ± 0.01, and log K (Cu2L2H + 2H2+ ⇌ 2 CuL2+) = −10.99 ± 0.03 for BPM and 4.56 ± 0.02, 2.64 ± 0.02, and −11.17 ± 0.03 for MBPM, respectively. In the presence of catalytic amounts of Cu2+, the ligands are oxygenated to the corresponding ketones at room temperature and neutral pH.With BPM and 2,4,6‐trimethylpyridine (TMP) as the substrate and the buffer base, respectively, the kinetics of the oxygenation can be described by the rate law

with k1 = (5.9 ± 0.2) · 10−13 mol l−1 s−1, k2 = (4.0 ± 0.6) · 10−4 mol−1 ls−1, k3 = (1.1 ± 0.1) · 10−12 mol l−1 s−1, and k4 = (9 ± 2) · 10−14 mol l−1 s−1.
Tobacco Mosaic Virus as a Carrier for Small Molecules I. The preparation and characterization of a TMV/α‐melanotropin conjugate
Authors: Kriwaczek Verena M. , Eberle Alex N. , Müller Martin , Schwyzer Robert 
Published: December 2004

AbstractThe use of tobacco mosaic virus (TMV) covalently loaded with hormones or other small molecules for various purposes including receptor detection and isolation is proposed. The basic principle is that of cooperative affinity interactions involving (large) numbers of artificially introduced sites (e.g. hormones) of the modified virus on the one hand and membrane‐bound sites (e.g. receptors) of a cell or of a cellmembrane particle on the other. In order to test the feasibility of such TMV/hormone conjugates, TMV carrying about 500 molecules of a biologically active α‐melanotropin analogue was synthesized, and characterized by its aspect under the electron microscope, by its infectivity, its melanophore‐stimulating activity, and its reaction with antisera against α‐melanotropin. The observed hormonal activity is in accordance with the idea of cooperative affinity interactions.
A (1,3) Strain in cis‐ and trans‐5, 6‐dihydro‐4, 6‐dimethyl‐4H, 8H‐pyrido [3,2,1‐de]phenanthridin‐8‐ones
Authors: Nagarajan Kuppuswamy , Shah Rashmi K. , Fuhrer Hermann , Puckett Reginal T. , Narasimhamurthy Mathur R. , Venkatesan Kailasam 
Published: December 2004

AbstractThe stereochemistry of trans‐ and cis‐2, 4‐dimethyl‐tetrahydroquinolines, 6 and 7 were derived from 1H‐NMR. studies. These were converted respectively into trans‐ and cis‐5, 6‐dihydro‐4, 6‐dimethyl‐4H, 8H‐pyrido [3, 2, 1‐de]phenanthridin‐8‐ones 18 and 20 by a Pschorr reaction on the anthranilamides 10 and 15. Bromophenanthridones 19 and 21 were similarly prepared from bromoanthranilamides 12 and 17. Detailed 1H‐NMR. studies on 18 and 20 indicated axial disposition of the methyl groups at C(2) in both compounds in contrast to the situation in 6 and 7. This is presumably to avoid adverse CH3CO group interaction of the A (1, 3) type. The severity of this is gauged by the preference of 20 for a normally forbidding 1, 3‐diaxial orientation of two methyl groups. X‐ray crystallographic studies on 19 and 20 confirm the stereochemical assignments.
[2+2]‐Cycloadditionen und ‐Cycloreversionen in Radikalanionen. Eine ESR.‐spektroskopische Beschreibung am Beispiel 2,2′‐disubstituierter Biphenyle
Authors: Müllen Klaus , Huber Walter 
Published: December 2004

[2+2]‐Cycloadditions and ‐cycloreversions in radical anions. An ESR. spectroscopic study for 2,2′‐disubstituted diphenyl derivativesThe radical anions derived from the polycyclic olefins 1, 2 and 3 are shown by ESR. spectroscopy to undergo [π2+π2]‐cycloaddition reactions even at low temperatures. Similarly, facile cleavage by [σ2+σ2]‐cycloreversion processes is observed for the radical anions of the corresponding cyclobutane species. This reactivity, which is in marked contrast with the thermal stability of the neutral parent compounds, is discussed taking into account the molecular geometry and the spin density distribution.
The Binding of Flavins by Apoflavodoxins from Peptostreptococcus elsdenii and Azotobacter vinelandii as Studied by Temperature‐Jump Technique
Authors: Gast Robert , Müller Franz 
Published: December 2004

AbstractThe binding of various flavins by apoflavodoxins from P. elsdenii and A. vinelandii has been studied by the temperature‐jump technique using fluorescence detection. P. elsdenii apoflavodoxin interacts only with flavins possessing 5 carbon atoms in the N(10) side chain and a terminal phosphate group. Employing a wide range of concentrations of deoxy‐FMNFlavin = 3,4‐dimethyl‐lO‐substituted isoalloxazine = 3,4‐dimethyl‐ lO‐substituted‐2,3,4,10‐tetrahydro‐benzo[g]‐pteridine‐2,4‐dione; FMN = riboflavin‐5′‐monophosphate.
and apoflavodoxin only one relaxation process was observed, indicating a one‐step binding mechanism. With native flavodoxin no relaxation could be observed.The kinetic parameters of the interaction of A. vinelandii apoflavodoxin with various flavin analogs (Structure I) have also been investigated. The interaction between apoflavodoxin and flavin derivatives carrying an ionizable, terminal functional group on the side chain becomes very weak when the number of the side chain carbon atoms is decreased below 4. This observation is interpreted in terms of repulsive forces due to negatively charged amino acid residues located in the flavin side chain binding region of the apoflavodoxin. All complexes studied revealed only one relaxation process. This observation is in contradiction with published results [10]. The published traces are instrumental artifacts.
1, 4, 5, 6‐Tetrahydro‐ν‐tetrazin‐Derivate
Authors: Seebach Dieter , Dach Rolf , Enders Dieter , Renger Bernd , Jansen Martin , Brachtel Gerold 
Published: December 2004

1, 4, 5, 6‐Tetrahydro‐ν‐tetrazin‐DerivateThe title compounds 2 and 13 are readily available from α‐lithiated N‐alkyl‐nitrosoamines 1 (see Tables 1 and 2) which decompose at − 73° to yield the N‐oxides 2. The ESR. spectra of two derivatives 1 are recorded (Fig. 1), and tentative mechanisms are proposed for the head to head dimerizations (la‐ 3‐ 4‐ 5‐ 2a and Scheme 1). Coupling of lithionitrosoamines with iodine (‐6) and alternative decomposition routes of representatives of this class of organometallics with special substitution [equations (2)‐(5)] are reported.The structures of the tetrazines are established by spectroscopic data [ESCA] (Fig. 2), IR., UV., 1H‐ (cf. Fig. 9) and 13C‐NMR., PE. (Scheme 2), by an X‐ray analysis of 2a (Fig. 4‐8 and Table 3), and by the chemical reactions. The crystal structure of 2a is a twisted boat with non planar terminal nitrogen atoms which reflects the electron repulsion in the 4‐atom‐6‐electron NNNN‐system. Comparisons are made with 2‐tetrazenes, the open chain analogues of 13, wherever possible. Raney‐Ni reductions of 2 or 13 gives diamines 14 to which is assigned the d, l‐configuration through the 1H‐NMR. spectra of the aminals 7 and 15. Neither the oxides 2 nor the tetrazines 13 undergo cycloaddition reactions [equation (6) and Section 4].Compound 2a is dimerized to the bis (nitrosoamino)‐2‐tetrazene 18 by treatment with acid, ZnII, CuI or iodomethane. 2a is oxidized at nitrogen to the ethylene diamine derivative 6a (through 20, with H2O2), or at the CH2‐groups of the ring to give oxo‐N‐oxide 21 (with MnO2 or the ring contracted oxo‐tetrazoline‐N‐oxide 22 (with KMnO4).Pyrolysis or photolysis of the dimethyl tetrahydrotetrazine 13a furnishes the trimer 26 of N‐methylimine, but no diazetidine 27. Silver and mercury complexes 29 are obtained from 13a, while Cr(CO)5. THF does not furnish a complex as with azocompounds, but rather replaces N2 in 13a by CO (→ 28). Oxidation with permanganate converts 13a into the oxalic acid derivative 30 with unchanged tetrazine structure.
Cyclooct‐1‐en‐5‐yne. Preparation, spectroscopic characteristics and chemical reactivity
Authors: Leupin Werner , Wirz Jakob 
Published: December 2004

AbstractCyclooct‐1‐en‐5‐yne (3) has been obtained as an isolable, but highly reactive hydrocarbon by oxidation of cyclooct‐5‐ene‐1, 2‐dihydrazone with lead tetraacetate (Scheme 2). Information regarding the structure and conformational mobility of 3 has been gained from the analysis of its 1H‐ and 13C‐NMR. spectra and was found to agree with the results of force field calculations. Photolysis (206 nm) of 3 in solution has induced cleavage to butatriene and butadiene. The first band in the photoelectron spectrum of 3 (Iv 9.10 eV) is attributed to ionization from a rather delocalized orbital with predominant weight of the double bond p‐AO's. Nevertheless, the high reactivity of 3 stems from the strained triple bond as evidenced by the reaction products obtained by pyrolysis, oxidation, Diels‐Alder addition, and 1, 3‐dipolar addition (Scheme 4).
Synthesen von Moniliformin, einem Mycotoxin mit Cyclobutendion‐Struktur
Authors: Belluš Daniel , Fischer Hanspeter , Greuter Hans , Martin Pierre 
Published: December 2004

Syntheses of Moniliformin, a Mycotoxine with a Cyclobutenedione StructureSix different routes to 3‐hydroxy‐3‐cyclobutene‐1, 2‐dione (4), the free acid of the mycotoxine Moniliformin (=alkali salt of 4) are described. A common feature of all pathways is the synthesis of cyclobutanes having the oxidation level 6. Moniliformin precursors which are easily transformed to 4 by acid catalysed hydrolysis include [2+2]‐cycloadducts of ketene with tetraalkoxy‐olefins, 3,4,4‐trialkoxycyclobutenes, derivatives of polyfluorinated cyclobutenes, the brominated [2+2]‐cycloadduct of ethyl vinyl ether and dichloroketene, tetrabromocyclobutanone, [2+2]‐photocycloadducts of dichlorovinylenecarbonate with dichloroethylenes, and the dimer of chloroketene. The most convenient synthesis via the [2+2]‐cycloadduct of tetraethoxyethylene and ketene (14b) is reported in detail and produces 4 in four simple steps in 57% overall yield. In addition, two new syntheses of squaric acid (56) are described.
Molluscicidal saponins from cornus florida L.
Authors: Hostettmann Kurt , Hostettmann‐Kaldas Maryse , Nakanishi Koji 
Published: December 2004

AbstractThe molluscicidal principle of Cornus florida L. (Cornaceae) has been isolated from the methanolic bark extract by droplet counter‐current chromatography (DCC). The structure of the active compounds has been determined as sarsapogenin‐O‐β‐D‐xylopyranosyl‐(1 → 2)‐β‐D‐galactopyranoside (2) and sarsapogenin‐O‐β‐D‐glucopyranosyl‐(1 → 2)‐β‐D‐galactopyranoside (3).
Radical Ions in the Pentalene Series. Part. I. 1,3,5‐tri‐t‐butylpentalene
Authors: Fürderer Peter , Gerson Fabina , Hafner Klaus 
Published: December 2004

AbstractThe ESR. spectra of the radical anion and cation of 1, 3, 5‐tri‐t‐butylpentalene (II) have been reexamined under higher resolution. With the assistance of the ENDOR. technique, the coupling constants of all protons in II⊖. and II⊖. could be determined. The experimental data agree satisfactorily with the values predicted by the simple MO model which suggests that the π‐spin distributions in II⊖. and II⊖. should not strongly differ from those in the corresponding radical ions of parent pentalene (I). As in the case of other non‐alternant hydrocarbons, the proton coupling constants for II⊖. are very sensitive to experimental conditions, due to the association of the radical anion with its counterion. Spectra of II⊖. taken at low temperatures (down to 133 and 163 K for ESR. and ENDOR., respectively) have not revealed specific line‐broadening which could arise from the bond shift between the two Kekulé‐structures of pentalene.
Cob(I)alamin als Katalysator 2. Mitteilung [1]. Reduktion von gesättigten Nitrilen in wasserfreier Lösung
Authors: Fischli Albert 
Published: December 2004

Cob (I)alamin as Catalyst 2. Communication [1]. Reduction of Saturated Nitriles in Anhydrous SolutionUsing cob (I)alamin as homogenous catalyst in glacial acetic acid saturated nitriles are reduced following the path of a reductive amination. The results prove the presence of an intermediate imine during the reduction of saturated nitriles with cob (I)alamine.
Zum stereochemischen Verlauf der elektrophilen Substitution an CH‐Gruppen in α‐Stellung zum N‐Atom behinderter Amide Vorläufige Mitteilung
Authors: Seebach Dieter , Wykypiel Werner , Lubosch Winfried , Kalinowski Hans‐Otto 
Published: December 2004

On the Sterochemical Course of Electrophilic Substitution at CH Groups in α‐Position to the N‐Atom of Hindered AmidesIt is shown by 1H‐NMR. analysis of the aminoalcohol derivatives 4b and 4c that the lithiation/hydroxyalkylation with acetone of 1‐nitroso‐and 1‐(2,4,6‐triiso‐propylbenzoyl)‐4‐phenyl‐piperidine leads to configurationally different products. The assigned cis and trans configuration of the substituents in 4b and 4c, respectively, is compatible with the electronic structures 2 and 1, respectively, which were previously proposed for the lithio‐derivatives 3 involved in such transformations.