bluuebunny/crossref_metadata_2025 huggingface dataset:
Chirale Synthesebausteine durch Kolbe‐Elektrolyse enantiomerenreiner β‐Hydroxy‐carbonsäurederivate. (R)‐ und (S)‐Methyl‐sowie (R)‐Trifluormethyl‐γ‐butyrolactone und ‐δ‐valerolactone
Authors: Seebach Dieter , Renaud Philippe
Published: December 2004

Chiral Building Blocks for Syntheses by Kolbe Electrolysis of Enantiomerically Pure β‐Hydroxybutyric‐Acid Derivatives. (R)‐ and (S)‐Methyl‐, and (R)‐Trifluoromethyl‐γ‐butyrolactones, and ‐δ‐valerolactones

The coupling of chiral, non‐racemic R* groups by Kolbe electrolysis of carboxylic acids R*COOH is used to prepare compounds with a 1.4‐ and 1.5‐distance of the functional groups. The suitably protected β‐hydroxycarboxylic acids (R)‐ or (S)‐3‐hydroxybutyric acid, (R)‐4,4,4‐trifluoro‐3‐hydroxybutyric acid (as acetates; see 1–6), and (S)‐malic acid (as (2S,5S)‐2‐(tert‐butyl)‐5‐oxo‐1,3‐dioxolan‐4‐acetic acid; see 7) are decarboxylatively dimerized or ‘codimerized’ with 2‐methylpropanoic acid, with 4‐(formylamino)butyric acid, and with monomethyl malonate and succinate. The products formed are derivatives of (R,R)‐1,1,1,6,6,6‐hexafluoro‐2,5‐hexanediol (see 8), of (R)‐5,5,5‐trifluoro‐4‐hydroxypentanoic acid (see 9,10), of (R)‐ and (S)‐5‐hydroxyhexanoic acid (see 11) and its trifluoro analogue (see 12, 13), of (S)‐2‐hydroxy‐ and (S,S)‐2,5‐dihydroxyadipic acid (see 23, 20), of (S)‐2‐hydroxy‐4‐methylpentanoic acid (‘OH‐leucine’, see 21), and of (S)‐2‐hydroxy‐6‐aminohexanoic acid (‘OH‐lysine’, see 22). Some of these products are further converted to CH3‐ or CF3‐substituted γ‐ and δ‐lactones of (R)‐ or (S)‐configuration (14, 16–19), or to an enantiomerically pure derivative of (R)‐1‐hydroxy‐2‐oxocyclopentane‐1‐carboxylic acid (see 24). Possible uses of these new chiral building blocks for the synthesis of natural products and their CF3 analogues (brefeldin, sulcatol, zearalenone) are discussed. The olfactory properties of (R)‐ and (S)‐δ‐caprolactone (18) are compared with those of (R)‐6,6,6‐trifluoro‐δ‐caprolactone (19).
5,6,7,8‐Tetrahydro‐4H‐1,2,5‐oxadiazocin‐6‐one durch Ringerweiterung nach Addition eines 3‐Isoxazolidinons mit 3‐Amino‐2H‐azirinen
Authors: Hostettler Bernhard , Obrecht Jean Pierre , Prewo Roland , Bieri Jost H. , Heimgartner Heinz
Published: December 2004

5,6,7,8‐Tetrahydro‐4H‐1,2,5‐oxadiazocin‐6‐ones, Ring Enlargement Products from a 3‐Isoxazolidinone and 3‐Amino‐2H‐azirines

3‐Dimethylamino‐2H‐azirines 1 and 4,4‐dimethyl‐3‐isoxazolidinone (7) undergo already at room temperature a ring enlargement reaction to yield 5,6,7,8‐tetrahydro‐4H‐1,2,5‐oxadiazocines of type 8. The structure of 8a has been confirmed by X‐ray crystallography. The conformation of the eight‐membered ring with a trans‐amide group is of particular interest (Fig. 1 and 2).
Selectivity and Charge Transfer in Photoreactions of α,α,α‐Trifluorotoluene with Olefins
Authors: Mattay Jochen , Runsink Jan , Gersdorf Joachim , Rumbach Thomas , Ly Cuong
Published: December 2004

In photoreactions of α,α,α‐trifluorotoluene with olefins, the mode of reaction strongly depends on the charge transfer between the starting materials. Substitution of an F‐atom is preferred if the electron transfer becomes exergonic, i.e. if ΔG <0 according to the Rehm‐Weller equation. In all other systems of ΔG > 0, the olefins undergo cycloaddition onto the arene ring. In the transition area of ΔG ≈︁ 0 eV, both the electron transfer and the reaction mode can be controlled by varying the solvent polarity. For instance, 1 and 9 mainly form cycloaddition products in dioxane (ΔG = + 0.11 eV), whereas in solvents with ε > 3 (ΔG < 0), substitution is the only observed photoreaction. Moreover, in systems of endergonic electron‐transfer processes, the degree and the direction of charge transfer influence both the regio‐ and the stereochemistry of the cycloaddition.
Anion Coreceptor Molecules. Linear Molecular Recognition in the Selective Binding of Dicarboxylate Substrates by Ditopic Polyammonium Macrocycles
Authors: Hosseini Mir Wais , Lehn Jean‐Marie
Published: December 2004

Three macrocyclic hexaamines 1, 2, and 4, and the acyclic tetraamine 5 and hexaamine 6 have been synthesized. The hexaamines 1, 2, and 4 are ditopic coreceptor molecules containing two triamine subunits which may bind anionic substrates when protonated. The stability constants of the complexes between the protonated forms of the macrocyclic polyamines and terminal dicarboxylates −O2C−(CH2)m‐ CO2− as well as amino‐acid and dipeptide dicarboxylates have been determined by pH‐metric measurements. Around neutral pH, 1 and 2 give mainly complexes of the fully protonated species 1·6H+ and 2·6H+, whereas 4 yields predominantly complexes of 4·5H+ and 4·4H+. The stability sequences of the complexes formed indicate preferential binding of the dianionic substrates whose length is compatible with the separation of the triammonium binding subunits in the protonated receptor molecules 1, 2, and 4. This selectivity pattern corresponds to a process of linear molecular recognition based on ditopic binding between the two ammonium subunits of the coreceptor and the terminal carboxylates of the substrate of complementary length. The complexes of the acyclic ligands 5 and 6 are much weaker and much less selective, indicating a marked macrocyclic effect on both stability and selectivity of binding, i.e. on recognition.
Crystal Structures of Chiral Ionophores: Bis(9,9′‐spirobifluorene)‐26‐crown‐4 and ‐32‐crown‐6
Authors: Egli Martin , Dobler Max
Published: December 2004

The X‐ray crystal structures of bis(9,9′‐spirobifluorene)‐26‐crown‐4βbenzene solvate (monoclinic, a = 15.47 Å, b 11.265 Å, c = 15.220 Å, β = 91.54°, space group C2) and bis(9,9′‐spirobifluorene)‐32‐crown‐6·dichloromethane solvate (tetragonal, a = 20.958 Å, c = 11.779 Å, space group P41212) are described. Both compounds act as enantioselective ionophores for α‐aminoalcohols.
Steric Effects on Reaction Rates. Part VIII. The Significance of Front Strain Release in Solvolysis of Bridgehead Derivatives
Authors: Müller Paul , Blanc Jacky , Mareda Jiri
Published: December 2004

The steric requirements of leaving groups for 14 bridgehead derivatives have been examined using MM2 calculations. The strain varies almost monotonously throughout the series upon variation of the leaving group from H to C1, OH, CH3, CH3CH2O, (CH3)3CO, (CH3)3C and no significant trends for differential F‐strain effects are detected expect for the perhydrophenalene derivative 13. The experimental rates of solvolysis of bridgehead derivatives correlate well with the calculated steric energy differences between substrate R‐X and the corresponding carbenium ion R⊕. However, the strain calculations using the more recent force‐fields (MM2) disagree, in part, with those reported in the literature: chloride and p‐toluenesulfonate leaving groups correlate with identical slopes, and the perhydrotriquinacene derivative 10 shows no anomalous behavior. The calculations suggest that F‐strain and C,C‐hyperconjugation should not play any dominant role in bridgehead solvolysis.
Über die thermische, katalytische und photochemische Stickstoff‐Eliminierung des 1‐Diazo‐3‐(1‐methylcyclopenta‐2,4‐dienyl)‐2‐propanons
Authors: Burger Ulrich , Zellweger Dominique
Published: December 2004

The Thermal, Catalytic, and Photochemical Denitrogenation of 1‐Diazo‐3‐(1‐methylcyclopenta‐2,4‐dienyl)‐2‐propanone

The synthesis of the title compound 12 is described. This diazoketone, distinguished by its Cs‐symmetry and by a built‐in cisoid diene unit, gives 5‐methyltricyclo[3.3.0.02,8]oct‐6‐ene‐3‐one (13) when subjected to thermal or catalytic denitrogenation with rhodium (II) acetate or copper (II) acetylacetonate. Direct irradiation of 12 at 350 nm causes Wolff rearrangement, whereas the benzophenone‐sensitized photolysis gives again ketone 13. A 1,4‐carbene or carbenoid addition was never observed under the conditions described. The ketone 13 equilibrates thermally or under base catalysis with 1‐methyltricyclo[3.3.0.02,8]oct‐6‐ene‐3‐one (17). The key step of this apparent CH3 migration is shown to be a Cope rearrangement of the corresponding enols (hydroxysemibullvalenes).
The Absolute Configuration of β‐Bisabolol
Authors: Ohloff Günther , Giersch Wolfgang , Näf Regula , Delay François
Published: December 2004

From bergamot oil (Citrus bergamia RISSO), (−)‐(4S, 8R)‐8‐epi‐α‐bisabolol (2) and (−)‐(4R, 8S)‐4‐epi‐β‐bisabolol (3) were isolated. The absolute configuration of their stereoisomers 4 and 5 was established by an enantioselective synthesis starting from (−)‐(S)‐p‐mentha‐1,8‐dien‐4‐ol.
A Comparative 1H‐ and 13C‐NMR Study of the Dianion and Dication of Biphenylene
Authors: Benken Rainer , Finneiser Klaus , Von Puttkamer Henning , Günther Harald , Eliasson Bertil , Edlund Ulf
Published: December 2004

Biphenylene dianion has been prepared by Li reduction of the parent hydrocarbon. It is stable below −30° and was characterized by its 1H‐ and 13C‐NMR spectra. A comparison of these data with those of the dication indicates the existence of ion pairs in the dianion case which are responsible for a different charge distribution. The diamagnetic ring currents of both ions, however, are of comparable magnitude, and both are more diatropic than the parent hydrocarbon. Predictions of the π‐charge‐density effect on 1H chemical shifts are improved by calculations that use the linear and quadratic electric‐field effect equation instead of the simple Spiesecke‐Schneider relation.
Acid‐Catalysed Cyclisation of p‐Mentha‐1,8(9)‐diene‐ and p‐Mentha‐1,8(10)‐diene‐9‐carboxylic Acid. Novel Access to the Bicyclo[3.2.1]octane Skeleton
Authors: Giersch Wolfgang , Brauchli Robert , Thommen Walter , Schulte‐Elte Karl H.
Published: December 2004

Treatment of the title compounds with either H3PO4 or BF3 · Et2O affords the bridged tricyclic lactones 3 and 7 as main products (57 and 70% yield, resp.). This is an efficient and novel access to specifically functionalised molecules possesing the bicyclo[3.2.1]octane skeleton. Lactones 4 and 5 and the bicyclic ketone 6 were formed as by‐products (2, 7, and 10% yield, resp.).
Die absolute Konfiguration des Spermin‐Alkaloides Aphelandrin
Authors: Guggisberg Armin , Prewo Roland , Hesse Manfred
Published: December 2004

The Absolute Configuration of the Spermine Alkaloid Aphelandrine

The relative configuration of aphelandrine (1) was established by X‐ray structure determination. The absolute configuration of the centers 11 and 18 was determined earlier by chiroptic measurements. Therefore, structure 1 with the configurations 11S, 17S, and 18S represents the absolute configuration of aphelandrine. In the presence of base, 1 was converted to (11S, 17R, 18R) orantine (2). The 1H‐NMR coupling constants between HC(17) and HC(18) (part of the dihydrofuran ring) are very much dependent on the substituent pattern of the amino N‐atoms N(6) and N(10).
Chinazolincarbonsäuren. XII. Mitteilung. Synthese von [2‐(Ethoxycarbonyl)‐3,4‐dihydro‐4‐oxochinazolin‐3‐yl]‐, [2‐(Ethoxycarbonyl)chinazolin‐4‐yloxy]‐ und (5,6,7,8‐Tetrahydro‐2‐phenylchinazolin‐4‐ylthio)alkansäure‐estern
Authors: Süsse Manfred , Adler Frank , Johne Siegfried
Published: December 2004

Quinazolinecarboxylic Acids. Synthesis of Alkyl [2‐(Ethoxycarbonyl)‐3,4‐dihydro‐4‐oxoquinazolin‐3‐yl]‐, [2‐(Ethoxycarbonyl)quinazolin‐4‐yloxy]‐ and (5,6,7,8‐Tetrahydro‐2‐phenylquinazolin‐4‐ylthio)alkanoates

The [(2‐aminobenzoyl)amino]alkanoic acids and their esters 1 showed a different reaction behaviour with diethyl oxalate. Compound 1 (n = 2,3) was converted into the quinazolinylalkanoates 3. o‐Aminohippurate yielded with ethyl (chloroformyl)formate a mixture of the amide 4 and the cyclized quinazolinone 7b. Ethyl 3,4‐dihydro‐4‐oxoquinazoline‐2‐carboxylate (6) reacted with 2‐bromoalkanoates, in the presence of NaH, to the [2‐(ethoxycarbonyl)‐3,4‐dihydro‐4‐oxoquinazolin‐3‐y1]acetates 7 in the case of alkyl bromoacetate, and to the O‐alkylated derivatives 8 with the ethyl 2‐bromopropionate and ‐butyrate. 2‐Aminobenzamide (5) gave with ethyl 3‐(chloroformyl)‐2‐propenoate and methyl 3‐(chloroformyl)propionate the amides 9 or 11, respectively, and not the expected quinazolinones. The cyclized product 12 was obtained from 11 and ethyl bromoacetate. Tetrahydroquinazolin‐4(3H)‐thione 14 was synthesized by the reaction of 13 with NH3, and it was alkylated at the S‐atom with bromoalkanoates to 15. The hydrazide 16 was synthesized from 15b with hydrazine hydrate.
Chemical Synthesis of Oligonucleotides Containing N6‐Methyladenine Residues in the GATC Site
Authors: Guy André , Molko Didier , Wagrez Laurence , Téoule Robert
Published: December 2004

To investigate by NMR the effects of adenine methylation, a set of oligodeoxynucleotides has been synthesized by phosphotriester or phosphoramidite procedures on silica‐gel support. The preparation of fully protected 2′‐deoxy‐N6‐methyladenosine 3′‐phosphate 4 and (2′‐deoxy‐N6‐methyladenosin‐3′‐O‐yl)(methoxy)morpholinophosphine 5 is described. The large‐scale chemical synthesis, purification by HPLC, and characterization by MS of these molecules containing N6‐methyladenine is reported.
1,3‐Dioxanone Derivatives from β‐Hydroxy‐carboxylic Acids and Pivalaldehyde. Versatile Building Blocks for Syntheses of Enantiomerically Pure Compounds. A Chiral Acetoacetic Acid Derivative Preliminary Communication
Authors: Seebach Dieter , Zimmermann Jürg
Published: December 2004

(R)‐3‐Hydroxybutyric acid (from the biopolymer PHB) and pivalaldehyde give the crystalline cis ‐ or (R,R)‐2‐(tert‐butyl)‐6‐methyl‐1,3‐dioxan‐4‐one (1a), the enolate of which is stable at low temperature in THF solution and can be alkylated diastereoselectively (→3, 4, 5, and 7). Phenylselenation and subsequent elimination give an enantiomerically pure enol acetal 10 of aceto‐acetic acid. Some reactions of 10 have been carried out, such as Michael addition (→11), alkylation on the CH3 substituent (→13), hydrogenation of the CC bond (→1a) and photochemical cycloaddition (→16). The overall reactions are substitutions on the one stereogenic center of the starting β‐hydroxy acid without racemization and without using a chiral auxiliary.
Comparison of the Complexation of Open‐Chain and Cyclic N2S2 Ligands with Cu+ and Cu2+
Authors: Kaden Thomas A. , Kaderli Susanne , Sager Wiebke , Siegfried‐Hertli Liselotte C. , Zuberbühler Andreas D.
Published: December 2004

The complexation properties of the open‐chain N2S2 ligands 1–4 are described and compared to those of analogous N2S2 macrocycles 5–7. With Cu2+, the open‐chain ligands give complexes with the stoichiometry CuL2+ and CuLOH+, the stabilities and absorption spectra of which have been determined. The ligand field exerted by these ligands is relatively constant and independent of the length of the chain. With Cu+, the species CuLH, CuLH2+, and CuL+ were identified and their stabilities measured. The redox potentials calculated from the equilibrium constants and measured by cyclic voltammetry agree and lie between 250 and 280 mV against SHE. The comparison between open‐chain and cyclic ligands shows that (1) a macrocyclic effect is found for Cu2+ but not for Cu+, (2) the ligand‐field strength is very different for the two types of ligands, and (3) the redox potentials span a larger interval for the macrocyclic than for the open‐chain complexes.
Control of the Diels‐Alder‐Addition Regioselectivity by Remote Olefins. Syntheses and Cycloadditions of 2,3,5‐Trimethylidenebicyclo[2.2.1]heptane and 2,3,5,6,7‐Pentamethylidenebicyclo[2.2.2]octane
Authors: Burnier Gérald , Schwager Luis , Vogel Pierre
Published: December 2004

The syntheses of 2,3,5‐trimethylidenebicyclo[2.2.1]heptane (1) and 2,3,5,6,7‐pentamethylidenebicyclo[2.2.2]‐octane (2) are reported. The Diels‐Alder additions of the diene moieties of these polyenes can be regioselective, probably because of a possible transannular interaction between the homoconjugated methylidene and s‐cis‐buta‐diene groups.
Direct Observation of Acetophenone Enol Formed by Photohydration of Phenylacetylene
Authors: Chiang Yvonne , Kresge A. Jerry , Capponi Marco , Wirz Jakob
Published: December 2004

The photohydration of phenylacetylene yields acetophenone enol as a transient primary product which was detected by flash photolysis. The identification of the transient intermediate rests on a quantitative comparison of its decay kinetics with that of authentic acetophenone enol generated by Norrish type‐II photoelimination from γ‐hydroxybutyrophenone in aqueous HCl and aqueous AcOH buffer solutions.
Triaziridines. Part V. A semiempirical MNDO study of nitrogen inversion and amide rotation in Formyltriaziridines
Authors: Kaneti José , Hoesch Lienhard , Dreiding André S.
Published: December 2004

Since we found certain structural features of triaziridine (1) obtained by MNDO calculations to be in qualitative agreement with those derived earlier from ab initio calculations, we used the MNDO method to derive properties of formyltriaziridine (2) and 1‐formyl‐2,3‐diisopropyltriaziridine (3) as models for the preparatively known 2,3‐dialkyl‐triaziridine‐1‐carboxylates 4 and 5. The main results are: (a) The triaziridine N‐atoms with H, alkyl, or formyl as substituents (see 2 and 3) are pyramidal. N(1) carrying the formyl group is flatter than N(2) and N(3) with H or alkyl substitent. Bond lengths and angles at N(2) and N(3) are almost identical with those calculated for the N‐atoms of 1. (b) The MNDO inversion barriers at the H‐substituted N(2) and N(3) of 2 are higher than those at the formyl‐substituted N(1), but similar to the ab initio barriers at the N‐atoms of 1. (c) The MNDO inversion barriers at N(1) of 2 and 3 are 53 to 92 kJ/mol, whereas the rotation barriers around the N(1)–C(4) bond are 7 to 23 kJ/mol; thus, the previously observed dynamic NMR phenomena in trans‐2,3‐diisopropyltriaziridine‐carboxylates (5) can now be assigned to the slowing down of N(1) inversion rather than N(1)–C(4) rotation.
Synthesis of 2′‐Deoxyribofuranosides of 8‐Aza‐7‐deazaguanine and Related Pyrazolo[3,4‐d]pyrimidines
Authors: Seela Frank , Steker Herbert
Published: December 2004

The N(1)‐ and N(2)‐(2′‐deoxyribofuranosides) 1 and 2, respectively, of 8‐aza‐7‐deazaguanine were prepared via phase‐transfer glycosylation in the presence or absence of Bu4NHSO4 as catalyst of 6‐amino‐4‐methoxy‐lH‐pyrazolo[3,4‐d]pyrimidine (7c) with 2‐deoxy‐3,5‐di‐O‐(p‐toluoyl)‐α‐D‐erythro‐pentofuranosyl chloride (10). On a similar route, but without catalyst and employing THF as organic phase, the 6‐amino‐4‐chloronucleosides 11b and 12b were synthesized from 7a and converted into the N(1)‐and N(2)‐substituted 4‐thioxo analogues 17a and 18a, respectively. The ratio of N(1)‐ to N(2)‐glycosylation was 2:1 for 7c and 1:1 for 7a, viz. depending on the nucleobase structure. The rate of the H+‐catalyzed N‐glycosyl hydrolysis was strongly decreased for the N(2)‐(β‐D‐2′‐deoxyribofuranosides) as compared to the N(1)‐compounds. However, the N(1)‐nucleoside 1, which is an isostere of 2′‐deoxyguanosine, is sufficiently stable to be employed later in solid‐phase oligonucleotide synthesis.
Synthese von 3‐Nitro‐1,1‐bis(triisopropylsilyl)‐1H‐cyclopropabenzol und Azocyclopropabenzol‐Derivaten
Authors: Neidlein Richard , Christen Detlev
Published: December 2004

Synthesis of 3‐Nitro‐1,1‐bis(triisopropylsilyl)‐1H‐cyclopropabenzene and Derivatives of Azocyclopropabenzene

1,1‐Bis(triisopropylsilyl)‐1H‐cyclopropabenzene (4) can be nitrated at C(3) without opening of the three‐membered ring. Further functionalized cyclopropabenzenes are available in this way.
Synthesis of 2,3,4,6,7,8‐Hexahydro‐5H‐1‐benzopyran‐5‐ones and 3‐(6‐Oxo‐1‐cyclohexenyl)alkanoic Acids by Reduction of 4,6,7,8‐Tetrahydro‐2H‐1‐benzopyran‐2,5(3H)‐diones
Authors: Hombrecher Hermann , Margaretha Paul , Tissot Paul
Published: December 2004

Comparative results on the reduction of 4,6,7,8‐tetrahydro‐7,7‐dimethyl‐2H‐1‐benzopyran‐2,5(3H)‐diones 1 are reported. Hydride reduction (LiAlH4 in Et2O or NaBH4 in i‐PrOH) affords 2,3,4,6,7,8‐hexahydro‐5H‐1‐benzopyran‐5‐ones 5 in 30‐60% isolated yield. Photochemical reduction of 1b and 1d (direct irradiation at λ = 300 or 254 nm in i‐PrOH, or sensitized irradiation in acetone/i‐PrOH or benzene/i‐PrOH) gives 3‐(6‐oxo‐1‐cyclohexenyl)alkanoic acids 6 in 50–80%, while 1c affords the isomeric 3‐(4,4‐dimethyl‐6‐oxo‐1‐cyclohexenyl)‐4‐methyl‐4‐pentenoic acid (9) in 73% isolated yield. Electrochemical reduction (Hg, CH3CN, Bu4N+ClO, −2.6 V vs. Ag/Ag+) requires more than 4 Farad/mol for the consumption of 1 without any major product being detected.
Assignment of the 5,6‐Double‐Bond Configuration in Iloprost and Isoiloprost from 13C‐NMR Shifts Determined by 2D Methods
Authors: Schenker Kurt V. , Von Philipsborn Wolfgang , Anderson Evans C. , Skuballa Werner , Hoyer Georg‐Alexander
Published: December 2004

The configurations of the 5,6‐double bond in the carbacyclins iloprost (3; (E)) and isoiloprost (4; (Z)) are based on a complete assignment of the 13C and 1H resonances determined by 1D and 2D 13C‐NMR and 1H‐NMR methods.
Neue 1,6‐Methano[10]annulen‐Derivate durch Umlagerungsreaktionen der Trimethylsilyl‐Gruppe
Authors: Neidlein Richard , Wirth Wolfgang
Published: December 2004

New Derivatives of 1,6‐Methano[10]annulene by Rearrangement of Trimethylsilyl Groups

Oxidation of derivatives of trimethylsilyl‐substituted bicyclo[4.4.1]undeca‐1,3,5,7‐tetraenes 1–3 leads to 1,6‐methano[10]annulenes. In the case of 2 and 3a, rearrangement of the trimethylsilyl group takes place. This rearrangement can be used to prepare 2,9‐disubstituted 1,6‐methano[10]annulenes.
Zur Photochemie von (Z,Z)‐2,7‐Cyclodecadien‐1‐on und 4,8‐Cyclododecadien‐1‐on. Synthese und Eigenschaften von Tricyclo[5.3.0.02,8]decan‐Systemen
Authors: Gleiter Rolf , Sander Wolfram , Butler‐Ransohoff Irmgard
Published: December 2004

On the Photochemistry of (Z,Z)‐2,7‐Cyclodecadien‐1‐one and 4,8‐Cyclododecadien‐1‐one. Synthesis and Properties of Tricyclo[5.3.0.02,8]decane Systems

Irradiation of (Z,Z)‐2,7‐cyclodecadien‐1‐one (3) yields (Z,Z)‐3,7‐cyclodecadien‐1‐one (12) or tricyclo‐[5.3.0.02,8]decan‐4‐one (16), depending on the reaction conditions. Irradiation of 4,8‐cyclododecadien‐1‐one (28) results also in a light‐induced transannular [2 + 2] cycloaddition, yielding tetracyclo[7.3.0.02,1003,6]dodecan‐1‐one (30). Starting from 16, the preparation of tricyclo[5.3.0.02,8]dec‐4‐ene (19), tricyclo[5.3.0.02,8]dec‐4‐ene (21) and tricyclo[5.3.0.02,8]deca‐3,5‐diene (24) is described. The 1H‐NMR and 13CNMR spectra of the newly prepared compounds are discussed. In the case of 19, 21, and 24, the electronic structure is discussed on hand of their PE spectra.
Regioselectivity and Deuterium Isotope Effects in Geraniol Hydroxylation by the Cytochrome P‐450 Monooxygenase from Catharanthus roseus (L.) G. DON
Authors: Fretz Heinz , Woggon Wolf‐Dietrich
Published: December 2004

The hydroxylation of geraniol (8) by cytochrome P‐450 (P‐450Cath.) from the subtropical plant Catharanthus roseus (L.) G. DON was optimised to give 8‐hydroxygeraniol (9) as the single product in 35% yield. Incubations of different 13C‐ and 2H‐labelled geraniols revealed that H‐abstraction is completely regioselective in favour of the CH3 group trans to the chain at C(6) of 8. An intramolecular isotope effect kH/kD = 8.0 was determined, suggesting that H‐abstraction is one of the major rate‐contributing steps; however, the intermolecular isotope effect was surprisingly inverse at low conversion kH/kD = 0.50, indicating the existence of rate‐contributing steps preceding the first irreversible, isotope‐sensitive reaction in the sequence.
Triaziridine. 6. Mitteilung. Substituententransformationen an Triaziridinen
Authors: Hilpert Hans , Hoesch Lienhard , Dreiding André S.
Published: December 2004

Substituent Transformations on Triaziridines

Several novel triaziridines were prepared by substituent transformations starting from the known dialkyl‐triaziridine‐carboxylates 1a–c, with the aim to study the influence of the substitution pattern on the properties of the triaziridine ring. The dialkyl‐triaziridines 2a–c were obtained by (t‐BuO−)‐mediated demethylation and decarboxylation and the dialkyl‐triaziridine‐methanols 4a–c by LiAlH4 reduction. Further reduction of the tosylates of 4a, b with LiAlH4 gave the methyl‐dialkyl‐triaziridines 3a, b. The dialkyl‐triaziridines 2a, c could not be N‐methylated directly with CH3I, but the anions 10a, c, obtained from 2a, c with CH3Li, yielded 3a, c. N‐Methylation of 2a with (CH3)3OBF4 did not afford 3a but rather the methyl‐triaziridinium salt 11. The dialkyl‐triaziridine 2c has pKa > 14, its protonated species < 2. A concept that the electron pairs on the triaziridine N‐atoms are more strongly localized than on amine N‐atoms explains (a) that the dialkyl‐triaziridine 2c is hardly basic, (b) that the LiAlH4 reductions of the esters 1 stop at the stage of the methanols 4, and (c) that the methanols 4a, b do not cleave like aminomethanols.
Synthesis and Biological Properties of N‐Acetyl‐4‐deoxy‐D‐neuraminic Acid
Authors: Hagedorn Heinz‐Werner , Brossmer Reinhard
Published: December 2004

N‐Acetylneuraminic acid (1) can be transformed into the methyl α‐D‐ketoside 2 which, by reaction with methanesulfonyl chloride, yields the corresponding 4‐O‐mesylate 3 and the 4,7‐di‐O‐mesylate 4 as a by‐product. Compound 3 reacts with Nal giving the 4‐deoxy‐4‐iodo compound 5 with equatorial orientation of the I‐atom. As second product, the dihydrooxazole 6 is produced. Catalytic hydrogenation of 5 is followed by ester cleavage and removal of the isopropylidene group yielding the methyl α‐D‐ketoside 8 which affords the title compound, N‐acetyl‐4‐deoxyneuraminic acid (9), by reaction with fowl plague virus sialidase. Further biochemical activities of 8 and 9 are reported.
New Mechanistic Proposal for Some Heptamolybdate‐Ion‐Catalyzed Isomerizations
Authors: Klaič Branimir , Raza Zlata , Sankovič Mauricio , Šunjič Vitomir
Published: December 2004

Heptamolybdate‐ion(HM)‐catalyzed C(2) epimerization of D‐glucose and racemization of D‐glyceraldehyde proceed with comparable rates and activation parameters; HM catalyzes the isomerization of glucal and galactal triacetates as well. For all of the above transformations, a common, new mechanism is proposed that invokes stabilization of 3‐oxa‐allylic cation species by the central Mo(VI) atom.
Coralloidolide A and Coralloidolide B, the First Cembranoids from a Mediterranean Organism, the Alcyonacean Alcyonium coralloides
Authors: D'Ambrosio Michele , Fabbri Daniele , Guerriero Antonio , Pietra Francesco
Published: December 2004

The alcyonacean Alcyonium ( = Parerythropodium) coralloides (PALLAS 1766) is the first Mediterranean organism shown to contain cembranoids. These are of unusual type like coralloidolide A ( = (−)‐(1R*, 2R*, 3R*, 12S*, 5Z, 7Z, 9Z)‐1, 2:7, 10‐diepoxy‐12‐isopropenyl‐5, 9‐dimethylcyclotetradeca‐5, 7, 9‐triene‐1, 3‐carbolactone; (−)‐6) and coralloidolide B ( =(−)‐(1R*,2S*,3R*,7S*,10S*,12S*,5Z,8Z,)‐2, 7:7, 10‐diepoxy‐1, 10‐dihydroxy‐12‐isopropenyl‐5, 9‐dimethylcyclotetradeca‐5,8‐diene‐1,3‐carbolactone; (−)‐8). Structural assignments are mainly based on 1D‐ and 2D‐NMR data and on chemical transformations.
Synthese von ‘D‐Isothreonin’ und ‘L‐Alloisothreonin’ aus L‐Alanin
Authors: Wolf Jean‐Pierre , Pfander Hanspeter
Published: December 2004

Synthesis of ‘D‐Isothreonine’ and ‘L‐Alloisothreonine’ Starting from L‐Alanine

Starting from L‐alanine, ‘D‐isothreonine’ ( = (2R, 3S)‐3‐amino‐2‐hydroxybutanoic acid) and ‘L‐alloisothreonine’ ( = (2S, 3S)‐3‐amino‐2‐hydroxybutanoic acid) were synthesized.
Ringerweiterung unter Lactonisierung von methylierten 1‐(3′‐Hydroxypropyl)‐2‐oxocyclododecan‐1‐carbonitrilen
Authors: Milenkov Branimir , Hesse Manfred
Published: December 2004

Ring Enlargement by Lactonization of Methylated 1‐(3′‐Hydroxypropy1)‐2‐oxocyclododecane‐1‐carbonitriles

The title compounds were prepared by Michael reaction of 2‐oxocyclododecane‐1‐carbonitrile (1) and acrylaldehyde and its derivatives followed by NaBH4 reduction or methylation of the aldehyde group with [(CH3)2Ti(i‐PrO)2] (Scheme 1). In all cases, the ring enlargement was performed with Bu4NF/THF to give different methylated derivatives of 12‐cyano‐15‐pentadecanolide (13) in 95–99% yield. The Yields of the rearrangement products are not dependent on the positions and numbers of the CH3 groups in the side chain of 3. The lactonization reaction is of unremarkable stereoselectivity.
Synthese von ω‐(5‐Oxo‐1‐cyclopentenyl)alkansäure‐methylestern aus 2‐Nitrocycloalkanonen
Authors: Stach Hans , Hesse Manfred
Published: December 2004

Synthesis of Methyl ω‐(5‐Oxo‐1‐cyclopentenyl)alkanoates Starting from 2‐Nitrocycloalkanones

A convenient synthesis of methyl ω‐(5‐oxo‐1‐cyclopentenyl)alkanoates 1 is described. 2‐Nitrocycloalkanones 2 are converted to 2‐(3,3‐dimethoxypropy1)‐2‐nitrocycloalkanones 4. Treatment of 4 with MeOH/MeONa led to the ring‐opened nitronates 5 which underwent a Nef reaction to form the corresponding oxo derivatives 6. Partial hydrolysis of followed by base‐catalyzed aldol reaction gave the desired products in high yields.
Cyclobut‐2‐enones from Alkynes via Dichlorocyclobut‐2‐enones
Authors: Ammann Adrian A. , Rey Max , Dreiding André S.
Published: December 2004

The [2 + 2]‐cycloaddition of dichloroketene (prepared in situ from CCl3COCl and Zn(Cu)) with three alkynes 1a–c to form 2,3‐dimethyl‐(2a), 2,3‐diethyl‐(2b) and 3‐butyl‐4,4‐dichlorocyclobut‐2‐enone (2c) proceeds rapidly in the absence of POCl3. The primary products 2a–c rearrange in situ to the 2,4‐dichlorocyclobut‐2‐enones 3a–c under the influence of ZnCL2 produced during the reaction. ZnCl2 converts both 2a and 3a into a 4:6 equilibrium mixture of the two; this isomerization does not occur with LiCl. The Cl‐atoms of both 2a, b and 3a, band of 2c may reductively be removed with Zn(Cu) in AcOH/pyridine to afford the alkylcyclobutenones 4a‐c. Without pyridine, this reduction gives ca. 1:1 mixtures of the double‐bond isomers 4 and 5 in low yields. The cyclobutenones 2c and 4c may be deuterated by CD3COOD in the presence of pyridine. D‐Atom is introduced into 2c at C(4) and at C(γ), and into 4c at C(2) and C(4). A mechanism for this deuteration is considered, which does not involve a cyclobutadienolate 7, but rather a cyclobutenolate of type 8. The reductions of 2 and 3 to 4 might also pass through the same type of intermediate 8.
Photodecarbonylation of 2,5,5‐Trimethyl‐2‐(1‐propynyl)cyclopentanone. 1,5‐ vs. 1,4‐ring Closure of a Propargyl‐Alkyl Biradical
Authors: Rudolph Andreas , Margaretha Paul , Agosta William C.
Published: December 2004

Propargyl‐alkyl biradical 12 generated by photodecarbonylation of title ketone 3 undergoes ring closure to cyclobutane 7 and to vinyl carbene 13, this latter intermediate rearranging to the 5‐ethylidenecyclopentenes 8a and 8b.
Synthese von 2‐Hydeoxy‐3‐methyl‐2‐hexen‐4‐olid
Authors: Stach Hans , Huggenberg Walter , Hesse Manfred
Published: December 2004

Synthesis of 2‐Hydroxy‐3‐methyl‐2‐hexen‐4‐olid

The title compound 13a, a substance used in food‐flavoring, was synthesized in 89% overall yield, starting from methyl 2‐hydeoxy‐3‐butenoate (3a). The key step in this transformation is the isomerization of the CC bond in 3a which yielded methyl 2‐oxobutanoate as an intermediate. The latter underwent a self‐condensation yielding 2‐hydroxy‐4‐(methoxycarbonyl)‐3‐methyl‐2‐hexen‐4‐olid (11a), which, after hydrolysis and decarboxylation, gave 13a. In addition, the syntheses of five other compounds related to 13a are reported.
Synthesis and Placental Binding Potencies of Photosensitive Analogues of Luteinizing Hormone Releasing Hormone (LHRH) with Agonistic and Antagonistic Structures
Authors: Mackiewicz Zbignew , Bélisle Serge , Bellabarba Diego , Gallo‐Payet Nicole , Lehoux Jean‐Guy , Lagacé Ginette , Escher Emanuel
Published: December 2004

The synthesis of new photolabeling analogues of luteinizing hormone releasing hormone is described. Peptides were prepared by the solid‐phase method, and the photolabeling moiety was introduced as the 4′‐nitrophenyl‐alanine precursor. This amino acid, either of the L or D configuration, was placed at different positions and was modified afterwards to 4′‐azidophenylalanine. Structures with agonistic or antagonistic character were prepared, together with a peptide containing simultaneously the photolabeling moiety and a biotin substituent for future receptor isolations. Binding studies on placental and pituitary membranes indicate that these compounds represent promising candidates for receptor labeling studies.
On the Purported Structure of Cyclodeca[1,2,3‐de: 6,7,8‐d′e′]dinaphthalene
Authors: Gleiter Rolf , Schaaff Hans Peter , Rodewald Hans , Jahn Reiner , Irngartinger Hermann
Published: December 2004

The reaction of the bis(sulfonium salt)7 in a solution of Na2CO3 in H2O/EtOH yielded three main products 8–10. The spectroscopic data of 8 were identical to those which led Mithcell and Sondheimer to assign them to cyclodeca[1,2,3‐de: 6,7,8‐d′e′]dinaphthalene (3). Our investigations show, however, that the correct structural assignment leads to the structure of 7,7a‐dihydrodibenzo[de,mn]naphthacene (8).
Complexes of 2,2′,2″‐Nitrilotriphenol. Part 2. Crystal and Molecular Structures of Three Boron Complexes
Authors: Müller Edgar , Bürgi Hans‐Beat
Published: December 2004

Crystal and molecular structures of a complex between B(III) and the tripod ligand 2,2′,2″‐nitrilotriphenol as well as of its pyridine and quinuclidine adducts are presented. The 2,2′,2″‐nitrilotriphenyl borate (III) molecule shows a strained, tricyclic chelate system with a central N–B donor‐acceptor bond of 1.681(5) Å. In the adducts with pyridine (IV) and quinuclidine (III‐quin), this bond is broken, the N‐atom inverts and is pushed out of the coordination sphere (B–Nintern = 2.82 Å for Py and 2.85 Å for quin), and a new bond is formed between the boron atom and the external nucleophile (B–Nextern = 1.631 Å for Py and 1.643 Å for quin).
The Microstructure of Selective Palladium Hydrogenation Catalysts Supported on Calcium Carbonate and Modified by Lead (Lindlar Catalysts), Studied by Photoelectron Spectroscopy, Thermogravimetry, X‐Ray Diffraction, and Electron Microscopy
Authors: Schlägl Robert , Noack Klaus , Zbinden Heinz , Reller Armin
Published: December 2004

A detailed analysis of the system Pd + Pb on CaCO3 is presented. This system known as Lindlar catalyst is used for selective hydrogenations of CC bonds to CC bonds. It was found to consist of seven distinct chemical phases. Essential ingredients are solid solutions of hydrogen and oxygen in Pd. The latter phase enables the metal particles to be attached to the support via an orientational relationship calcite (113)∥Pd + O (111). The addition of Pb neither changes the micromorphology of the disk‐shaped Pd particles nor does it modify the electronic structure of Pd as studied by chemisorption experiments. The addition of Pb seems to block certain active sites and, thus, to enhance the selectivity. The support was found to be a multi‐domain mixture of calcite and aragonite with domain sites of several hundred Å. The free surface of the pore‐free solid is covered by a calcium‐hydroxide carbonate. This phase as well as several other Pb phases seem to represent only spectator materials. Verification of this as well as finding the correlation between structure and function of the various components requires a kinetic analysis which is outside the scope of this paper. It is demonstrated that a variety of analytical techniques is required to unravel the complex nature of such a ‘simple' catalyst’ as it is Pd on CaCO3.
Synthesis and Copper(I) Complexes of a Series of 9‐ to 13‐Membered N3 Macrocycles
Authors: Briellmann Markus , Kaderli Susan , Meyer Charles J. , Zuberbühler Andreas D.
Published: December 2004

Eight cyclic triamines with ring sizes between 9 and 13 were synthesized by the p‐toluenesulfonate method. The open‐chain triamines bis(2‐aminoethyl)amine (dien) and bis(3‐aminopropyl)amine (diprop) were used as starting materials. In some cases, the corresponding dimeric cyclic hexaamines have been isolated and characterized as major by‐products. The complexation of Cu(I) by the triamines has been studied potentiometrically in CH3CN/H2O. All ligands L form ternary complexes [Cu(CH3CN)L]+. The corresponding association constants vary between 1011 and 107, decreasing with increasing ring size. In addition, complexes [Cu(CH3CN)yLH]2+, y = 1 or 2, are found as less important species with maximum concentrations of 7 to 50%.
Brominations of Cyclic Acetals from α‐Amino Acids and α‐ or β‐Hydroxy Acids with N‐Bromosucinimide
Authors: Zimmermann Jürg , Seebach Dieter
Published: December 2004

The preparation of novel electrophilic building blocks for the synthesis of enantiomerically pure compounds (EPC) is described. Thus, the 2‐(tert‐butyl)dioxolanones, ‐oxazolidinones, ‐imidazolidinones, and ‐dioxanones obtained by acetalization of pivalaldehyde with 2‐hydroxy‐, 3‐hydroxy‐, or 2‐amino‐carboxylic acids are treated with N‐bromosuccinimide under typical radical‐chain reaction conditions (azoisobuytyronitril/CCl4/reflux). Products of bromination in the α‐position of the carbonyl group of the five‐membered‐ring acetals are isolated or identified (2, 5, and 8; Scheme 1). The dioxanones are converted to 2H, 4H‐dioxinones under these conditions (12, 14, 15, 21, and 22; Schemes 2 and 3). The products can be converted to chiral derivatives of pyruvic acid (methylidene derivatives 3 and 6) or of 3‐oxo‐butanoic and ‐pentanoic acid (16 and 23). The mechanism of the brominations is interpreted. The conversion of serine to enactiomcrically pure dioxanones 26–28 (Scheme 4) is also discussed.
Stereoselektive Alkylierung an C(α) von Serin, Glycerinsäure, Threonin und Weinsäure über heterocyclische Enolate mit exocyclischer Doppelbindung
Authors: Seebach Dieter , Aebi Johannes D. , Gander‐Coquoz Marlyse , Naef Reto
Published: December 2004

Steroselective Alkylation at C(α) of Serine, Clyceric Acid, Threonine, and Tartaric Acid Involving Heterocyclic Enolates with Evocyelic Double Bonds

The chiral, non‐racemic title acids are converted to methyl dioxolane‐(cf.13), oxazoline‐(4) and oxazolidinecarboxylates (cf.9). Deprotonation by Li(i‐Pr)2N at dry‐ice temperature gives solutions of the lithium enolates A–D With exocyclic enolate double bonds. These are stable crough with respect to β‐elimination (Scheme 1) to be alkylated with or without cosolvents such as HMPA or DMPU The products are formed in good to excellent yields and, with the exception of the tartrate‐derived acetonlde (see Scheme 2), with diastereoselectivities above 90%. While the tartrate‐and threonine‐derived enolates (AandB, resp.) are chiral due to the second stereogenic center of the precursors, the serine‐ and glyceric‐acid‐derived enolates (AandB, resp.) are chiral due to the second sterogenic center of the precursors, the serine‐nd glyceric‐acid‐derived enolates are non‐racemic due to atertbutyl‐substituted (pivalaldehyde‐derived) acetal center (CandD, resp.). The products of alkylation can be hydrolyzed to give α‐branched tartaric acid (Scheme 2), allothreonine (Scheme 3), serine (Scheme 4), and glyceric‐acid derivatives (Scheme 5) with quaternary stereogenic centers. The configurations of the products are determined by NOE‐NMR measurements and by chemical correlation. These show that the dioxolane‐derived enolatesAandDare alkylated preferentially from that face of the ring which is already substituted (‘syn’‐attack), while the dihydrooxazol‐and oxazolidine‐derived enolatesBandCare alkylated from the opposite face (‘anti’‐attack). The ‘syn’‐attack is postulated to arise from strong folding of the heterocyclic ring due to electronic repulsion between the enolate π‐system and non‐bonding electron pairs on the heteroatoms (see Scheme 6).
Thermodynamic trans‐Effects of the Nucleotide Base in the B12 Coenzymes
Authors: Kräutler Bernhard
Published: December 2004

The thermodynamic effects of the nucleotide coordination on the Co‐C bond strengths in the B12 coenzymes were analyzed. Methyl group transfer reactions from methylcob(III)inamides to cob(II)inamides and cob(I)inamides in neutral aqueous solution were used in equilibration experiments to determine the effect fo the intramolecular coordination of the nucleotide function on the Co‐C bond dissociation energies of methylcob(III)alamin (4). In the equilibrium between 4, cob(I)inamide (11), cob(I)alamin (10) and methylcob(III)inamide 6 (Scheme 2), 4 and 11 were found to predominate (4+11⇆10+6, equilibrium constant KI/III≈0.004), while the equilibrium between 4, cob(II)inamide 9, cob(II)alamin (5), and 6 (Scheme 1) proved to be well balanced (4+9⇄5+6, equilibrium constant KII/III=0.60). These equilibrium values indicate the nucleotide coordination to stabilize the Co–C bond in 4 both against homolysis (slight effect) and against nucleophilic heterolysis (considerable effect). They reflect a stabilization of the complete corrins 4 and 5by the nucleotide coordination, which is also indicated for 4 and 5 by their (nucleotide) basicity. The latter information, where available for other organocobalamins, allows the analysis of the thermodynamicnucleotide trans effect there as well: e.g. in coenzyme B12 (1), the nucleotide coordination is found this way to weaken the Co–C bond towards homolysis by ca. 0.7 kcal/mol.
Synthese von 3‐(2‐Carboxy‐4‐Pyridyl)‐ und 3‐(6‐Carboxy‐3‐pyridyl)‐DL‐alanin
Authors: Hilpert Hans
Published: December 2004

Synthesis of 3‐(2‐Carboxy‐4‐pyridyl)‐and 3‐(6‐Carboxy‐3‐pyridyl)‐DL‐alanine

As starting materials for potential photochemical approaches to betalaines C(R = COOH) and to muscaflavine F(R = COOH), β‐(2‐carboxy‐4‐pyridyl)‐ and β‐(6(carboxy‐3‐pyridyl))‐DL‐alanine (A and D with R = COOH or 4 and 11), respectively, were prepared (Scheme 1). The synthesis of 4 (= A, R = COOH) started with the 2‐[(4‐pyridyl)methyl]malonate 1 and proceeded via the N‐oxide 2, cyanation and hydrolysis (Scheme 2). Amino acid 11 was obtained from (3‐pyridyl)methyl‐bromide (6) via the malonate 7 by an analogous sequence of reactions (Scheme 3).
Glycosylphosphonates of 2‐Amino‐2‐deoxy‐aldoses. Synthesis of a Phosphonate Analogue of Lipid X
Authors: Briner Karin , Vasella Andrea
Published: December 2004

A preparation of glycosylphosphonates (27, 28, 36, 38, and 39) from 2‐azido‐2‐deoxy‐glycoses (26,35, and 37) and the synthesis of the non‐isosteric phosphonate analogue 3a of lipid X(2) are described. The 2‐azido group was introduced by azidonitration. Treatment of the 1‐O‐acetyl‐2‐azido‐2‐deoxy‐β‐D‐galactopyranose 22 with 1.5‐3 equiv. of P(OMe)3 and 1.2‐2.5 equiv. of TfOSiMe3 gave mainly recovered starting material. In P(OMe)3 as the solvent, the dimethyl phosphoramidate 24 was obtained by way of a Staudinger reaction, even in the presence of TfOSiMe3. Treatment of the benzylated α‐D‐galacto‐trichloroacetimidate 26, however, with P(OMe)3 and TfOSiMe3 gave a 1:1 mixture of the α‐ and β‐D‐galacto‐phosphonates 27 and 28, while the acetylated α‐D‐gluco‐ imidate 35 led to the α‐D‐gluco‐configurated phosphonate 36. The stereoselectivity of the phosphonate formation is related to the relative ease of formation of oxonium‐ion intermediates from 26 and 35. Starting from the phosphonate 36, deacetylation, benzylidenation, reduction of the azido group, acylation with (R)‐3‐(benzyloxy)tetradecanoic acid and deprotection yielded the desired compound 3a which was crystallized in the presence of 2 equiv. of (aminomethylidyne)trimethanol (Tris.). The structure of the phosphonates was deduced from their 1H‐, 13C‐, and 31P‐NMR spectra.
Cyclopentenone Annulation of 2‐Oxocycloalkane‐1‐carbonitriles
Authors: Vassil I. Ognyanov , Hesse Manfred
Published: December 2004

Phase‐transfer alkylation of the 2‐oxocycloalkane‐l‐carbonitriles 1a and 1b with ethyl 4‐bromo‐3‐methoxy‐2‐butenoate (2), followed by deprotection and base‐catalyzed cyclization gave the annulated cyclopentenones 5a and 5b, respectively, in high overall yields (Scheme 1). Stereoselective catalytic hydrogenation of 5b followed by de‐ethoxycarbonylation afforded 14‐oxo‐cis‐bicyclo[10.3.0]pentadecane‐l‐carbonitrile (7). Treatment of 7 with LiN(i‐Pr)2 in THF gave the known synthetic muscone precursor 8 (Scheme 2). The tricyclo[10.4.0.01,15]hexadecan‐14‐one (14) was prepared from 7 in 5 steps by a reaction sequence proceeding without affecting the chiral centres (Scheme 2). The structure of 14 was established by X‐ray structure analysis (Figure).
MNDO Analysis of Regio‐ and Stereoselectivity in Hydroboration
Authors: Egger Martin , Keese Reinhard
Published: December 2004

The origin of regioselectivity in hydroboration of olefins has been analyzed by MNDO methodology. With a standard transition structure derived from full MNDO optimizations, a linear correlation between calculated and experimental regioselectivities has been found. A similar approach applied to asymmetric inductions of hydroboration with chiral hydroborating agents lead also to an acceptable linear correlation between calculated and experimental results. The MNDO method has been used for a search of alternative hydroborating agents.
Alkylation of Imidazolidinone Dipeptide Derivatives: Preparation of Enantiomerically Pure Di‐ and Tripeptides by ‘Chirality Transfer’ via a Pivalaldehyde N,N‐Acetal Center. Preliminary Communication
Authors: Polt Robin , Seebach Dieter
Published: December 2004

Glycylglycine, glycyl‐(S)‐alanine, and (S)‐alanylglycine esters are cyclized through pivalaldehyde imines to give dipeptide‐derived 3‐(benzyloxycarbonyl)‐2‐(tert‐butyl)‐5‐oxoimidazolidine‐1‐acetates 1–3. These are alkylated diastereoselectively by Li‐enolate formation and addition of alkyl bromides or iodides (products 4–6). Starting from (S)‐alanine and glycine, (S)‐alanyl‐(S)‐alanine or (R)‐alanyl‐(R)‐alanine, and (R)‐alanyl‐(R)alanyl‐(S)‐alanine‐ have thus been prepared, with the (tert‐butyl)‐substituted N,N‐acetal center playing the role of a pivot or lever for diastereoselective formation of new stereogenic centers under kinetic or thermodynamic control.
EPC‐Synthesis of Tetrahydroisoquinolines by Diastereoselective Alkylation at the 1‐Position of Phenylalanine‐Derived Precursors. Synthesis of the Alkaloid (+)‐Corlumine
Authors: Huber Isabelle M. P. , Seebach Dieter
Published: December 2004

The 1,2,3,4‐tetrahydro‐N‐pivaloyl‐isoquinoline‐3‐carboxylic acids1d,2d, and3d, derived from (R)‐ or (S)‐phenylalanine, (S)‐dopa, and (S)‐α‐methyldopa, respectively, are doubly deprotonated with (tert‐butyl)lithium in THF and alkylated at the 1‐position (products5–10). The major diastereoisomers formed are the result of electrophilic attack from the face opposite to the carboxylate group (rel. topicityul‐1,3). Even the addition to benzaldehyd (→7,8) is highly stereoselective (oneof four diastereoisomers is formed exclusively (300‐MHz1H‐NMR analysis)), if MgBr2etherate is added prior to the electrophile. Some of the obtained amino‐acid derivatives are decarboxylated by anodic oxidation inMeOH(→11,12,17) and NaBH3CN reduction, and converted to the known 1‐methyl‐ and 1‐benzyltetrahydroisoquinolines (15,16) of > 95% ee as well as to the phthalide isoquinoline alkaloid (+)‐corlumine of ≥80% ee. The synthetic approach described here is compared with other methods of synthesizing enantiomerically pure 1‐substituted tetrahydroisoquinolines (and thus an important group of alkaloids,Scheme 1).
Adriadysiolide, the First Monoterpenoid Isolated from a Marine Sponge
Authors: Mancini Ines , Guella Graziano , Guerriero Antonio , Boldrin Alfredo , Pietra Francesco
Published: December 2004

Spectra and chemical transformations allow to establish the gross structure 6,7‐epoxy‐4,7‐dimethyl‐l‐oxa‐spiro[4.4]non‐3‐en‐2‐one for adriadysiolide (1), the first monoterpenoid isolated from a marine sponge, a Dysidea sp. of the Adriatic Sea. Its configuration 5R*, 6S*, 7S* as given in 1a is derived from diastereoselective total syntheses of both 1a and its diastereoisomer 1b via stereochemically predictable peracid epoxidations of olefinic precursors. Thus, OH assistance in allylic alcohol 8 leads to oxirane 13 which is subjected to methyl cuprate conjugate addition to give epiadriadysiolide (1b), whilst electronic deactivation by a neighboring heterocyclic O‐atom in intermediate 5, derived from 8 mainly leads to adriadysiolide (1a). Comparative 1H‐NMR shift‐reagent effects with 1a and 1b, evaluated with the aid of molecular‐mechanics calculations, support these conclusions.