bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformational Analysis of Didemnins. A multidisciplinary approach by means of X‐Ray, NMR, molecular‐dynamics, and molecular‐mechanics techniques
Authors: Kessler Horst , Will Martin , Antel Jochen , Beck Holger , Sheldrick George M. 
Published: December 2004

AbstractWe present the application of several homo‐ and heteronuclear 1D‐ and 2D‐NMR techniques to assign the 1H‐NMR chemical shifts of the dominant conformation of didemnin B (2; three different conformations in (D6)DMSO solution in the ratio 8:1:1) and its conformational analysis, as well as the solution conformation of didemnin A (1). The conformations were refined by restrained molecular‐dynamics calculations using the GROMOS program and by MOMO, a novel personal‐computer‐based interactive molecular‐graphics and molecular‐mechanics package, using experimental distances (via a H…H pseudo potential function) as restraints. The solution structures of 1 and 2 obtained by GROMOS and MOMO calculations were compared with each other and related to the recently solved crystal structure of 2. Focusing on the main conformer, the two kinds of the distance‐restrained conformational calculations for 2 yielded a ‘solution structure’ close to the crystal structure. Almost all of the 40 restrained H…H distances coincided (within the estimated standard deviations) with those observed in the crystal structure. One more hydrogen bond was detected in solution involving the lactoyl OH group (disordered in the crystal structure) and the dimethyltyrosine (Me2Tyr5) carbonyl O‐atom. The macrocyclic ring system in the modeled solution structure of 1 exhibited a topology close to those of the solution and crystal structures of 2. The main difference between 1 and 2 could be traced back to a significant change in the Ψ angle of the N‐methyl‐D‐leucine (MeLeu7) residue. In 1, the N‐methyl moiety of MeLeu7 points inward within the macrocyclic ring toward the 1st and Hip region. We also tested the suitability of structures obtained from NMR data as ‘search fragments’ in the ‘Patterson search approach’ of crystal‐structure analysis. It proved possible to resolve the crystal structure of 2 a posteriori with the Patterson search program PATSEE, in this way.
β‐Cleavage of Potassium Bicyclo[2.2.2]oct‐5‐en‐2‐olates. Stereoselective synthesis of (±)‐trichodiene
Authors: Snowden Roger L. , Brauchli Robert , Sonnay Philippe 
Published: December 2004

AbstractThe transformations of 12 bicyclo[2.2.2]oct‐5‐en‐2‐ols (V or VI) to 3‐(cyclohex‐3‐enyl)‐2‐alkanones (III or IV), via β‐cleavage of their potassium alkoxides in HMPA, has been investigated (cf. Table 1). As an illustration of this synthetic methodology, a stereoselective synthesis of (±)‐trichodiene ((±)‐1) is described which involves the β‐cleavage of the tricyclic potassium alkoxides 46a and 47a to cyclopentanone 4 (cf. Scheme 7).
Mono‐ and Dialkylation of Derivatives of (1R, 2S)‐2‐Hydroxycyclopentanecarboxylic Acid and ‐cyclohexanecarboxylic acidviabicyclic dioxanones: Selective generation of three contiguous stereogenic centers on a cyclohexane ring
Authors: Herradón Bernardo , Seebach Dieter 
Published: December 2004

AbstractEthyl (1R, 2S)‐2‐hydroxycyclopentanecarboxylate and ‐cyclohexanecarboxylate (1aand2a, respectively) obtained in 40 and 70% yield by reduction of 3‐oxocyclopentanecarboxylate and cyclohexanecarboxylate, respectively (Scheme 2), with non‐fermenting yeast, are converted to bicyclic dioxanone derivatives3and4with formaldehyde, isobutyraldehyde, and pivalaldehyde (Scheme 3). The Li‐enolates of these dioxanones are alkylated (→5a–5i,5j,6a–6g), hydroxyalkylated (→51, m, 6d, e), acylated (→5k, 6c) and phenylselenenylated (→7–9) with usually high yields and excellent diastereoselectivities (Scheme 3, Tables and 2). All the major isomers formed under kinetic control are shown to havecis‐fused bicyclic structures. Oxidation of the seleno compounds 7–9 leads to α, β‐unsaturated carbonyl derivatives10–13(Scheme 3) of which the products12a–cwith the CC bond in the carbocyclic ring (exocyclic on the dioxanone ring) are most readily isolated (70–80% from the saturated precursors).Michaeladdition of Cu(I)‐containing reagents to12a–cand subsequent alkylations afford dioxanones14a–iand16a–dwithtrans‐fused cyclohoxane ring (Scheme 4). All enolate alkylations are carried out in the presence of the cyclic urea DMPU as a cosolvent. The configuration of the products is established by NMR measurements and chemical correlation. Some of the products are converted to single isomers of monocyclic hydroxycyclopentane (17–19) and cyclohexane derivatives (20–23;Scheme 5). Possible uses of the described reactions for EPC synthesis are outlined. The observed steric course of the reactions is discussed and compared with that of analogous transformations of monocyclic and acyclic derivatives.
Synthesis of 11‐Oxaestrogens via Dye‐Sensitized Photo‐oxygenation of a 9,11‐Didehydroestrone Derivative
Authors: Planas Antoni , Sala Nuria , Bonet Juan‐Julio 
Published: December 2004

AbstractThe 3‐methoxy‐1 1‐oxaestrone (13) has been synthetized from estrone (3) following an approach that involves the ring‐C fragmentation of the estrogenic skeleton by dye‐sensitized photo‐oxygenation of the properly C(17)‐protected 9,11‐didehydroestrone derivative 6 as the key step. The C(13)‐side‐chain degradation of the 9‐oxo‐9,11‐seco‐aldehyde 7 followed by reduction to the 9β, 12‐diol 10 and further cyclization yields the 11‐oxaestrogenic skeleton. By this procedure, 13 is obtained in 9 steps from 3 with a non‐optimized overall yield of ca. 15%.
Notiz über mikrobiologische Umsetzungen mit Halobacterium halobium: Reduktion von 3‐Oxobutansäure‐ethylester und Hydrolyse von 3‐Hydroxybutansäure‐ethylester. Cooperative Effekte von Reduktase und Hydrolase
Authors: Ehrler Jürg , Seebach Dieter 
Published: December 2004

AbstractNote on Biotransformations with Halobacterium halobium: Reduction of Ethyl 3‐Oxobutanoate and Hydrolysis of Ethyl 3‐Hydroxybutanoate. Cooperative Effects of Reductase and HydrolaseThe archaebacterium Halobacterium halobium, growing in saturated NaCl solution, is tested for its ability to achieve biotransformations. We found that this microorganism does accept only a small variety of compounds as substrates. Ethyl acetoacetate (1) is reduced to ethyl (S)‐3‐hydroxybutanoate (2) of optical purity of 40–76%, but in low chemical yields. The reduction is accompanied by hydrolysis of the hydroxy‐ester to 3‐hydroxybutanoic acid (3). Hydrolysis of rac‐ester 2 by Halobacterium halobium gives (R)‐2 of optical purity of up to 88%, depending upon reaction time, together with the almost racemic hydroxy‐acid 3, both in low chemical yields. Hopes that the ‘extremist’ Halobacterium halobium would be able to effect unique conversions were not fulfilled.
Radikalische Cyclisierungen von Alkenyl‐substituierten 4,5‐Dihydro‐1,3‐thiazol‐5‐thiolen
Authors: Jenny Christjohannes , Wipf Peter , Heimgartner Heinz 
Published: December 2004

Radical Cyclizations of Alkenyl‐Substituted 4,5‐Dihydro‐1,3‐thiazole‐5‐thiolsHeating of 5‐alkenyl‐ or 5‐alkinyl‐4,5‐dihydro‐1,3‐thiazole‐5‐thiols of type 5 in the presence of a radical initiator gave dithiaspirobicycles in fair‐to‐excellent yield (Scheme 3). Under analogous conditions, the 4,5‐dihydro‐4‐vinyl‐1,3‐thiazole‐5‐thiol 5d underwent a cyclization to give the annellated dithiabicycle 7 (Scheme 4). In this reaction, a minor product 8 was formed by an unknown reaction mechanism. The structure of 8 was established by X‐ray crystallography. The starting 1,3‐thiazole‐5‐thiols 5 have been synthesized by carbophilic alkylation of me CS group of 1,3‐thiazole‐5(4H)‐thiones with Grignard‐reagents or alkylcuprates. The thiazolethiones were obtained by the reaction of 3‐amino‐2H‐azirines with thiobenzoic acid followed by sulfurization and cyclization. The 4‐benzyl derivative 1b was thermally rearranged via 1,3‐benzyl migration to yield the benzyl (1,3‐thiazol‐5‐yl) sulfide 11 (Scheme 5).
Einelektronen‐Redoxreaktionen von 4‐(1‐Pyridinio)phenolat‐Betain: ESR/ENDOR‐Charakterisierung seiner Radikalionen und ‘Batterie‐Effekt’
Authors: Bock Hans , Herrmann Hans‐Friedrich 
Published: December 2004

One‐Electron Redox Reactions of 4‐(1‐Pyridinio)phenolate Betaine: ESR/ENDOR Characterization of its Radical Ions and ‘Battery Effect’Blue zwitterionic 2,6‐Di(tert‐butyl)‐4‐(2,4,6‐triphenyl‐1‐pyridinio)phenolate 1a can be reduced to its blue‐green radical anion \documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{- \atop \dot{}}$\end{document} using alkaline metals, and oxidized to its colorless radical cation 1 by Ag(OOCCF3) or electrochemically. ESR/ENDOR spectra of their aprotic THF solutions indicate predominant spin population either in the pyridinium (\documentclass{article}\pagestyle{empty}\begin{document}${\bf 1a}^{- \atop \dot{}}$\end{document}) or in the phenolate ring (\documentclass{article}\pagestyle{empty}\begin{document}${\bf 1a}^{+ \atop \dot{}}$\end{document}). Reduction with other alkaline metals Li, Na, or Cs yields no changes in the ESR/ENDOR signal patterns, i.e. provides no indication of radical ion pair formation. The cyclovoltammetrically determined first reduction and oxidation potentials at −1.11 V and +0.26 V, respectively, are both reversible and, in principle, allow to construct a molecular battery.
Cascade Reactions. A Simple One‐pot Synthesis of the Mitomycin Skeleton
Authors: Defoin Albert , Geffroy Guillaume , Le Nouen Didier , Spileers Didier , Streith Jacques 
Published: December 2004

AbstractNitroso‐arene dienophiles 1 react regiospecifically with the conjugated dienals 2 and 3a/3b, and lead thereby to the unstable Diels‐Alder cycloadducts 4 and 5. These undergo two types of cascade reactions which give pyridinium betaines 6 and pyrrolo‐indoles 8 as the major reaction products. The one‐pot syntheses of pyrroloindoles 8 represent a new and easy access to the basic skeleton of mitomycins 10. The scope and limitations of the cascade reactions were investigated.
A Novel Allenic Epoxycyclohexane and Related Compounds from Eutypa lata (Pers: F.) Tul
Authors: Renaud Jean‐Marc , Tsoupras Georges , Stoeckli‐Evans Helen , Tabacchi Raffaele 
Published: December 2004

AbstractThe novel allenic epoxycyclohexanes 1, and related compounds 2 and 3 have been isolated from the culture medium of Eutypa lata. Their structures were established by combination of spectroscopic and chemical techniques. Biogenetic origin and biological activity of these compounds are also discussed.
Ethylene Biosynthesis part 10. Synthesis and study of racemic, (1R, 2S)‐, and (1S, 2R)‐1‐Amino‐2‐(hydroxymethyl)cyclopropanecarboxylic Acid
Authors: Pirrung Michael C. , Dunlap Steven E. , Trinks Uwe P. 
Published: December 2004

AbstractThe preparation of optically active 1‐amino‐2‐(hydroxymethyl)cyclopropanecarboxylic acid has been achieved by a route involving cycloalkylation of dimethyl malonate with epichlorohydrin and subsequent Hofmann rearrangement. The reaction of epichlorohydrin with nucleophiles may occur al either electrophilic site, epoxide or halide. Based on the absolute configuration of the starting materials and the lactones obtained, it has been shown that the initial step of the cycloalkylation occurs at the epoxide moiety. The 1‐amino‐2‐(hydroxymethyl)‐cyclopropanecarboxylic acid, an analogue of the precursor to the plant growth hormone ethylene, is to be used in affinity purification techniques and in generation of antibodies.
Solid‐phase Synthesis of C‐Terminal Peptide Amino Alcohols
Authors: Neugebauer Witold , Escher Emanuel 
Published: December 2004

AbstractThe solid‐phase syntheses of enkephalin and somatostatin analogues with C‐terminal OH functions instead of the normal carboxylates are described. The OH function of the N‐terminal amino alcohol was acylated with succinic acid and esterified to the solid support. Normal Boc‐TFA solid‐phase strategy can be applied to build up and cleave these peptides. The succinic ‘handle’ can be removed by mild basic hydrolysis after cleavage.
Rearrangements of Radical Cations of [2.2]Paracyclophanes and of a bridged [14]annulene to those of pyrenes: An ESR and ENDOR study
Authors: Gerson Fabian , Huber Walter , Wellauer Thomas 
Published: December 2004

AbstractESR and ENDOR studies have been carried out on the radical cations obtained consecutively by reaction of trans‐10b, 10c‐dimethyl‐10b, 10c‐dihydropyrene (4) with AlCl3 in CH2C12. The primarily formed \documentclass{article}\pagestyle{empty}\begin{document}${\bf 4}^{+ \atop \dot{}}$\end{document} rearranges at 253 K to the radical cation(s) of 1,6‐ (5a) and/or 1,8‐dimethylpyrene (5b). At 323 K, the spectra of \documentclass{article}\pagestyle{empty}\begin{document}${\bf 5a}^{+ \atop \dot{}}$\end{document}/\documentclass{article}\pagestyle{empty}\begin{document}${\bf 5b}^{+ \atop \dot{}}$\end{document} are replaced by that of the highly persistent radical cation of 1,3,6,8‐tetramethylpyrene (6). Surprisingly, \documentclass{article}\pagestyle{empty}\begin{document}${\bf 6}^{+ \atop \dot{}}$\end{document} is also the only observable paramagnetic product resulting from a treatment of 4,5,7,8‐ (1), 4,7,13,16‐ (2), and 4,5,12,13‐tetramethyl[2.2]paracyclophane (3) with AlCl3 in CH2Cl2 at 353 K. The structures of the intermediates in the rearrangement [\documentclass{article}\pagestyle{empty}\begin{document}${\bf 1}^{+ \atop \dot{}}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}${\bf 2}^{+ \atop \dot{}}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}${\bf 3}^{+ \atop \dot{}}$\end{document}] → \documentclass{article}\pagestyle{empty}\begin{document}${\bf 6}^{+ \atop \dot{}}$\end{document} are discussed.
New chromonocoumarin (=6H, 7H‐[1]Benzopyrano[4,3‐b][1]benzopyran‐6,7‐dione) derivatives from Polygala fruticosa BERG
Authors: Di Paolo Ermindo R. , Hamburger Matthias O. , Stoeckli‐Evans Helen , Rogers Colin , Hostettmann Kurt 
Published: December 2004

AbstractThree chromonocoumarins ( =6H, 7H‐[1]benzopyrano[4,3‐b][1]benzopyran‐6,7‐diones) 1–3 have been isolated from the leaves and the root bark of polygala fruticosa BERG. (syn. Polygala oppositifolia L.; Polygalaceae). The structure of frutinone A (1) was established by X‐ray diffraction analysis. The structures of the previously undescribed compounds frutinone B (2) and C (3) were deduced by spectroscopic methods (EI‐MS, UV, IR, 1H‐and 13C‐NMR, including NOE and COSY) in comparison with 1. Chromonocoumarins 1–3 are the first representatives of a new type of naturally occurring compounds. Frutinone A shows strong fungicidal activity against Cladosporium cucumerinum.
Dihydropentalene und 6‐Vinylfulvene aus cyclopentadienylcyclopropenen. Notiz zur Umsetzung von 1,2,3‐Tris[(tert‐butyl)thio]cyclopropenylium‐tetrafluoroborat mit cyclopentadienid
Authors: Gugisberg Dominik , Bigler Peter , Neuensehwander Markus , Engel Peter 
Published: December 2004

Dihydropentalenes and 6‐Vinylfulvenes from Cyclopentadienyl‐cyctopropenes. Reaction of 1,2,3‐Tris[(tert‐butyl)thio]cyclopropenylium Tetrafluoroborate with Cyclopentadienide.Reaction of 1,2,3‐tris[(tert‐butyl)thio]cyclopropenylium tetrafluoroborate (6a) with sodium Cyclopentadienide gives, besides of 7,8‐bis{(tert‐buty)thio calicene (7a), rearranged products 7,8,8‐tris[(tert‐butyl)thio]‐6‐vinylpentafulvene (9a) and 4,5.6‐tris[(tert‐butyl}thio]‐1,2‐dihydropentalene (10a)) in varying amounts depending on reaction conditions. Vinyl‐carbenes 12 and 13 are supposed to be possible intermediates.
Synthesis of Naphtho[2,3‐b]pyrandiones: (−)‐Cryptosporin
Authors: Brade Walter , Vasella Andrea 
Published: December 2004

AbstractA new method for the synthesis of naphtho[2,3‐b]pyrandiones from sulfonyllactones and 1‐nitroglycals is presented. Thus, the sulfonyllactone 6 reacted with the 1‐nitroglycal 7 in the presence of LDA at room temperature to give the naphthopyrandione 9 in high yields (Scheme 1). Reaction at a lower temperature led to the (intermediate) Michael‐addition products 8. The sulfonyllactone 4 and the 1‐nitroglycal 5 were prepared for the synthesis of the naphthopyrandione 18 (Scheme 2). The base‐promoted condensation of 4 and 5 gave 17, which was deprotected to give 18, the enantiomer of the fungal metabolite (+)‐cryptosporin 1.
Interconversion of (η3‐Allyl)(η4‐conjugated‐diene)(η5‐cyclopentadienyl)zirconium and ‐hafnium Stereoisomers. Evidence for the simultaneous rearrangement of diene and allyl ligands
Authors: Sontag Christoph , Berke Heinz , Sarter Christian , Erker Gerhard 
Published: December 2004

AbstractReaction of (η3‐allyl)(cyclopentadienyl)zirconium(4+) chloride with (2,3‐dimethylbutadiene)magnesium or (2‐phenylbutadiene)magnesium gave the (η3‐allyl)(η4‐conjugated diene)(cyclopcntadienyl)zirconium complexes 3c and 3d, respectively. The analogous reaction between (η/3‐allyl)(cyclopentadienyl)hafnium(4+) chloride with (buta‐diene)magnesium afforded (η3‐allyl)(η4‐butadiene)(η5‐cyclopentadienyl)hafnium 3e. Photolysis of the complexes 3 produced their stereoisomers 4. The open‐chain π ligands in 3 open themselves towards the apical Cp ligand, in 4 they both are turned around by 180°. The Gibbs activation energy of the 4→3 rearrangement of the Hf complex does not deviate significantly from those of the Zr‐containing systems (4c→3e: ΔG≠ rearr. (−10°) = 81.3 ± 1.3 kJ/mol; 4d→3d: ΔG≠ (‐10°) = 85.7 ± 1.3 kJ/mol; 4e→3e: ΔG≠ (‐5°) = 84.4 ± 1.3 kJ/mol). A modified ex‐tended‐Hückel theory (MEHT) was used in order to simulate the thermally induced rearrangement of the diene ligand in 3/4. The calculations indicate that there should be a combinational interconversion of both the diene and allyl ligand. A diene inversion becomes energetically favoured, if a simultanous allyl rotation occurs. The transition state 9 lies ca. 90 kJ/mol above the optimized geometry of 4a and 115kJ/mol above 3a. Orbital considerations show that a spatially different ‘valence’ orbital of the [Zr(allyl)Cp] fragment 6 in comparison with [ZrCp2]7 causes the conformational preference of the diene ligand in 3a with a higher rearrangement barrier.
A Short, Simple Synthesis of (±)‐Monomorine
Authors: Jefford Charles W. , Tang Qian , Zaslona Alexander 
Published: December 2004

AbstractRacemic monomorine (12) is prepared in six steps in 26% overall yield from 2‐butyl‐1H‐pyrrole and ethyl (E)‐but‐2‐enoate by exploiting the rhodium(II)‐acetate‐catalyzed decomposition of (4RS)‐4‐(2′‐butyl‐1′ H‐pyrrol‐1′‐yl)‐1‐diazopentan‐2‐one (7).
Tilcotil® Studies. Part 2. [4 + 2] Additions with Isothiazol‐3(2H)‐one 1,1‐Dioxide
Authors: Burri Kaspar F. 
Published: December 2004

AbstractThe isothiazole 1 is not only a dipolarophile but also a reactive and versatile dienophile: especially with oxy‐substituted ‘donor’ 1,3‐butadienes, it readily combines in Diels‐Alder fashion; the regiospecificity of the addition is governed by the carbonyl group of the dienophile, whereas the sulfo group can be ignored for the purpose of predicting regioselectivity. upon dehydrobromination of the [4 + 2] adducts with DBN, the cycloaromatization process is completed, generating saccharin‐like compounds. Besides the parent substance saccharin (14b), several hydroxylated derivatives have been synthesized by this new method; two of them, i.e. 16b and 18c, are of potential interest as non‐nutritive sweetening agents (Scheme 3). In an alternative version of this principle, the isothiazole 22 is reacted with the renowned oxazole 21, affording, after acid‐promoted rearrangement, pyrido‐annelated isothiazoles 25 (Scheme 4). Since both processes generate saccharin‐related structures, they may serve in syntheses of oxicams and analogs of ipsapirone. To demonstrate the viability of the approach, one representative of each series, i.e. 26a and 29, has been converted to an oxicam (7b and 31c, resp.; Scheme 5).
Synthesis and Properties of a 2‐Diazohistidine Derivative: A New Photoactivatable Aromatic Amino‐Acid Analog
Authors: Jaganathen Algen , Ehret‐Sabatier Laurence , Bouchet Marie‐Jeanne , Goeldner Maurice P. , Hirth Christian G. 
Published: December 2004

AbstractNα[(tert‐Butoxy)carbonyl]‐2‐diazo‐L‐histidine methyl ester 1 was synthesized starting from the corresponding L‐histidine derivative. The physico‐chemical properties of this new photoactivatable amino‐acid derivative were established. The synthetic precursor of 1, 2‐amino‐L‐histidine derivative 3, was best isolated and characterized as 2‐amino‐Nα‐[(tert‐butoxy)carbonyl]‐Nτ‐tosyl‐L‐histidine methyl ester (4). Selective deprotections of 4 (Nα‐Boc, Nα‐Tos, COOMe) were achieved, thus allowing the use of the corresponding products in peptide synthesis. The optically active dipeptides 8 and 9 were synthesized by coupling 2‐amino‐Nτ‐tosyl‐L‐histidine methyl ester (5) with N‐[(tert‐butoxy)carbonyl]‐L‐alanine and Nα‐[(tert‐butoxy)carbonyl]‐Nτ‐tosyl‐L‐histidine (6) with L‐alanine methyl ester, respectively. The question of selective diazotization of a 2‐aminohistidine residue in a synthetic peptide was studied using competitive diazotizations between 2‐amino‐1H‐imidazole and several amino‐acid derivatives susceptible to undergo nitrosylation. The results show that synthetic photoactivatable peptides incorporating a 2‐diazohistidine residue might become useful photoaffinity probes.
A Novel Nitrone Cycloaddition/Rearrangement
Authors: Toder Bruce H. , Mullen George B. , St. Georgiev Vassil 
Published: December 2004

AbstractAdamantanone‐derived nitrone 4 and some other keto‐nitrones, when reacted with aromatic and aliphatic aldehydes in refluxing toluene or tetrahydrofuran, formed the corresponding aldonitrones (Z)‐10, the latter arising from the fragmentation of an initially formed 1,4,2‐dioxazolidine 6 to adamantan‐2‐one and an oxaziridine intermediate 11, which then rearranges to (Z)‐10.
A New Catalytic System for the Hydroformylation of Styrene Using Alkene Complexes of Platinum(0)
Authors: Botteghi Carlo , Paganelli Stefano , Matteoli Ugo , Scrivanti Alberto , Ciorciaro Rocco , Venanzi Luigi M. 
Published: December 2004

AbstractThe platinum(0) complexes [Pt(C2H4)(PP)] (PP = 1,2‐bis[(diphenylphosphino)methyl]benzene (2) and (+)‐DIOP = (+)‐1,4‐bis(diphenylphosphino)‐1,4‐dideoxy‐2,3‐O‐isopropyliden‐D‐threitol), when promoted by CH3SO3H, become active catalysts for styrene hydroformylation with total yields of aldehydes ranging from 44 to 67% und selectivities towards 3‐phenylpropanal ranging from 80 to 88%. Smaller amounts of the corresponding alcohols (3–18%) are also obtained with a selectivity towards 3‐phenylpropanol of 94–96%. When DIOP complexes were used, no stereoselectivity for asymmetric hydroformylation was observed.
A Facile Synthesis of Optically Pure (−)‐(S)‐Ipsenol Using a Chiral Titanium Complex
Authors: Oertle Konrad , Beyeler Harry , Duthaler Rudolf O. , Lottenbach Willi , Riediker Martin , Steiner Eginhard 
Published: December 2004

AbstractA stereocontrolled synthetic route to optically pure (−)‐(S)‐ipsenol (1), the pheromone of Pityokteines curvidens and various other bark‐beetle species is described. Key step of the synthesis is an enantioselective aldol reaction using a chiral titanium–carbohydrate complex (Scheme 1). The carboxylate function of the optically pure β‐hydroxy acid 5 thus obtained in mol quantities is then elaborated to the diene moiety by standard methodology (Scheme 2).
Herstellung von ‘Semialdehyd’‐Derivaten von Asparaginsäure‐ und Glutaminsäure durch Rosenmund‐Reduktion
Authors: Bold Guido , Steiner Heinz , Moesch Luzia , Walliser Bernhard 
Published: December 2004

Preparation of ‘Semialdehyde’ Derivatives of Aspartic and Glutamic Acid via the Rosenmund ReductionSuitably protected aspartic‐acid ‘β‐semialdehyde’ and glutamic‐acid ‘γ‐aldehyde’ derivatives can be obtained, in good yield by Rosenmund reduction of the corresponding acid chlorides. Benzyloxycarbonyl (Z) and (tert‐butoxy)carbonyl (Boc) protecting groups are not affected under these reaction conditions. The sensitive aldehydes, which are obtained in higher purity than by hydride reductions, can directly be used for further transformations like aldol‐type reactions.