bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sulfoborierung cyclischer Ether — ein präparativer Weg zu Mercaptoalkanolen und Bis(hydroxyalkyl)sulfiden
Authors: Köster Roland , Kucznierz Ralf 
Published: July 2007

Sulfoboration of Cyclic Ethers — A Preparative Route to Mercaptoalkanols and Bis(hydroxyalkyl) SulfidesBis(1,5‐cyclooctanediylboryl) sulfide (1) reacts slowly with the cyclic ethers A–D to give the O,S‐bis(9‐BBN)mercaptoalkanols 2a–d in excellent yields. From oxetane (E) and 1, however, 2e is obtained rapidly, which further reacts with E to yield the bis(9‐BBN‐oxypropyl) sulfide 3ee. 2a and c react with E to form mixed thioethers 3ae and 3ce, respectively. The methanolysis of 2a–e leads to the O‐(9‐BBN)mercaptoalkanols 4a–e. The compounds 2 and 3 react with acetylacetone or with 2‐aminoethanol to yield the mercaptoalkanols 7a–c, e and the bis(hydroxyalkyl) sulfides 8ae, 8ce and 8ee, resp., in high yields beside the 9‐BBN‐chelates 5 or 6.
Isolation of 4‐Hydroxy‐5‐methoxycanthin‐6‐one from Picrasma quassioides and Revision of a Previously Reported Structure
Authors: Liu Jian , Davidson R. Stephen , Heijden Robert Van Der , Verpoorte Robert , Howarth Oliver W. 
Published: July 2007

AbstractA new alkaloid, 4‐hydroxy‐5‐methoxycanthin‐6‐one (1), has been isolated from Picrasma quassioides (Simaroubaceae), and its structure has been determined by high‐field 1H‐ and 13C‐NMR, 13C,1H‐HETCOR, 1H,1H‐2D‐COSY, and NOE‐difference spectra. Previous data, interpreted by other workers as being from this compound, is instead tentatively reassigned to another new alkaloid structure, 4‐hydroxy‐3‐methylcanthine‐5,6‐dione (2).
Untersuchungen zur Charge‐Transfer‐Wechselwirkung von Phenolen mit Tetracyanethylen (TCNE)
Authors: Spange Stefan , Maenz Karsten , Stadermann Dietmar 
Published: July 2007

Investigations on the Charge‐Transfer Interaction of Phenols with Tetracyanoethylene (TCNE)The donor properties of some phenol derivatives were determined by measuring the UV/Vis spectra of their CT complexes with tetracyanoethylene in 1,2‐dichloroethane and acetonitrile at room temperature. The ionization potentials of the phenolic compounds have been calculated by using the longest visible charge‐transfer absorption of the donor‐acceptor complex by linear correlation analysis. The charge‐transfer spectra are discussed in dependence on the ring substituents in terms of electronic and steric factors. Increasing donor strength of the substituents decreases the ionization potential of the phenols as demonstrated by an LFE relationship using the Hammett constants. However, ortho donor substituents enhance the donor strength of the aromatic ring as well.
Oxidation of 8‐Methoxypsoralen (8‐MOP) by Dimethyldioxirane. Evidence for the Formation of a Furocoumarin Epoxide by Methanol Trapping, a Potential Mutagenic Agent
Authors: Adam Waldemar , Sauter Markus 
Published: July 2007

AbstractThe reaction of 8‐methoxypsoralen (1) with dimethyldioxirane in methanol at 25°C yields the methanol adduct 3, namely the 2,3‐dihydro‐2‐hydroxy‐3,9‐dimethoxy‐7H‐furo[3,2‐g][1]benzopyran‐7‐one, whose structure was unequivocally assigned by means of spectroscopic data. Methanol adduct 3 is produced by dioxirane epoxidation of the furan double bond of 1 to 2 followed by nucleophilic attack by methanol at the benzylically activated C‐3. The direct observation of the 8‐methoxypsoralen epoxide (2) was not possible, because at low temperature (below 0°C) dimethyldioxirane does not epoxidize 1, while at 25°C this labile epoxide decomposes. On the basis of these results, a rational explanation is offered as to the origin of the regioisomeric methanol adduct 5, namely 2,3‐dihydro‐3‐hydroxy‐2,9‐dimethoxy‐7H‐furo[3,2‐g][1]benzopyran‐7‐one, observed in traces (ca. 0.2%), when 1 is treated with sodium hypochlorite and hydrogen peroxide in aqueous methanol.
Zur Struktur cyclotrimerer 1,4‐Chinone
Authors: Laatsch Hartmut , Beck Holger , Egert Ernst 
Published: July 2007

On the Structure of Cyclotrimeric 1,4‐QuinonesAccording to a crystal structure analysis the quinone units of the anthraheptaphene derivative 1b are heavily deformed, due to steric interference. The central ring, however, is plain and shows only slightly alternating bond lengths. So in 2a, which is easier accessible, the central double bonds have retained in part their quinonoid properties: When boiling with piperidine, 2a reacts to 5a, which gives 8a and 9 on reductive acetylation. With sodium hydroxide, 2a forms the pentaphenediquinone 7a and further unidentified products.
Diastereoselective Michael Additions of Chiral Imidazolidines to Trityl Enones
Authors: Seebach Dieter , Pfammatter Elmar , Gramlich Volker , Bremi Tobias , Kühnle Florian , Portmann Stefan , Tironi Ilario 
Published: July 2007

AbstractThe enolatesAandCoft‐butyl (R)‐2‐t‐butyl‐3‐methyl‐4‐oxo‐1‐imidazolidinecarboxylate (1, Boc‐BMI) and of 1‐t‐butyl 5‐methyl (2R,5S)‐2‐t‐butyl‐3‐methyl‐1,5‐imidazolidinedicarboxylate (3) andt‐butyl (R)‐2‐t‐butyl‐5‐lithio‐3‐methyl‐1‐imidazolidinecarboxylate (B, from2) add in a Michael‐type reaction to trityl enones (E, 4, 5). With one exception (product8) a single diastereoisomer is formed (≫98% ds). — In two cases (6, 10), the crystal structures of the products are determined by X‐ray diffraction. The steric course of the reactions (the relative topicity isunlikewith the enolates) is discussed and compared with that of other conversions of the same reagents. — The trityl groups of two adducts (8and9) are cleaved off by treatment with LiBH4/cat. LiBHEt3to give diaminopentanol derivatives (12and13).
Donorsubstituierte Benzenderivate als Dienophile in der [4 + 2]‐Cycloaddition mit inversem Elektronenbedarf
Authors: Hoferichter Reinhard , Seitz Gunther 
Published: July 2007

Donor‐Substituted Benzenes as Dienophiles in the [4 + 2] Cycloaddition with Inverse Electron Demand[4 + 2] Cycloadditions of various donor‐substituted benzenes (2a, 2b, 12, 15, 21 and 24) with 3,6‐bis(trifluoromethyl)‐1,2,4,5‐tetrazine (1), are described. 1 exhibits the highest diene reactivity so far observed in Diels‐Alder reactions with inverse electron demand. The unusual reactivity is in accord with frontier orbital theory; for instance with 2a, 2b and 24 [4 + 2] cycloaddition takes place with high site selectivity in 3,4‐ and 1,2‐position of the donor‐substituted benzenes, resulting in preferential formation of the 6‐substituted phthalazines 5a, 5b and 28, respectively. Main side products are in each case the (E)‐4.4′‐Ethylenebis[3,6‐bis(trifluoromethyl)pyridazine] (9) and the phthalazine 11. In addition, with 24 as dienophile the azine 32 is formed in 24% yield. Its formation proceeds presumably via the reaction sequence 29→31→30→32.
Chemie und Stereochemie der Iridoide, XVIII. Enantiomerenreines (+)‐Cyclosarkomycin aus Catalpol
Authors: Weinges Klaus , Ziegler Hans Jürgen , Schick Hartmut 
Published: July 2007

Chemistry and Stereochemistry of Iridoids, XVIII. — Enantiomerically Pure (+)‐Cyclosarkomycin from CatalpolThe reaction of hexaacetylcatalpol (2) with peroxyformic acid results in hexaacetyl‐3‐formyloxy‐4‐hydroxycatalpol (3), which is cleaved to4and sorbit (4a) by reduction with LiAlH4. The mixture of4/4awas acetylated and the resulting acetates5/5aseparated by column chromatography. The following reactions from5to9(reactions e—i of Scheme 1) are each nearly quantitative. Therefore, the isolation of the intermediates6–8was not necessary. The constitutions of6–8were proven by13C‐NMR spectroscopy. The (1S,2RS,5R)‐2‐hydroxy‐3‐oxabicyclo[3.3.0]octan‐6‐one (9) was purified by column chromatography and its oxidation by pyridinium chlorochromate (PCC) in dichloromethane leads to crystalline (+)‐cyclosarkomycin (10) [yield 85%, based on5].
Hydrazidine, V. Synthese und Reaktionen aromatischer und aliphatischer Hydrazidine und deren N1‐substituierter Derivate
Authors: Neunhoeffer Hans , Karafiat Ute , Köhler Gernot , Sowa Birgit 
Published: July 2007

Hydrazidines, V. — Synthesis and Reactions of Aromatic and Aliphatic Hydrazidines and Their N1‐Substituted DerivativesAromatic hydrazidines 3 have been synthetized by reaction of aromatic orthocarboxylates 4 with tert‐butyl carbazate (5) and reaction of the protected hydrazidines 7 with HCl/methanol or HBr/acetic acid. Aliphatic N1‐methylhydrazidines 8 have been prepared by methylation of bis (tert‐butoxycarbonyl)‐hydrazidines 7 and deprotection with HBr/acetic acid. Aromatic N1‐methylhydrazidines 8 have been obtained by methylation of N1‐methyl(thiohydrazides) 11, reaction of 12 with tert‐butyl carbazate (5) and deprotection of 13 with HCl/methanol. — Attempts to remove both protecting groups in N1‐alkyl‐N2,N4‐bis
Photooxygenation of α‐Ionone and Oxygen Transfer Reactions of the Resulting Allylic Hydroperoxides
Authors: Adam Waldemar , Griesbeck Axel G. , Wang Xiaoheng 
Published: July 2007

AbstractThe photooxygenation of α‐ionone (4) in different solvents leads, with higher than 90% regioselectivity, to a mixture of two diastereomeric allylic hydroperoxides 5a and 5b (diastereomeric ratio 77:23). These compounds are transformed in the presence of Ti(OiPr)4 into the corresponding epoxy alcohols 8a and 8b (cis selectivity) and the allylic alcohols 7a and 7b with high diastereoselectivity. In these cases the substrate configuration exhibits a pronounced control of type selectivity: the cis allylic hydroperoxide 5a is preferentially reduced to the allylic alcohol 7a, whereas the diastereomeric trans compound 5b is preferentially (syn selectivity) converted to the epoxy alcohol 8b. Epoxidation of the allylic alcohol 7a with meta‐chloroperbenzoic acid leads, in contrast to the Ti(IV)‐catalyzed reaction, to a mixture of diastereomeric epoxy alcohols 8a and 8c, with the anti product 8c as major diastereomer (diastereomeric ratio 28:72). These reactions serve as a route to three of the four possible diastereomeric epoxides of 3‐hydroxy‐γ‐ionone.
Über die radikalische Desoxygenierung sekundärer Alkohole
Authors: Weinges Klaus , Schick Hartmut , Zöllner Peter 
Published: July 2007

On the Radical Deoxygenation of Secondary AlcoholsThe derivatives 1c–1f were prepared from tetramethyl‐(+)‐catechin (1b). Their radical reduction with tri‐n‐butyltin hydride or tris(trimethylsilyl)silane in the presence of azobis‐(isobutyronitrile) as initiator led to (2R)‐(—)‐3′,4′,5,7‐tetramethoxyflavan (1g). The best yield of 1g (about 75% from 1b) was achieved via the N‐(imidazolyl)thiocarbonyl derivative 1c. Analogously the enantiomeric (2S)‐(+)‐3′,4′,5,7‐tetramethoxyflavan (2g) was obtained from tetramethyl‐(+)‐epicatechin (2b) via 2c. Experimental evidence is given which shows that in aqueous solution, with a catalytic amount of potassium hydrogen carbonate, (+)‐catechin (1a) epimerises at the C‐2 position of the flavan skeleton to give (+)‐epicatechin (2a).
Dithiocarboxylierung von CH‐aciden Sulfoxiden und Thioethern
Authors: Rudorf Wolf‐Dieter , Uhlig Gabriele , Dargatz Manfred 
Published: July 2007

Dithiocarboxylation of CH‐Acidic Sulfoxides and ThioethersReaction of (arylsulfinyl)acetonitriles or (arylthio)acetonitriles 1 (X = SO, S) with carbon disulfide in the presence of sodium hydride and subsequent alkylation yield the open‐chain or cyclic ketene S,S‐acetals 3 or 4, respectively. Using two equivalents of an α‐CH‐acidic halo compound as alkylating agent, thiophenes 5 are formed. Treatment of 3a with 2‐mercaptoethanol affords the 1,3‐oxathiolane 6. The 1H‐NMR spectra of phenylsulfinyl‐substituted compounds 3b, 4a, 4b, 5a and 6 show a typical AB system for the methylene group caused by the chiral sulfoxide group.
Ring Transformation of 2,4,6‐Tris(aminoalkenyl)‐1,3,5‐triazines to 4‐Aminopyrimidines
Authors: Schulz Hans‐Joachim , Liebscher Jürgen , Maas Gerhard 
Published: July 2007

AbstractAcid hydrolysis of 2,4,6‐Tris(aminoalkenyl)‐1,3,5‐triazines 1 gives 4‐amino‐5‐aryl‐2‐benzylpyrimidines 3 by ring transformation including elimination of amine, formic acid, and carboxylic acid.
Hochsubstituierte Cyclopentadiene mit Methylthio‐ und Methylsulfonyl‐Gruppen
Authors: Hartke Klaus , Lee Kyung‐Hee 
Published: July 2007

Highly Substituted Cyclopentadienes with Methylthio and Methylsulfonyl GroupsSodium cyclopentadiene (1) reacts with S‐methyl methane‐thiosulfonate (2) to yield the hexakis(methylthio)cyclopentadiene (3), which is transformed into the pentakis(methylthio)‐cyclopentadienides 4 by S‐nucleophiles. Oxidation of 4 gives rise to pentakis(methylsulfonyl)cyclopentadienide, isolated as tetraphenylarsonium salt 7.
Pyridinium N‐Phenoxide Betaines and Their Application to the Characterization of Solvent Polarities, XX. – Synthesis, Solvatochromism, and Halochromism of Chromoionophoric Crown Ether‐substituted Pyridinium N‐Phenolate Betaine Dyes
Authors: Reichardt Christian , Asharin‐Fard Siamak , Schäfer Gerhard 
Published: July 2007

AbstractSynthesis, negative solvatochromism (Table 1, Figure 1), and negative halochromism (Tables 2–3, Figures 2–3) of the new crown ether‐substituted pyridinium N‐phenolate betaine dyes 3–6 are described. In contrast to other known chromoionophores, 3–5 exhibit a cation‐selective negative halochromism, which manifests itself as a hypsochromic shift of the longwavelength intramolecular charge‐transfer (CT) absorption band of the betaine chromophore on addition of salts. As this CT absorption band lies within the visible spectral region, the cation‐induced colour change can be followed easily by eye, which suggests an application of these new chromoionophoric betaine dyes as cation indicators. The halochromism of 3–6 constitutes a new type of true halochromism, in contrast to the trivial halochromism first defined by Baeyer and Villiger in 1902.
Alkylaluminium Dichloride Induced Friedel‐Crafts Acylation of Unsaturated Carboxylic Acids and Alcohols
Authors: Metzger Jürgen O. , Biermann Ursula 
Published: July 2007

AbstractThe ethylaluminium dichloride induced Friedel‐Crafts acylation of unsaturated carboxylic acids, for example 10‐undecenoic acid (1a) and oleic acid (5a), and of the respective alcohols 1b and 5b with acyl chlorides and cyclic acyl anhydrides gave the corresponding long‐chain β,γ‐unsaturated ketones 3, 6/7, 11 and 13/14 with ω‐carboxy and ω‐hydroxy functions, respectively. The intramolecular cyclization of petroselinic acid chloride (17) yielded (E)‐2‐dodecylidenecyclohexanone (18). Catalytic hydrogenation gave the respective saturated ketones 4, 8/9, 12, 15/16 and 19.
Anomeric O‐alkylation, 11. Anomeric O‐Alkylation of O‐Unprotected Hexoses and Pentoses – Convenient Synthesis of Decyl, Benzyl, and Allyl Glycosides
Authors: Klotz Wolfgang , Schmidt Richard R. 
Published: July 2007

AbstractThe base‐promoted reaction of O‐unprotected aldoses 1–6 with didecyl sulfate in DMPU affords decyl glycosides 1aα–6aα and 1aβ, 3aβ–6aβ in good overall yields. Similarly, the treatment of O‐unprotected hexoses 1–4 and pentoses 5 and 6 with benzyl bromide and allyl bromide yields after subsequent O‐acetylation monosaccharides 1cα–6cα, 1cβ, 3cβ–6cβ and 1dα–6dα, 1dβ, 3dβ–6dβ, respectively. The regio‐ and stereoselectivity in these reactions was determined by 1H‐NMR spectroscopic data of the O‐acetylated derivatives.
Synthesis of Tetramethyl 2,6‐Dihydroxybicyclo[3.3.1]nona‐2,6‐diene‐1,3,5,7‐tetracarboxylate (Meerwein Ester). – Use of tert‐Butyl Methyl Ether Instead of Benzene in Azeotropic Distillation
Authors: Quast Helmut , Witzel Martina 
Published: July 2007

AbstractIn the condensation of dimethyl malonate with formaldehyde, leading eventually to the title compound 5, water is formed which is removed by azeotropic distillation with benzene in the original procedure. It is shown that benzene may be replaced by tert‐butyl methyl ether without any loss in the yield.
Sequential Analysis of Oligosaccharide Structures by Selective NMR Techniques. – 1D Multistep‐relayed COSY‐ROESY
Authors: Schröder Harald , Haslinger Ernst 
Published: July 2007

AbstractSequential analysis of oligosaccharide structures by 1D multistep‐relayed COSY‐ROESY experiments is described. Selective excitation is performed by Gaussian‐shaped soft pulses. The application to saponins and flavonoids is demonstrated.
Secondary Metabolites by Chemical Screening, 25. New Cyclic Polysulfides from Hyperthermophilic Archaea of the Genus Thermococcus
Authors: Ritzau Michael , Keller Martin , Wessels Peter , Stetter Karl O. , Zeeck Axel 
Published: July 2007

AbstractFrom the intact cells of the sulfur‐metabolizing hyperthermophilic archea Thermococcus tadjuricus (strain Ob9) and Thermococcus acidaminovorans (strain Vc6bk) 23 predominantly new cyclic polysulfides could be isolated by using chemical screening methods. The structures of nine preparatively separated compounds were determined by spectroscopic methods, whereas those of 14 compounds were established by GC‐MS only. Most of the polysulfides are derivatives of 1,2,4‐trithiolane, 1,2,4,5‐tetrathiane and 1,2,3,5,6‐pentathiepane. They differ from each other by aliphatic or aromatic side chains, derived from predominantly metabolized proteinogenic amino acids. The building mechanism and the relevance of the polysulfides are discussed.
Combretastatin Analogs via Hydration of Stilbene Derivatives
Authors: Mannila Erkki , Talvitie Antti 
Published: July 2007

AbstractHydration of the double bond of some stilbene congeners of Picea abies bark by TiCl4·NaBH4 reagent is described. Five racemic 1,2‐diphenylethanol derivatives (9–13), structurally related to (R)‐(·)‐combretastatin [(R)‐1], have been obtained and characterized mainly by 13C‐ and 1H‐NMR as well as mass spectrometry. The antileukemic activity of each compound has preliminarily been tested by the mouse leukemia L1210 system. Compound 10 has been synthesized by Friedel‐Crafts acylation.
Enantiomerically pure chiral building blocks for syntheses of carbocyclic nucleoside analogues: A formal synthesis of aristeromycin
Authors: Helmchen Günter , Krotz Achim , Neumann Hans‐Peter , Ziegler Manfred L. 
Published: July 2007

Abstract(+)‐(1R,4R)‐Bicyclo[2.2.1]hept‐5‐en‐2‐one (7) was prepared in 78.5% yield by oxidative degradation of (+)‐(1R)‐endo‐bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylic acid (4) by using an improved procedure for the oxidation of the dianion of 4 with dioxygen. Dihydroxylation of 7 with osmium tetroxide furnished the cis exo addition product 8c and, via reversible retro aldol reaction, the trans isomer 8t which was characterized by X‐ray crystal structure analysis. 8c was transformed in four reaction steps into the lactone 2 which is a known starting material for a synthesis of the antiviral antibiotic aristeromycin (1). 8t is a potential starting material for syntheses of carbocyclic analogues of arabinofuranosyl nucleotides, e.g., the antiviral agent cyclaradine (3).
A New Asymmetric Synthesis of both Enantiomers of Coniine by 1,2‐Addition of RLi/YbCl3 to Aldehyde SAMP Hydrazones
Authors: Enders Dieter , Tiebes Jörg 
Published: July 2007

AbstractBoth enantiomers of the hemlock alkaloid coniine 8 are prepared by asymmetric synthesis in 98% ee using only one enantiomer of the auxiliary. The key step of the synthesis consists in the 1,2‐addition of organoytterbium reagents to aldehyde SAMP hydrazones with virtually complete asymmetric induction, followed by N–N bond cleavage and cyclization.
Synthesis of Methyl 2,6‐Dideoxy‐4‐thio‐α‐D‐ribo‐hexopyranoside (methyl 4‐thiodigitoxoside) – a Constituent of the Calicheamicins and Esperamicins
Authors: Claßen Arnold , Scharf Hans‐Dieter 
Published: July 2007

AbstractThe 4‐thio analog of 2,6‐dideoxy‐D‐ribo‐hexopyranose (D‐digitoxose) is part of the saccharide chain of the calicheamicins and esperamicins. A straightforward synthesis of the 4‐thiodigitoxoside 12 as its diacetate 13 starting from methyl α‐D‐galactopyranoside (1) is described. Properties and structure of 13 are presented.
Synthese von Calcitonin‐Derivaten durch Fragmentkondensation in Lösung und am 2‐Chlortrityl‐Harz
Authors: Barlos Kleomenis , Gatos Dimitrios , Papaphotiou Georgios , Schäfer Wolfram 
Published: July 2007

Synthesis of Calcitonin Derivatives by Fragment Condensation in Solution and on 2‐Chlorotrityl ResinSer2,Val8,Gly33)‐human calcitonin (13) was synthesized in 45% yield by sequential assembly of protected fragments on 2‐chlorotrityl resin. An analogous synthesis by fragment condensation in solution yielded (Ser2,Val8)‐human calcitonin (21) in 10% yield.
Diastereoselektive Diels‐Alder‐Reaktionen mit α‐Chlornitrososacchariden
Authors: Braun Heinz , Felber Helena , Kresze Günter , Schmidtchen Franz P. , Prewo Roland , Vasella Andrea 
Published: July 2007

Diastereoselective Diels‐Alder Reactions with α‐Chloronitroso SaccharidesThe α‐chloronitroso reagent 2 obtained from ribose via the lactone oxime 3 reacts with the dienes 6–10 at low temperature to give the chiral dihydrooxazines 11–16 in 63–96% yield and > 96% enantiomeric excess. The reagents 1 and 2 which are approximately mirror images in the vicinity of the chloronitroso function lead to opposite enantiomers of 11–16. The absolute configuration of the products was determined by chemical degradation and comparison with authentic amino and hydroxy acids.
Synthesis of Sphingosines, Part 8. Synthesis of Methyl‐branched Sphingosines
Authors: Bär Thomas , Kratzer Bernd , Wild Robert , Sandhoff Konrad , Schmidt Richard R. 
Published: July 2007

AbstractTreatment of 2,4‐O‐benzylidene‐D‐threose (3) with the Wittig reagent obtained from 2‐bromopentadecane furnished 5‐methyloctadec‐4‐ene derivatives (E,Z)‐8. The introduction of the azido group into the 2‐position and acid‐catalyzed removal of the benzylidene protective group afforded 5‐methyl‐substituted azidosphingosines (E)‐10 and (Z)‐10 which were converted via azide reduction into the corresponding sphingosines (E)‐1 and (Z)‐1, respectively. Reaction of 3 with methylmagnesium bromide, ensuing selective 2‐O‐mesylation, and then 4‐O‐oxidation gave ketone 13. The Wittig reaction of 13 with triphenyltetradecylphosphorane afforded exclusively 4‐methyloctadec‐4‐ene derivative (Z)‐16 which was transformed into 4‐methyl‐substituted sphingosine (Z)‐2 as described above. For the synthesis of the corresponding E isomer, 3 was converted into carbinols 21h,l. 2‐O‐Silyl protection and then water elimination furnished 4‐methyl‐substituted (4E)‐octadec‐4‐ene derivative (E)‐23 which was transformed into (E)‐2.
Bausteine von Oligosacchariden, CV. Synthese des Pentasaccharids L‐α‐D‐Hep‐(1→3)‐L‐α‐D‐Hep‐(1→5)‐α‐Kdo‐(2→6)‐β‐D‐GlcNhm‐(1→6)‐D‐GlcNhm der linearen Core‐ und Lipoid‐A‐Struktur von Lipopolysacchariden
Authors: Paulsen Hans , Höffgen Elisabeth C. 
Published: July 2007

Building Units of Oligosaccharides, CV. – Synthesis of the Pentasaccharide L‐α‐D‐Hep‐(1→3)‐L‐α‐D‐Hep‐(1→5)‐α‐Kdo‐(2→6)‐β‐D‐GlcNhm‐(1→6)‐D‐GlcNhm of the Linear Core and Lipoid A Structure of LipopolysaccharidesUsing the trichloroacetimidate method we synthesized a trisaccharide donor containing the sequence L‐α‐D‐Hep‐(1→3)‐L‐α‐D‐Hep‐(1→5)‐α‐Kdo. This block was coupled stereoselectively with a lipoid A analogue acceptor 22, composed of two glucosamin units, giving the pentasaccharide 23. After deblocking we obtained the pentasaccharide L‐α‐D‐Hep‐(1→3)‐L‐α‐D‐Hep‐(1→5)‐α‐Kdo‐(2→6)‐β‐D‐GlcNhm‐(1→6)‐D‐GlcNhm (28), which represents the linear structure of the inner core and lipoid A chain of lipopolysaccharides. Sheep erythrocytes can be coated with compound 28 by incorporation of the fatty acids into the cell membrane. This complex presents the antigenic determinant composed of two heptose residues and one Kdo residue above the cell surface.
Borane Reduction of the Steroid 20‐Ketone Group in the Presence of Various Chiral β‐Amino Alcohols
Authors: Göndös György , Orr James C. 
Published: July 2007

AbstractThe direction of reduction of 20‐carbonyl group of 3α‐hydroxy‐5β‐pregnan‐20‐one (1) with a complex of borane‐methyl sulfide and chiral β‐amino alcohols, depends on the chirality of the amino alcohol. Where there is a 2‐phenyl or 2‐benzyl substituent, then the S enantiomer gives exclusively the steroid 20R alcohol 3. The R enantiomer of 2‐amino‐2‐phenyl‐1‐ethanol gives the highest steroid 20S (2):20R (3) alcohol ratio.