bluuebunny/crossref_metadata_2025 huggingface dataset:
Inter‐ and intramolecular hetero Diels‐Alder reactions, 28. Synthesis of (±)‐secologanin aglucone O‐ethyl ether and derivatives by tandem Knoevenagel hetero Diels‐Alder reaction
Authors: Tietze Lutz F. , Meier Heinrich , Nutt Heinrich
Published: July 2007

The tandem Knoevenagel hetero Diels‐Alder reaction of 4,4,4‐trichloro‐3‐oxobutanal (4), the malondialdehyde derivative 11a, and the enol ether 13 was followed by separation of the diastereomers and treatment with DBU in methanol. Thermolysis in xylene then gave the secologanin derivative 25a in 14% yield with the correct relative stereochemistry at all stereogenic centers. Hydrolysis of the dithiane moiety afforded secologanin aglucone O‐ethyl ether 9 in 86% yield. In a similar way, 25b and 25c were obtained in 14% and 28% yield from the malondialdehyde derivatives 11b and 11c, respectively. Reduction of 9 with sodium borohydride gave swerosid aglucone O‐ethyl ether 24 in 69% yield. The dihydrosecologanin derivative 32 was obtained in 20% yield by reaction of 5, 11c, and 26 followed by methanolysis. In this transformation the initially formed cycloadducts 27 and 28 were isolated; 33, the other type of product obtained by reaction of the second heterodiene moiety in the intermediate Knoevenagel product 18, was also found.
New acetylenes from Chrysanthemum coronarium L.
Authors: Sanz Juan Francisco , Falcó Enrique , Marco Juan Alberto
Published: July 2007

The investigation of the aerial parts of Chrysanthemum coronarium yielded, in addition to several known compounds, two new acetylenic sulfoxides 9 and 10, and a new thiophene spiroacetal enol ether 11. Their structures were deduced by spectroscopic and chemical methods.
Synthesis of (+)‐disparlure using the reaction of 6‐methylheptyl phenyl sulfone with trimethylsilyloxirane and asymmetric epoxidation
Authors: Marczak Stanislaw , Masnyk Marek , Wicha Jerzy
Published: July 2007

Reaction of lithiated sulfone 3 with trimethyl(oxiranyl)silane 4, followed by acid hydrolysis, afforded the (Z)‐allylic alcohol 6 contaminated with its (E) isomer. Epoxidation of 6 by the Sharpless procedure yielded the hydroxy epoxide, which was isolated as its enantiomerically pure 3,5‐dinitrobenzoyl derivative 7 and transformed into (+)‐disparlure 1 via alcohol 8 and tosylate 9.
N‐Geschützte 3‐Hydroxypyrrole
Authors: Flitsch Wilhelm , Hohenhorst Manfred
Published: July 2007

N‐Protected 3‐Hydroxypyrroles

Starting from symmetrical imides and (α‐haloacetylmethylene)‐phosphoranes 2, N‐acyl‐3‐hydroxypyrroles 4 have been prepared by an intramolecular Wittig olefination. The deacylation of 4 was proved using 4 b as an example.
Synthese von stereoisomeren 3‐substituierten Cyclobutancarbonsäure‐Derivaten
Authors: V. Dehmlow Eckehard , Schmidt Stefan
Published: July 2007

Synthesis of Stereoisomeric 3‐Substituted Cyclobutanecarboxylic Acid Derivatives

The preparation of 3‐substituted cyclobutanecarboxylic acids by ring forming malonic ester cycloalkylation/saponification/decarboxylation leads to 50:50 cis/trans mixtures. Only some polar ester derivatives 2 can be separated by chromatographic methods. Catalytic hydrogenation of 3‐substituted cyclobutenecarboxylic acids 3, however, gives the cis acids 4 with 90–95% selectivity. Reduction of the same acids 3 by Zn in aqueous HCl/THF leads to the trans acids 6 with 90–93% selectivity.
Transition metal‐ and acid‐induced transformations of 6‐siloxy‐substituted 5,6‐dihydro‐4H‐1,2‐oxazines: Preparation of pyrroles, nitrones, 1,4‐dicarbonyl compounds and derivatives thereof
Authors: Hippeli Claudia , Zimmer Reinhold , Reißig Hans‐Ulrich
Published: July 2007

A variety of 6‐siloxy‐substituted 5,6‐dihydro‐4H‐1,2‐oxazines (abbreviation: 1,2‐oxazines) 1, 3 could be transformed into di‐ and trisubstituted pyrroles 2, 4 by means of molybdenum hexacarbonyl. The mechanism of this deoxygenating ring contraction is discussed. With two bicyclic 1,2‐oxazines an acid‐catalyzed fragmentation affording α‐methylenecycloalkanones 7 has been observed, while other 1,2‐oxazines rearrange in methanolic acid to give nitrones 9, 10. The desilylation of 6‐siloxy‐substituted 1,2‐oxazines 1, 3 employing NEt3 · 3 HF is a very general and smooth process providing 6‐hydroxy‐1,2‐oxazines 11, 12 or their corresponding acyclic tautomers 13, 14 in high yields. For two examples of 11 deoximations by use of formalin could be achieved with moderate efficiency giving 1,4‐dicarbonyl compounds 15.
Investigation of the one‐pot synthesis of N‐(5,6,7,8‐tetrahydro‐7,7‐dimethyl‐2,5‐dioxo‐2H‐1‐benzopyran‐3‐yl‐2,5‐dioxo‐2H‐1‐benzopyran‐3‐yl)benzamide
Authors: Kočevar Marijan , Polanc Slovenko , Verček Bojan , Tišler Miha
Published: July 2007

A detailed investigation of the reaction of hippuric acid (2) with dimedone (1) and triethyl orthoformate or other one‐carbon sources in acetic anhydride yielding the benzopyran derivative 3 and many byproducts is described. An explanation of this complex process, several attempts to optimize it, and some new approaches to 3 are given.
Biologically active glycosides from asteroidea, XXV. Glycosphingolipids from the starfish Asterina pectinifera, 2. Structure of three ganglioside molecular species and a homogeneous ganglioside, and biological activity of the ganglioside
Authors: Higuchi Ryuichi , Inagaki Kouji , Natori Takenori , Komori Tetsuya , Kawajiri Shinichi
Published: July 2007

Three ganglioside molecular species and a homogeneous ganglioside [GP‐1a (1), GP‐1b (2), GP‐2 (3) and asterinaganglioside A (4)] were obtained from the water‐soluble lipid fraction of the chloroform/methanol extract of the starfish Asterina pectinifera. On the basis of chemical and spectral evidence, the structure of 1–4 were elucidated. GP‐2 (3) was a known ganglioside molecular species, but the other three compounds were new gangliosides. Partial hydrolysis of oligosaccharide moieties with hot water was useful for structure elucidation of the gangliosides. NOE Correlation Spectroscopy (NOESY) was also useful for characterization of the complex sugar moiety. For the isolation of homogeneous ganglioside from the complex molecular species, reversed‐phase HPLC with methanol/ammonia/water as solvent was effective. Moreover, the main ganglioside molecular species, GP‐2 (3), was found to support the survival of cultured cerebral cortex cells, most of which were neuronal cells, of rat fetuses.
Biologically active glycosides from asteroidea, XXVII. Stereochemistry of the C‐17 side chain of 26‐homothornasterol B: Novel triethylaluminum‐promoted rearrangement and alkylation of epoxy alcohols
Authors: Honda Masanori , Igarashi Takashi , Marubayashi Nobuhiro , Komori Tetsuya
Published: July 2007

The absolute configuration of 3,6‐di‐O‐acetyl‐26‐homothornasterol B (3) obtained previously besides the 3,6‐di‐O‐acetyl derivative (2) of (20S,24S)‐24‐ethylthornasterol A by aldol reaction2a) of the mixture of (3S)‐3‐ethyl‐4‐methyl‐2‐(trimethylsiloxy)‐1‐pentene (7) and 3,4‐dimethyl‐2‐(trimethylsiloxy)‐1‐hexene (8) with (+)‐diacetylasterone (1) has been determined by X‐ray structural analysis as (20S,24S,25R)‐3β,6α‐diacetoxy‐20‐hydroxy‐24‐methyl‐26‐homo‐5α‐cholest‐9(11)‐en‐23‐one. On the basis of these results a novel rearrangement and alkylation of the epoxy alcohols 6, 9, 13, and 15 with triethylaluminium have been discovered and investigated. The reaction occurs when the C‐4 position adjacent to the epoxide ring is congested.
Über die Synthese von 2′,3′‐Didesoxy‐3′‐(phosphonomethyl)nucleosiden, Phosphonat‐Analogen von 2′‐Desoxy‐3′‐nucleotiden
Authors: Morr Michael , Ernst Ludger , Schomburg Dietmar
Published: July 2007

Synthesis of 2′,3′‐Dideoxy‐3′‐(phosphonomethyl)nucleosides, Phosphonate Analogs of 2′‐Deoxy‐3′‐nucleotides

1,2‐Di‐O‐acetyl‐5‐O‐benzoyl‐3‐deoxy‐3‐(diethoxyphosphorylmethyl)‐β‐D‐ribofuranose (8) is linked (a) to the protected purine bases ABz, GiB and T, respectively, in the presence of potassium nonaflate and (b) to the silylated pyrimidine bases C, U and UF (= 5‐fluoro‐U) according to the Hilbert‐Johnson method by using stannic tetrachloride. Selective 2′‐O‐deacetylation by hydroxylammonium acetate or hydrazine hydrate employing Ishido's procedure, followed by reaction with phenyl thionochlorocarbonate/4‐(dimethylamino)pyridine, furnishes thionocarbonates 14a–f. These are converted to the deoxy derivatives 15a–f with tributyltin hydride/azobis(isobutyronitrile). For the preparation of the free 2′‐deoxy‐3′‐phosphonic acids 18a–f a special strategy is developed. Hydrolysis of the phosphonic esters is carried out by using bromotrimethylsilane or iodotrimethylsilane, the latter being prepared in situ. 3′‐Deoxy‐3′‐(phosphonomethyl)guanosine (10b1) is described for the first time. The structures of the new compounds follow from their 1H‐, 13C‐ and 31P‐NMR spectra. X‐ray structure analyses were carried out for 8, for 9‐(5‐O‐benzoyl‐3‐deoxy‐3‐diethoxyphosphorylmethyl‐β‐D‐ribofuranosyl)‐6‐hydroxy‐2‐isobutyramidopurin (12b) and its 2,3‐dideoxy analog 15b.
Carbohydrates as chiral templates: Stereoselective Strecker synthesis of D‐α‐amino nitriles and acids using O‐pivaloylated D‐galactosylamine as the auxiliary
Authors: Kunz Horst , Sager Wilfried , Schanzenbach Dirk , Decker Mathias
Published: July 2007

The asymmetric synthesis of N‐galactosyl D‐α‐amino nitriles is accomplished by application of 2,3,4,6‐tetra‐O‐pivaloyl‐β‐D‐galactopyranosylamine (4) as the stereodifferentiating template in Strecker reactions. Aldimines 6 derived from 4 and aromatic or aliphatic aldehydes react with trimethylsilyl cyanide in 2‐propanol or tetrahydrofuran in the presence of Lewis acids, e.g. ZnCl2 or SnCl4′ to give the N‐galactosyl α‐amino nitriles 5 in high yield and with diastereomeric ratios between 6:1 and 13:1 favoring the D diastereomers. Pure D‐amino nitrile diastereomers D‐5 are obtained in high yields by recrystallization from n‐heptane. Acid‐catalyzed hydrolysis of compounds D‐5 delivers the free D‐amino acids. A mechanistic interpretation of the stereoselection observed is given in terms of stereoelectronic, steric and complexing effects exhibited by the carbohydrate.
Herstellung chiraler elektrophiler Glycin‐ und (E)‐2,3‐Dehydroaminosäure‐Derivate aus 2‐t‐Butyl‐3‐methyl‐4‐oxo‐1‐imidazolidincarbonsäure‐t‐butylester (Boc‐BMI)
Authors: Schickli Christof P. , Seebach Dieter
Published: July 2007

Preparation of Chiral Electrophilic Glycine and (E)‐2,3‐Dehydroamino Acid Derivatives from t‐Butyl 2‐t‐Butyl‐3‐methyl‐4‐oxo‐1‐imidazolidinecarboxylate (Boc‐BMI)

Boc‐BMI, the compound specified in the title, is brominated under radical‐chain conditions (NBS/AIBN) to give trans‐bromo‐BMI 2, which is highly reactive in nucleophilic substitutions [see the 5‐carbo‐ and ‐hetero‐substituted (N, O, S, P) 2‐t‐butyl‐3‐methylimidazolidinones 4 – 23 and Tab. 1]. The substitutions occur preferentially with inversion of the configuration, the mechanism being not clear at all. – The Boc‐BMI dimethyl phosphonate 23 (Michaelis‐Arbusov product from 2) reacts with aldehydes (15 examples) to give preferentially (E)‐5‐alkylidene‐imidazolidinones, chiral α‐aminoacrylic acid derivatives which are available in either the R or the S form, see 24 – 38 (Tab. 2). Best yields and highest (E) selectivities (> 25:1), with short reaction times, are obtained by using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene. (DBU)/LiBr in dry THF in a very special variant of the Horner olefination. α‐Branched, racemic aldehydes may give alkylidene derivatives with efficient kinetic resolution (38). Some speculations are made about the mechanism and the observed stereochemical outcome of the reaction (I, J, K). A comparison is made with other chiral electrophilic glycine (A – C) and α,β‐dehydroamino acid derivatives (D, E), as well as with other methods for the preparation of enantiomerically pure methylenedioxolan‐, ‐oxazolidin‐, and ‐imidazolidinones (H), containing an α,β‐unsaturated carbonyl system.
A novel synthesis of indanopyrazolopyrimidines by CT‐complexation
Authors: Hassan Alaa A. , Ibrahim Yusria R. , Mohamed Nasr K. , Mourad Aboul‐Fetouh E.
Published: July 2007

Intermolecular charge‐transfer (CT) complexes of arylazoaminopyrazoles as donors with 2‐(dicyanomethylen)indane‐1,3‐dione (CNIND) and 9‐(dicyanomethylene)‐2,4,7‐trinitrofluorene (DTF) as π‐acceptors have been investigated spectroscopically. Arylazoaminopyrazoles react with CNIND via charge‐transfer complexes to yield indanopyrazolo[1,5‐α]‐pyrimidines 5.
Synthesis of 5‐amino‐4‐cyano‐1‐imidazolyl 2‐Deoxy‐β‐D‐ribofuranoside by photolysis of 2‐aza‐2′‐deoxyadenosine or glycosylation
Authors: Kazimierczuk Zygmunt , Seela Frank
Published: July 2007

The photolysis of 2‐aza‐2′‐deoxyadenosine (1) results in the formation of a single reaction product. Its structure was assigned as 5‐amino‐4‐cyano‐1‐imidazolyl 2‐deoxyribofuranoside (2). The latter is also obtained independently from the glycosylation of the 5‐amino‐4‐imidazolecarbonitrile (4) anion with the halogenose 5. The reaction is stereoselective but regioisomers are formed: the N‐1 compound 6 in 21% and the N‐3 regiosomer 7 in 45% yield. The structures of the regioisomeric imidazole nucleosides 2 and 3 have been assigned by 13C‐NMR and 1H‐NMR NOE difference spectroscopy.
Synthesis of isoquinoline alkaloids. Total synthesis of (±)‐tetrahydroescholamine and its (±)‐threo‐ and (±)‐erythro‐α‐hydroxy analogs
Authors: Rozwadowska Maria D. , Matecka Dorota , Brózda Danuta
Published: July 2007

The studied tetrahydroisoquinolines 1, 2 and 3 were synthesized from a common intermediate 6, which was prepared by addition of the lithium salt of dithiane 5 to hydrastinine chloride (4).
2‐Deoxyglycosyl fluorides in oligosaccharide synthesis
Authors: Jünnemann Josef , Lundt Inge , Thiem Joachim
Published: July 2007

3,4‐Di‐O‐acetyl‐2,6‐dibromo‐2,6‐dideoxy‐α‐D‐mannopyranosyl fluoride (1) was treated with Lewis acid catalysts to give α‐glycosides exclusively. Reactions with α‐ and β‐glucosyl analogs yield α/β mixtures under the same conditions. With no assistance of anchimeric substituents at C‐2 the stereoselectivity is directed by a glycosyl fluoride/catalyst/solvent complex. As shown in the 2‐deoxy‐arabino‐hexopyranosyl series this leads to improved α/β ratios and yields.
Chiral organometallic reagents, IV. Stereoselective formation of β‐silyloxy‐α‐bromoalkyllithium compounds
Authors: Hoffmann Reinhard W. , Julius Manfred
Published: July 2007

The diastereomeric carbenoids 4 have been generated by diastereoselective (84:16) exchange of the diastereotopic bromine atoms in the dibromo compound 3 for lithium at −120°C. The implication of the observed diastereoselectivity for the Nozaki ring‐expansion method is discussed.
Asymmetric Syntheses via Heterocyclic Intermediates, XLIV. Asymmetric Synthesis of Methyl (2R,3S)‐2‐Amino‐3‐cyclopropyl‐3‐hydroxyalkanoates via Diastereoselective Simmons‐Smith Reactions
Authors: Groth Ulrich , Schöllkopf Ulrich , Tiller Thomas
Published: July 2007

The cyclopropanation of the bislactim ethers 3 with diiodomethanes and diethylzinc proceeds in good yields and with high diastereoselectivities, affording the cyclopropyl bislactim ethers 6. Protection of the hydroxy group and subsequenthydrolysis furnish virtually enantiomerically and diastereomerically pure methyl (2R,3S)‐2‐amino‐3‐cyclopropyl‐3‐hydroxyalkanoates 8. The bislactim ethers of type 3 are obtained by a known method diastereomerically pure, starting from the bislactim ether of cyclo(‐L‐Val‐Gly‐).
Synthesis of isopentabromopseudilin
Authors: Hanefeld Ulf , Laatsch Hartmut
Published: July 2007

Isopentabromopseudilin (4) and the analogous compounds 12g, 12h have been synthesized by base‐catalyzed cyclization of substituted benzaldehydes with isocyanoacetic acid methyl ester (6). In contrast to the highly antibiotic and cytotoxic active natural product 1, compounds 4, 12g and 12h have been shown to be inactive.
Chemie der Ginkgolide, IV. Herstellung von Ginkgolid B aus Ginkgolid C
Authors: Weinges Klaus , Schick Hartmut
Published: July 2007

Chemistry of Ginkgolides, IV1). – Synthesis of Ginkgolide B from Ginkgolide C

The reaction of ginkgolide C (3) with tert‐butylchlorodiphenylsilane results exclusively in the formation of the 1‐O‐tert‐butyldiphenylsilyl ether 5, which when treated with O‐phenylchlorothioformate leads to the 7‐phenyloxythiocarbonyl derivative 6. The reduction of 6 with tributyltin hydride/AIBN yields the 1‐O‐tert‐butyldiphenylsilyl ether 7 of ginkgolide B (2). Removal of the silyl protective group with tetrabutylammonium fluoride gives pure ginkgolide B (2). The structures of the reaction products were confirmed by analytical and spectroscopic methods.
Total synthesis of all four diastereomers of 2‐acetamido‐2,4‐dideoxy‐D‐hexapyranose as potential competitive inhibitors of N‐acetylneuraminic acid synthase
Authors: Mulzer Johann , Seilz Carsten , Luger Peter , Weber Manuela , Reutter Werner
Published: July 2007

A nine‐step gram‐scale total synthesis of all four diastereomers 3–6 of 2‐acetamido‐2,4‐dideoxy‐D‐hexapyranose from aldehyde 9, a known derivative of (S)‐malic acid, is described.
Lipidic peptides, VII. Synthesis and structure elucidation of γ‐aminobutyric acid conjugates with lipidic acids, lipidic amino acids and lipidic peptides
Authors: Hussain Rohanah , Toth Istvan , Gibbons William A.
Published: July 2007

A series of γ‐aminobutyric acid esters of lipidic acids, lipidic peptides and γ‐aminobutyric acid amides of lipidic α‐amino acids and oligomers were synthesised. The GABA conjugates with ester linkages (6j–r) were prepared by coupling the lipidic acids and peptide conjugates to the carboxyl terminus of GABA. Two types of GABA conjugates linked by amide bonds were synthesised. This class included compounds 5d–f in which the amino group of the lipidic amino acid is condensed with the carboxyl function of GABA and compounds 7a–b with the carboxyl terminus of the α‐amino acid coupled to the amino group of GABA. The lipidic amino acid peptide oligomers were varied from 1–3 units, and the alkyl side chains ranged from 5–17 carbon atoms in length in order to impart different lipophilicities to the GABA molecule conjugates.
Photooxygenation of some potentially skin‐photosensitizing furocoumarins: Imperatorin, alloimperatorin and its methyl ether and acetate derivatives
Authors: Abou‐Elzahab Mohamed M. , Adam Waldemar , Saha‐Möller Chantu R.
Published: July 2007

The photooxygenation of imperatorin (1a) afforded the corresponding allylic hydroperoxides 2a and 3a in very good yields. Similarly, the photooxygenation of alloimperatorin derivatives 1c, d gave the allylic hydroperoxides 2c, d and 3c, d in quantitative yields. On the other hand, on photooxygenation of alloimperatorin (1b) exclusively the dienone hydroperoxide 4b was obtained. When the reaction time was prolonged, the bis(hydroperoxide) 5b was also formed by successive photooxygenation of 4b.
Concave reagents, 8. Concave pyridines and 1,10‐phenanthrolines with sulfonamide bridgeheads. Increased basicity by 4‐diethylamino substitution of the pyridine unit
Authors: Lüning Ulrich , Baumstark Roland , Müller Michael
Published: July 2007

Bimacrocyclic concave pyridinebissulfonamides 2 and concave 1,10‐phenanthrolinebissulfonamides 4 have been synthesized by bridging macrocyclic pyridinediamines 12 or 1,10‐phenanthrolinediamines 16 with alkylenebis(sulfonyl chloride)s 14. In contrast to concave pyridine‐ and 1,10‐phenanthrolinebislactams 1 and 3, the new compounds 2 and 4 exhibit simpler 1H‐NMR spectra and sharper melting points due to the absence of amide conformers; in comparison to 1, the basicities of 2 are decreased by a factor of ca. 100. By introduction of donor substituents into the 4‐position of the pyridine ring the basicity loss can be easily compensated. The 4‐diethylamino substituent increases the basicity of the concave pyridines 1 and 2 as expected (ca. + 4 pK units). Since no deviations from the expected basicity and reactivity for the amino‐substituted concave pyridines 1 and 2 have been found, also in these sterically hindered pyridines, the pyridine nitrogen atom is the centre of basicity and reactivity. – The synthesis of new building blocks is described, i.e. 4‐diethylamino‐2,6‐pyridinedicarbaldehyde (9c), the polyether‐based bis(sulfonyl chloride) 14b, the monomacrocyclic diamines 12e–h with a pentaethyleneglycol chain or a 4‐diethylamino substituent.
Steroids, XLIV. Neighbouring group participation, XI. Decomposition of 2‐amidomethylene‐3‐hydroxysteroids
Authors: Vincze Irén , Somlai Csaba , Schneider Gyula
Published: July 2007

During reduction with sodium tetrahydroborate the 2‐[acetyl‐(alkyl)aminomethylene]‐3‐keto steroids 1aa, ba and 2aa – ca undergo transformation into the 2,4‐diene‐2‐aldehydes 5a and 6, respectively. These compounds are the decomposition products of the cyclic orthoester amides of the type 4a, b, formed by NAc‐6 neighbouring group participation from the 3‐hydroxy derivative A, which cannot be isolated.
Preparative bioorganic chemistry, XV. Preparation of optically pure 2,4,4‐trimethyl‐2‐cyclohexen‐1‐ol, a new and versatile chiral building block in terpene synthesis
Authors: Mori Kenji , Puapoomchareon Prapai
Published: July 2007

Enzymatic hydrolysis of (±)‐2,4,4‐trimethyl‐2‐cyclohexenyl acetate [(±)‐3] with pig liver esterase yielded (R)‐(+)‐2,4,4‐trimethyl‐2‐cyclohexen‐1‐ol [(R)‐2] and unchanged (S)‐(−)‐acetate (S)‐3. Enantiomerically pure (S)‐2 was converted into (R)‐dihydro‐α‐ionone (10).
Glycosyl imidates, 47. Stereospecific synthesis of α‐ and β‐L‐fucopyranosyl phosphates and of gdp‐fucose via trichloroacetimidate
Authors: Schmidt Richard R. , Wegmann Barbara , Jung Karl‐Heinz
Published: July 2007

Reaction of the benzyl‐ and acetyl‐protected α‐trichloroacetimidates 1 and 6α with dialkyl and diaryl phosphates in the presence of traces of acid affords stereoelectively the thermodynamically more stable α‐L‐fucopyranosyl phosphates 2, 7 and 8, respectively, in high yields. The use of very pure, recrystallized dibenzyl phosphate results in the stereoeletive formation of the β‐L‐fucopyranosyl phosphates 3 and 9. In each case separation of the anomers is not required because of the very high stereoselectivity of the reactions. After deprotection the fucose 1‐phosphate 12 is coupled with GMP morpholidate 10 to yield GDP‐fucose 13. After the development of a new purification procedure for GDP‐fucose 13 we have obtained a very pure compound suitable for biochemical investigations. Analytical and preparative HPLC has been performed on reversed‐phase columns using a volatile buffer system (triethylammonium hydrogen carbonate) as the eluant.
Structural Variations on N‐acetylneuraminic acid, 20. Synthesis of some 2,3‐didehydro‐2‐deoxysialic Acids structurally varied at C‐4 and their behavior towards Sialidase from Vibrio cholerae
Authors: Schreiner Erwin , Zbiral Erich , Kleineidam Reinhard G. , Schauer Roland
Published: July 2007

The peracetylated methyl ester 1 of N‐acetylneuraminic acid was transformed into the oxazoline derivative 2, which was hydrogenated with Pd/C/H2 to give the 4‐deoxy‐Neu5Ac2en derivative 3. Acid cleavage of the oxazoline 2 by trifluoroacetic acid (THF) gave the 4‐epi‐Neu5Ac2en derivative 4a, which was saponified to the known 4‐epi‐Neu5Ac2en 4b. Treatment of 4a with triphenylphosphane/diethylazodicarboxylate (DEAD)/HN3 in toluene gave the 4‐azido‐4‐deoxy‐Neu5Ac2en derivative 5a as well as the 4‐epi‐azido‐4‐deoxy‐Neu5Ac2en derivative 6a. Both epimers could be saponified yielding the free dehydrosialic acid derivatives 5b and 6b. Furthermore, 4‐formamido‐4‐deoxy‐Neu5Ac2en 7b was prepared via the derivative 7a, which was formed from 5a by reaction with triphenylphosphane/formyl acetate. In addition, the free dehydrosialic acid derivatives 5b and 6b were transformed into the stable PN ylides 8 and 10, but only 8 could be hydrolyzed to the triethylammonium salt of 4‐amino‐4‐deoxy‐Neu5Ac2en 9a, which was converted into the zwitter ionic compound 9b. Finally 4‐acetamido‐4‐deoxy‐Neu5Ac2en 11e was prepared from 4‐acetamido‐4‐deoxy‐N‐acetylneuraminic acid 10 via the derivatives 11a and 11b by well‐known methods. The compounds 4b, 5b, 6b, 7b, 9b, and 11c were investigated as inhibitors of Vibrio cholerae sialidase, and their Ki values were determined.
Synthesis and conformational analysis of methyl 2‐O‐(α‐D‐Mannopyranosyl)‐α‐D‐mannopyranoside
Authors: Peters Thomas
Published: July 2007

NMR experiments such as steady state NOE experiments and spin lattice 1H relaxation time measurements were performed on the synthetic disaccharide 10 that constitutes part of the polysaccharide backbone in fungal mannans. The spectro‐scopic data were compared with a theoretical model that is based upon the HSEA force field and statistical mechanics, taking into account the flexibility around the glycosidic linkage. Potential energy calculations were performed with a modified version of the GESA program in order to derive the global minimum conformation of disaccharide 10 and to calculate ensemble average NOE and T1 values by averaging all energetically accessible conformational microstates, using a normalized Boltzmann distribution function. The fit between experimental and theoretical results improved significantly when we applied a dynamic model instead of a single state model based solely on the global minimum conformation of 10. Efficient synthesis of 10 was achieved by a recently published protocol for the in situ activation of thioglycosides.
Enzymes in organic synthesis, 4. Investigation of the pancreatin‐catalyzed acylation of cis‐cyclopent‐2‐ene‐1,4‐diol with various trichloroethyl and vinyl Alkanoates
Authors: Theil Fritz , Schick Hans , Lapitskaya Margarita A. , Pivnitsky Kasimir K.
Published: July 2007

During the pancreatin‐catalyzed acetylation of the meso‐diol 1 with 2,2,2‐trichloroethyl acetate (2a) in tetrahydrofuran/tri‐ethylamine, the enantiomeric monoacetates 3a and ent‐3a are formed at nearly equal rates. ent‐3a is rapidly acetylated in a second enzyme‐catalyzed step, forming 4a, whereas 3a resists further enzymatic acetylation. Thus, the monoacetate 3a can be obtained in 48% yield with an enantiomeric excess (e.e.) of more than 99%. 2,2,2‐Trichloroethyl propanoate and butanoate give the corresponding monoacylation products even in slightly better yield, whereas the octanoate affords the mono‐acylation product with a lower enantiomeric excess. 2,2,2‐Trichloroethyl monochloroacetate provides the monoacylation product in a 40% yield with an e.e. of 90%. The dichloroacetate, however, affords the diacylation product exclusively in an enzyme‐independent chemical reaction. With the 2,2,2‐trichloroethyl esters of isobutyric, phenylacetic, and benzoic acid no transesterification could be achieved within 24 hours. The application of vinyl acetate, however, represents a significant improvement in the synthesis of enantiomerically pure monoacetate 3a from meso‐diol 1.
Pheromone synthesis, CXXVI. Synthesis and biological activity of four stereoisomers of 6,10,14‐trimethyl‐2‐pentadecanol, the female‐produced sex pheromone of rice moth (Corcyra cephalonica)
Authors: Mori Kenji , Harada Hironori , Zagatti Pierre , Cork Alan , Hall David R.
Published: July 2007

The synthesis of four stereoisomers of the female‐produced sex pheromone [(2R,6R,10R)‐, (2S,6R,10R)‐, (2S,6S,10S)‐, and (2R,6S,10S)‐1a] of the rice moth (Corcyra cephalonica) was achieved by starting from (R)‐2a, (R)‐ or (S)‐3a, and (R)‐ or (S)‐4 and using alkylation of alkyl phenyl sulfones as the coupling reaction. Behavioral bioassay of each isomer revealed (2R,6R,10R)‐1a to be eight times more active than a diastereomeric mixture of equal amounts of the eight possible stereoisomers, indicating that (2R,6R,10R)‐1a is probably the natural pheromone or at least the major component of the female blend. Electrophysiological bioassay also confirmed the high activity of (2R,6R,10R)‐1a.
Enzym‐katalysierte Reaktionen, 8. Stereoselektive Darstellung von 2‐Aminoalkoholen aus (R)‐ und (S)‐Cyanhydrinen
Authors: Effenberger Franz , Gutterer Beate , Ziegler Thomas
Published: July 2007

Enzyme‐Catalyzed Reactions, 8. – Stereoselective Synthesis of 2‐Amino Alcohols from (R)‐ and (S)‐Cyanohydrins

erythro‐2‐Amino alcohols (1R,2S)‐ and (1S,2R)‐4 may be synthesized stereoselectively by addition of Grignard compounds to cyanohydrins (R)‐, (S)‐1 and their O‐trimethylsilyl derivatives 3, respectively, followed by hydrogenation. The threo‐2‐amino alcohols (1S,2S)‐ and (1R,2R)‐4 are easily accessible by inversion at C‐1 of the (1R,2S) and (1S,2R) compounds.
Boussingoside D1, a new triterpenoid saponin from Boussingaultia baselloides
Authors: Espada Alfonso , Rodríguez Jaime , Villaverde M. Carmen , Riguera Ricardo
Published: July 2007

Four triterpenoid saponins have been isolated from the leaves of Boussingaultia baselloides by a combination of DCCC with HPLC. One is the new triterpenoid saponin boussingoside D1,3‐O‐[β‐D‐xylopyranosyl‐(1→3)‐O‐β‐D‐glucoronopyranosyl]‐30‐noroleana‐12,20(29)‐dien‐28‐oic acid, the structure of which has been elucidated by 1H‐ and 13C‐NMR spectroscopy, FAB‐MS and chemical methods.
Short enantioselective approach to a building block for macrolide syntheses
Authors: Stürmer Rainer
Published: July 2007

The protected α,β‐dihydroxy aldehyde 2 a key building block for several macrolide antibiotics, has been synthesized from the epoxy alcohol 6. Oxidation furnishes the corresponding aldehyde 7, which is acetalized with ketones in the prescence of SnCl4 with complete inversion of configuration at C‐3.
(10E,12Z)‐9‐Hydroxy‐10,12‐octadecadiensäure, ein Aromatase‐Hemmstoff aus dem Wurzelextrakt von Urtica dioica
Authors: Kraus Rupert , Spiteller Gerhard , Bartsch Wilfried
Published: July 2007

(10E,12Z)‐9‐Hydroxy‐10,12‐octadecadienoic Acid, an Aromatase Inhibitor from Roots of Urtica dioica

Aqueous‐methanolic extracts from roots of Urtica dioica were fractionated and tested for aromatase‐inhibition activity. After derivatization the most active fraction was separated by GC/ MS. Besides common fatty acids (10E,12Z)‐9‐hydroxy‐10,12‐octadecadienoic acid (1) was identified as a main component and confirmed to be the active principle. Lipoxygenase from tomatoes was used for synthesis of (9S)‐1, which caused also inhibition of aromatase. Stereo models of the compound showed some structural similarity to steroidal natural substrates of aromatase. For that reason (10E,12Z)‐9‐oxo‐10,12‐octadecadienoic acid (2) was also synthesized. It showed an about tenfold higher activity compared to 1.
Pheromone synthesis, CXXVII. A new synthesis of the enantiomers of grandisol and lineatin
Authors: Mori Kenji , Nagano Eiki
Published: July 2007

The enantiomers of grandisol (1) and lineatin (2) have been synthesized by resolving the key (±)‐hydroxy ether (±)‐7 as its diastereomeric esters 8 and 8′ with (−)‐camphanic acid.
Zur Selbstzersetzung von 2‐Chlor‐4‐methoxy‐1‐naphthol
Authors: Laatsch Hartmut
Published: July 2007

On the Self‐Decomposition of 2‐Chloro‐4‐methoxy‐1‐naphthol

On standing, 2‐chloro‐4‐methoxy‐1‐naphthol (1a) rapidly decomposes under formation of the dinaphthofuranol 10a. The reaction is interpreted as a dehalogenation of 1a yielding 6, oxidation of the latter and acid‐catalyzed cyclisation of the intermediate 9.
Synthese und Geruch von Homoisocamphanylcyclohexanolen
Authors: Spreitzer Helmut , Laszloffy Beata , Lebada Phillipine , Buchbauer Gerhard
Published: July 2007

Synthesis and Odour of Homoisocamphanylcyclohexanols

Diels‐Alder reaction of dienone 2 with 3‐methoxystyrene (3) leads to 4, which has been converted into a mixture of homoisocamphanylcyclohexanols (±)‐9a/b. The epimeric axial and equatorial alcohols have been separated by TLC, and their olfactory properties are described.
Organic azides in heterocyclic synthesis, 12. Thermal cyclization of 4‐azido‐3‐formyl‐2‐quinolones to isoxazolo[4,3‐c]quinolones
Authors: Roschger Peter , Stadlbauer Wolfgang
Published: July 2007

Thermolysis of the 4‐azido‐3‐formyl‐2‐quinolone 6, which was prepared from the 4‐hydroxy‐2‐quinolone 1, afforded the ringclosed isoxazoloquinolone 7. 3‐(Arylaminomethylene)‐2,4‐quinolinediones 2 could not be transformed into an azide precursor in order to obtain the corresponding pyrazoloquinolone but yielded by attempted chlorination either 5‐methyldibenzo[b,h][1,6]naphthyridine‐6(5H)‐one (9) or 4‐chloro‐3‐formyl‐1‐methyl‐2(1H)‐quinolone (5).
Chirale Lactole, X. Allose als Hauptprodukt der Glycolaldehyd‐Trimerisierung
Authors: Noe Christian R. , Knollmüller Max , Ettmayer Peter
Published: July 2007

Chiral Lactols, X1). – Allose as the Main Product of the Glycolaldehyde Trimerization2)

The reaction products of the aldol reaction of acetal‐protected glycolaldehyde 2 with KOH or NaOH as catalysts have been characterized as their O‐methyl‐O‐tritylalditol derivatives by a newly developed sugar analysis procedure. The products are compared to reference substances of defined configurations which have been synthesized for the first time from sugar alcohols. Besides allose as the main product, mannose and threose are formed in the aldolization reaction. The exact composition of the carbohydrate mixture is detected by only one HPL chromatogramm.
Glycosyl imidates. 49. Synthesis of the octasaccharide moiety of the dimeric Lex antigen
Authors: Bommer René , Kinzy Willy , Schmidt Richard R.
Published: July 2007

A versatile synthesis of the basic Galβ (1→4)[Fucα(1→3)]‐GlcNAc trisaccharide building block of the Lex antigen family based on two important findings could be developed. Firstly, selective 3‐O‐allylation of the readily available azidolactose derivative 3 led to an efficient synthesis of the 3‐O‐unprotected fucosyl acceptor 9. Secondly, α‐fucosylation of 9 with O‐fucosyl trichloroacetimidate 11 as donor exhibited a dramatic increase in yield when carried out by an “inverted procedure”, i,e, the donor was added to an acceptor/catalyst solution. The obtained trisaccharide building block 12 could be readily transformed into acceptor 13 and donor 15, respectively. Thus, the dimeric hexasaccharide 16 was obtained, which was then transformed into donor 19. Its reaction with the 3′‐O‐unprotected lactose acceptor 20 provided the desired ocetasaccharide 21, which gave upon azido group reduction, acetylation of the amino groups, and complete O‐deprotection the desired target molecule 2 characterized as its fully O‐acetylated product 24.
Synthesis of 3‐deoxy‐D‐manno‐2‐octulosonic acid (KDO)
Authors: Frick Wendelin , Krülle Thomas , Schmidt Richard R.
Published: July 2007

[(Benzyloxy)(benzyloxycarbonyl)methyl]triphenylphosphonium bromide (8), obtained from glyoxylic acid via a convenient one‐pot procedure, reacted in a Wittig reaction with 4‐O‐benzyl‐2,3:5,6‐di‐O‐isopropylidene‐D‐mannose (7), readily synthesized on a large scale from D‐mannose, to provide the KDO derivative 9. Hydrogenolytic removal of the benzyl groups furnished directly the 4,5:7,8‐di‐O‐isopropylidene protected KDO 11. Its treatment with diazomethane led to the known ester derivative 12α,ß (2:1 anomeric mixture) which could be also obtained by transesterification of 9 and subsequent hydrogenolytic debenzylation.
Epoxidation of allylic hydroperoxides by dimethyldioxirane and peroxy acids
Authors: Abou‐Elzahab Mohamed , Adam Waldemar , Saha‐Möller Chantu R.
Published: July 2007

The epoxidation of allylic hydroperoxides 2a–h by dimethyldioxirane afforded the epoxy hydroperoxides 3a–h in very good yields. On the other hand, only the substrates 2a, b and 2d–f can be converted into the corresponding epoxy hydroperoxides by peroxy acids in reasonable to good yields. The peroxy acid and dimethyldioxirane epoxidations of allylic hydroperoxides proceed, in contrast to those of the allylic alcohols, in low but opposite diastereoselectivity. The configuration of diastereomeric epoxy hydroperoxides were determined by NMR‐NOE experiments and chemical correlation.
Pheromone synthesis, CXXX. Synthesis of (4S,8S)‐ and (4S,8R)‐4,8‐dimethyldecanal, the stereoisomers of the aggregation pheromone of Tribolium castaneum
Authors: Mori Kenji , Takikawa Hirosato
Published: July 2007

(4S,8S)‐ and (4S,8R)‐4,8‐Dimethyldecanal (1) were synthesized by starting from (R)‐citronellic acid (2a), methyl (S)‐3‐hydroxy‐2‐methylpropanoate (3a), and (S)‐2‐methyl‐1‐butanol (4a).
Synthesis of methyl (±)‐2,3‐O‐isopropylideneglycerate by electrochemical oxidation of (±)‐1,2‐O‐isopropylideneglycerol
Authors: Schwarz Karl‐Heinz , Kleiner Katharina , Ludwig Ralf , Schrötter Eberhard , Schick Hans
Published: July 2007

The anodic oxidation of (±)‐1,2‐O‐isopropylideneglycerol at a silver/silver oxide electrode with a controlled potential of +0.9 V vs. SCE in 2.5 N sodium hydroxide affords sodium (±)‐2,3‐O‐isopropylideneglycerate in a yield of 75%. Treatment of this salt with dimethyl sulfate and potassium carbonate in boiling acetone leads to methyl (±)‐2,3‐O‐isopropylideneglycerate in a yield of 81%.
Synthese und Reaktivität von 3‐Oxazolinen
Authors: Weber Maya , Jakobxht Jürgen , Martens Jürgen
Published: July 2007

Synthesis and Reactivity of 3‐Oxazolines.

3‐Oxazolines 1 have been prepared from α‐hydroxy aldehydes, ammonia, water and a second oxo compound (aldehyde or ketone) in a one‐pot reaction. Carboxylic acid chlorides add to the azomethine bond of 1 to yield 3‐acyl‐4‐chlorooxazolidines 2. 4‐Hydroxy and 4‐alkoxyoxazolidines 3 are obtained from 2 upon treatment with aqueons sodium hydroxide or alkanol/ triethyl amine, respectively. Some oxazolidines 3 are formed with high diastereoseselectivity.
Pyridazines, LX. Telesubstitution and Dismutation Reactions in the Series of Phenyl‐3‐pyridazinylmethane Derivatives
Authors: Heinisch Gottfried , Huber Thierry
Published: July 2007

Reactions of 3‐α‐chlorobenzylpyridazine (4) with alkoxides have been found to yield 6‐substituted or 4‐substituted 3‐benzylpyridazines (7a–c, 8a–c) rather than the usual ethers (6a–c). Introduction of an electron‐donating substituent into the 6‐position of the pyridazine nucleus of 4 has been shown to suppress such telesubstitution processes. With phenyl‐3‐pyridazinylmethanol (3), thermally induced dismutation affording 3‐benzylpyridazine (17) and 3‐benzoylpyridazine (11) has been observed.
Pseudo‐sugars, 30. Synthesis of Amino‐5a‐carba‐deoxyhexopyranoses from 2(3)‐Acetoxy‐5‐acetoxymethyl‐3(2)‐p‐toluenesulfonamido‐7‐oxabicyclo[2.2.1]heptanes
Authors: Ogawa Seiichiro , Tsunoda Hidetoshi , Yoshikawa Masaru , Uemura Masaki , Orihara Masaru
Published: July 2007

cis‐Hydroxyamination of endo‐2‐acetoxymethyl‐7‐oxabicyclo[2.2.1]hept‐5‐ene (1) under Sharpless conditions affords two positional isomers 3 and 7 of 5‐endo‐acetoxymethyl‐2(3)‐exo‐hydroxy‐3(2)‐exo‐p‐toluenesulfonamido‐7‐oxabicyclo[2.2.1]heptanes. Cleavage of the 1,4‐anhydro ring of the corresponding acetyl derivatives 4 and 8 with 18% hydrogen bromide in acetic acid at 80°C produces several bromodeoxy aminocyclitol derivatives, from which, on hydrolysis or nucleophilic substitution with an acetate ion, the known 2‐acet‐amido‐5a‐carba‐2‐deoxy‐α‐DL‐allo (25) and ‐gulopyranose tetraacetates (26), and new 3‐acetamido‐5a‐carba‐3‐deoxy‐α‐DL‐allopyranose tetraacetate (30) have been obtained. Likewise, the new 3‐acetamido‐5a‐carba‐3‐deoxy‐β‐DL‐talopyranose tetraacetate (39) has been prepared by starting from the exo‐isomer 2.
Pseudo‐sugars, 31. New Synthesis of 2‐Amino‐5a‐carba‐2‐deoxy‐α‐DL‐glucopyranose and Its Transformation into Valienamine and Valiolamine Analogues
Authors: Ogawa Seiichiro , Tsunoda Hidetoshi
Published: July 2007

The positional isomers 2, 4, and 6 of respective validamine (1), valiolamine (3), and valienamine (5), derived from 2‐amino‐5a‐carba‐2‐deoxy‐α‐D‐glucopyranose, were synthesized as racemates from DL‐(1,3/2,4,6)‐3‐acetamido‐1,2‐di‐O‐acetyl‐4‐bromo‐6‐bromomethyl‐1,2‐cyclohexanediol (8). Compounds 2, 4, and 6 showed very weak inhibitory activities against yeast α‐D‐glucosidase.
Synthesis and Spectroscopic Characterization of Dimeric Steroidal Oximes
Authors: Duddeck Helmut , Frelek Jadwiga , Snatzke Günther , Szczepek Wojciech J. , Wagner Petra
Published: July 2007

Hydrolysis of 3β‐5‐diacetoxy‐5β‐cholestan‐6‐one oxime (1) gave seven products which, in addition to 3β‐acetoxy‐ and (6E)‐3β‐hydroxy‐5‐methoxy‐5α‐cholestan‐6‐one oxime (3 and 4), are identified as the dimeric steroids (6E,6′E)‐6‐(6′‐hydroxyimino‐5′α‐cholestan‐5′‐yl‐oximino)cholestanes 6–10. On the other hand, the 3α epimer 3α,5‐diacetoxy‐5β‐cholestan‐6‐one oxime (2) afforded the monomeric (6E)‐3α‐hydroxy‐5‐methoxy‐5α‐cholestan‐6‐one oxime (5) and (6E)‐3α‐hydroxy‐4‐cholesten‐6‐one oxime (11) only. All new compounds are characterized by NMR and MS methods. The CD spectra of 1–12 are documented.
Chiral Organometallic Reagents, VIII. On the Configurational Stability of α‐Hetero‐Substituted Benzyllithium Compounds
Authors: Hoffmann Reinhard W. , Rühl Thomas , Harbach Jürgen
Published: July 2007

A test based on kinetic resolution was applied to probe the configurational stability of various α‐substituted benzyllithium compounds 1. It was found that the trimethylsilyl‐ (1b), phenylsulfenyl‐ (1c), and the phenylselenyl‐substituted (1d) benzyllithium compounds enantiomerized more rapidly than they added to the chiral aldehyde 6. In contrast, the carbamoyloxy‐ (1e), (16), and the phenylsulfonyl‐substituted (1g) benzyllithium compounds were found to be configurationally stable on the time scale set by their addition to the aldehyde 6.
Synthesis and Reactivity of a p‐Methoxyphenyl‐Substituted Enediyne. A Case of Electronic Influence on the Rate of the Bergman Cycloaromatization
Authors: Maier Martin E. , Greiner Beate
Published: July 2007

Bicyclo[7.3.1]diynes 19a and 19b were prepared by using dibromo olefin 11 and ketone 12 as building blocks. The key step of the synthetic sequence is an intramolecular Nicholas reaction of 17 to give the bicyclo[7.3.1]diyn‐10‐one dicobalthexacarbonyl adducts 18a and 18b (66% total yield). Oxidative decomplexation of 18a and 18b with cer(IV) ammonium nitrate gave the diynes 19a and 19b, respectively. Both diynes 19a and 19b could be oxidatively converted into the enediyne 20 by using DDQ. In contrast to the unsubstituted enediyne 4, compound 20 can be isolated at room temperature Quantitative kinetic measurements of the rate of the Bergman cyclization of 20 gave ΔG# (37°C) = 111 kJ mol−1. This value is 12.3 kJ mol−1 higher than that of 4. The difference in the free activation energy between 20 and 4 is attributed to electronic effects.
One‐Pot Synthesis of a 2‐Dialkylaminoalkyl‐Substituted Tetrahydro‐β‐carboline‐hydantoin System
Authors: Braña Miguel Fernandez , De Miguel Pilar , Klebe Gerhard , Martin Nazario , Walker Nigel
Published: July 2007

A new and convenient method for the synthesis of pharmacologically interesting compounds containing the tetrahydro‐β‐carboline‐hydantoin moiety linked to a basic chain, together with a structural study, are reported.
2,3‐Dihydroxy‐3‐{3‐[3‐(trifluoromethyl)diazirin‐3‐yl]phenyl}propionic Acid. A Cleavable Carbene‐Generating Reagent Used for Photocrosslinking
Authors: Kogon Alexander A. , Bochkariov Dmitry E. , Baskunov Boris P. , Cheprakov Andrew V.
Published: July 2007

The synthesis of 2,3‐dihydroxy‐3‐{3‐[3‐(trifluoromethyl)diazirin‐3‐yl]phenyl}propionic acid (8), a new cleavable carbenegenerating reagent used in photocrosslinking experiments in molecular biology is described. This synthesis starts with the bromination of trifluoroacetophenone. The resulting compound 2 is converted into the corresponding diazirine 6 via oxime 3, O‐tosyloxime 4, and diaziridinyl 5 derivatives. The cleavable cis‐diol bond is formed via a cinnamic acid derivative 7 by permanganate oxidation resulting in the title compound 8.
Studies on the Synthesis of 3‐Vinylcephalosporins
Authors: Pitlik János , Batta Gyula , Sztaricskai Ferenc
Published: July 2007

Several novel cephalosporins 4–19 having substituted vinyl functionalities at C‐3 were synthesized. The title compounds were prepared by a short and simple reaction sequence starting from protected 7‐aminocephalosporanic acid derivatives 1–3 and involving cleavage with iodotrimethylsilane, phosphonium salt formation, and subsequent Wittig reaction. The effect of the substituents are also discussed.
Synthese 2‐Heteroaryl‐substituierter 3,3,3‐Trifluoralanin‐ und 3,3,3‐Trifluormilchsäure‐Derivate
Authors: Sewald Norbert , Burger Klaus
Published: July 2007

Synthesis of 2‐Heteroaryl‐Substituted 3,3,3‐Trifluoroalanine and 3,3,3‐Trifluorolactic Acid Derivatives

Trifluoromethyl‐substituted alkynyl α‐amino acid as well as alkynyl α‐hydroxy acid esters and 1,3‐dipoles (nitrile oxides, diazoalkanes, phenyl azide) react regioselectively to give α‐trifluoromethyl‐substituted heterocyclic α‐amino and α‐hydroxy acid derivatives, respectively.
Synthesen von hydroxylierten Bipyridinen, III. Synthese von unsymmetrischen und symmetrischen Dihydroxybipyridinen
Authors: Dehmlow Eckehard V. , Sleegers Arthur
Published: July 2007

Syntheses of Hydroxylated Bipyridines, III. — Synthesis of Unsymmetrically and Symmetrically Structured Dihydroxybipyridines

Fifteen symmetrical and asymmetrical dimethoxybipyridines and the pertinent diols are prepared and characterized. Reductive cross coupling of halopyridines with Ni(0) may result in complex mixtures. The same is true for an alternative reaction of (trimethylstannyl)pyridines with halopyridines in the presence of Pd(0). UV, 1H‐, and 13C‐NMR spectra of the bipyridine derivatives are tabulated.
Glycosyl Imidates, 56. Synthesis of the Hexasaccharide Moiety of Pectinioside E
Authors: Jiang Zi‐Hua , Schmidt Richard R.
Published: July 2007

The synthesis of the hexasaccharide moiety 2 of pectinioside E (1), isolated from the whole bodies of the starfish Asterina pectinifera Müller et Troschel, is described. Building block 4 was prepared by a six‐step procedure from D‐glucose. A reasonable yield was obtained via selective glycosylation of 4 at 2‐OH with donor 5 to give the desired disaccharide 6 which served as an acceptor in the following fucosylation with 9 to afford the crucial trisaccharide 10. This was easily transformed into trichloroacetimidate 12. Disaccharide 17, obtained in high yield by glycosylation of donor 13 with acceptor 14 followed by deacetylation, turned out to be more reactive at 4b‐OH than at 2b‐OH. Thus, the reaction of donor 12 with acceptor 17 gave the desired pentasaccharide 18 β in an acceptable yield; 18 β was readily transformed into the hexasaccharide 20 by glycosylation with donor 15. Debenzylation of 20 followed by deacylation furnished the target hexasaccharide 2 which was characterized by its per‐O‐acetylated product 21.
Synthesis of a Hydroxymethylene‐Bridged Galβ(→3)Gal c‐Disaccharide
Authors: Schmidt Richard R. , Beyerbach Armin
Published: July 2007

Direct lithiation of the readily available 2‐phenylsulfinyl‐D‐galactal 3S furnishes with aldehyde 8 as electrophile in a diastereocontrolled reaction the C‐disaccharide intermediate 9. Subsequent removal of the phenylsulfinyl group with Raney nickel and diastereospecific 2b‐hydrogen and 3b‐hydroxy transfer provide the β(1→3)‐connected C‐disaccharide 11 in high yield. The structure of 11 was deduced from its derivative 12 on the basis of 1H‐NMR data. Hydrogenolytic O‐debenzylation gives compound 13, which is characterized as O‐acetylated compound 14.
Use of α‐Bromo Oxime Ethers in the Synthesis of 1,2‐Diamines
Authors: Shatzmiller Shimon , Bercovici Sorin
Published: July 2007

Oxime ethers 1 react with ammonia and primary amines to give α‐amino oxime ethers. The reaction of α‐bromo oxime ethers with sodium azide affords α‐azido oxime ethers. Hydrogenolysis of the azido compounds using 5% palladium on calcium carbonate as catalyst yields the α‐amino oxime ethers. The reaction of α‐azido oxime ethers with lithium aluminum hydride gives 1,2‐ethanediamine derivatives. The reaction of azido oxime ether 13 with LiAlH4, and subsequently the reaction of the resulting mixture of the diamines 14 and 15 with phosgene, preferably gives cis‐4‐pentyl‐5‐methyl‐2‐imidazolidone (16) indicating that the reduction of 13 proceeds in a stereoselective manner to furnish mainly the syn‐1,2‐ethanediamine 15.