bluuebunny/crossref_metadata_2025 huggingface dataset:
Regioselectivity of the Amination of Some Nitroquinoxalines by Liquid Ammonia/potassium Permanganate
Authors: Woźniak Marian , Barański Andrzej , Nowak Krystyna , Poradowska Henryka
Published: July 2007

5‐ and 6‐Nitroquinoxalines and some of their derivatives are aminated in a liquid ammonia solution of potassium permanganate to yield the corresponding 2‐ and/or 3‐ and/or 5‐amino compounds. Quantum‐chemical calculations are made to explain the regioselectivity of the amination reactions.
Dithio‐ und Thionester, 56. Zur Reaktion von Thioestern und Thioamiden mit Azodicarbonsäurederivaten
Authors: Hartke Klaus , Brutsche Andreas , Gerber H.‐D.
Published: July 2007

Dithio and Thiono Esters, 56. — Reaction of Thio Esters and Thio Amides with Azodicarboxylic Acid Derivatives

Dithio and thiono esters 1 react with azodicarboxylates 3 to form the addition products 4 or the oxidation products 5 in varying ratios. With malonates, malonamides and dithionomalonates only the addition products 7 were obtained. N,N,N′,N′‐Tetramethyldithiomalonamide yields with azodicarboxylic acid derivatives 3 either the normal addition product 8, the β‐elimination product 9 or N,N,N′,N′‐tetramethyltrithiomesoxalamide (10A), the first stable vicinal trithiocarbonyl compound.
Novel 1,6‐Stannylenes of Glucose, Galactose and Mannose
Authors: Köpper Sabine , Brandenburg Anna
Published: July 2007

Treatment of 2,3,4‐tri‐O‐benzyl‐gluco‐, manno‐ and ‐galactopyranose with dibutyltin oxide leads to the 1,6‐di‐O‐stannylene products 2, 5 and 7, whereas no such products are formed by treatment of the 3‐O‐axially configured ido and allo sugars. Spectroscopic studies show that the tin atom is hexacoordinated in these compounds. The gluco derivative mainly exists as a dimer while the manno and galacto compounds are monomeric. All stannylenes easily eliminate the 3‐O‐benzyl group and are stereospecifically opened to give 6‐substituted α,β‐unsaturated aldehydes 3, 8 and 9. Both formation and further reactions can be correlated with the tendency of the tin atom to extend its coordination.
Lipidic Peptides, XIV. Conversion of Racemic Lipidic Amino Acids into Sphingosine and Ceramide Analogues and 1,2‐Diamines
Authors: Kokotos George , Constantinou‐Kokotou Violetta , Fernandez Esther Del Olmo , Toth Istvan , Gibbons William A.
Published: July 2007

N‐Protected racemic lipidic amino acids 1a–h were converted directly into ceramide analogues 2a–h by chemoselective reduction of their corresponding mixed anhydrides with sodium tetrahydroborate. Conversion of the compounds 1a, b into the corresponding acyl azides, followed by catalytic hydrogenation gave the N‐monoprotected lipidic 1,2‐diamines 5a, b. The sphingosine analogues 7a–c and the free 1,2‐diamines 6a, b were synthesized by deprotection of the compounds 2a–c and 5a, b, respectively.
Pheromone Synthesis, CXL. Synthesis of Four Macrolide Pheromones to Define the Scope and Limitation of Enzymatic Macrolactonization
Authors: Mori Kenji , Tomioka Hiroki
Published: July 2007

The macrolides, (R)‐ferrulactone II (2), (Z)‐3‐dodecen‐12‐olide (3) and (5Z,13R)‐5‐tetradecen‐13‐olide (4), could be synthesized by enzymatic macrolactonization with lipases by starting from (±)‐12, 17 and (±)‐24, respectively. Ferrulactone I (1) was prepared by the Corey macrolactonization, and the S enantiomers of 2 and 4 by chemical macrolactonization of (S)‐11 and (S)‐23, respectively.
Structure‐Odor Correlation XVII. Synthesis and Olfactory Properties of further Theaspirane Analogs
Authors: Weyerstahl Peter , Schneider Kathleen
Published: July 2007

Alkylation of ethyl geranate (5) with the bromo esters 7 and 8 gave the β,γ‐unsaturated esters 10 and 11, which could be isomerized to 13 and 14 by treatment with DBU. The α,β‐unsaturated esters 12–14 were cyclized to 15–17, and subsequent reduction of 15–17 led to the diols 18–20. Final cyclization afforded the spiro ethers 2–4. – The olfactive properties (intensity and quality) of the theaspirane analogs 1–4 are determined by the conformational flexibility of the respective molecule. Thus, the rigid 1 and 2 have strong camphoraceous odors. Augmenting flexibility (→3, →4) results in weaker, fruity‐woody notes.
Tetrahydrofurane und γ‐Lactone, V[1,2] Optisch aktive δ‐Hydroxy‐γ‐lactone aus Cyclooctin und Furan — Synthese von (—)‐(R,R)‐ und (+)‐(S,S)‐Muricatacin sowie verwandter Verbindungen
Authors: Tochtermann Werner , Scholz Gerhard , Bunte Gudrum , Wolff Christian , Peters Eva‐Maria , Peters Karl , von Schnering Hans Georg
Published: July 2007

Tetrahydrofurans and γ‐Lactones, V[1,2]. — Optically Active δ‐Hydroxy‐γ‐lactones from Cyclooctyne and Furan — Synthesis of (—)‐(R,R)‐ and (+)‐(S,S)‐Muricatacin and Related Compounds

The γ‐lactone 1a, easily available from cyclooctyne and furan is converted to enantiomerically pure (—)‐(R,R)‐ and (+)‐(S,S)‐muricatacin (2e). Compound 2e was isolated recently as a biologically active (R,R/S,S) mixture from the seeds of Annona muricata. Optically active compounds were obtained by chromatographic separation of the diastereomeric camphanoates (4R)‐4a and (4S)‐4b and subsequent highly diastereoselective reduction with L‐Selectride≫ to give finally (4R,5R)‐ and (4S,5S)‐2c. The necessary side chain was introduced via Wittig reaction of the aldehyde 3c. Absolute configuration of all new products were established by X‐ray structural analysis of the δ‐lactone 7a and by comparison of (–)‐2f with its known dextrorotatory enantiomer as well. According to Mosher ester analysis of (—)‐2c and (—)‐2e the ee is ≥98%. The synthesis of rac‐muricatacin is also described. The scope of this new approach to functionalized dodecane (di)acid derivatives 3a–3c with (4R,5R) and (4S,5S) configuration is discussed.
Pheromone Synthesis, CXXXV. Synthesis of (4R,5R,6S,7E,9E)‐4,6,8‐Trimethyl‐7,9‐undecadien‐5‐ol and Its Antipode, the Female Specific Compound of the Woodroach Cryptocercus punctulatus
Authors: Mori Kenji , Itou Masamichi
Published: July 2007

(4R,5R,6S,7E,9E)‐4,6,8‐Trimethyl‐7,9‐undecadien‐5‐ol (1) and its antipode 1′, the female specific compound of the woodroach Cryptocercus punctulatus, were synthesized by starting from methyl (R)‐3‐hydroxy‐2‐methylpropanoate (C).
Steroids, L. Ring D Cleavage of D‐Trisubstituted Steroids
Authors: Vincze Irén , Somlai Csaba , Schneider Gyula
Published: July 2007

In alkaline medium, 17β‐hydroxy‐15‐(hydroxymethylene)androst‐5‐en‐16‐one (2a) is cleaved in two ways to give D‐seco compounds. Dilute bases in protic solvents cause 1,3‐dicarbonyl splitting to the 15‐formyl‐15,16‐seco‐16‐oic acid 3, while the use of sodium methanolate in benzene solution gives rise to 16,17‐splitting to afford the 15‐formyl‐16,17‐seco‐16,17‐dioic acid 5. Both seco compounds readily undergo lactolone ring closure to give 4a and 6a, respectively. The malonaldehyde moiety of 5 is transformed in two directions: either loss of the formyl group to give 3β‐hydroxy‐16,17‐secoandrost‐5‐ene‐16,17‐dioic acid (7a) or decarboxylation to 3β‐hydroxy‐16‐oxo‐16,17‐secoandrost‐5‐en‐17‐oic acid (9) is observed.
Photochemistry of the Phthalimide System, 44. Photoinduced Reactions, 122. Regioselective Remote Photocyclization: Examples of a Photochemical Macrocyclic Synthesis with Sulfide‐Containing Phthalimides
Authors: Hatanaka Yasumaru , Sato Yasuhiko , Nakai Hideo , Wada Masao , Mizoguchi Tomishige , Kanaoka Yuichi
Published: July 2007

S‐Substituted N‐(thioalkyl)phthalimides 2 underwent photocyclization to give azathiacyclols, up to 16‐membered ring compounds, in good yields. The cyclization occurred between an imide carbonyl group and a terminal sulfide group located in a remote position from the carbonyl group. The quantum yield of cyclization was determined as 0.042 (acetonitrile) for N‐(5‐methylthiopentyl)phthalimide (2a) and the efficiency of remote cyclization was not significantly affected by the chain length examined. Quenching studies of 2a using isoprene or 1,3‐cyclohexadiene showed linear Stern‐Volmer plots with the slopes of kqτ = 340 M−1 or 630 M−1, respectively. The effective concentration (Ceff) of photocyclization was estimated within the limits of 0.01 M < Ceff < 0.1 M for 2a from a competition experiment with the intermolecular photoaddition of dimethyl sulfide. The efficient cyclophilic nature of remote photocyclization can be rationalized by an enhanced proton transfer from the sulfide group which is possibly located close to the carbonyl group to form a radical ion pair complex by an electron transfer process.
Pheromone Synthesis, CXLV. Synthesis of the Enantiomers of Rhynchophorol [(E)‐6‐Methyl‐2‐hepten‐4‐ol], the Male‐Produced Aggregation Pheromone of the American Palm Weevil, Rhynchophorus palmarum
Authors: Mori Kenji , Ishigami Ken
Published: July 2007

Both the enantiomers of rhynchophorol [(E)‐6‐methyl‐2‐hepten‐4‐ol (1)], the male‐produced aggregation pheromone of the American palm weevil (Rhynchophorus palmarum), have been synthesized by reducing their precursors, (R)‐ and (S)‐6‐methyl‐2‐heptyn‐4‐ol (2), which have been prepared by lipasemediated asymmetric hydrolysis of the corresponding acetate and propionate.
Polycyclic Aromatic Alkaloids, 8. The Structure of Neocalliactine Acetate — Proof by Total Synthesis
Authors: Bracher Franz
Published: July 2007

The pentacyclic compound 1 is prepared in six steps by starting from 5,8‐quinolinedione (7). Its spectral data are in accordance with those of neocalliactine acetate, a derivative or the marine alkaloid calliactine. This represents the first definite confirmation of the structure of neocalliactine acetate.
[3 + 5]‐Anellierung mit Homophthalaldehyd: Schlüsselreaktion zur Gewinnung zentral wirksamer Tricyclen
Authors: Wünsch Bernhard , Zott Matthias , Höfner Georg
Published: July 2007

[3 + 5] Annulation with Homophthalaldehyde: Key Step in the Synthesis of Central Active Tricycles

[3 + 5] Annulation of the dinucleophile 11 with homophthalaldehyde (9) or homophthalaldehyde monoacetal 10 yielded regioselectively the β‐keto ester 12. The tricyclic ketone 4, obtained by saponification and decarboxylation of 12, was reductively aminated with dimethylamine/NaBH3CN to give the tricyclic amines 5a and 5b. The ketone 4 was transformed into the 1,2‐amino alcohol 17 by Neber rearrangement as the key step. Schmidt rearrangement of 4 followed by LiAlH4 reduction afforded the regioisomeric epoxybenzazonines 20a and 21a. In the mouse writhing test 21a and 5b exhibited strong analgesic effects with ED50 values in the range of those of pethidine and tramadol.
Ringöffnungen von 1,2‐Didehydroprolinen, I Darstellung von 4‐Hydroxyornithin und geschützten 4‐Amino‐3‐hydroxybutyronitrilen
Authors: Häusler Johannes
Published: July 2007

Ring‐Opening Reactions of 1,2‐Didehydroprolines, I. — Synthesis of 4‐Hydroxyornithine and Protected 4‐Amino‐3‐hydroxybutyronitriles

The cyclic azomethines 6a, b, d and f easily undergo ringopening reaction with hydroxylamine and its O‐alkyl derivatives leading to the oximino compounds 3a, b, d and f–i. Dissolved alkali metals in amines (Birch conditions) give satisfactory yields of reduction products with a stereochemistry depending on the substitution pattern in 3b, d, f–i. In case of 3d, the (2R,4R) stereoisomer 9b is the sole product, which can subsequently be cleaved to give 8b. Compounds 3g–i give predominantly the (2S,4R) product 8a. Acylation under alkaline conditions decarboxylates the oximino compounds 3b and d to the corresponding protected butyronitriles 14a–h. Trifluoroacetic anhydride transforms 3b into the nitrile 14i together with the cyclization product 15.
Thermochrome Furofurane, II. Synthese und Thermolyseverhalten substituierter Spirochinolether der Naphthalinreihe
Authors: Laatsch Hartmut , Ernst Bernd Peter
Published: July 2007

Thermochromic Furofuranes, II. — Synthesis and Thermolytic Behavior of Spiroquinole Ethers with Naphthalene Nucleus

To obtain further insight into the new photochromic system 2/3, various 3,4‐disubstituted spiroquinole ethers 7 have been synthesized by oxidation of 2‐alkyl‐4‐methoxy‐1‐naphtholes 5 via the corresponding quinone methides 6. Unlike 7a, the ethers 7b–d did not yield dimeric quinone methides or furofuranes (type 2/3) on heating, but decomposed by retro‐diene reaction yielding monomeric methides 6. The sterically hindered methides 6e, 6f are stable yellow compounds; 6c rearranged forming 12 which led to the naphthopyranes 11a/11b on further reaction with 6c.
Synthese von 1,2,4‐Triazinen, XV. Synthese von 1,2,4‐Triazin‐6(1H)‐onen
Authors: Neunhoeffer Hans , Klein‐Cullmann Birgit
Published: July 2007

Synthesis of 1,2,4‐Triazines, XV. — Synthesis of 1,2,4‐Triazin‐6(1H)‐ones

1,2,4‐Triazin‐6(1H)‐ones 3 have been prepared by cyclization of α‐ketoacyl chlorides 15 with amidrazones 14. 4,5‐Dihydro‐1,2,4‐triazin‐6(1H)‐ones 5 were obtained by cyclization of amino acid hydrazides 10 with orthocarboxylates 11.
Enzym‐katalysierte Reaktionen, 14. Stereoselektive Darstellung von Thiozuckern aus achiralen Vorstufen mittels Enzymen
Authors: Effenberger Franz , Straub Alexander , Null Volker
Published: July 2007

Enzyme‐Catalyzed Reactions, 14. — Stereoselective Synthesis of Thiosugars from Achiral Starting Compounds by Enzymes

A novel synthesis for thiosugars starting from achiral compounds by using enzymes as catalysts is described. 5‐Thio‐D‐threo‐2‐pentulofuranose (4), for example, is prepared either by the RAMA (rabbit muscle aldolase)‐catalyzed reaction of mercaptoacetaldehyde (1b) with dihydroxyacetonephosphate (2) or by the yeast transketolase‐catalyzed reaction of 2‐hydroxy‐3‐mercaptopanal (R/S)‐6 with lithium 3‐hydroxypyruvate (9). 6‐Thio‐D‐arabino‐2‐hexulopyranose (8a) and 6‐thio‐L‐xylo‐2‐hexulopyranose (8b) are obtained by the RAMA‐catalyzed reaction of racemic (R/S)‐6 with 2.
Bausteine von Oligosacchariden, CIV. Synthese von verzweigten Tetrasaccharid‐ und Pentasaccharid‐Strukturen von N‐Glycoproteinen, methyliert an 4′‐OH des Verzweigungsgliedes
Authors: Paulsen Hans , Wilkens Roland , Reck Folkert , Brockhausen Inka
Published: July 2007

Building Units of Oligosaccharides, CIV. — Synthesis of Branched Tetrasaccharide and Pentasaccharide Structures of N‐Glycoproteins Methylated at 4′‐OH of the Branching Unit

The tetrasaccharide α‐D‐Manp‐(1→3)[α‐D‐Manp‐(1→6)]‐4‐O‐methyl‐β‐D‐Manp‐(1→4)‐D‐GlcNAc (15) and the pentasaccharide β‐D‐GlcpNAc‐(1→2)‐α‐D‐Manp‐ (→3)[α‐D‐Manp‐(→6)]‐4‐O‐methyl‐β‐D‐Manp‐ (→4)‐D‐GlcNAc (23) were synthesized by adding the respective functionalized building blocks. The compounds are useful for studies of the substrate specificities of GlcNAc transferases I and II in the biosynthesis of N‐linked oligosaccharides, respectively. In addition we developed an effective synthesis for the β‐glycosidically linked building block β‐D‐Manp‐(→4)‐α‐D‐GlcpNAc. The trichloroacetimidate method was particularly successful for synthesizing these glycosidic linkages.
β‐Carbolin‐Alkaloide, I. Synthese von 1‐Aryl‐ und 1‐Alkenyl‐β‐carbolinen durch Palladium‐katalysierte Kupplungsreaktionen
Authors: Bracher Franz , Hildebrand Dirk
Published: July 2007

β‐Carboline Alkaloids, I. — Syntheses of 1‐Aryl‐ and 1‐Alkenyl‐β‐carbolines by Palladium‐Catalyzed Coupling Reactions

1‐Chloro‐β‐carboline (6) is prepared in three steps starting from tryptamine (3). Palladium‐catalyzed coupling reactions of 6 with aryl boronic acids offer an easy access to the alkaloids komaroine (11) and perlolyrine (15). Pavettine (16) is prepared by coupling of 6 with tributylvinylstannane.
Synthesis of 2′,5′‐Dideoxyuridine‐5′‐phosphonates
Authors: Aly Youssef L. , Abdel‐Megied Ahmed E.‐s. , Pedersen Erik B. , Nielsen Claus
Published: July 2007

Methyl 2,5‐dideoxy‐5‐iodo‐3‐O‐pivaloyl‐D‐erythro‐pentofur‐anoside (5) was synthesized from 2‐deoxy‐D‐ribose and treated with triethyl phosphite to give the phosphonate 6. Reaction of 6 with silylated 2,4‐dihydroxypyrimidine 7 in the presence of trimethylsilyl trifluoromethanesulfonate as catalyst afforded nucleoside phosphonates 8 and 9 which were deprotected with C2H5ONa in ethanol to give the diethyl 2′,5′‐dideoxyuridine‐5′‐phosphonate 10 and its α‐anomer 11. No activity was found for the nucleosides 8–11 against HIV or HSV‐1.
Total Synthesis of rac‐Sesquiterpenoid AE 1
Authors: Schinzer Dieter , Feßner Klaus , Ruppelt Martin
Published: July 2007

rac‐Sesquiterpenoid AE 1 (rac‐1) can be obtained in an 11‐step sequence starting from 5‐methylresorcinol (2). The key compound 9 is synthesized by the use of a diastereoselective dienone cyclization with the allylic silane 8. Subsequent transformation of 9 leads to rac‐1.
Formylimin versus Isocyanat — eine ungewöhnliche Tautomerie eines Trifluoralanin‐Derivates
Authors: Matthies Dieter , Siewers Stefan
Published: July 2007

Formylimine versus Isocyanate — an Unusual Tautomerism of a Trifluoroalanine Derivative

The intermediate 7a formed by hydrogen chloride elimination of 6 can easily tautomerize to the isolable isocyanate 7b. Depending on the reaction conditions nucleophiles react with 7a and 7b to give the corresponding products 8 or 9, respectively.
Synthese aromatisch anellierter ϵ‐Lactone
Authors: Meise Werner , Arth Christoph
Published: July 2007

Synthesis of Aromatic Annulated ϵ‐Lactones

The synthesis of three isomeric benzoxepinones 2, 7 and 8 by oxidation of the ω‐diols 1 and 6 with silver carbonate on Celite is reported.
Lipidic Peptides, IX. Synthesis and Structural Elucidation of Lipophilic Azidothymidine Conjugates
Authors: Hussain Rohanah , Toth Istvan , Gibbons William A.
Published: July 2007

Azidothymidine (AZT) esters of lipidic amino acid and oligomers, together with AZT‐5′‐lipidic sulphide were synthesised. The AZT conjugates with ester linkages (3a–e) were prepared by coupling the lipidic amino acids and their oligomers to the 5′‐hydroxyl terminus of AZT. The sulphide conjugate 5 was synthesised by treating AZT‐5′‐tosylate (4) with octadecanethiol. In order to examine the effect of different lipophilicities on the activity of the AZT molecule conjugates, the lipidic amino acid units were varied from 1 to 3 and the length of the alkyl chain from 9 to 17 carbon atoms.
Zur Synthese von β‐Alkyl‐α‐methylen‐γ‐butyrolactonen
Authors: Röder Erhard , Krauß Hiltrud
Published: July 2007

Synthesis of β‐Alkyl‐α‐methylene‐γ‐butyrolactones

The ylene 1 reacts with aldehydes to give 3‐alkylidenesuccinic acid monoethyl esters 2, which form β‐alkylidene‐γ‐butyrolactones 3 when treated with sodium diethyldihydroaluminate. Hydrogenation of the double bond leads to the β‐alkyl‐γ‐butyrolactones 4. The β‐alkyl‐α‐methylene‐γ‐butyrolactones 5 are obtained by Mannich reaction.
Stereokontrollierte Synthesen von Mannich‐Basen und γ‐Aminoalkoholen
Authors: Risch Nikolaus , Esser Achim
Published: July 2007

Stereocontrolled Syntheses of Mannich Bases and γ‐Amino Alcohols

The reaction of enantiomerically pure SMP enamines 2 with iminium tetrachloroaluminates 3 yields optically active Mannich bases 4. Diastereoselective reduction of 4 gives γ‐amino alcohols 5 with the desired configuration.
Electrophile Aminierung von C‐H‐aciden Verbindungen mit 1‐Oxa‐2‐azaspiro[2.5]octan
Authors: Andreae Siegfried , Schmitz Ernst , Wulf Jens‐Peter , Schulz Burkhard
Published: July 2007

Electrophilic Amination of C‐H‐Acidic Compounds with 1‐Oxa‐2‐azaspiro[2.5]octane

The reactions of 1‐oxa‐2‐azaspiro[2.5]octane (1, 3,3‐pentamethyleneoxaziridine) with malonic (e.g. 4, 35) and cyanoacetic acid derivatives (e.g. 11, 13 20) and other C‐H acids [e.g. barbituric acid (6), Meldrum's acid, (diphenylmethyleneamino)‐acetonitrile (26) 1‐benzyl‐3‐hydroxy‐4‐methyl‐1 H‐pyrazol‐5(4H)‐one, and phenylbutazone (33)] have been studied. After the introduction of a 1‐hydroxycyclohexylamino group at the acidic position, five different stabilisation reactions of the intermediate 2 could be classified. The most important one is an intramolecular nucleophilic attack to a nitrile group giving disubstituted 1,4‐diazaspiro[4.5]decanones 2a. Their ring transformations (e.g. 2a → 3) or the introduction of a second amino group at the same carbon atom (2a → 3a) are further new reactions. Geminal diamino acid derivatives 3a thus obtained can be stable or rearrange to 3 (R1  NH2) or eliminate cyclohexanone (formation of 42) and/or ammonia (formation of 41 or 43). Amination of N‐cyanoacetyl‐protected amino acid esters (20, NHR = amino acid unit) with 1 yields cyclic dipeptide derivatives 41.
Isolation and Structure Determination of new Iridals from Iris sibirica and Iris versicolor
Authors: Marner Franz‐Josef , Longerich Irmgard
Published: July 2007

Four novel iridals (compounds 8, 11, 12, and 13), representing new examples of these unusual monocyclic triterpenoids from sword lilies, have been isolated from rhizome extracts of I. sibirica and I. versicolor. Their structures have been elucidated by spectroscopic methods combined with oxidative degradation. Based on the stereochemistry of the 10‐deoxy‐17‐hydroxyiridal 13, the possible biosynthesis of these compounds is discussed.
Zur Umsetzung von N‐substituierten N′‐Chloramidinen mit Kalium‐S‐methyl‐N‐cyanimidodithiocarbonat — eine neue Thiadiazolsynthese
Authors: Sonnenschein Helmut , Walek Wolfgang , Schmitz Ernst , Reck Günter
Published: July 2007

Reaction of N‐Substituted N′‐Chlorobenzamidines with Potassium S‐Methyl N‐Cyanimidodithiocarbonate — a New Thiadiazole Synthesis

In contrast to a known procedure for the synthesis of 1,2,4‐thiadiazoles 3 from N‐unsubstituted N′‐chlorobenzamidines 1a and potassium S‐methyl cyanimidodithiocarbonate (2) the substituted amidines 1b–1e form thiadiazoles 5a–d containing both nitrogen atoms of amidines in the ring system.
Notiz zur Synthese des 3,7‐Dicyan‐1,5‐dimethylsemibullvalens
Authors: Hüsing Nicola , Rothe Wolfgang , Kiefer Wolfgang , Quast Helmut
Published: July 2007

Note of the Synthesis of 3,7‐Dicyano‐1,5‐dimethylsemibullvalene

The crystalline mixture of the tetrabromodinitriles 6 and 7, which is readily available in three steps from 1,5‐dimethylbicyclo[3.3.0]octane‐3,7‐dione, is reduced by the zinc‐copper couple in dry tetrahydrofuran in the presence of copper(I) chloride under ultrasonic radiation affording brominated semibullvalenes. Addition of water to the reaction mixture and resumption of the procedure eventually results in complete reduction producing the title compound 3a in good yield.
Oxidationen an Thiourethanen, 10. Synthese, Kristallstruktur, Oxidation und Photochemie der Thion‐S‐oxide cyclischer Dithiourethane und Dithiocarbazate
Authors: Hanefeld Wolfgang , Schlitzer Martin , Schütz Harald , Wocadlo Sigrid , Massa Werner
Published: July 2007

Oxidations of Thiourethanes, 10. — Synthesis, Crystal Structure, Oxidation and Photochemistry of Thione S‐Oxides of Cyclic Dithiourethanes and Dithiocarbazates

Several cyclic dithiocarbamates and dithiocarbazates (2–4) have been oxidised with mCPBA to give the corresponding thione S‐oxides 5–7. The sulfine structure was confirmed by oxidation to the corresponding oxo derivatives and X‐ray crystal structure analysis. Photolysis of the sulfines gave the corresponding oxo as well as the thioxo derivatives. The isolation of both the oxo and the thioxo derivatives is reported here for the first time, it provides an other evidence for the postulated thioxirane intermediate in the photolysis of sulfines.
Synthesen und Umsetzungen von 2,6‐Epoxy‐4H‐3‐benzoxocin‐4‐onen
Authors: Wünsch Bernhard , Bauschke Gerd
Published: July 2007

Syntheses and Transformations of 2,6‐Epoxy‐4H‐3‐benzoxocin‐4‐ones

Four variations for the preparation of 5 are described: acid‐catalyzed cyclisation of the methoxy acid 4a, base‐catalyzed lactonisation of the hydroxy ester 6b, DCC‐mediated dehydration of the hydroxy acid 6a and PCC oxidation of the hemiacetals 17a and 17b. By three steps the key intermediate 4a is prepared by addition of the lithium enolate of methyl acetate to the aldehyde 7 with subsequent cyclisation and saponification. Alternatively, addition of the acetic acid dianion to 7 followed by acidic work‐up yields 4a in a one‐pot procedure. Hydrolysis of 4a and 4b with dilute HCl gives the hemiacetals 6a and 6b, respectively. After deprotonation with LDA, 5b reacts with CH3I and aldehydes to afford the 5‐substituted epoxybenzoxocinones 18 and 20.
Asymmetric Synthesis via Heterocyclic Intermediates, XLVII. Asymmetric Synthesis of (+)‐(1R,2S)‐allo‐Coronamic Acid
Authors: Groth Ulrich , Halfbrodt Wolfgang , Schöllkopf Ulrich
Published: July 2007

allo‐Coronamic acid (1) was synthesized in five steps enantiomerically and diastereomerically virtually pure by starting from the bislactim ethers of cyclo(‐L‐Val‐Gly‐) (3a) or cyclo‐(‐L‐tert‐Leu‐Gly‐) (3b) in an overall yield of 31%. The key step of this synthesis is the intramolecular alkylation of the lithium azaenolate derived from the allylic chloride 4.
Totalsynthese von Thymosin β4, 2. Klassische Synthese des Fragments [20–30] von Thymosin β4
Authors: Kapurniotu Afroditi , Voelter Wolfgang
Published: July 2007

Total Synthesis of Thymosin β4, 2. — Conventional Synthesis of the Fragment [20–30] of Thymosin β4

As part of the total synthesis of thymosin β4 three synthetic pathways for the synthesis of the thymosin β4 fragment [20–30] are described. The side‐chain functions are protected by tert‐butyl and the α‐amino residues by Z groups. As temporary protection of the carboxyl function the phenyl ester is successfully used.
Syntheses of Some Biologically Active Compounds from Stilbenes Isolated from the Bark of Picea abies
Authors: Talvitie Antti , Mannila Erkki , Kolehmainen Erkki
Published: July 2007

From the four stilbenes 1–4 isolated from the bark of Picea abies seven compounds 5–11 were obtained by hydrogenation or permethylation. 1H‐, 13C‐NMR and mass spectra were used for their characterization. The antileukemic activity of each compound was preliminary tested. Some compounds were further tested for their anti‐HIV activity.
Thiazol‐ und Thiazolidin‐Derivate aus Benzoylthioharnstoffen
Authors: Wobig Dieter
Published: July 2007

Derivatives of Thiazoles and Thiazolidines from Benzoylthioureas

The thioureas 1a–c react with the derivatives of γ‐bromocrotonic acid 2a and 2b to give the thiazoles 3a–f. Contrary to this, the treatment of 1d or 1e with 4 or 2a and 2b leads to the thiazolidines 5a and 5b or 6a–d, respectively. 3g can be synthesized by the reaction of N‐benzimidoyl‐N′‐phenylthiourea (7) with 2a.
4,4′‐Bis(dimethylamino)benzophenon (Michlers Keton) — ein universeller Indikator zur Bestimmung der Acidität, Dipolarität und Polarisierbarkeit von Reaktionsmedien
Authors: Spange Stefan , Keutel Dietmar
Published: July 2007

4,4′‐Bis(dimethylamino)benzophenone (Michler's Ketone) — a Common Indicator of the Acidity and Dipolarity/Polarizability of Reaction Media

The solvatochromisms of Michler's Ketone (1) and the iron (II) complex Fe(phen)2(CN)2 (2) has been investigated in 73 solvents of different polarity. The solvent‐induced UV/Vis‐absorption shifts of 1 and 2 are mainly attributed to both the hydrogen‐bond donor acidity and dipolarity/polarizability of the solvent as verified by a Kamlet‐Taft correlation analysis and comparison with common solvent‐polarity scales such as Reichardt's ET(30) values and the acceptor scale of Gutmann. Michler's Ketone exhibits the largest positive solvatochromism known so far. The specific role of phenolic solvents has been discussed with regard to a charge‐transfer complexation between the positively polarized ring of 1, caused by the hydrogen‐bond formation at the carbonyl oxygen, and the aromatic ring of the phenol.
Biogenetic Studies on Oxazolomycin, a Metabolite of Streptomyces albus (Strain JA 3453)
Authors: Gräfe Udo , Kluge Heinz , Thiericke Ralf
Published: July 2007

Feeding experiments with sodium [13C]‐labelled acetate, sodium [1‐13C]propionate, L‐[methyl‐13C]methionine, L‐[1‐13C]‐alanine, and [1‐13C]glycine on Streptomyces albus (strain JA 3453) produced oxazolomycin (1), whose NMR analysis provided information about the biogenetic construction of its carbon skeleton. Both the (E,E)‐diene and the (Z,Z,E)‐triene chains are built up from acetate via the polyketide pathway each starting with a glycine‐derived building block. The use of glycine predicts an uncommon biosynthetic pathway leading to oxazole rings in actinomycetes. The spiro‐ring system in 1 is formed from acetate, glycine, and a C3 unit of unknown origin. The oxazolomycin producing organism combines carbon, oxygen, and nitrogen methylation activity via methionine (C1 pool) for the biosynthesis of 1.
Thermal Degradation of Glycosides, V. Hydrothermolysis of Triterpenoid and Steroid Glycosides
Authors: Kim Youn Chul , Higuchi Ryuichi , Komori Tetsuya
Published: July 2007

In this paper the hydrothermolysis of triterpenoid and steroid glycosides is described. By mere heating with water or water/1,4‐dioxane solution, the triterpenoid and steroid glycosides 1, 4 and 15, 16, 25, 29, respectively, are converted into their aglycones and prosapogenins. Furthermore, hydrothermolysis of the triterpenoid 3,28‐O‐bisglycosides 5, 6, 8, 9, 12 affords the corresponding 3‐O‐glycosides and reduced oligosaccharides formed by selective cleavage of the ester glycosidic linkage. It is expected that this hydrothermolysis is useful for the structure determination of some triterpenoid and steroid glycosides and for yielding new oligosaccharides. The hydrothermolyzed products have been isolated by chromatography and their structures elucidated by spectroscopic methods.
Versuche zur Synthese von Strychnopivotin und eine einfache Synthese des Isochinuclidin‐Gerüsts
Authors: Teuber Hans‐Joachim , Tsaklakidis Christos , Bats Jan Willem
Published: July 2007

Experiments Directed to the Synthesis of Strychnopivotine and a New Synthesis of the Isoquinuclidine Framework

The 2‐azabicyclo[3.3.1]nonane (keto‐morphane) 2 can be transformed via the enamine 4 into the dithio‐dioxolane derivative 6 of the corresponding 6,7‐diketone. After hydrolysis of the dithio group and formation of the monoprotected diketone 3 Fischer cyclisation yields the isodasycarpidone derivative 7, an intermediate to a synthesis of strychnopivotine (1a). — In view of the likewise desired tricyclus 8 for a synthesis of strychnopivotine, a cyclisation of ketoamide 9 was tried under standard conditions. By aldol‐ring closure, however, not the expected 2‐azabicyclo[3.3.1]nonane 14 was formed, but instead the 2‐azabicyclo[2.2.2]octane derivative (isoquinuclidine) 15. The preparation of 9 via the intermediates 10–13 is described.
Kondensierte 1.2‐Dithiole, I. Synthese von Thiolutin und verwandten Verbindungen
Authors: Stachel Hans‐Dietrich , Nienaber Juliane , Zoukas Thomas
Published: July 2007

Ring‐Fused 1,2‐Dithioles, I. — Synthesis of Thiolutine and Related Compounds

The 1,2‐dithiolopyrrole 1 (thiolutine) has been obtained on two different routes. Firstly, by synthesis of the dithiolopyrrole 6a and introduction of the acetamino function into compound 6d by nitration followed by ester saponification and decarboxylation. 6d is also available from 9k by oxidative ring contraction which occurs with simultaneous dealkylation of the benzylamino group. Secondly, by synthesis of the dithiinopyrrole 15b and introduction of the acetamino function into compound 15g by Beckmann rearrangement followed by ring contraction.
Bausteine von Oligosacchariden, CI. Synthese von modifizierten Oligosacchariden der N‐Glycoproteine zur Untersuchung der Substratspezifität der N‐Acetylglucosaminyltransferase II des Trimming‐Prozesses
Authors: Paulsen Hans , van Dorst Johannes A. L. M. , Reck Folkert , Meinjohanns Ernst
Published: July 2007

Building Units of Oligosaccharides, CI. — Synthesis of Modified Oligosaccharides of the N‐Glycoproteins Intended for Substrate Specificity Studies of N‐Acetylglucosaminyltransferase II of the Trimming Process

The trichloroacetimidate method was very successful for the synthesis of the tetrasaccharide octyl O‐(2‐acetamido‐2‐deoxy‐β‐D‐glucopyranosyl)‐(1→2)‐O‐(α‐D‐mannopyranosyl)‐(1→3)‐O‐[(α‐D‐mannopyranosyl)‐(1→6)]‐β‐D‐mannopyranoside (10). Further derivatives of the tetrasaccharide with a 4‐O‐methyl group 20 and with a 4‐deoxy group 28 were synthesized. The tetrasaccharides are intended for substrate specificity studies of the N‐acetylglucosaminyltransferase II of the trimming process in the biosynthesis of N‐glycoproteins.
Glycosylimidates, 54. Synthesis of the GlcNAcβ(1→4)MurNAcβ(1→4)GlcNAcβ(1→4)MurNAc tetrasaccharide of bacterial peptidoglycan
Authors: Termin Andreas , Schmidt Richard R.
Published: July 2007

From 2‐azido‐2‐deoxy‐D‐glucose have been prepared at 1‐O and/or 4‐O selectively protected glucosamine and muramic acid derivatives, which were transformed into glycosyl donors 6 and 14a, b and into glycosyl acceptors 7 and 15. The reaction of these donors and acceptors yielded disaccharides 8 and 11–13. Selective 1a‐O‐deprotection of disaccharide 12 and subsequent treatment with trichloroacetonitrile afforded disaccharide donor 17; selective removal of the 4b‐O‐protective groups in disaccharides 8 and 11 furnished disaccharide acceptor 9. These building blocks were employed in the synthesis of β‐connected tetrasaccharide 18 which gave upon azido group reduction, acetylation of the amino groups, and complete O‐deprotection the desired target molecule 1 characterized as its fully O‐acetylated product 2.
Regioselective Conversion of Nonactivated CH Bonds, VI. Selective ω‐ to (ω – 2)‐Chlorination of Fatty Acids by Way of Adsorption on Alumina
Authors: Hinkamp Ludger , Schäfer Hans J. , Wippich Barbara , Luftmann Heinrich
Published: July 2007

Fatty acids 4–7 can be chlorinated with high selectivity in the (ω — 2)‐ to ω‐position. For that purpose the acid is adsorbed on alumina and allowed to react with gaseous chlorine or t‐BuOCl at 20 and −35°C. The resulting chloroalkanoic acids 10–13 can be converted into macrocyclic lactones 14–17 by treatment with DBU.
Photodynamic Perylenequinones, Photodemethylation and Photooxidation of Dimethylcercosporin
Authors: Arnone Alberto , Luogo Daniela Dal Pio , Merlini Lucio , Nasini Gianluca
Published: July 2007

Regiospecific photodemethylation of the perylenequinone dimethylcercosporin (DMC0 (2) in methanol involved the two methoxy groups in ortho position to the carbonyl quinone functions, affording 2,11‐dihydroxy‐3,10‐perylenequinone (3) and the dihydrofuran‐containing derivative 4. When irradiated in acetonitrile in the presence of oxygen 2 was converted into two photooxidation products 5 and 7 whose structure was assigned on the basis of 13C‐NMR studies.
Derivate natürlicher Tetrapyrrole für die Photodynamische Therapie, 2 Modellreaktionen zur direkten CC‐Verknüpfung von Porphyrinen
Authors: Risch Nikolaus , Mackenbrock Ursula
Published: July 2007

Natural Tetrapyrrol Derivatives for the Photodynamic Therapy, 2. — Model Reactions for Direct C–C Linkages of Porphyrins

Until now, there is a lack of information about the structure of the active components in the diagnosis and photodynamic therapy of cancer with hematoporphyrin derivatives (HPD). We describe the formation of HPD in terms of benzyl cation chemistry. Selective formation of the C—C‐linked model compounds 4, 5 by reaction of protoporphyrin dimethyl ester (2) with electron‐rich aromatic compounds as well as of 9—12, 15–17, obtained by reaction of the porphyrin dimethyl esters 2, 6, 7, and 8, with carbon electrophiles (preformed Mannich salts), results from this concept.
Enoletherepoxide und ihre Reaktionsprodukte mit Nucleophilen
Authors: Meyer Claudia , Spiteller Gerhard
Published: July 2007

Enol Ether Epoxides and Products Resulting from Their Reaction with Nucleophiles

1,2‐Epoxydecyl pentyl ether (9a) was synthesized by treatment of 1‐decenyl pentyl ether (5) with diemthyldioxirane (8). The enol ether epoxide 9a, characterized by its mass, 1H‐ and 13C‐NMR spectra, reacts readily with hydride, O‐, S‐ and N‐nucleophiles. Similar reactions are expected to take place in the organism after biological oxidation of plasmalogens to their epoxides. This hypothesis is verified by detection of mixed acetals after tissue workup.
Thioalkylation of enolates, II. – α‐Thioalkylation of Zinc Enolates to α,α‐Disubstituted Ketones
Authors: Groth Ulrich , Huhn Thomas , Richter Norbert
Published: July 2007

An α‐alkylation of the 2‐methylcycloalkanones 1 and 4 at the higher substituted carbon can be achieved by thioalkylation of the corresponding zinc enolates with the α‐chlorosulfides 3. The desulfurization can be carried out with either Raney nickel or lithium in diethylamine for compounds which contain double or triple bonds.
Steroidal cyclobutanones, III. The Synthesis and Stereochemistry of 3‐Spiro‐5α‐cholestane Derivatives with Three‐, Four‐, and Five‐membered Carbon Rings—A Double Cine Substitution in Spiro‐α,α‐dichlorocyclobutan‐3‐ones
Authors: Paryzek Zdzislaw , Błaszczyk Krzysztof
Published: July 2007

Diastereomeric [(3S)‐5α]‐ and [(3R)‐5α]‐2′,2′‐dichlorospiro‐[cholestane‐3,1′‐cyclobutan]‐3′‐ones (1 and 2), prepared by cycloaddition reaction of dichloroketene with 3‐methylene‐5α‐cholestane, served as starting material for the synthesis of the related spirane derivatives. Thus, the synthesis of spiro‐cyclopentane (3–6), spirocyclobutane (9, 11, 13, 17–20) and spirocyclopropane steroids (12, 14, 15) is described. The sterically dependent reaction of spiro‐α,α‐dichlorocyclobutan‐3‐ones with an excess of sodium methanolate in methanol is reported. Thus, the reaction of 1 with sodium methanolate gives 9, the product of the double cine substitution, while the corresponding reaction of compound 2, which is sterically more hindered for similar nucleophilic attack, gives mainly the spirocyclopropane 12. The stereochemistry of the spiro compounds is assigned on the basis of 1H‐ and 13C‐NMR spectra.
Synthesis of (3R,4R)‐3‐Amino‐4‐hydroxyhexahydroazepine, the Chiral Constituent of the Antibiotic Ophiocordin
Authors: Müller Alexander , Takyar Dinesh K. , Witt Sandra , König Wilfried A.
Published: July 2007

(3R,4R)‐3‐Amino‐4‐hydroxyhexahydroazepine (2), the optically active constituent of the antifungal antibiotic ophiocordin (1), was prepared in a multistep synthesis starting from D‐serine. The absolute configuration was unambigously assigned by a comparison of the synthesized stereoisomer 2 with its racemate and the chiral moiety of the antibiotic ophiocordin by enantioselective gas chromatography.
Chemical Interactions between Aminopyrazoles and 2,3‐Dicyano‐1,4‐naphthoquinone
Authors: Hassan Alaa A. , Mohamed Nasr K. , Ibrahim Yusria R. , Mourad Aboul‐Fetouh E.
Published: July 2007

2,3‐Dicyano‐1,4‐naphthoquinone (DCNQ), the easily obtainable isomer of 2‐(dicyanomethylene)indane‐1,3‐dione (CNIND), reacts with arylazo‐, pyridylazo‐ and arylaminopyrazoles 1–3 via charge‐transfer (CT) complexation to yield pyrazolo[2,3‐α]quinazolinediones 10a–f and pyrazolo[2,3‐α]‐quinazolinyl acetates 11a–e. Furthermore, aminopyrazole 3 reacts with 2,3‐dichloronaphthoquinone (DCHNQ) to afford the naphthoquinoimidazopyrazole 13. The mechanism of the formation of products 10 and 11 is discussed.
Synthese des Azocino[4.3‐b]indol‐Grundgerüstes von Strychnos‐Alkaloiden
Authors: Fritz Helmut , Soleymani‐Jamarani Mohammad , Bats Jan Willem , Teuber Hans‐Joachim
Published: July 2007

Synthesis of the Azocino[4.3‐b]indole Core Structure of Strychnos Alkaloids

Michael addition of ethylmalonic dimethyl or diethyl ester with cyclohexenone and subsequent Fischer indole ring closure afford the (tetrahydrocarbazolyl)malonic esters 4a–c. Decarboxylation of 4a leads to the corresponding butyric acid methyl ester 5 which is oxidized by DDQ to the 4‐oxo derivative 6a (byproduct: carbazole 7). Oximation of 6a to 8a and acylation of the oxime group to 8b, c as well as hydrogenation of this group yield 9a, b. Subsequent hydrogenation of the tetrahydrocarbazole ring by means of borane/pyridine yields the hexahydrocarbazole derivatives 10a and b. By cyclisation in boiling o‐xylene (sodium hydride catalysis) 10a is converted into the tetracyclic 1,5‐methanoazocino[4.3‐b]indole derivative 11a with an alkaloid analogous ethyl side chain. The X‐ray structural analysis of the corresponding phenylsulfonyl derivative 11b confirms constitution and stereochemistry. As a diastereoisomer of 11a the byproduct 11c could be isolated.
Asymmetric Synthesis via Heterocyclic Intermediates, LII. Synthesis of tert‐Leucine and Related Amino Acids
Authors: Groth Ulrich , Huhn Thomas , Porsch Bettina , Schmeck Carsten , Schöllkopf Ulrich
Published: July 2007

The 2,5‐dialkoxypyrazines 3a and b were prepared in three steps from methyl glycinate hydrochloride (1) in an overall yield of 18 and 63%. Upon the addition of lithium organyls to 3b and subsequent acidic hydrolysis the ethyl glycinates rac‐7 were obtained.
Pseudosugars, 32. – Synthesis of 1,4‐Imino‐linked Carbadisaccharides Composed of a 2‐Amino‐5a‐carba‐2‐deoxyglucopyranosylamine Residue and Its Congeners
Authors: Ogawa Seiichiro , Tsunoda Hidetoshi
Published: July 2007

Carbadisaccharide 5, containing a 2‐acetamido‐5a‐carba‐2‐deoxyhexopyranosylamine residue, was synthesized by coupling of methyl 4‐amino‐4‐deoxy‐α‐D‐glucopyranoside (41) with the N‐(2,4‐dinitrophenyl)epimino compound 16 followed by deprotection. The 6′‐acetamido‐6′‐deoxy analog 3 of a potent α‐glucosidase inhibitor methyl acarviosin (1) was synthesized from a condensate 50 obtained by coupling of 41 with the protected epimino compound 18, possessing an exo‐methylene function. This process involves a sequence of reactions: replacement by a benzoate ion and successive dehydrobromination of the dibromide 52 obtained from 50. Hydroxymercuration of 50 followed by demetalation and deprotection gave two carbadisaccharide analogs 7 and 9 containing the valiolamine‐type branched aminocyclitol moieties. The free amines 4, 6, 8, and 10 were prepared by treatment of the corresponding N‐protected derivatives with Amberlite IRA 400 (OH−) resin. Biological assays of all carbadisaccharides were carried out with three sugar hydrolases. Only compounds 6 and 8 were shown to be very weak α‐mannosidase inhibitors. The introduction of the acetamido or amino function instead of the hydroxyl group into the C‐6′ position of the methyl acarviosin analog 2 resulted in an appreciable decrease of the inhibitory activity.
Enzymes in Organic Synthesis, 18. Lipase‐catalyzed Asymmetric Alcoholysis of 3‐Substituted Pentanedioic Anhydrides
Authors: Ozegowski Rüdiger , Kunath Annamarie , Schick Hans
Published: July 2007

The influence of several enzymes, alcohols, and solvents on the stereochemical outcome of the asymmetric alcoholysis of 3‐substituted pentanedioic anhydrides was investigated. The alcoholysis of 3‐acetoxypentanedioic anhydride (5a) in diethyl ether with 2‐methylpropanol afforded the (3S)‐monoester (S)‐6a with an enantiomeric excess of > 98% when the lipase from Candida sp. 382 was used as the enzyme. Under the same conditions, 3‐methoxypentanedioic anhydride (5c) was converted by the lipase of Pseudomonas cepacia (Amano PS) into the (3R)‐monoester (R)‐6c with an e.e. of 90%.
Facile and General Synthesis of 2‐, 3‐, or 4‐[(Dialkylamino)alkyl]pyridines and ‐piperidines
Authors: Cohen Victor I. , Jin Biyun , Reba Richard C.
Published: July 2007

Reaction of (dialkylamino)alkyl chloride with picolyllithiums provides the corresponding pyridine derivatives from which the piperidines are obtained by catalytic hydrogenation.
Simple and Condensed β‐Lactams, XVII. Monobactams Acylated with Isoxazoleacetic and Isoxazolecarboxylic Acids
Authors: Nagy József , Nyitrai József , Kajtár‐Peredy Mária
Published: July 2007

Analogues of aztreonam (1a) and carumonam (1b) were prepared by acylation of 3‐aminomonobactamic acid derivatives with several new and known isoxazoleacetic and isoxazolecarboxylic acid derivatives 3–10. None of the resulting new monobactams 11–18, 41a, 41b, and 54a exhibited any significant antibacterial activity.
Glycosyl Imidates, 61. – Synthesis of the Hexasaccharide Moiety of the Saponin Holotoxin A
Authors: Han Xiao‐Bing , Jiang Zi‐Hua , Schmidt Richard R.
Published: July 2007

Reaction of O‐(3‐O‐methylglucosyl) trichloroacetimidate 2a as glycosyl donor and 1,2:5,6‐di‐O‐isopropylidene‐D‐glucofuranose (3) as glycosyl acceptor furnished in the presence of TMSOTf as catalyst the β‐(1→3)‐connected disaccharide 5a. Similarly, from O‐quinovosyl trichloroacetimidate 2b and 3 the disaccharide 5b was obtained. Compound 5a was transformed via acid‐catalyzed O‐deisopropylidenation, O‐acetylation, and selective 1‐O‐deacetylation into 7. Treatment of 7 with trichloroacetonitrile in the presence of DBU furnished trichloroacetimidate 8 as glycosyl donor. Reaction of 8 with 2,4‐O‐unprotected xylopyranoside 9 as glycosyl acceptor afforded selectively trisaccharide 10. Similarly, reaction of 8 with 2,4‐O‐unprotected quinovoside 12 furnished selectively trisaccharide 13 which gave upon O‐acetylation, 1‐O‐desilylation, and then treatment with trichloroacetonitrile in the presence of DBU trichloroacetimidate 15 as triosyl donor. Reaction of 10 with 15 in the presence of TMSOTf as catalyst led to hexasaccharide 16; ensuing hydrogenolytic O‐debenzylation and then O‐acetylation afforded the desired hexasaccharide 17.
Glycosyl Imidates, 62. – Synthesis of the Heptasaccharide Moiety of Ganglioside BGM1
Authors: Greilich Ulrike , Zimmermann Peter , Jung Karl‐Heinz , Schmidt Richard R.
Published: July 2007

The synthesis of the O‐acetyl protected heptasaccharide moiety (2) of BGM1 was performed according to the following reaction sequence: Reaction of 2,3‐di‐O‐acetyl‐4,6‐O‐benzylidenegalactosyl trichloroacetimidate 4 (as donor) with 3‐O‐unprotected 2‐azidogalactose 5 (as acceptor) gave β(1→3)‐connected disaccharide 6. Subsequent O‐deacetylation followed by reaction with galactosyl donor 8 afforded regioselectively trisaccharide 9 which was converted into tetrasaccharide 12 by treatment with fucosyl donor 11. Transformation of 12 via acid‐catalyzed O‐deisopropylidenation, O‐acetylation, anomeric O‐desilylation, and then base‐catalyzed treatment with trichloroacetonitrile afforded trichloroacetimidate 16 as tetraosyl donor. Reaction of 16 with the known 4b‐O‐unprotected sialyllactose derivative 17 gave in acetonitrile at −40°C in the presence of TMSOTf as the catalyst the desired heptasaccharide 18. Azido group reduction with propanedithiol, N‐acetylation, hydrogenolytic O‐debenzylation, and O‐debenzylidenation under acidic conditions followed by O‐acetylation afforded the target molecule 2. The structural assignments were based on the 1H‐NMR data.
Pheromone Synthesis, CLIV. Synthesis of the Stereoisomers of 3‐Methyl‐4‐octanol to Determine the Absolute Configuration of the Naturally Occurring (3S,4S)‐Isomer Isolated as the Male‐produced Aggregation Pheromone of the African Palm Weevil, Rhynchophorus phoenicis
Authors: Mori Kenji , Kiyota Hiromasa , Rochat Didier
Published: July 2007

The relative configuration of the naturally occurring 3‐methyl‐4‐octanol (1), the male‐produced aggregation pheromone of Rhynchophorus phoenicis, was determined as syn by a GC comparison of the synthetic (±)‐syn‐ and (±)‐anti‐1 with the natural product. Enantioselective synthesis of both (3R,4R)‐and (3S,4S)‐1 was achieved by starting from the optically active epoxide 9, and the natural product was shown to be (3S,4S)‐1 by a GC comparison on a chiral stationary phase.
Pheromone synthesis, CXLVII. – Synthesis of (1R,3S,6R,9S,10S)‐9,10‐Epoxytetrahydroedulan, the Main Component of the Hairpencil Secretion of Male Danaid Butterfly Euploea klugii
Authors: Mori Kenji , Aki Shinji , Kido Masaru
Published: July 2007

The natural and (+)‐enantiomer of 9,10‐epoxytetrahydroedulan 1, (1R,3S,6R,9S,10S)‐9,10‐epoxy‐1,3,7,7‐tetramethyl‐2‐oxabicyclo[4.4.0]decane, the main component of the hairpencil secretion of Euploea klugii, was synthesized via (−)‐dihydroedulan II (2) by starting from (S)‐2,4,4‐trimethyl‐2‐cyclohexen‐1‐ol (D).