bluuebunny/crossref_metadata_2025 huggingface dataset:
Azomethine ylides from the reaction of 4‐(dicyanomethylene)‐3‐methyl‐1‐phenyl‐2‐pyrazoline‐5‐one with α‐amino acids and their esters
Authors: Metwally Saoud A. M. , Aly Moustafa F. , Abd‐Alla Mohamed A. , Atta Ferial M. , Abd‐El‐Monem Maisa E.
Published: July 2007

4‐(Dicyanomethylene)‐3‐methyl‐1‐phenyl‐2‐pyrazoline‐5‐one (1) readily reacts with α‐amino acids and their esters by Michael addition and subsequent elimination of HCN to the adducts 2a–k. One of these, 2i (obtained from methyl glycinate), adds stereoselectively to N‐phenylmaleimide with loss of the remaining cyano group. It is believed that the endo‐transition state of lower energy leads to the major cycloadduct 5, whereas the exo‐transition state gives 6 as the minor one.
Base‐catalyzed rearrangement of marginalin into a 2‐phenylbenzo[b]furan
Authors: Barbier Michel
Published: July 2007

Marginalin [(E)‐1 or (Z)‐2] is rearranged by bases to the strongly fluorescent 5‐hydroxy‐2‐(4′‐hydroxyphenyl)‐3‐benzo[b]furancarboxylic acid (3) or to methyl 5‐hydroxy‐2‐(4′‐hydroxyphenyl)‐7‐methoxy‐3‐benzo[b]furancarboxylate (4).
Ein effektiver Weg zu GABA‐analogen Aminosäuren: Cyclopropanierung vonN‐silylierten Allylaminen und Enaminen
Authors: Paulini Klaus , Reißig Hans‐Ulrich
Published: July 2007

An Efficient Route to GABA‐Analogous Amino Acids: Cyclopropanation ofN‐Silylated Allylamines and Enamines

N‐Silylated allylamines1are effectively transformed into methyl cyclopropanecarboxylates2by methyl diazoacetate under Rh2(OAc)4catalysis. Derivatives2aand2bare smoothly converted intotrans‐substituted amino acids6aand6b, respectively, and to bicyclic γ‐lactams5aand5b. The pharmacologically interesting γ‐aminobutyric acid (GABA) analoguetrans‐6ais now available in few steps. Photochemical and thermal Fe(CO)5‐induced hydrogen shift converts allylamine derivatives1intoN‐silylated enamines7. While enamine (E)‐7acan be cyclopropanated with methyl diazoacetate under Cu(acac)2catalysis to afford the desired cyclopropane derivatives8ain good yield, the other enamines are rather unreactive towards the carbenoid. Use of an optically active catalyst provides8awith an ee of 56% (cis) and 20% (trans). Acid‐induced ring cleavage of8agives the β‐formyl ester10a, and reduction of8afollowed by desilylation provides the aminocyclopropane14in good overall yield, thus demonstrating that cyclopropanes like8acan serve as useful synthetic intermediates.
Amphiphilic carbohydrate‐based mesogens, VII. Synthesis of mesogenic 4‐ and 6‐O‐alkyl‐D‐glucitols
Authors: Dahlhoff Wilhelm V.
Published: July 2007

Both the hemiacetal and acetal groups of 4,6‐O‐alkylidene‐α/β‐D‐glucopyranoses (hexylidene–decylidene, 1a–e) are quantitatively reduced by ethyldiboranes(6) in the presence of 9‐methylsulfonyloxy‐9‐borabicyclo[3.3.1]nonane (MSBBN) after conversion to their 1,2,3‐tri‐O‐diethylboryl derivatives 2a–e. Subsequent deboronations give ca. 1:1 mixtures of 4‐O‐alkyl‐D‐glucitols 3a–e and 6‐O‐alkyl‐D‐glucitols 4a–e, which are separated to give mesogenic 3 and 4. Both 3 and 4 exhibit smectic A liquid crystalline phases.
Addition von Dialkylphosphiten und Dialkyl(trimethylsilyl)phosphiten an 2‐(Benzyloxy)propanal Darstellung aller vier stereoisomeren (1,2‐Dihydroxy‐[1‐2H1]propyl)phosphonsäuren aus chiralen Lactaten
Authors: Hammerschmidt Friedrich
Published: July 2007

Addition of Dialkyl Phosphites and Dialkyl Trimethylsilyl Phosphites to 2‐(Benzyloxy)propanal – Preparation of all Four Stereoisomeric (1,2‐Dihydroxy‐[1‐2H1]propyl)phosphonic Acids from Chiral Lactates

Dimethyl trimethylsilyl phosphite, diisopropyl trimethylsilyl phosphite, dimethyl phosphite, and diisopropyl phosphite were added to 2‐(benzyloxy)propanals 4 and 6 at different temperatures in THF and CH2Cl2. The ratio of diastereomers formed was highest for diisopropyl trimethylsilyl phosphite (erythro/threo 3:1) and dropped to about 1:1 for diisopropyl phosphite. Starting from chiral lactates all four stereoisomeric diisopropyl (2‐benzyloxy‐1‐hydroxy‐[1‐2H1]phosphonates were prepared and deprotected. The (1,2‐dihydroxy‐[1‐2H1]propyl)phosphonic acids formed were purified as cyclohexylammonium salts. The relative configuration of phosphonic acid of (−)‐11 was determined by comparison with the salt (1R,2R)‐12 derived from fosfomycin.
Efficient EPC synthesis of β‐aminobutanoic acid
Authors: Gmeiner Peter
Published: July 2007

A practical approach to enantiomerically pure (R) ‐3‐amino‐butanoic acid (6) from L‐asparagine (1) is presented. The key step of the synthesis is the chemoselective reduction of the β‐homoserine derivative 2.
Syntheses with Nitriles, IXC. Preparation, Structure, and Color of 4‐[(Cyano)indolylmethylene]‐ and 4‐[(Cyano)pyrrolylmethylene]‐1H‐pyrazol‐5(4H)‐ones
Authors: Dworczak Renate , Fabian Walter M. F. , Sterk Heinz , Kratky Christoph , Junek Hans
Published: July 2007

(Dicyanomethylene)pyrazolones 1a, b are treated with some indoles and pyrroles. The resulting disubstituted malono‐nitriles 2a–f, 4a–e, 6 yield cyanomethylene compounds 3a–f, 5a–e, 7 by irreversible thermal or photochemical decomposition. The compounds exist in different isomeric forms. Structures are proven by NMR spectroscopy and X‐ray analysis. UV‐Vis data are discussed by means of AM1 and INDO/S‐CI calculations.
Chirale 2‐Benzopyran‐3‐carbonsäure‐Derivate durch Oxa‐Pictet‐Spengler‐Reaktion von (S)‐3‐Phenylmilchsäure‐Derivaten
Authors: Wünsch Bernhard , Zott Matthias
Published: July 2007

Chiral 2‐Benzopyran‐3‐carboxylates by Oxa‐Pictet‐Spengler Reaction of (S)‐3‐Phenyllactic Acid Derivatives

Starting with (S)‐tyrosine, the methyl (S)‐3‐(3,4‐dihydroxy‐phenyl)lactate (15b) was prepared by acylation, desamination and Dakin oxidation. The phenyl moiety of 15b was sufficiently activated for the reaction with aromatic and aliphatic aldehydes and ketones to yield the alkyl (3S)‐2‐benzopyran‐3‐carboxylates 16 and 19. On the other hand, the oxa‐Pictet‐Spengler reaction of the aryl unsubstituted (S)‐3‐phenyllactic acid (6) succeeds only with aromatic aldehydes. It was shown that the enantiomeric purity of the compounds 13, 14, 15, 16 and 19 was greater than 96% ee.
Thermal Degradation of Glycosides, VI. Hydrothermolysis of Cardenolide and Flavonoid Glycosides
Authors: Kim Youn Chul , Higuchi Ryuichi , Komori Tetsuya
Published: July 2007

The hydrothermolysis of cardenolide and flavonoid glycosides is described. On heating with water or water/dioxane, cardenolide (1, 5, 11) and flavonoid glycosides (16, 20, 23, 27) are converted into their genuine aglycones and partially hydrolyzed products, together with saccharide components. Meanwhile, the glycosidic linkage of 2‐deoxy sugar moieties in cardenolide glycosides is more readily cleaved than that of the common sugar moieties by means of hydrothermolysis. Therefore, hydrothermolysis of the uzarigenin triglycoside (13), bearing a 2‐deoxy sugar moiety which is directly attached to the aglycone, leads to selective cleavage of the sugar—aglycone linkage. The hydrothermolyzed products have been isolated by chromatography and their structures elucidated by spectroscopic methods.
Chiral Organometallic Reagents, VI. Diastereomeric α‐Phenylseleno Alkyllithium Compounds, Generation and Reactions
Authors: Hoffmann Reinhard W. , Bewersdorf Martin
Published: July 2007

The selenoacetals 4 having a chiral center in the β‐position were subjected to selenium/lithium exchange by butyllithium in ether. The resulting α‐phenylseleno alkyllithium compounds 5 undergo rapid epimerization at −78°C. Trapping of these organolithium compounds by ketones or aldehydes appears to be faster than the epimerization. The ratio of the trapping products therefore reflects the equilibrium ratio of the diastereomeric α‐phenylseleno alkyllithium compounds. The dependence of this equilibrium on various structural parameters has been evaluated.
Mitrariosides, Five Bitter Labdane Glycosides from Mitraria coccinea (Gesneriaceae)
Authors: Cárdenas Luz Clarena , Rodríguez Jaime , Riguera Ricardo , Chamy Maria Cristina
Published: July 2007

From Mitraria coccinea Cav. (Gesneriaceae), five strongly bitter labdane glycosides named mitrariosides A1, A2, B, C and D (1 — 5) were obtained. The structures were deduced by chemical and spectroscopic evidence (COSY, 13C‐1H CORR, NOESY and MS‐FAB) and found to be: mitrarioside A1 (1): (6S)‐19‐(β‐D‐galactopyranosyloxy)‐6‐hydroxy‐15‐(α‐Lrhamno‐pyranosyloxy)labda‐8(17),13‐diene, mitrarioside A2 (2): (6S)‐19‐(β‐D‐glucopyranosyloxy)‐6‐hydroxy‐15‐(α‐L‐rhamnopyranosyloxy)labda‐8(17),13‐diene, mitrarioside B (3):(6S)‐19‐(β‐D‐glucopyranosyloxy)‐6‐hydroxy‐15‐(β‐D‐glucopyranosyloxy)‐labda‐8(17),13‐diene, mitrarioside C (4): (6S)‐19‐(β‐D‐glucopyranosyloxy)‐6,15‐dihydroxylabda‐8(17), 13‐diene, and mitrarioside D (5): (6S)‐19‐(α‐L‐rhamnopyranosyloxy)‐6,15‐dihydroxy‐labda‐8(17),13‐diene. The known compounds acteoside and calceolarioside C were also isolated.
Properties and Reactions of Substituted 1,2‐Thiazetidine 1,1‐Dioxides: 4‐Alkylidene‐β‐sultams
Authors: Müller Martin , Otto Hans‐Hartwig
Published: July 2007

4‐α‐Hydroxyalkylated β‐sultams 1/5 are transformed into 4‐alkylidene‐β‐sultams 4/7 by elimination and desilylation reactions. Another route to an exocyclic double bond in the β‐sultam system has been found to be the Peterson olefination starting from 4 silylated β‐sultams 8, 10, and 11. The elimination‐reaction sequence yields stereochemically defined products with either E or Z configuration but by use of the Peterson reaction we have always obtained mixtures of diastereomers, which have to be separated. The stereochemistry of all products is elucidated by spectroscopic methods.
Photochemische Studien, 63. Photostabilität einiger 1,4‐Benzodiazepine in kristallinem Zustand
Authors: Reisch Johannes , Ekiz‐Gücer Nurten , Tewes Gregor
Published: July 2007

Photochemical Studies, 63. — Photostability of Some 1,4‐Benzodiazepines in the Crystalline State.

UV irradiation of chlorodiazepoxide (1) and its hydrochloride led to three photoproducts: 2‐<[(3‐chlorophenyl)phenylmethylene]amino>‐N‐methylacetamide (2), 1‐benzoyl‐7‐chloro‐1,2‐dihydro‐3‐methylaminoquinoxaline (3) and 7‐chloro‐3,4‐dihydro‐2‐methylamino‐4‐phenyl‐5H‐1,4‐benzodiazepine‐5‐one (4). The photochemical degradation of 1, 1‐hydrochloride, diazepam and nitrazepam in the crystalline state have been investigated and determined densitometrically.
5‐(4‐Pyridyl)‐1,3‐dioxan‐4,6‐dione — Darstellung und Reaktionen mit O‐, N‐ und C‐Nucleophilen
Authors: Henning Hans‐Georg , Stemplinger Gunter , Rothe Kathrin
Published: July 2007

5‐(4‐Pyridyl)‐1,3‐dioxan‐4,6‐diones — Preparation and Reactions with O‐, N‐ and C‐Nucleophiles

The reaction between alkyl chloroformates, pyridine and 1,3‐dioxane‐4,6‐diones yields 5‐[1‐alkoxycarbonyl‐4(1H)‐pyridylidene]‐1,3‐dioxane‐4,6‐diones 3 via the dihydro intermediates 2. The compounds 3 transfer the alkoxycarbonyl group readily to O‐, N‐ and C‐nucleophiles. Hydrolysis of 3a–e affords 2,2‐dimethyl‐5‐(4‐pyridyl)‐1,3‐dioxane‐4,6‐dione (4a), which in solution exists in the NH tautomeric form. Nucleophilic reagents attack 4a at one of the carbonyl groups to yield derivatives of (4‐pyridyl)acetic acid. These reactions admit a convenient access to a number of 4‐pyridyl‐substituted heterocycles.
N‐Vinyl‐, N‐Allyl‐, N‐Propenyl‐ and N‐Propargyl‐benzotriazoles: Reactions of Their Lithium Derivatives
Authors: Katritzky Alan R. , Li Jianqing , Malhotra Nageshwar
Published: July 2007

1‐Vinylbenzotriazole undergoes lithiation at the α‐carbon and subsequent reactions with electrophiles to afford 1‐(1‐substituted vinyl)benzotriazoles (3a–d). Similarly, 1‐(1‐substituted propenyl)‐ (9a–c, 9e, 10a–c, 10e) and 2‐(1‐methylpropenyl)‐benzotriazoles (14 and 15) were prepared by lithiation of the corresponding 1‐ and 2‐propenyl‐benzotriazoles followed by alkylation. 1‐ and 2‐Allylbenzotriazoles 4 and 5 are also lithiated at the α‐carbon and the intermediates react with electrophiles at this position. The structures of the propenyl derivatives were supported by an alternative synthetic route via rearrangements of the corresponding allyl isomers. 1‐Propargylbenzotriazole (16) undergoes lithiation first at the acetylenic CH and then at the CH2 group. The dilithiated species, produced by treatment of 16 with two equivalents of butyllithium, reacts with an electrophile first at the carbon atom adjacent to the nitrogen atom, and then at the terminal carbon atom. Hence lithiation of 16 and subsequent reactions with electrophiles afford alkylated products 17a–d, 18a–d, 19a–b and 20a–c depending upon the amount of butyllithium and of the electrophile(s) used. The structures of each class of product were supported by spectral and analytical data.
A Mild and Facile Preparation of Sulfoxides from Sulfides by Use of the H2O2‐Urea/Phthalic Anhydride System
Authors: Balicki Roman , Kaczmarek Lukasz , Nantka‐Namirski Pawel
Published: July 2007

The use of the system hydrogen peroxide‐urea/phthalic anhydride in the safe oxidation of dialkyl, diaryl and alkyl aryl sulfides under mild conditions is reported. The corresponding sulfoxides are formed in excellent yields.
Untersuchung der allergenen Prinzipien aus Kolophonium: Autoxidation, Synthese und Sensibilisierung
Authors: Krohn Karsten , Budianto Emil , Flörke Ulrich , Hausen Björn M.
Published: July 2007

Investigation of the Allergenic Principles from Colophony: Autoxidation, Synthesis, and Sensitization

The autoxidation of abietic acid (1a), levopimaric acid (2a), and dehydroabietic acid (3a) was studied and the compounds 3a as well as (after esterification) 8b, 9b, 10b, 11b (from 1a); 6b (from 2a); and 4b, 5b (from 3a) were isolated for the first time. Some derivatives (6a, 6b, 13b/14b, and 7b) were semisynthezised. The isolated autoxidation products, the synthetic compounds and some polar fractions of natural colophony were tested for their sensitizing capacity. Compounds 4a, 10b, 16, and 18 as well as the combined polar fraction A–D of colophony show enhanced sensitizing capacity. Methylation of the acids to the ester significantly reduces their activity.
Thermal Degradation of Glycosides, VII. Application of Hydrothermolysis to the Studies on the Constituents of the Merck Saponin
Authors: Kim Youn Chul , Higuchi Ryuichi , Komori Tetsuya
Published: July 2007

Two new triterpenoid 3,28‐O‐bisglycosides, MS‐1 and MS‐2, were isolated from the Merck Saponin (origin: Gypsophila paniculata L.). Their structures were elucidated on the basis of chemical and spectral data as follows. MS‐1 (1): 3‐O‐β‐D‐galactopyranosyl‐(→2)‐[α‐L‐arabinopyranosyl‐(→3)]‐β‐D‐glucuronopyranosyl gypsogenin 28‐O‐β‐D‐xylopyranosyl‐(→3)‐ β‐D‐xylopyranosyl‐(→4)‐α‐L‐rhamnopyranosyl‐(→4)‐[β‐D‐quinovopyranosyl‐(→2)]‐β‐D‐ fucopyranoside. MS‐2(2): 3‐O‐β‐D‐galactopyranosyl‐(→2)‐[α‐L‐ arabinopyranosyl‐(→3)]‐β‐D‐glucuronopyranosyl quillaic acid 28‐O‐β‐D‐xylopyranosyl‐(→3)‐β‐D‐xylopyranosyl‐(→4)‐α‐L‐rhamnopyranosyl‐(→4)‐[β‐D‐quinovopyranosyl ‐(→2)]‐β‐D‐fucopyranoside. The hydrothermal degradation, which led to selective cleavage of the ester glycosidic linkage, was useful for the structure elucidation.
Synthesis of the Ring D‐Building Block of (24S)‐24‐Hydroxy Vitamin D3 from Menthol, I
Authors: Daniewski Andrzej Robert , Warchol Tadeusz
Published: July 2007

Natural (—)‐menthol (4) was oxidized to the lactone 9 which was alkylated with allyl bromide to a single product 10. The latter compound was transformed into bromo epoxide 33 which was cyclized with the highly reactive copper to the desired ring D Building block 18 of (24S)‐24‐hydroxy vitamin D3. The title compound 18 was synthesized also by free‐radical cyclization of enaldehyde 40.
Biologically Active Glycosides from Asteroidea, XXIX. X‐Ray Crystallographic Analysis of Desulfated Asterosaponin P1 Isolated from the Starfish Asterina pectinifera
Authors: Cho Yuko , Higuchi Ryuichi , Marubayashi Nobuhiro , Ueda Ikuhiko , Komori Tetsuya
Published: July 2007

By X‐ray crystallographic analysis of desulfated asterosaponin P1 the absolute configuration at C‐24 in the aglycone moiety is confirmed. The unique conformation of the side chain part possessing the carbohydrate moiety is also revealed. This is the first report of an X‐ray crystallographic analysis of a steroid glycoside whose carbohydrate moiety is located in the C‐17 side chain.
Synthesis of the Enatiomers of Lasiol, the Major Volatile Component of the Mandibular Gland Secretion of Lasius meridionalis
Authors: Kuwahara Shigefumi , Shibata Yasuo , Hiramatsu Akira
Published: July 2007

Both enantiomers of lasiol, erythro‐2,3,6‐trimethyl‐5‐hepten‐1‐ol (1), were synthesized in 6 steps from the enantiomers of 3‐methyl‐4‐butanolide (2).
Sulfidierung ausgewählter Carbonsäure‐ und Kohlensäureamide mit dem (9‐BBN)2S‐Reagenz
Authors: Köster Roland , Kucznierz Ralf
Published: July 2007

Sulfidation of Selected Carboxylic and Carbonic Acid Amides with the (9‐BBN)2S‐Reagent

The sulfidation of eight carboxylic and carbonic acid amides (A–H) with bis(1,5‐cyclooctanediylboryl) sulfide (1) is described. From the aliphatic acyclic amide A and the N‐substituted lactams C–E the corresponding thiocarbonyl compounds 2a and 2c–e, resp., are obtained in high yields. N,N‐Dimethylbenzamide (B) reacts with 1 to give monothiobenzoic acid 9‐BBN ester (3) and further dithiobenzoic acid 9‐BBN ester (4). From N‐methylphthalimide (F) and 1 the dithio derivative 5f is formed at room temperature. The carbonic acid amides (urea derivative G, caffeine H) are sulfidated slower than the carboxylic acid amides with formation of the monothio derivatives 2g and 2h, resp. H reacts regioselectively with 1 to yield 6‐thiocaffeine (2h) and further to give 2,6‐dithiocaffeine (5h).
Selective Acetate Hydrolysis of Diastereomers with Porcine Pancreatic lipase (PPL) as an Access to Useful Chiral Building Blocks
Authors: Mulzer Johann , Greifenberg Stefan , Beckstett Anne , Gottwald Matthias
Published: July 2007

The diastereomeric mixture of the propargylic acetates 2 was diastereomer selectively hydrolyzed with porcine pancreatic lipase (PPL) in water to give the acetate syn‐2 and the alcohol anti‐3, both more than 95% diastereomerically pure. From these products stereocontrolled routes to other useful chiral building blocks (4, 6, 11, 14, 15, 16) were developed.
Terpenes and Terpene Derivatives, XXX. Isolation and Synthesis of Isohumbertiol, the First Naturally Occurring Sesquiterpene Alcohol with a Humbertiane Skeleton
Authors: Weyerstahl Peter , Christiansen Christian , Marschall Helga
Published: July 2007

From Vassoura oil (Baccharis dracunculifolia DC.) the four isomeric isohumbertiols A–D (7–10), the first naturally occurring sesquiterpene alcohols with a humbertiane skeleton could be isolated and assigned unambiguously by establishing a correlation with the known cabreuva oxides A–D (3–6). Reaction of the ketone (+)‐16 with vinylmagnesium bromide gave a mixture of the isohumbertiols B and D [(+)‐8 and ent‐10]. Treatment of 8/10 with SnCl4 furnished the tetraline derivative 18, whereas with hydrochloric acid the cabreuva oxides B and D (4 and 6) were obtained.
Pyrylium‐Mediated Synthesis of N‐(Benzyloxy)pyridinium Salts
Authors: Balaban Teodor Silviu , Tâmâşan Iuliana , Deleanu Câlin
Published: July 2007

Pyrylium salts 3 react with (benzyloxy)amines 2 generated by hydrazinolysis from their N‐(benzyloxy)phthalimides to afford in moderate (35–65%) yields the corresponding title salts 4. The 13C‐ and 1H‐NMR spectra of the latter compounds are reported.
Synthesis of Substituted Dibenzo[a,d]azepines via a Base‐Mediated Ring Expansion
Authors: Groth U. , Richter L. , Schöllkopf U.
Published: July 2007

Substituted dibenzoazepines5and10were synthesized in three steps by starting from acridine (6). The key step of the synthesis is a base‐mediated ring expansion reaction of the mesylates1.
A Facile Synthesis of [1]Benzopyrano[4,3‐b]pyridin‐5‐ones
Authors: Ivano Ivo C. , Karagiosov Stoyan K. , Simeonov Mario F.
Published: July 2007

The title compounds 5a‐c and 7a‐m have been prepared by Vilsmeier formylation of 4‐aminocoumarins 1 yielding aldehydes 2, and subsequent condensation of 2 with C‐H acids in the presence of piperidine. This condensation probably proceeds via the intermediate ylidenemalonic esters 4. By means of detailed 1H‐ and 13C‐NMR studies a Dimroth‐type rearrangement of intermediates 6f‐m has been found to take place in the course of the formation of products 7f‐m.
A New Stereoselective Synthesis of Grandisol
Authors: Langer Klaus , Mattay Jochen , Heidbreder Andreas , Möller Manfred
Published: July 2007

Grandisol (10) is stereoselectively synthesized in 9 steps, starting from commercially available 3‐methyl‐3‐buten‐1‐ol (1). The key step of the synthesis is the Cu(I)‐catalyzed [2 + 2]‐photocycloaddition of 3 to 4a or 4b. Moreover, solvent effects on the endo/exo product ratio of the [2 + 2]‐photocycloaddition are investigated.
Anwendungen der Phasentransfer‐Katalyse, 55. Neue Versuche zur enantioselektiven Phasentransfer‐Katalyse mit optisch aktiven Kronenethern
Authors: Dehmlow Eckehard V. , Knufinke Volker
Published: July 2007

Applications of Phase‐Transfer Catalysis, 55. — New Experiments towards Enantioselective Phase‐Transfer Catalysis with Optically Active Crown Ethers

Optically active crown ethers 1a–1o,2, 3a, b, 4a, b, 5a–5d, 6a, b and the acyclic analogue 7 were used for three Michael‐type additions, benzoin condensation, a C‐alkylation, a base‐catalyzed autoxidation and a hypochlorite epoxidation. Important observations include a possible reversal of product stereochemistry when changing potassium for sodium ions and when increasing the number of side groups at the crown. Crowns with nonequivalent upper and lower faces are not useful. Additional stereogenic centers in the side chains and OH groups are not advantageous — at least in the studied cases.
Solution Synthesis of Phytochelatins, Isopeptides from the Plant Kingdom
Authors: Zeng Weiguang , Hemmasi Bahram
Published: July 2007

Phytochelatins which are linear peptide polymers of the γ‐glutamylcysteine portion of glutathione with the general formula H‐[γ‐Glu‐Cys]n‐Gly‐OH (n = 2–11) are the main components for the detoxification of heavy metals in the plant kingdom. So far these peptides have been mostly obtained by isolation from cell suspension cultures. We have now prepared some of these (n = 2–4) by the classical solution synthesis under mild conditions. For the protection of amino, carboxyl and thiol functions Nps, tBu and StBu protecting groups have been employed, respectively. The characterization of the peptide intermediates and final products has been achieved by mass spectrometry, 13C‐NMR spectroscopy and amino acid analysis.
Antibiotics from Gliding Bacteria, XLVII. Thiangazole: A Novel Inhibitor of HIV‐1 from Polyangium spec.
Authors: Jansen Rolf , Kunze Brigitte , Reichenbach Hans , Jurkiewicz Elke , Hunsmann Gerhard , Höfle Gerhard
Published: July 2007

Using a biological screening with a HIV‐1/MT‐4 cell assay indicating antiviral activity and cell toxicity, we detected and isolated a new inhibiting metabolite from gliding bacteria, thiangazole (1). The structure of 1 was determined by spectroscopic methods to be a tris(thiazoline) derivative, showing a remarkable similarity to tantazole B (2). Chemical degradation and comparison with a synthetically prepared reference compound as well as with the degradation product from 2 furnished the (5R,8S,11S) configuration of the asymmetric centers in 1.
Anomeric O‐Alkylation, 9. Disaccharide Synthesis via Anomeric O‐Alkylation
Authors: Tsvetkov Yury E. , Klotz Wolfgang , Schmidt Richard R.
Published: July 2007

Base‐promoted reaction of tetra‐O‐benzyl‐glucose 1a with secondary alkyl trifluoromethanesulfonates 2 and 3 in toluene provides in the presence of 15‐crown‐5 preferentially β‐glycosides 2aβ and 3aβ, respectively, in high yields. For reactions carried out at lower temperatures and with trifluoromethanesulfonates derived from secondary hydroxy groups of sugars aprotic dipolar solvents (HMPT/DMF, HMPT/THF) are required. Thus, treatment of 1‐O‐unprotected hexoses 1a–e with trifluoromethanesulfonates 4, 6, and 7 affords the corresponding (1→4)‐connected disaccharides 4a–e and the (1→3)‐connected disaccharides 6b and 7b, respectively, in high yields. Under these conditions the α:β ratio of the products resembled the anomeric ratio of the starting material.
Ambidoselective Dithiocarboxylation and Thiocarbamoylation of β‐Keto Enolates
Authors: Rudorf Wolf‐Dieter , Köditz Jens , Tersakian Ani , Chatterjee Swapan Kumar
Published: July 2007

Treatment of β‐keto enolates 1 with carbon disulfide in the presence of sodium hydride and subsequent alkylation yield the open‐chain or cyclic acylformylketene S,S‐acetals 3 and 4, respectively. Thiophenes 5, 6, or 7 and thieno[2,3‐b]thiophenes 8 are formed by using as alkylating agents first methyl iodide and then an α‐CH‐acidic halo compound or only two equivalents of the latter. β‐Keto enolates 1 also react with phenyl isothiocyanate to give acylformylketene S,N‐acetals 10, aroylthiophenes 11 or thiazolidin‐4‐ones 12.
(2R,4R,6R,8R)‐2,4,6,8‐Tetramethyldecan‐ und ‐undecansäure aus dem Bürzeldrüsenwachs der Hausgans, Anser a. f. domesticus: Isolierung, Synthese einiger Derivate sowie der rac‐2,4,6,8‐Tetramethyldecansäure
Authors: Morr Michael , Wray Victor , Fortkamp Jens , Schmid Rolf D.
Published: July 2007

(2R,4R,6R,8R)‐2,4,6,8‐Tetramethyldecanoic‐ and ‐undecanoic Acid of the Preen‐gland Wax from the Domestic Goose, Anser a.f. domesticus: Isolation, Synthesis of Derivatives and of the rac‐2,4,6,8‐Tetramethyldecanoic Acid

Large quantities of (2R,4R,6R,8R)‐2,4,6,8‐tetramethyldecanoic‐ and ‐undecanoic acid methyl ester (3 and 4) were obtained after transesterification and Spaltrohr® distillation of the preen‐gland wax of the domestic goose. Hydrolysis with NaOH/dioxan afforded the acids 5 and 6. Reduction of 3 with LiAlH4 gave (2R,4R,6R,8R)‐2,4,6,8‐tetramethyldecanol (7). Esterification of 5 and 6 with octadecanol yielded the pure wax esters 1 and 2, while 5 with glycerol gave the triglyceride 9 and 5 with 7 afforded 8. Alcohol 7 and octadecyl bromide, in the presence of NaH/DMF, afforded the ether 10. The racemic acid 22, corresponding to 5, was obtained synthetically by starting with a modified Wittig reaction of 2‐(diethoxyphosphoryl)propionic acid ethyl ester on 2‐methylbutyraldehyde. Transesterification of the ethyl ester 21 with octadecanol gave the racemic wax ester 23, corresponding to 1. The optical activity and 13C data of the compounds are reported.
Synthese von Östronderivaten aus Siloxycyclopropancarbonsäureestern
Authors: Schnaubelt Jürgen , Zschiesche Ruth , Reißgi Hans‐Ulrich , Lindner Hans Jörg , Richter Jens
Published: July 2007

Synthese of Estrone Derivatives from Siloxycyclopropanecarboxylic Acid Esters

Syntheses of new rac‐estrone analogues such as 10, 19, 21 and 22 are reported. Key intermediate 3 has been efficiently prepared by alkylation of the lithium enolate of the methyl cyclopropanecarboxylate 1 employing 2 as electrophile. One‐pot ring opening/Michael addition procedures have been developed to convert 1 and 3 into polyfunctionalized compounds 5, 7, 8, and 9. Diketo diester 8 can be cyclized with acid to give tetracyclic dienes which are immediately reduced by triethylsilane under acidic conditions providing steroid derivatives 10 and 11. Depending on the purification method, in addition to 10/11 the isomer 12 and the oxidized products 13/14 have been isolated. The structures of 10 and 13 have been confirmed by X‐ray analyses. Acid‐induced cyclization of precursor 9 affords the tetracyclic diene 19 and the pentacyclic lactone 20. Catalytic hydrogenation of the diene 19 provides the estrone derivative 21 in good yield, but with the unnatural cis‐C/D‐ring junction. Ionic reduction of 19 gives the steroid derivative 22 together with the alcohols 23.
Radikalische Cyclisierung von Dienen, VI. Substratkontrollierte asymmetrische Synthese von (3aS,6aR)‐(+)‐3,3a,6,6a‐Tetrahydro‐2H‐cyclopenta[b]furan‐2‐on
Authors: Weinges Klaus , Schwarz Georg
Published: July 2007

Radical‐Type Cyclization of Dienes, VI. – Substrate‐Controlled Asymmetric Synthesis of (3aS,6aR)‐(+)‐3,3a,6,6a‐Tetrahydro‐2H‐cyclopenta[b]furan‐2‐one

(R)‐(−)‐Carvone (1) was converted via straightforward reactions into 10‐hydroxycarvone (4) which was cyclized to 5 via the mercury‐mediated free‐radical method. Periodate cleavage of 5 yields the bicyclic dione 6. Regio‐ and stereoselective reduction of 6 with lithium tri(tert‐butyloxy)hydridoaluminate results in 7 (80% yield). 7 was directly converted into γ‐lactone 8 via Baeyer‐Villiger oxidation. Saponification of 8 to 9, mesylation of 9 to 10 followed by elimination of methanesulfonic acid yield enantiomerically pure (3aS,6aR)‐(+)‐3,3a,6,6a‐Tetrahydro‐2H‐cyclopenta[b]furan‐2‐one (11). The synthesis can be carried out with readily available, and economical, (S)‐(+)‐carvone to yield ent‐11.
Oxidative Methylamination of Nitroquinolines
Authors: Woźniak Marian , Grzegożek Maria
Published: July 2007

3‐, 5‐, 6‐, 7‐ and 8‐nitroquinoline as well as 5,7‐ and 6,8‐dinitroquinoline are methylaminated with a liquid methylamine solution of potassium permanganate (LMA/PP) to the corresponding mono‐ and bis(methylamino)‐substituted compounds. 2‐Nitroquinoline is aminated with LMA/PP to 2‐(methylamino)quinoline. The intermediate methylamino σ‐adducts of 3‐nitro‐ and 5,7‐ and 6,8‐dinitroquinoline are detected by1H‐NMR spectroscopy. Quantum chemical calculations for the mononitroquinolines suggest that the experimentally observed regioselectivity of the methylamination is controlled by an interaction of frontal molecular orbitals (FMO) of the reagents.
β‐Carbolin‐Alkaloide, II Tributyl(1‐ethoxyvinyl)stannan als C2‐Baustein für die Synthese von β‐Carbolin‐Alkaloiden
Authors: Bracher Franz , Hildebrand Dirk
Published: July 2007

β‐Carboline Alkaloids, II. – Tributyl(1‐ethoxyvinyl)stannane as a C2‐Building Block in the Syntheses of β‐Carboline Alkaloids

1‐Acetyl‐β‐carboline (4) is prepared by palladium‐catalyzed coupling of 1‐chloro‐β‐carboline (1) with tributyl(1‐ethoxyvinyl)stannane (3) and subsequent hydrolysis with aqueous acid. Reduction of 4 with NaBH4 gives the alkaloid 5. Nitramarine (7) and annomontine (9) are prepared from 4 by one‐pot conversions of the acetyl group to a quinoline or an aminopyrimidine ring, respectively.
Total Synthesis of Angucyclines, 1. – Synthesis of a Daunomycinone–Rabelomycin Hybrid
Authors: Krohn Karsten , Ballwanz Frank , Baltus Wolfgang
Published: July 2007

The synthesis of the racemic angucyclinone hybrid 3 which combines the structural features of rabelomycin (1) and daunomycinone (2) is described. Key steps are the cyclization of the bromide 6b by a Marshalk‐type reaction to yield the angular skeleton 7b, introduction of the tertiary hydroxy group by bromination to 11, solvolysis to 12 and photoinduced oxygenation to afford the C‐1 ketone 3.
Herstellung von 6,14‐Ethenomorphinan‐Derivaten
Authors: Marton János , Szabó Zoltán , Hosztafi Sándor
Published: July 2007

Preparation of 6,14‐Ethenomorphinane Derivatives

Buprenorphine (5j) and diprenorphine (5k) were synthesized from N‐formyl‐northebaine (1c) and N‐benzyl‐northebaine (1d) via new intermediates. N‐cyclopropylmethyl‐dihydronorthevinone 3d is a suitable compound for the synthesis of both 5j and 5k. We carried out detailed 1H‐ and 13C‐NMR analysis of the new compounds.
Synthesis of Spiro[indoline‐3,2′(3′H)‐[1,3,4]thiadiazoline]‐2‐ones by Acetylation of Isatin‐β‐thiosemicarbazones
Authors: Somogyi László
Published: July 2007

The synthesis of spiro[indoline‐3,2′(3′H)‐[1,3,4]thiadiazoline]‐2‐ones 2a–g by cyclization of isatin‐β‐thiosemicarbazones 1a–f is reported. The structure determination of 2a–g by IR, 1H‐ and 13C‐NMR measurements is also described.
Studies on Ketoses, 8. Disaccharide Building Blocks from Isomaltulose: Glucosyl‐α‐(1→5)‐D‐arabinonic Acid and Ensuing Products
Authors: Lichtenthaler Frieder W. , Klimesch Roger , Müller Volkhard , Kunz Markwart
Published: July 2007

A convenient one‐pot procedure, simply involving air oxidation in strongly alkaline solution, is detailed for the high‐yield conversion of bulk accessible D‐glucosyl‐α(1→6)‐D‐fructose (isomaltulose, 1) into the salt of the next lower aldonic acid, i.e. glucosyl‐α(1→5)‐D‐arabinonate (4). Being only two steps away from sucrose, 4 is capable of providing a variety of disaccharide building blocks with potential industrial application profiles: open‐chain esters, amides or alditols (8–12), or – via the respective 1,4‐lactone 5 and suitable elimination reactions – various enantiopure 2‐(5H)‐furanones (14–17) with a preparatively useful (5S)‐hydroxymethyl group, O‐protected with an acid‐labile glucosyl residue.
Untersuchungen zur Polarität wäßriger Harnstoff‐ und Zucker‐Lösungen mit der Methode der vergleichenden Solvatochromie
Authors: Spange Stefan , Keutel Dietmar
Published: July 2007

Investigations on the Polarity of Aqueous Solutions of Urea and Various Sugars by Means of the Solvatochromic Technique

The dipolarity/polarizability and acidity of aqueous solutions of urea derivatives and sugars have been investigated by means of the solvatochromic technique employing several indicator dyes such as various pyridinium N‐phenoxide betaine dyes, Michler's ketone and Fe(phen)2(CN)2. Increasing concentration of both urea and sugars decreases the polarity and acidity of the aqueous solution as a whole. Advantageously, in the case of urea derivatives, increasing concentration significantly improves the polarizability of aqueous solutions, which is responsible for the solubility of hydrophobic compounds in water.
Pheromone synthesis, CLV. Synthesis of (2E,4E,6R,10R)‐4,6,10,12‐Tetramethyl‐2,4‐tridecadien‐7‐one (matsuone) – the Primary Component of the Sex Pheromone of Three Matsucoccus Pine Bast Scales – and its Antipode
Authors: Mori Kenji , Harashima Susumu
Published: July 2007

(2E,4E,6R,10R)‐4,6,10,12‐Tetramethyl‐2,4‐tridecadien‐7‐one (1; matsuone) – the primary component of the sex pheromone of the red pine scale (Matsucoccus resinosae) and two other pine scales – and its antipode were synthesized by starting from (R)‐ or (S)‐citronellol (3) and employing the asymmetric epoxidation (11 → 12) and the palladium‐catalyzed reductive cleavage of the epoxy ring (15 → 16) as the key steps.
Synthesis and Conformational Analysis by CD Spectroscopy of Lantibiotic Leader, Pro‐ and Pre‐Peptides
Authors: Beck‐Sickinger Annette G. , Jung Günther
Published: July 2007

In order to investigate the conformational properties of the precursor proteins of lanthionine‐containing bacteriocins we synthesized the leader peptides of the pre‐lantibiotics of gallidermin, epidermin, Pep5, nisin, subtilin, the C‐terminal 30‐mer segment of pre‐cinnamycin, propeptide segments of Pep5 and gallidermin and the complete pre‐gallidermin, which consists of 52 residues. The peptides were synthesized in a step‐by‐step synthesis by the Fmoc/tBu strategy using an optimized procedure for the synthesis of large peptides. All peptides were analyzed by HPLC and characterized by electrospray mass spectrometry and amino acid analysis. Circular dichroism spectra exhibited strong α‐helical Cotton effects even at a low concentration of trifluoroethanol for all N‐terminal leader peptides. Comparative investigations of the C‐terminal propeptide segments led to a model of the conformation of the prepeptides of Pep5 and gallidermin in aqueous and lipophilic environments. In addition, circular dichroism investigations on the synthetic precursor protein of gallidermin and the isolated natural pre‐Pep5 were performed.
Radikalische Cyclisierung von Dienen, VI. Totalsynthese von (−)‐Coriolin und (−)‐Epicoriolin aus (S)‐(+)‐Carvon
Authors: Weinges Klaus , Braum Ralf , Huber‐Patz Ursula , Irngartinger Hermann
Published: July 2007

Radical‐Type Cyclization of Dines, VI. – Total Synthesis of (−)‐Coriolin and (−)‐Epicoriolin from (S)‐(+)‐Carvone

(3aR,4S,6aS)‐(+)‐4‐(4‐Methoxybenzyloxy)‐6a‐methyl‐3,3a,4,6a‐tetrahydro‐2H‐cyclopenta[b]furan‐2‐one (10) and (3aR,3bR,4R,6aS,7S,7aS)‐(−)‐decahydro‐4,7‐dihydroxy‐3a,5,5‐trimethyl‐3‐methylene‐2H‐cyclopenta[a]pentalen‐2‐one (21) are the key intermediates in the synthesis of the title compounds 1 and 1a. Enantiomerically pure 10 is produced from (S)‐(+)‐carvone (4) in seven straightforward reactions. Compound 21 is produced from 10 by analogy with the method developed for the synthesis of (−)‐hirsutene. Through the introduction of the double bond into 21 via the silylenolether 23 one arrives at precoriolin 25, which is converted into (−)‐coriolin (1) and the C‐3 epimer (−)‐epicoriolin (1a) (63:37) with hydrogen peroxide. The structures of 1 and 1a were confirmed via X‐ray crystallography.
Tripyrrylmethane als Bausteine zur Synthese funktioneller Porphyrine
Authors: Berlin Kurt , Breitmaier Eberhard
Published: July 2007

Tripyrrylmethanes as Building Bocks for the Preparation of Functionalized Porphyrins

Tripyrrylmethanetricarbaldehyde 4 is prepared in three steps from the tripyrrylmethanetricarboxylate 2. The mono‐meso‐pyrrylporphyrines 6a and b are obtained in moderate yields by MacDonald condensation of 4 with the di‐2‐pyrrylmethyanes 5a and b.
Terpenes and Terpene Derivatives, XXXI. New Bisabolene Derivatives and a Salsolene Ketone from Artemisia sieberi Bess.
Authors: Weyerstahl Peter , Schneider Sabina , Marschall Helga , Rustaiyan Abdolhossein
Published: July 2007

From the essential oil of Artemisia sieberi growing near Tehran some new bisabolene derivatives could be isolated. The structures of (−)‐dehydro‐1,8‐sesquicineole (1), (E)‐dehydro‐1,8‐sesquicineol‐12‐yl acetate (4), bisabola‐2,11‐dien‐10‐one inner 1,7‐acetal (14) and salsolene ketone 15 could be established by their 1H‐ and 13C‐NMR spectra. Sesquiphellandren‐7‐ol (11), a trace constituent of the oil, was identified by a comparison of its 1H‐NMR spectrum with that of sesquiphellandren‐9‐ol (bisacurol).
Studies on Heterocyclic Enaminonitriles, XV. A Convenient One‐pot Synthesis of Ethyl 4‐Amino‐2,3‐dihydrothieno‐[2,3‐b]pyridine‐5‐carboxylates
Authors: Maruoka Hiroshi , Yamagata Kenji , Yamazaki Motoyoshi
Published: July 2007

The reaction of 2‐amino‐4,5‐dihydro‐3‐thiophenecarbonitriles 1a–c with ethyl acetoacetate in the presence of titanium(IV) chloride gave the corresponding ethyl 4‐amino‐2,3‐dihydro‐6‐methylthieno[2,3‐b]pyridine‐5‐carboxylates 3a–c. Similarly, compounds 1a–c reacted with diethyl malonate or ethyl cyanoacetate to give the corresponding ethyl 4‐amino‐2,3,6,7‐tetrahydro‐6‐oxothieno[2,3‐b]pyridine‐5‐carboxylates 4a–c or ethyl 4,6‐diamino‐2,3‐dihydrothieno[2,3‐b]pyridine‐5‐carboxylates 5a–c.
β‐Carbolin‐Alkaloide, IV. – Synthese von 1‐Alkyl‐β‐carbolinen und Strukturrevision von Lycii‐Alkaloid I
Authors: Bracher Franz , Hildebrand Dirk
Published: July 2007

β‐Carboline Alkaolids, IV. – Synthese of 1‐Alkyl‐β‐carbolines and Structure Revision of Lycii Alkaloid I

Palladium‐catalyzed coupling reactions of 1‐chloro‐β‐carboline (1) with triethylborane and trimethylaluminum give the alkaloids 1‐ethyl‐β‐carboline (2) and harman (5). The intermediate 4 on treatment with ethyl formiate gives 9‐formylharman (6). Comparison of the spectroscopic data shows, that lycii alkaloid I does not have the structure 6, but is identical with the alkaloid 1‐acetyl‐β‐carboline (7).
Diethylborylierung und Sulfidierung von ω‐Lactamen
Authors: Köster Roland , Kucznierz Ralf , Schüßler Wilhelm , Bläser Dieter , Boese Roland
Published: July 2007

Diethylborylation and Sulfidation of ω‐Lactams

Several reaction modes of ω‐lactams [A (n = 3), B (4), C (5), D (6), E (7), F (11)] with Et3B are observed between 20 and 110°C. The Et2B lactims (1) having various degrees of association [(1a)x; 1b; (1d)2 (X‐ray structure); 1e; (1f)4] are formed by elimination of 1 mol of ethane. The condensation products [2b; 2c (X‐ray structure)] result by elimination of 1.33 mol of ethane together with the lactim derivatives (3b; 3c). Thermolysis (≥ 125°C) of (1d)2, 1e, and (1f)4 leads to mixtures, in which the compounds 2d, e, f and 3d, e, f, resp., have been identified (NMR, MS). Differences of the thermal behaviour of 1a–f (s‐cis/trans conformers, cis/trans lactims, association degree) are discussed. – From 2b, c and Hacac the N‐acylamidines (4b, c) are obtained, which react with (9‐BBN)2S to yield the monomeric 9‐BBN‐ω‐thiolactims [5b; 5c (X‐ray structure)]. The latter react with MeOH to give the ω‐thiolactams (6b, c) and 9‐MeO‐9‐BBN, from which the 2:2 MeOH addition compound (7)2 (X‐ray structure) is obtained.
Darstellung eines (Diphenylverdazylylphenyl)propargylethers
Authors: Dulog Lothar , Breitenbücher Joachim
Published: July 2007

Preparation of a Diphenylverdazylylphenyl Propargyl Ether

2,4‐Diphenyl‐6‐[4‐(propargyloxy)phenyl]verdazyl (6) has been synthesized by the reaction of 4‐hydroxybenzaldehyde with propargyl bromide, phenylhydrazine and phenyldiazonium chloride. The corresponding formazane yields with formaldehyde after air oxidation the stable radical.
Biologically Active Glycosides from Asteroidea, XXXI. Glycosphingolipids from the Starfish Asterias amurensis versicolor sladen, 2. Structure and Biological Activity of Ganglioside Molecular Species
Authors: Higuchi Ryuichi , Inukai Kazuyoshi , Jhou Jian Xin , Honda Masanori , Komori Tetsuya , Tsuji Shuichi , Nagai Yoshitaka
Published: July 2007

Two ganglioside molecular species [GAA‐6 (1) and GAA‐7 (4)] have been obtained from the water‐soluble lipid fraction of the chloroform/methanol extract of the whole bodies of the starfish Asterias amurensis versicolor Sladen. The structures of these ganglioside molecular species have been determined on the basis of chemical and spectroscopic findings. GAA‐6 (1) is a starfish ganglioside molecular species resembling a mammalian brain ganglioside, GM3. In contrast, GAA‐7 (4) is assigned the same structure as that of the main ganglioside[3] from Asterias amurensis[4] for the oligosaccharide moiety. Partial hydrolysis of oligosaccharide moieties with hot water or dilute acetic acid has proved useful for the structure elucidation of the ganglioside molecular species. Moreover, the Mayn ganglioside molecular species, GAA‐7 (4), shows neuritogenic and growth‐inhibitory activities towards the mouse neuroblastoma cell line (Neuro 2a). The structure‐activity relationship of starfish gangliosides is also discussed.
Synthese von (+)‐Castanospermin und 1‐Epicastanospermin aus D‐Glucofuranurono‐6,3‐lacton durch Reformatsky‐Reaktion
Authors: Graßberger Vera , Berger Andreas , Dax Karl , Fechter Martin , Gradnig Günther , Stütz Arnold E.
Published: July 2007

Synthesis of (+)‐Castanospermine and 1‐Epicastanospermine from D‐Glucofuranurono‐6,3‐lactone by Reformatsky Reaction

Starting from 5‐O‐(tert‐butyldimethylsilyl)‐1,2‐O‐isopropylidene‐α‐D‐gluco‐ (2a) or ‐β‐L‐idofuranurono‐6,3‐lactone (2b), 7‐deoxyoctofuranose derivatives 5a, 5b, 7a and 7b have been synthesized by chain extension at C‐6 by Reformatsky reaction followed by reduction with calcium borohydride. The respective configuration of the products was determined by transformation into the known 7,8‐dideoxyoctofuranoses 5o, 5p, 7k and 7l. From the mixture of 7a and 7b, formed in a proportion of approximately 4:1, the glycosidase inhibitors (+)‐castanospermine (1a) and 1‐epicastanospermine (1b) have been prepared in 8 and 9 simple steps, respectively, in overall yields of 33.4 and 9.5%.
Synthesis of (±)‐Sterpurene and Hydroxylated Derivatives by 1,6‐Addition of Organocuprates to Acceptor‐substituted Enynes
Authors: Krause Norbert
Published: July 2007

The synthesis of (±)‐sterpurene (1), 14‐/15‐hydroxysterpurene (13), and 11,14‐/11,15‐dihydroxysterpurene (14) is described. Key steps are the 1,6‐addition of lithium dimethylcuprate to the 2‐en‐4‐ynoate 11 and the regioselective trapping of the allenyl enolate with methyl triflate. The vinylallene 6 thus obtained undergoes an intramolecular Diels‐Alder reaction to give the tricyclic ester 5, which serves as a common precursor of 1, 13, and 14.
Secondary Metabolites by Chemical Screening, 23. Waraterpols, New Penicillium Metabolites and Their Derivatives
Authors: Henne Petra , Thiericke Ralf , Grabley Susanne , Hütter Klaus , Wink Joachim , Jurkiewicz Elke , Zeeck Axel
Published: July 2007

Substituted phenols can easily be recognized by using the chemical screening method, whereby they are found to be widely spread secondary metabolites of microorganisms. In the culture filtrate of Penicillium sp. (strain FH‐A 6260) new phenols named waraterpols were detected by a striking purple coloration by using anisaldehyde/sulfuric acid. These secondary metabolites (1 to 3 and 6 to 8) exhibit a C15‐carbon skeleton and can be characterized as hydroxylated branched‐chain sesquiterpenoids with a benzoide moiety. The minor compounds were O‐acetyl (2 and 3) and dehydrated derivatives (6 to 8) of the parent compound waraterpol (1), which was shown to be 6‐[2‐hydroxy‐4‐(hydroxymethyl)phenyl]‐2‐methylheptane‐1,6‐diol. Derivatization of 1 resulted in the quinone and hydroquinone compounds 10 and 5 as well as in the cyclic derivatives 11 and 12. The waraterpols exhibit distinct antibacterial and antifungal activities whereas an inhibition of HIV‐1 in a MT‐4 cell assay was found for 11.
Stereoselective synthesis of (2S,3S)‐norstatine derivatives by addition of lithiated methoxyallene to amino aldehydes and subsequent ozonolysis
Authors: Hormuth Stephan , Reißig Hans‐Ulrich , Dorsch Dieter
Published: July 2007

Addition of lithiated methoxyallene 2 to optically active N‐benzyl‐Boc‐protected amino aldehydes 12–14 and to aldehyde 16 provides products 17–20 with good to excellent diastereoselectivity. These adducts are subsequently cleaved by ozonolysis to give α‐hydroxy‐β‐amino acid derivatives 21–25 in good overall yield. By conversion into an oxazolidone derivative, the configuration of the major diastereomer was determined to be anti (2S,3S). Thus, the additions of 2 follow the course proposed by the Felkin‐Anh model and are not ruled by chelation effects. The diastereoselective synthesis of 22 constitutes one of the simplest routes to a protected norstatine derivative. magnified image
Properties and reactions of substituted 1,2‐thiazetidine 1,1‐dioxides: Synthesis of 1,2‐thiazetidine‐2,3‐diacetic acid derivatives and their rearrangement to 1,2‐thiazinan‐3‐ones
Authors: Schwenkkraus Peter , Otto Hans‐Hartwig
Published: July 2007

β‐Sultam‐3‐acetic acid ester 3 prepared from rac‐S‐benzyl‐β‐homocysteine is alkylated with bromoacetates yielding diacetates 9 which are transformed into the phenylthio esters 11. The thiazinanone derivatives 12 are obtained from 11 by rearrangement with lithium bis(trimethylsilyl)amide in excellent yields, and the syntheses of the derivatives 13, 14, and 15 are described. The stereochemistry of all products is elucidated by spectroscopic methods, and a reaction pathway is proposed. It is supported by the synthesis of the isomeric β‐sultam‐2,3‐diacetate 20, which does not rearrange to a thiazinanone derivative. Some side reactions are described. magnified image
Antibiotics from gliding bacteria, LVII. Tartrolons: New boron‐containing macrodiolides from Sorangium cellulosum
Authors: Schummer Dietmar , Irschik Herbert , Reichenbach Hans , Höfle Gerhard
Published: July 2007

The antibacterial metabolites tartrolon A1, A2, A3 (1a–1c) and B (2) were isolated from the myxobacterium Sorangium cellulosum, strain So ce678. Large‐scale production was achieved by fermentation in the presence of the adsorber resin XAD‐16, extraction, and separation by RP chromatography followed by crystallization. The 42‐membered macrodiolide structure of 1a–1c and 2 was determined by spectroscopic methods. Compound 2 was identified as a boric acid ester of 1c, whereas 1a and 1b are stereoisomers of 1c. All components could be chemically converted into each other. A correlation between the production of 2 and the borate concentration in the medium was found, depending on nutrients and container material used. magnified image