bluuebunny/crossref_metadata_2025 huggingface dataset:
Photochemistry of δ‐hydroxybutyl α,β‐unsaturated γ,δ‐epoxy nitriles. Formation of spiro ketals
Authors: Ishii Keitaro , Kotera Masashi , Nakano Takao , Zenko Tatsuya , Sakamoto Masanori , Iida Ikuo , Nishio Takehiko
Published: July 2007

Photocyclization reactions of δ‐hydroxybutyl α,β‐unsaturated γ,δ‐epoxy nitriles 4a, b at 254 nm lead to spiro ketals 5a, b and 6a, b arising from the carbonyl ylide intermediate A. The spiro ketal 6b containing an endocyclic double bond is transformed to spiro ether 16 by an acid‐catalyzed 1,3‐sigmatropic rearrangement. The ratio of spiro ketals 5 and 6 has been shown to depend on solvent polarity and acidity of additives. Application to the synthesis of pheromones is presented. X‐ray crystal structure analyses are performed on dispiro compound 18 and spiro ester 25.
Bausteine von Oligosacchariden, CX. Synthese von potentiellen Inhibitoren für die N‐Acetylglucosaminyltransferase I
Authors: Paulsen Hans , Springer Matthias , Reck Folkert , Brockhausen Inka , Schachter Harry
Published: July 2007

Building Units of Oligosaccharides, CX. — Synthesis of Potential Inhibitors of N‐Acetylglucosaminyltransferase I

Modified derivatives of the trisaccharide octyl α‐D‐Man‐(1→3)‐[α‐D‐Man(1→6)]‐β‐D‐Man were synthesized by attaching reactive groups via a pentyl spacer to the 4′‐OH and 6′‐OH group. Glycosylation steps were carried out by using the trichloroacetimidate method with suitable building blocks. The compounds substituted at 6′‐OH are of special interest. The epoxide 27 and the diazirine 25 are reversible inhibitors of N‐acetylglucosaminyltransferase I (GlcNAc‐T I). Product 26 with a spacer‐linked iodoacetamide is an irreversible inhibitor of GlcNAc‐T I.
Ungesättigte 6‐Alkylpyrone aus dem Schleimpilz Ceratiomyxa fruticulosa (Myxomycetes)
Authors: Velten Robert , Josten Ingrid , Steglich Wolfgang
Published: July 2007

Unsaturated 6‐Alkylpyrones from the Slime Mould Ceratiomyxa fruticulosa (Myxomycetes)

From plasmodia of the common slime mould Ceratiomyxa fruticulosa five 6‐alkyl‐4‐methoxypyran‐2‐ones with varying degrees of unsaturation in the side chain have been isolated. Their structures have been determined by spectroscopic and chemical investigations.
Teil‐ und perfluorierte Thioketone und Thioaldehyde Chemische Speicherung, in‐situ‐Freisetzung und ungewöhnliche 1,3‐dipolarophile Reaktivität gegenüber Bis(trimethylstannyl)diazomethan (BTSD) und C,N‐Bis(triisopropylsilyl)nitrilimin (NI)
Authors: Hasserodt Jens , Pritzkow Hans , Sundermeyer Wolfgang
Published: July 2007

Partially and Perfluorinated Thioketones and Thioaldehydes: Chemical Storage, In Situ Generation and Surprising Reactivity towards Bis(trimethylstannyl)‐diazomethane (BTSD) and C,N‐Bis(triisopropylsilyl)nitrilimine (NI)

The hetero‐Diels‐Alder anthracene adducts 1a‐d are synthesized in a one‐pot reaction from the corresponding partially and perfluorinated carbonyl compounds in good yields. By their thermolysis in solution in presence of BTSD or NI the 1,3‐dipolar 1:1 cycloadducts 12a, d, 14a, b, d are obtained without any detectable by‐products. The method can be of wide applicability predominantly for any aliphatic CS‐unsaturated species, which are not accessible in substance due to tendency towards polymerisation, but can be stabilized as anthracene adducts. Other 1,3‐dipolar cycloaddition products of BTSD and NI are obtained from reaction with iso‐lable hexafluorothioacetone (6f) or bis(trifluoromethyl)sulfine (7f). Comparative studies were carried out with hexafluoroacetone (8), 12a, d, e, 13 are consecutive products from a 1,2‐metallotropic migration of the primary addition compounds. 14a, b, d, 15, 16 are useful thiadiazolines with respect to the synthesis of active substances because of their seldom found peripheral functionality. Desilylation was achieved by fluoride support. An X‐ray structure determination of 12a and 14d was carried out. In addition trifluoromethylsulfine (7c) was trapped at low temperatures. It dimerizes at ambient temperature to unsymmetrical 1,2‐dithietane 11.
Synthese von Naturstoffen mit Alkyl‐methoxy‐1,4‐benzochinon‐Struktur
Authors: Pfeifer Jochen , Gerlach Hans
Published: July 2007

Synthesis of Natural Compounds with Alkyl‐methoxy‐1,4‐benzoquinone Structure

The 1,4‐benzoquinones1–7occurring in various plants and having interesting biological properties have been synthesized from the tetrahydropyranyl ethers17and21. Reaction withn‐butyllithium gave selectively theortho‐lithiated compounds. These could be alkylated with the haloalkenes13–16and haloalkanes to give the substituted phenols18–20and22–25in high yield after methanolysis. Alkylations of the methoxyisopropylether8of 10‐undecyn‐1‐ol with bromobutane and bromohexane gave9and10. These alkynols could be selectively hydrogenated with Lindlar‐Palladium catalyst to give the (Z)‐alkenols11and12which could be converted into the bromoalkenes13, 14and the iodoalkenes15, 16. Oxidation of the phenols18–20and22–25with molecular oxygen in the presence of salcomine as catalyst produced the substituted 1,4‐benzoquinones1–3and26–29in high yield. Selective hydrolysis with perchloric acid converted26–29into the natural products4–7.
New taxoids from Taxus baccata L.
Authors: Barboni Luciano , Gariboldi Pierluigi , Appendino Giovanni , Enriù Renata , Gabetta Bruno , Bombardelli Ezio
Published: July 2007

A side‐cut of the industrial purification of an extract of yew needles afforded eight new taxoids, including two derivatives of taxine A, the 7‐O‐acetyl‐ (2) and the 2‐deacetyl‐ (3) derivatives. The new structures were established by spectroscopic methods, and some unusual features of the 1H‐NMR spectra of taxine A and its derivatives are discussed.
Synthesis of 2‐(aminophenyl)‐2‐hydroxyethylphosphonates and their incorporation in short peptides
Authors: Shalem Hutti , Shatzmiller Shimon , Feit Ben‐Ami
Published: July 2007

The synthesis of 2‐(Aminophenyl)‐2‐hydroxyethylphosphonates rac‐4a‐c is based on the formation of a hydroxyl function via addition of the lithium salt of dimethyl methylphosphonate (2) to aldehydes 1a‐c. The amino function in rac‐ 4a‐c is obtained by catalytic reduction of the nitro group in 3 at low pressure. The incorporation of the aminophosphonates rac‐4a‐c in short peptides, enables the formation of potential bioactive materials 12–14.
Studies on the constituents of the stems of Tinospora sinensis, II. . Isolation and structure elucidation of two new dinorditerpene glucosides, tinosineside A and B
Authors: Yonemitsu Michiko , Fukuda Naomichi , Kimura Takeatsu , Isobe Ryuichi , Komori Tetsuya
Published: July 2007

Two new dinorditerpene glucosides, tinosineside A (1) and B (2‐O‐acetyltinosineside A, 2), were isolated from the fresh stems of Tinospora sinensis Merr. (Menispermaceae). Their structures were established on the basis of chemical and spectroscopic findings.
The structure of hellebrin
Authors: Muhr Petra , Kerek Franz , Dreveny Dieter , Likussar Werner , Schubert‐Zsilavecz Manfred
Published: July 2007

The structure of hellebrin (1) was investigated by using 2D NMR techniques (COSY, TOCSY, ROESY, HMQC, HMBC) and its structure determined as 3‐β‐O‐(β‐D‐glucopyranosyl‐(1→4)‐α‐L‐rhamnopyranosyl)hellebrigenin. The complete assignment of the proton and carbon NMR signals is given.
Synthesis of 2‐acetonyl‐, 2‐phenacyl‐, and 2‐(dioxocycloalkyl)‐substituted thieno[2,3‐d][1,3]thiazin‐4‐ones
Authors: Gütschow Michael , Leistner Siegfried
Published: July 2007

The reaction of ethyl 2‐isothiocyanato‐3‐thiophenecarboxylates 1 with anions of acyclic as well as of cyclic 1,3‐diketones or diethyl malonate affords diacylthioacetamide derivatives 2. Upon treatment with concd. sulfuric acid 2a‐1 are transformed into novel 2‐substituted thieno[2.,3‐d][1,3]thiazin‐4‐ones 3a‐j. Ring cleavage of 3a‐f with sodium alkoxides gives N‐(3‐alkoxycarbonyl‐2‐thienyl)thioacetamides 4a‐h.
Crystal Structure of η3‐lithio‐1,3,3‐triphenylpropyne‐(diethyl ether)2 and [1‐lithio‐1‐(2‐methoxyphenyl)‐3,3‐diphenylallene–diethyl ether]2: Propargyl‐ versus allenyl‐type structures
Authors: Dem'yanov Piotr , Boche Gernot , Marsch Michael , Harms Klaus , Fyodorova Galina , Petrosyan Valery
Published: July 2007

Crystal structure investigations reveal that η3‐lithio‐1,3,3‐triphenylpropyne‐(diethyl ether)2 [6 · (OEt2)2] is of the propargyl structural type while [1‐lithio‐1‐(2‐methoxyphenyl)‐3,3‐diphenylallene‐(diethyl ether)]2 {[7 · OEt2]2} is of the allenyl type. The assignment of the different structural types is mainly based on a comparison of the bond lengths C1‐C2 and C2‐C3 as well as of the difference ΔCC of these two bond lengths with the corresponding values of theoretical models of the propargyl and allenyl type. This leads also to a correction of an earlier assigned structural type.
Glycosyl imidates, 69. Synthesis of flavone C‐glycosides vitexin, isovitexin, and isoembigenin
Authors: Mahling Jürgen‐Andreas , Jung Karl‐Heinz , Schmidt Richard R.
Published: July 2007

2‐Hydroxy‐4,6‐dimethoxyacetophenone (4) was glycosylated with O‐(2,3,4,6‐tetra‐O‐benzyl‐α‐D‐glucopyranosyl) trichloroacetimidate (5) and trimethylsilyl triflate as promoter to yield directly the C‐glycoside 6. Construction of the flavone system by application of a Baker‐Venkataraman‐type rearrangement followed by deprotection yielded isoembigenin (2). Glycosylation of 4,6‐bis(tert‐butyldimethylsilyloxy)‐2‐hydroxyacetophenone (17) with the trichloroacetimidate 5 afforded the O‐glycoside intermediate 18 which was converted via Fries rearrangement into the C‐glycoside 21. Applying again the Baker‐Venkataraman rearrangement and cyclization gave isovitexin and vitexin derivatives 25 and 26, which were completely deprotected to yield isovitexin (1b) and vitexin (1a), respectively.
Perylenamidine‐imide dyes
Authors: Langhals Heinz , Sprenger Sylvia , Brandherm Marie‐Theres
Published: July 2007

Perylene‐3,4:9,10‐tetracarboxylic acid 3,4‐anhydride‐9,10‐imides are condensed with primary diamines to a number of new basic chromophores with amidine‐imide structures. Lightfast dyes are obtained which exhibit a strong fluorescence in solution. The absorption and fluorescence spectra of the title compounds are bathochromically shifted compared to those of the perylene dyes.
On 3,5,6‐trihalo‐2‐(pyrrol‐2‐yl)‐1,4‐benzoquinones
Authors: Ribó Josep M. , Acero Carles
Published: July 2007

In the reaction of pyrroles with tetrahalo‐1,4‐benzoquinones two different processes occur: the oxidation of pyrrole and the coupling reaction to 3,5,6‐trihalo‐2‐(pyrrol‐2‐yl)‐1,4‐benzoquinones. Excess of pyrrole results in doped polypyrrole as the principal reaction product. Excess of tetrahalobenzoquinone and dilution, provides the title compounds. The UV/Vis spectra and the electrochemical behaviour show that the title compounds have the HOMO localized at the pyrrole and the LUMO at the quinone ring.
Thermolabile hydrocarbons, 34. . Kinetics of the generation of 1,3‐di‐tert‐butylallyl radicals by thermal CC bond cleavage reactions
Authors: Herberg Clemens , Verevkin Sergej P. , Nölke Margot , Beckhaus Hans‐Dieter , Rüchardt Christoph
Published: July 2007

The title radicals were generated by thermal decomposition of (E,E)‐meso‐ and (E,E)‐(±)‐5,6‐di‐tert‐butyl‐2,2,9,9‐tetramethyl‐3,7‐decadiene (4a, b), (E)‐5‐(1,1‐dimethylethyl)‐2,2,6‐trimethyl‐6‐phenyl‐3‐heptene (6), and (E)‐5‐(diphenyl‐methyl)‐2,2,6,6‐tetramethyl‐3‐heptene (7). The activation parameters of these reactions were calculated from the rate constants which were followed over a 40°C temperature range. The enthalpies of formation of 4a, b were determined from the enthalpies of combustion and enthalpies of vaporization, those of 6 and 7 by MM2 calculation. From these data and their comparison with those of comparable saturated hydrocarbons of similar strain the radical stabilization enthalpy of the title radical RSE = 11.4 ± 1.5 kcal/mol was determined, which is in good agreement with results obtained from other model compounds (12.6 kcal/mol) previously.
Ein einfacher Weg zu D‐Apio‐β‐D‐furanosyl‐ und 2′‐Desoxyapio‐β‐D‐furanosylnucleosiden
Authors: Hammerschmidt Friedrich , Öhler Elisabeth , Polsterer Johann‐Peter , Zbiral Erich , Balzarini Jan , Declercq Erik
Published: July 2007

A Convenient Route to D‐Apio‐β‐D‐furanosyl‐ and 2′‐Deoxyapio‐β‐D‐furanosyl Nucleosides

2,3‐O‐Isopropylidene‐D‐apio‐β‐D‐furanose (1), available in 40% overall yield by modified literature procedures, is acylated regioselectively to the new 3′‐O‐benzoyl‐derivative 2. This is converted to the anomeric triacetates 4 (β‐4; α‐4 = 1.8:1) by cleavage of the isopropylidene protecting group from 2 followed by peracetylation. Reaction of compounds 4 with silylated nucleobases and subsequent deprotection gives the D‐apio‐β‐D‐furanosyl nucleosides 8–10 in good yields. Regioselective hydrazinolysis of the protected nucleosides 5 and 6 affords the 2′‐hydroxy‐derivatives 11 and 12, respectively, which are converted to the 2′‐deoxyapio‐β‐D‐furanosyl nucleosides 17 and 18, respectively, via deoxygenation of the corresponding thionocarbonates 13 and 14 with tris(trimethylsilyl)silane and subsequent deprotection. The 2′‐deoxyapio‐β‐D‐furanosyl cytosine 20 is prepared from the 2′‐deoxyapio‐β‐D‐furanosyl uracil derivative 16.
The Isolation and Structure Elucidation of Debromoaxinohydantoin
Authors: Groszek Grażyna , Kantoci Darko , Pettit George R.
Published: July 2007

A new pyrrololactam, the debromoaxinohydantoin (2b), has been discovered in Monanchora sponge along with the known pyrrologuanidines 1a, 1b, and the pyrrololactam 2a. The structure of 2b was confirmed by extensive NMR studies and MS data.
Synthesis of α‐amino‐3‐chloro‐4,5‐dihydro‐5‐methyl‐5‐isoxazoleacetic acid, a ring‐methylated analogue of the antitumor agent acivicin (AT‐125)
Authors: Griesbeck Axel G. , Hirt Joachim , Peters Karl , Peters Eva‐Maria , von Schnering Hans‐Georg
Published: July 2007

α‐Amino‐3‐chloro‐4,5‐dihydro‐5‐methyl‐5‐isoxazoleacetic acid (8), a ring‐methylated analogue of the potent antitumor agent acivicin (AT‐125), is synthesized in a 6‐step procedure in 63% overall yield from (S)‐valine. Key step is the 1,3‐dipolar addition of bromonitrile oxide to theN,C‐protected (S)‐isodehydrovaline (6) available from (S)‐valine in four steps involving the photoisomerization ofN‐phthaloylvaline methyl ester (1). The stereochemical course of the 1,3‐dipolar cycloaddition is proven by means of a X‐ray structure analysis of the major diastereoisomer7aformed in the chloronitrile oxide cycloaddition. The absolute configuration of the major (u) diastereomer7aand the bromo derivative7bis (αS,5R).
Synthesis of substituted chiral piperazinones as building blocks for peptidomimetics
Authors: Kolter Thomas , Dahl Christina , Giannis Athanassios
Published: July 2007

A new approach to 3,6‐disubstituted chiral piperazinones 6a, b and 7a, b from D‐glucosamine hydrochloride (1) or N‐Z‐D‐glucosamine (8) and L‐amino acid derivatives 2a, b or 9a, b is presented. Both final products and the intermediate pseudopeptides constitute valuable starting materials for the synthesis of peptidomimetics.
Azobenzene‐Based Photoswitchable Catenanes
Authors: Bauer Martin , Manfred Müller Walter , Müller Ute , Rissanen Kari , Vögtle Fritz
Published: July 2007

Four catenanes (1–4) and the corresponding tetracationic monocycles 5–8 are synthesized. X‐ray structural analyses allow a prediction of the mobility (circumrotation) of the „interlocked”︁ rings in the catenanes, which is proven by 1H‐NMR spectroscopy. An unexpected order in the crystal packing of 6 is demonstrated. (E/Z) isomerization in one ring influences the second ring of 1–4 and inversely. An existing obstacle inside the cavity of the switchable macrocycle can block this isomerization completely.
Reactions of 6‐[bis(trimethylsilyl)amino]‐5,6‐dihydro‐4H‐1,2‐oxazines
Authors: Paulini Klaus , Gerold Andreas , Reißig Hans‐Ulrich
Published: July 2007

1,2‐Oxazine 1 was converted into an unusual condensation product 5 by treatment with tetra‐n‐butylammonium fluoride. The hydrogenolysis of 1 with Pd/C as catalyst provided the expected primary amine 9, whereas the same reaction with the ethoxycarbonyl‐substituted 1,2‐oxazine 2 as starting material gave the 4‐methylproline derivative 10 after N‐protection. Deprotonation at C‐4 of 1 required rather harsh conditions but cleanly afforded the corresponding lithiated intermediate 11. Treatment of 11 with electrophiles provided the C‐4‐substituted derivatives 12–16 in good to moderate yield, but generally with very high diastereoselectivity. The overall substitution process preferentially occurs with retention of configuration which is explained by assuming ion pair structure B for intermediate 11.
Antibiotics from Gliding Bacteria, LXIII. Ratjadone: A New Antifungal Metabolite from Sorangium cellulosum
Authors: Schummer Dietmar , Gerth Klaus , Reichenbach Hans , Höfle Gerhard
Published: July 2007

The antifungal metabolite ratjadone (1) was isolated from the myxobacterium Sorangium cellulosum, strain So ce360. Production was achieved by fermentation in the presence of the adsorber resin XAD‐16, extraction and separation by RP chromatography. The structure of 1 was determined by spectroscopic methods. It is characterized by a 4‐hydroxytetrahydropyran and a 5,6‐dihydropyran‐2‐one ring which are connected by an unsaturated C11 carbon chain. The polyketide origin of 1 was proven by feeding experiments with 13C‐labeled precursors and NMR spectroscopic examinations.
Pheromone synthesis, CLXVIII. Synthesis of cruentol [(4S,5S)‐5‐methyl‐4‐octanol], the aggregation pheromone of palmetto Weevil, Rhynchophorus cruentatus
Authors: Mori Kenji , Murata Noriaki
Published: July 2007

Cruentol [(4S,5S)‐1], the male‐produced aggregation pheromone of Rhynchophorus cruentatus, was synthesized by starting from the epoxy alcohol 3 obtained by lipase‐catalyzed asymmetric hydrolysis of the meso‐diacetate 2.
Axinastatin 1 or malaysiatin? proof of constitution and 3D structure in solution of a cyclic heptapeptide with cytostatic properties
Authors: Konat Robert K. , Mathä Barbara , Winkler Johannes , Kessler Horst
Published: July 2007

Recently, a cyclic heptapeptide with cytostatic activity was isolated from marine sources by three different groups independently. The sequence of the isolated peptide was ambiguous, since two different isomers have been proposed: cyclo(‐Asn1‐Pro2‐Phe3‐Val4‐Val5‐Pro6‐Val7‐) (1) also called axinastatin 1 resp. pseudoaxinellin and cyclo(‐Asn1#‐Pro2#‐Pro3# ‐Phe4#‐Val5#‐Val6#‐Val7#‐) (2) called malaysiatin. We synthesized both peptides 1 and 2 and compared their optical rotation, FAB‐MS, 1H‐ and 13C‐NMR data with those of the native compounds. Our results prove that peptide 1 has been assigned correctly, whereas the data of 2 differ significantly from those of the natural peptide. Peptide 1 adopts two conformations (90:10 ratio) in DMSO, interconverting slowly on the NMR time scale. According to MD simulations, using NOEs and J couplings as experimental restraints, a βVIa‐turn with a cis peptide bond between Val5‐Pro6 and a βI‐turn in the Asn1‐Val4 region are the characteristic secondary structural elements of the major conformer. Its backbone conformation is very similar to the X‐ray structure of a related peptide cyclo(‐Asna‐Leub‐Serc‐Phed‐Leue‐Prof‐Valg‐) called evolidine.
Ring‐chain tautomerism provides a route to 7a‐hydroxy‐3a‐methyl‐2,7‐dioxoperhydrobenzofuran. Synthesis of the hydroxy γ‐lactone substructure of myrocin and other bioactive natural products
Authors: Langschwager Wolf , Hoffmann H. Martin R.
Published: July 2007

(2‐Oxocyclohexyl)acetic acid 10 was converted into bicyclic alkoxy γ‐lactones 12a–d via intermediate chloro lactone 11 and alkanolysis. Similarly, lactones 15a, b and 18 were prepared. In contrast, simple ring‐chain tautomerism directly afforded the title heterocycle 28, a crystalline, stable and well‐defined compound. The angular methyl group seems essential for the spontaneous lactonization. 5,5‐Dialkoxy‐4‐oxocarboxylic acids 26a, b without an angular methyl group did not cyclize to bicyclic hydroxy γ‐lactones.
Cytostatic activity against HeLa cells of a series of indazole and indole derivatives; synthesis and evaluation of some analogues
Authors: Arán Vicente J. , Flores María , Muñoz Pilar , Ruiz José R. , Sánchez‐Verdú Prado , Stud Manfred
Published: July 2007

The remarkable cytostatic activity of 1‐substituted indazolols 2a,b, condensed indazolinones 4a–c and indoxyl derivatives 5a, b against HeLa cells is reported. Three different approaches to the synthesis of indazolophthalazinone 4a, representing alternatives to those previously reported, were studied. Several compounds related to the mentioned indazolols and indazolinones were obtained and their cytostatic activity against HeLa cells was tested. Among them we can mention the tetracyclic SO2 analogue 14 and the condensed pyridine derivative 18, the tricyclic pyrazolophthalazinone 22 and the bicyclic pyrazolodiazepinone 25, which were prepared by taking advantage of the reactivity of heterocyclic spiro aminimides.
Silyl enol ethers in Paternò‐Büchi reactions. Functional group tolerance and the effect of β‐alkyl substitution
Authors: Bach Thorsten
Published: July 2007

The photochemically induced diastereoselective formation of 3‐(silyloxy)oxetanes from silyl enol ethers and aromatic aldehydes was studied. It is shown that many heteroatom‐ and double bond‐containing substituents (ether, ester, acetal, amide, alkene) withstand the reaction conditions and may therefore be attached either to the carbonyl compound (e.g. 9) or to the silyl enol ether (e.g. 1). The formation of several functionalized oxetanes such as 2 and 11 was achieved in decent yields (42–70%). Furthermore the effect of β‐substituents at the silyl enol ether was investigated. A stereoconvergent Paternò‐Büchi reaction of aromatic aldehydes afforded the corresponding oxetanes (13, 16–18) in fair to excellent yields (45–87%) and with diastereoselectivities (ds) of 65–95%. No detrimental influence of the steric bulk in the β‐position (R1 = Me, Et, and iPr) on the regiochemistry of the reaction was observed. Large substituents in the α‐position of the enol ether [R = iPr, tBu, C(OCH2)2Et, CMe2CHCH2] proved beneficial, isolated yields of the major diastereoisomeric oxetane ranging between 60 and 87%. The configuration of the products was elucidated by 1H‐NMR spectroscopy. In the major isomer all large vicinal substituents Ar (at C‐2), R (at C‐3), and R1 (at C‐4) at the oxetane nucleus are oriented trans to each other. The stereoselective formation of three stereogenic centers at a time can be explained by a non‐concerted mechanism which invokes the intermediacy of 1,4‐diradicals as intermediates.
Four new carotenoids from Polyangium fumosum (myxobacteria): 3,3′,4,4′‐tetradehydro‐1,1′,2,2′‐tetrahydro‐1,1′‐dihydroxy‐Ψ,Ψ‐carotene (di‐O‐demethylspirilloxanthin), its β‐glucoside and glucoside fatty acid esters
Authors: Jansen Rolf , Nowak Alexander , Kunze Brigitte , Reichenbach Hans , Höfle G.
Published: July 2007

The intense red color of the cell extracts of Polyangium fumosum, the producer of the tristhiazoline metabolite thiangazole A, is mainly caused by four new carotenoid pigments, i.e. di‐O‐demethylspirilloxanthin (1), its β‐glucoside 2 and the glucoside fatty acid esters 3 and 4. Their structures were elucidated by IR, UV, and NMR spectroscopy and by mass spectrometry.
Substituent effects on the CC bond strength, 17. Formation and stability of α‐carbamoylbenzyl radicals
Authors: Züffle Stephan , Beckhaus Hans‐Dieter , Rüchardt Christoph
Published: July 2007

Products and kinetics of the homolytic thermolyses reactions of the three tertiary amides 6a–c of 2,3,3‐triphenylpropanoic acid were studied in solution. The steric effects on the C‐C bond homolysis processes were evaluated from MM2 calculations. Taking this into account, we deduced radical stabilization enthalpies RSE for the α‐carbamoylbenzyl radicals 3a–c from the activation enthalpies ΔH≠ [RSE (kcal/mol): 8.3 ± 2.8 (3a), 10.3 ± 2.7 (3b), 9.0 ± 2.2 (3c)].
Enantioselective synthesis of the polyketide antibiotic (3R,4S)‐(−)‐citrinin
Authors: Rödel Thomas , Gerlach Hans
Published: July 2007

The fungal metabolite (−)‐citrinin (1) was synthesized for the first time. Reaction of the Grignard reagent of 2,4‐bis(benzyloxy)‐6‐bromotoluene (3) with (2S)‐trans‐(−)‐2,3‐dimethyloxirane (6) in the presence of 1,5‐cyclooctadienecopper(I) chloride as catalyst leads to the formation of (2S,3S)‐(−)‐7 with erythro configuration. Compound (−)‐7 could be transformed into (2R,3S)‐(−)‐9 with threo configuration via the formate (1R,2S)‐(+)‐8 by a Mitsunobu reaction. Reaction of the Grignard reagent of 3 with the achiral cis‐2,3‐dimethyl‐oxirane yielded directly (±)‐9. The starting material 3 was readily available from 1,3‐bis(benzyloxy)‐5‐bromobenzene (4). Formylation of 4 furnished the aldehyde 5 which could be reduced to 3 with borane. Hydrogenolysis of the benzyl ether groups in (−)‐9 gave (−)‐2 with threo configuration. The remaining steps to produce citrinin [(−)‐1] from (−)‐2 required carboxylation to 11, formylation and in situ ring closure with ethyl orthoformate to produce the required quinomethide structure. Application of the same reactions to (±)‐9 and (±)‐2 afforded (±)‐citrinin in 40% overall yield.
Efficient synthesis of sphingosine‐1‐phosphate, ceramide‐1‐phosphate, lysosphingomyelin, and sphingomyelin
Authors: Kratzer Bernd , Schmidt Richard R.
Published: July 2007

Readily available D‐erythro‐azidosphingosine is transformed into 3‐O‐silyl‐protected derivative 6. Reduction of the azido group afforded 3‐O‐silyl‐protected sphingosine 7 which was either converted into N‐Fmoc‐protected derivative 8 or via N‐acylation into ceramide derivatives 16 and 17, respectively. Treatment of 6, 8, and 16 with bis(2‐cyanoethoxy)(diiso‐propylamino)phosphane as monofunctional phosphitylating agent, subsequent oxidation and then removal of the protective groups furnished azidosphingosine‐1‐phosphate (11), sphingosine‐1‐phosphate (2), and ceramide‐1‐phosphate (4), respectively. Treatment of 8 and 17 with bis(diisopropyl‐amino)(2‐cyanoethoxy)phosphane as bifunctional phosphitylating agent and then with choline afforded after oxidation and subsequent deprotection lysosphingomyelin (3) and sphingomeylin (1), respectively in high overall yields. All final products are stereochemically pure and possess D‐er‐ythro configuration in the sphingosine moiety.
New alkaloids from ants: Identification and synthesis of (3R,5S,9R)‐3‐butyl‐5‐(1‐oxopropyl)indolizidine and (3R,5R,9R)‐3‐butyl‐5‐(1‐oxopropyl)indolizidine, constituents of the poison gland secretion in Myrmicaria eumenoides (hymenoptera, formicidae)
Authors: Francke Wittko , Schröder Frank , Walter Felix , Sinnwell Volker , Baumann Horst , Kaib Manfred
Published: July 2007

The (3R,5S,9R) and (3R,5R,9R) stereoisomers of 3‐butyl‐5‐(1‐oxopropyl)indolizidine (9) were identified as major constituents of the poison gland secretion of the African ant, Myrmicaria eumenoides. Racemates of the four diastereomers of 9 were synthesized via the corresponding ethyl 5‐(5‐butylpyrrolidin‐2‐yl)pentanoates (6). Enantiomerically pure samples of the (3R)‐stereoisomers of 9 were obtained by starting from (2R)‐2,3‐O‐isopropylideneglyceric aldehyde (21) and 6‐methylpyridine‐2‐carboxaldehyde (20). In addition, the enantiomeric separation by chiral gas chromatography and unambiguous structure assignment of the target compounds are described.
Synthesis and characterization of 1,3‐bis‐(2‐dialkylamino‐5‐thiazolyl)‐substituted squaraines and their 2‐(dialkylamino)thiazole precursors
Authors: Keil D. , Hartmann H.
Published: July 2007

By condensation of squaric acid (1) with 2‐(dialkylamino)‐substituted thiazoles 8 a novel type of heterocyclic‐substitued squaraines of the general structure 9 was prepared in moderate yield mostly. The squaraines 9 obtained are sparingly soluble in the most organic solvents and exhibit, in these solvents, narrow absorption bands in the visible range at about 620–700 nm. In dispersed form, the absorption bands of the squaraines 9 are, however, broadened and shifted into the NIR region at about 900 nm. These unique properties of the new squaraines 9 suggest the use of these dyes as spectral sensitizers for laser‐driven data recording or data storage media.
Synthesis and characterization of amphiphilic chlorins for photodynamic tumor therapy (PDT)
Authors: Kusch Dirk , Meier Axel , Montforts Franz‐Peter
Published: July 2007

Chlorindicarboxylic acids with different alkyl side chains were prepared and their amphiphilic properties studied. The chemical purity, photophysical properties and the lipophilicity due to the alkyl side chains make the chlorins potential candidates for applications in photodynamic therapy.
Studies on electron transfer as mechanistic concept for [4 + 2] cycloadditions, 2. Cycloadditions of 2,3‐bis(dimethylaminomethylene)bicyclo[2.2.1]heptane and 2,3‐bis(dimethylaminomethylene)bicyclo[2.2.2]octane with electron‐deficient olefins
Authors: Rese Michael , Dern Mechthild , Lücking Karin , Sustmann Reiner
Published: July 2007

Electron transfer as initiating step in [4 + 2] cycloadditions was studied with 2,3‐bis(dimethylaminomethylene)bicyclo‐[2.2.1]heptane (1) and 2,3‐bis(dimethylaminomethylene)bicyclo[2.2.2]octane (2) as models. These dienes, having the necessary synperiplanar configuration for a concerted [4 + 2] cycloaddition were allowed to react with dienophiles of increasing acceptor capacity. Slightly activated alkenes like methyl acrylate and acrylonitrile undergo smooth cycloaddition in contrast to the corresponding open‐chain dienes where cycloaddition with these dienophiles could not be observed. The use of dimethyl fumarate and dimethyl maleate lead to identical cycloaddition products due to an isomerization of dimethyl maleate catalyzed by 1 and 2. Fumaronitrile and maleonitrile proved to be stable under the reaction conditions and lead to different stereoisomers in the cycloaddition to 2. The introduction of three and four acceptor groups, different combinations of cyano and methoxycarbonyl groups, leads to a sudden increase in reactivity towards 1 and 2. At the same time the cycloadditions are no longer stereospecific in those cases where they could be checked, and radical ions could be detected either by ESR spectroscopy or by stopped‐flow visible spectroscopy. This applies in particular to dichloromethane as solvent. Stopped‐flow measurements in combination with a rapid‐scan unit reveals a transient absorption at λ ∽ 420 nm in acetonitrile for 1,1‐dicyano‐2,2‐bis(methoxycarbonyl)ethene and dimethyl dicyanofumarate as dienophiles which is ascribed to zwitterionic intermediates by a comparison with related systems. The cycloadditions of TCNE to 1 and 2 lead to thermally unstable adducts in both cases. Electron transfer was not only observed in solution but could also be detected in the isolated solid products, in particular if they were placed in a polar environment like KBr where complete dissociation in radical ions seems to take place. The relevance of these studies for the mechanism of Diels‐Alder reactions is that suitable model systems can be constructed where electron transfer can be observed. Due to the loss of stereospecificity in these cases it is concluded that complete electron transfer is not the principal mechanism of these [4 + 2] cycloadditions which in their majority occur with retention of stereochemistry in the reactants.
Efficient and convergent synthesis of (R)‐(−)‐10‐methyltridecan‐2‐one, the sex pheromone of the spotted cucumber beetle, by iron‐mediated chirality transfer
Authors: Enders Dieter , Jandeleit Bernd
Published: July 2007

The synthesis of (R)‐(−)‐10‐methyltridecan‐2‐one, the female sex pheromone of the southern corn root worm (Diabrotica undecimpunctata howardi Barber) [(R)‐1] in high enantiome‐ric purity (ee ≥ 99%) and excellent overall yield (75%, five steps) is described. In the crucial step the stereogenic center is generated by nucleophilic addition of allyltrimethylsilane to an enantiopure planar chiral (π‐allyl)tetracarbonyl‐iron(1 + ) complex.
Asymmetric michael additions via SAMP/RAMP hydrazones enantioselective synthesis of 2‐substituted 4‐oxophosphonates
Authors: Enders Dieter , Wahl Heiner , Papadopoulos Kyriakos
Published: July 2007

Asymmetric Michael addition of lithiated methyl ketone SAMP hydrazones (S)‐3 to a variety of alkenylphosphonates (E)‐2 followed by oxidative cleavage of the 1,4‐adducts (S,S)‐4 by ozonolysis afforded 2‐substituted 4‐oxophosphonates (S)‐5 in usually moderate to very good overall yields (14–77%) and with mostly high enantiomeric excesses (ee = 20–>95%). In addition, asymmetric Michael Michael tandem additions were carried out in good overall yields by trapping the intermediate lithio phosphonate anions with alkenylphosphonate or enoate Michael acceptors.
[4+ + 2] Cycloadditions with an N‐Methyl‐4H‐pyrazolium cation as electron‐deficient diazadiene system
Authors: Frenzena Gerlinde , Gerninghaus Christian , Meyer‐Dulheuer Christiane , Paulus Erich F. , Seitz Gunther
Published: July 2007

3,6‐Diphenyl‐1,2,4,5‐tetrazine (6) reacts with dimethoxycarbene (7), generated from the 1,3,4‐oxadiazoline 8, to yield the 4H‐pyrazole 10. This is alkylated to the N‐methyl‐4H‐pyrazolium tetrafluoroborate 12 in high yield. The alkylated, cationic azine system of 12 serves as electron‐deficient diene in a [4+ + 2] cycloaddition with inverse electron demand and reacts diastereoselectively with several cyclic olefins as electron‐rich dienophiles. The initially formed cationic [4+ + 2] adduct, e.g. 15, is unstable and rearranges probably via 16 to a racemic phthalazinecarboxylic ester of type 17. The crystal structures of the epoxyphthalazinecarboxylic ester 25 and of the trans‐annulated cycloocta[d]pyridazine 27 were determined by X‐ray diffraction. In contrast to the cyclic olefins, cyclooctyne (28) reacts with the pyrazolium cation 12 to yield the cyclooctapyridiazinium tetrafluoroborate 30 via the cycloadduct 29.
Chiral lactols, XIII. On the determination of the absolute configuration of aromatic cyanohydrins and structurally related compounds
Authors: Noe Christian R. , Knollmüller Max , Gärtner Peter , Katikarides Elias , Gaischin Larissa , Völlenkle Horst
Published: July 2007

Synthesis and conformational analysis of diastereomeric acetals 4–7 of aromatic cyanohydrins and structurally related compounds are described. Based on 1H‐NMR spectroscopic and X‐ray data it is shown that the absolute configuration of such compounds can be assigned according to a method, which has been presented previously for secondary arylalkyl alcohols.
Zum konzertierten oder nichtkonzertierten Verlauf von Reaktionen; Thermolyse von Dispiro[2.2.2.2]deca‐4,9‐dien
Authors: Roth Wolfgang R. , Unger Christian
Published: July 2007

Concerted and Nonconcerted Reaction Path; Thermolysis of Dispiro[2.2.2.2]deca‐4,9‐diene

The enthalpy profile for the equilibrium 1 ⇄ 2 ⇄ 3 has been determined by oxygen trapping. From the oxygen dependence at low (0.0005–0.2 bar) and high pressure (1–180 bar) between 130 and 190°C the enthalpy wells of the diradicals 3 and 2 have been derived (3 17.1, 2 3.7 kcal · mol−1). The observation of a nonconcerted path for the equilibrium 1 ⇄ 3 is important with respect to the understanding of the controlling factor of the concerted and nonconcerted path of a reaction. The existence of a favourable potential energy path obviously is not of prime importance.
Synthesis of medium and large ring compounds, XXXIX. Stereoselective synthesis of both enantiomers of 13‐tetradecanolide by ring enlargement with different chiral building blocks and olfactory comparison with (12R)‐(+)‐ and (12S)‐(−)‐12‐methyl‐13‐tridecanolide
Authors: Kraft Philip , Tochtermann Werner
Published: July 2007

Starting from a cycloalkanone and the chiral building blocks 2 or 3 both enantiomers of 13‐tetradecanolide (1, n = 14) were prepared by ring‐enlargement reactions. Cycloundeca‐none (4) was α‐alkylated with the protected hydroxy halide 2 derived from (S)‐(−)‐methyl lactate. Acid‐catalyzed cyclization, oxidative cleavage of the enol ether double bond by PCC, and reduction of the carbonyl group via a tosylhydrazone led to the (S)‐configured target molecule (+)‐8 (98.0% ee), thus indicating the sequence proceeded with clean retention of configuration. Likewise, the naturally occurring (R)‐enantiomer (−)‐8 (>99.8% ee) was synthesized from cyclodecanone (9) and the chiral building block 3. Aided by CD conformational analysis the olfactory properties of both enantiomers were compared with those of the regioisomers (12R)‐( + )‐ and (12S)‐(−)‐12‐methyl‐13‐tridecanolide previously prepared by the same method.
Synthesis of epimeric pure spiro N,S‐acetals of L‐menthone
Authors: Altenbach Hans‐Josef , Roth Peter R. , Brauer David J.
Published: July 2007

By acetalisation of L‐menthone (2) with mercaptoacetic acid and derivatives of benzylamine, the spirocyclic N,S‐acetals 3 were obtained as single diastereomers. The reaction of an epimeric mixture of unsubstituted thiazolidinones 4 with acetic anhydride or allyl iodide afforded homochiral N‐acetyl (5) or N‐allyl N,S‐acetals (6), respectively. The configuration of the new stereogenic centres were proven by X‐ray crystallography.
Regioselective monometalation of 2,5‐pyridinedicarboxamides with (2,2,6,6‐tetramethylpiperidino)magnesium chloride (TMPMgCI)
Authors: Schlecker Wolfgang , Huth Andreas , Ottow Eckhard , Mulzer Johann
Published: July 2007

The 2,5‐pyridinecarboxamides 9–15 were synthesized in one or two steps from diester 1 by addition of an excess of dimethylaluminium amide or successive addition of two different dimethylaluminium amides with or without intermediate workup. For the carboxamides 16 and 17 this method failed; they were, however, available by other procedures. Metalation of the carboxamides 9–17 with TMPMgCI and subsequent reaction with electrophiles led to the 2,3,5‐ and 2,4,5‐substituted pyridines 9a/b‐17a/b, 18 and 19 with regioselectivities ranging from predominant 4‐substitution to complete 3‐substitution.
Macrocyclic (1,3)‐ and (1,4)‐benzena‐(1,4)‐piperazinacyclophanes
Authors: Huuskonen Juhani , Schulz Jürgen , Rissanen Kari
Published: July 2007

New large, up to 45‐membered macrocycles were synthesised from piperazine and m‐ and p‐2,6‐bis(bromomethyl)xylene under high dilution conditions. X‐ray structures of compounds 3a, 4a, 5a, and 8b were determined. Surprisingly, none of the macrocycles prepared showed any inclusion properties towards small guest molecules. Instead, the compounds were found to self‐organize during the packing process into larger structures due to the complementary of the molecular skeletons. In the crystalline state 3a forms nets, where the macrocycles are bound by HCH…︁N interactions to each other. 4a exits in a dimeric structure, which, in turn, further extends to a sheet structure. The positively charged phane 8b (di‐dihydrochloride salt) adopts a chair‐chair conformation, confirming that protonation of the N atoms does not change the conformation.
Dimethyldioxirane epoxidation of chalcone and isoflavone glycoside acetates
Authors: Adam Waldemar , Jekõ József , Lévai Albert , Nemes Csaba , Patonay Tamás
Published: July 2007

Epoxides of chalcone and isoflavone glycoside acetates were synthesized in high yields and under mild conditions by using dimethyldioxirane. No enantiofacial selectivity was observed during the epoxidation of the enone system.
Acetonitrile inclusion complexes of piperazine‐based macrocycles
Authors: Huuskonen Juhani , Rissanen Kari
Published: July 2007

New piperazine‐based macrocycles with single small cavities were prepared by using high dilution technique. The inclusion of acetonitrile into the cavity (7, 8) or clathrate formation (3) was studied by 1H‐NMR spectroscopy in solution and by X‐ray diffraction in the crystalline state. The cycle 3 forms a molecular cleft, a molecular pocket, where the acetonitrile molecule is held by four weak N…︁H interactions reinforcing the clathrate formation. The cycles 7 and 8 contain a rigid cavity for an exact sterical fit with the methyl group of a linear compound like acetonitrile. The acetonitrile inclusion complex with 7 proved to be stable under normal conditions and was studied by means of thermogravimetry. It is stable up to 80°C and the breakdown is complete when the temperature is raised over 120°C. Solid‐state IR studies show a shift of the cyano band of 5 cm−1 to smaller wave numbers when compared with free acetonitrile. The acetonitrile methyl group is shielded and in the 1H‐NMR spectrum its signal is shifted to δ = 1.85.
Studies on the constituents of the stems of Tinospora tuberculata, V. Isolation and structure elucidation of the new furanoid diterpene glucoside borapetoside H
Authors: Fukuda Naomichi , Yonemitsu Michiko , Kimura Takeatsu
Published: July 2007

The new diterpene glucoside borapetoside H (1) was isolated from the fresh stems of Tinospora tuberculata Beumée (Menispermaceae). Its structure as 2‐O‐β‐D‐glucopyranosylborapetoside B was elucidated on the basis of chemical and spectroscopic findings.
Organofluorine compounds and fluorinating agents, 15. O‐difluoromethylations of monosaccharides by trifluoromethylzinc bromide
Authors: Miethchen Ralf , Hein Martin , Naumann Dieter , Tyrra Wieland
Published: July 2007

1,2:3,4‐Di‐O‐isopropylidene‐α‐D‐galactopyranose (1), methyl 2‐O‐(cyclohexylcarbamoyl)‐3,4‐O‐(2,2,2‐ trichloroethylidene)‐α‐D‐altropyranoside (4), methyl 4,6‐O‐benzylidene‐2‐O‐to‐syl‐α‐D‐glucopyranoside (6), and methyl 4,6‐O‐benzylidene‐α‐D‐glucopyranoside (8) were O‐difluoromethylated with tri‐fluoromethylzinc bromide (ZnBrCF3. 2 CH3CN) in a convenient procedure giving the difluoromethyl ethers 2, 5, 7, 9, and the bis(difluoromethyl) ether 10 in moderate yields. The 6‐O‐difluoromethyl‐1,2:3,4‐di‐O‐isopropylidene‐ α‐D‐galacto‐pyranose (2) was deprotected by treatment with aqueous tri‐fluoroacetic acid forming 6‐O‐difluoromethyl‐D‐galactopyranose (3).
Carbenes in constrained systems, 3. Solid‐State photolysis of cycloheptane‐ and cyclooctanespirodiazirine within cyclodextrins and zeolites
Authors: Kupfer René , Brinker Udo H.
Published: July 2007

Inclusion complexes of cycloheptanespirodiazirine (1) and cyclooctanespirodiazirine (8) in α‐, β‐, and γ‐cyclodextrin, and faujasite type zeolites (NaX and NaY), have been prepared. The guest‐host complexes (1‐ and 8@CD and 1‐ and 8@zeolite) were irradiated with UV light in the solid state and the reaction products were separated from the host and analyzed. Product ratios from photolysis of complexes were compared with those obtained from pure compounds and in solution. Cycloheptanespirodiazirine (1) gives cycloheptene (2), bicyclo[4.1.0]heptane (3), and methylenecyclohexane (4). Photolysis products from cyclooctanespirodiazirine (8) are cyclooctene (9), bicyclo[3.3.0]octane (10), and bicyclo‐[5.1.0]octane (11). 10 results from a 1,5‐C–H insertion reaction of the carbene derived from 8. As the cavity size of the cyclodextrins becomes larger, the formation of 10 seems to increase. In β‐cyclodextrin and in non‐polar solvents substantial amounts of azine were found. In addition to hydrocarbons, photolyses in zeolites afforded alcohols and small amounts of the corresponding ketones.
2,5‐dichloropentacyclo[4.3.0.02,5.03,8.04,7]non‐3‐ene: Generation and trapping of a homocubene and ab initio mo calculations on this and related molecules
Authors: Rosendorfer Karin , Jarosch Oliver , Polborn Kurt , Szeimies Günter
Published: July 2007

Reaction of bromotrichlorohomocubane 8 with MeLi in the presence of anthracene, 9,10‐dimethoxyanthracene, 1,2,3‐tri‐methylisoindole, diphenylisobenzofuran, and 2,5‐dimethyl‐furan furnished Diels‐Alder adducts of the title compound 2,5‐dichlorohomocubene 7 in reasonable yields. Adduct 14a was dechlorinated by reduction with Na in tert‐butyl alcohol to afford 14b. This compound could be selectively isomerized by AgBF4 to 20 and by the rhodium(I) complex 22 to a sensitive intermediate which could be reduced to 25. The structures of adduct 15a and of 14b were confirmed by X‐ray analysis, ensuring that bridgehead olefin 7 had been trapped. Ab initio MO calculations show that 7 is lower in energy than 11 and 12. The extension of the MO calculations to all parent homocubenes (2, 3, 26, 27, 28) and to dehydrohomocubanes 6 and 29 was carried out to obtain information on their relative energies, their structures, and their singlet‐triplet energy separation.
New anthranilic and methylsulfonylpropenoic acid amides from thai Glycosmis species
Authors: Hofer Otmar , Zechner Gabriela , Vajrodaya Srunya , Lutz Gerda , Greger Harald
Published: July 2007

Five new methylsulfonylpropenamides were isolated from different Glycosmis species collected in Thailand. Four of these derivatives contain 4‐geranyloxy‐3‐hydroxy‐substituted phenethylamine moieties, Sakerine (1) has a simple geranyloxy side chain; sakerone (2), sakerol (3), and dihydroisosakerol (4) are characterized by different states of oxidation in the geranyloxy residue. Methylgerambullal (5) contains a 4‐geranyloxy‐substituted phenethylamine unit with a terminal formyl group. Two additional amides, doisuthine (6) and methoxydoisuthine (7), exhibit the structures of N‐methylanthranilic acid amides with phenethylamine and p‐methoxyphenethylamine as amine components. All structures were elucidated by IR, UV, 1H‐, 13C‐, 2D‐NMR spectroscopy, mass spectrometry, and CD spectroscopy.
Influence of conformational factors on acid‐catalyzed cyclizations of germacranolides: Molecular structure of the cyclization products of gallicin and 8α‐hydroxygallicin (shonachalin a)
Authors: Marco J. Alberto , Sanz‐Cervera Juan F. , García‐Lliso Vicente , Domingo Luis R. , Carda Miguel , Rodríguez Santiago , López‐Ortiz Fernando , Lex Johann
Published: July 2007

Acid‐catalyzed cyclization of the natural germacranolide gallicin (8) yielded, among other products, the 1,4‐epoxyeudes‐manolide 9, which has a trans‐fused decaline system. Under the same conditions the closely related germacranolide shonachalin A (8α‐hydroxygallicin) (3) cyclized to the eudesmanolide 4 with a cis fused decaline system. The structures of these cyclization products were secured by means of chemical correlations and X‐ray diffraction analyses.
Synthetic routes to 1,4‐difunctionalized cycloheptenes
Authors: Maier Martin E. , Langenbacher Diane , Rebien Frank
Published: July 2007

Two routes to 1,4‐difunctionalized cycloheptenes are described. The first one is based on a fluoride‐induced fragmentation reaction of the bicyclic [3.2.0]heptanesilyl monosulfate 10. This compound in turn was prepared by a ketene‐cyclopentene cycloaddition route. An alternative strategy took advantage of a ring‐closing metathesis (RCM) reaction of the diolefin 18 with the ruthenium catalyst 21. This reaction proved to be reliable even on a larger scale and allowed the isolation of the cycloheptene 19a in reasonably good yield.
Syntheses and CD studies of optically active substituted 1,3,4,5‐tetrahydro‐2H‐1,5‐benzodiazepin‐2‐ones
Authors: Malik Farnaz , Hasan Mashooda , Khan Khalid Mohammed , Perveen Shahnaz , Snatzke Günther , Duddeck Helmut , Voelter Wolfgang
Published: July 2007

A route to optically active variously substituted 4‐methyl‐ and 4‐methyl‐7‐substituted 1,3,4,5‐tetrahydro‐2H‐1,5‐benzo‐diazepin‐2‐ones as analogues of commercially available Lofendazam (7‐chloro‐5‐phenyl‐1,3,4,5‐tetrahydro‐2H‐1,5‐benzodiazepin‐2‐one, 1) was developed. Fortyone variously substituted optically active compounds having the same configuration were prepared and the UV and CD spectra of the parent compounds bearing no additional substitution in the benzene ring are discussed.
Acid‐catalysed rearrangement of tetracyclo[4.3.0.02,9.04,8]nonane skeleton to substituted brendene derivatives
Authors: Mlinarić‐Majerski Kata , Kragol Goran , Šindler‐Kulyk Marija , Pavlović Dražen
Published: July 2007

The synthesis of 2‐exo‐substituted brendene derivatives 3a, 5a and 6 as well as 2,5‐disubstituted brendene derivative 7 is described, starting from the readily available tetracyclo‐[4.3.0.02,9.04,8]nonanone 1. The cationic rearrangement reactions of tetracyclic skeleton of 1 and 2 have been studied. The mechanism of these reactions is discussed. The preparation of inaccessible exo‐alcohol 2a by reduction of ketone 1 is presented.
Resolution of racemic 1‐azaadamantane derivatives by pig liver esterase catalysis
Authors: Mölm Detlef , Risch Nikolaus
Published: July 2007

The first kinetic resolution of racemic 1‐azaadamantane derivatives with PLE led to the enantiomers (−)‐1 and (−)‐2. An unexpected formation of 3 from 1 in aqueous solution was observed.