bluuebunny/crossref_metadata_2025_split huggingface dataset:
New taxoids from Taxus baccata L.
Authors: Barboni Luciano , Gariboldi Pierluigi , Appendino Giovanni , Enriù Renata , Gabetta Bruno , Bombardelli Ezio 
Published: July 2007

AbstractA 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

AbstractThe 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

AbstractTwo 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

AbstractThe 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

AbstractThe 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

AbstractCrystal 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

Abstract2‐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

AbstractPerylene‐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

AbstractIn 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

AbstractThe 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 Nucleosides2,3‐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

AbstractA 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

Abstractα‐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

AbstractA 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

AbstractFour 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

Abstract1,2‐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

AbstractThe 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

AbstractCruentol [(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

AbstractRecently, 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

Abstract(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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractProducts 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

AbstractThe 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

AbstractReadily 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

AbstractThe (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

AbstractBy 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

AbstractChlorindicarboxylic 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.