bluuebunny/crossref_metadata_2025_split huggingface dataset:
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 EthersOptically 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

AbstractPhytochelatins 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

AbstractUsing 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

AbstractBase‐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

AbstractTreatment 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 AcidLarge 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 EstersSyntheses 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

Abstract3‐, 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 Alkaloids1‐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

AbstractThe 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 DerivativesBuprenorphine (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

AbstractThe 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

AbstractA 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 TechniqueThe 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

Abstract(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

AbstractIn 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 PorphyrinsTripyrrylmethanetricarbaldehyde 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

AbstractFrom 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

AbstractThe 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 IPalladium‐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‐LactamsSeveral 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 Ether2,4‐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

AbstractTwo 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 ReactionStarting 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

AbstractThe 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.