bluuebunny/crossref_metadata_2025_split huggingface dataset:
Katalytische Carbonylierung von Aceton‐oxim an Bisoximato‐diruthenium‐Komplexen: Ein einfacher Zugang zu wasserfreiem Acetonin. Isolierung und Molekülstruktur von [Ru2(CO)5(Me2CNO)2(Me2CNOH)]
Authors: Langenbahn Meinhard , Stoeckli‐Evans Helen , Süss‐Fink Georg 
Published: December 2004

Catalytic Carbonylation of Acetone Oxime at Bisoximatodiruthenium Complexes: A Simple Access to Anhydrous Acetonine. Isolation and Molecular Structure of [Ru2(CO)5(Me2CNO)2(Me2CNOH)]In the presence of catalytic amounts of [Ru2(CO)4(Me2CNO)2(Me2CNOH)2] (1), acetone oxime reacts with carbon monoxide to give 2,3,4,5‐tetrahydro‐2,2,4,4,6‐pentamethylpyrimidine (‘acetonine’). CO2, and NH3. The reaction proceeds presumablyviacarbonylation of Me2CNOH to the unstable intermediate Me2CNOCHO which undergoes decarboxylation to give the corresponding imine Me2CNH. The final product is assumed to result from the cyclotrimerisation of Me2CNH with elimination of NH3. Evidence for the intermediacy of the imine comes from the analogous reaction of acetophenone oxime, PhMeCNOH, which gives the corresponding imine PhMeCNH as a stable product. The isolation of the complex [Ru2(CO)5(Me2CNO)2(Me2CNOH)] (2) suggests the carbonylation to take place at the bridging oximato ligand of1.
Synthesis and Properties of Sodium and Europium(III) Cryptates Incorporating the 2,2′‐Bipyridine 1,1′‐Dioxide and 3,3′‐Biisoquinoline 2,2′‐Dioxide Units
Authors: Lehn Jean‐Marie , Roth Christine O. 
Published: December 2004

AbstractThe sodium and europium cryptates of the new macrobicyclic ligands 2 and 3 incorporating the 2,2′‐bipyri dine 1,1′‐dioxide and 3,3′‐biisoquinoline 2,2′‐dioxide units, respectively, have been prepared. The EuIII complexes present characteristic 1H‐NMR spectra, showing large shifts, and are strongly luminescent in aqueous solution. These markedly improved luminescent properties, compared to the europium cryptate of the parent macrobicyclic ligand 1, may be ascribed at least in part to a better shielding of the bound cation by the N‐oxide sites.
Lithium‐Salt Effects in Peptide Synthesis. Part II. Improvement of Degree of Resin Swelling and of Efficiency of Coupling in Solid‐Phase Synthesis
Authors: Thaler Adrian , Seebach Dieter , Cardinaux Francis 
Published: December 2004

AbstractThe course of solid‐phase peptide‐coupling reactions as well as the swelling properties of a peptide‐resin are influenced by the addition of inorganic salts (LiCl, LiBr, LiClO4, KSCN). Used as additives, these salts can (i) improve coupling yields (e.g., for Fmoc‐(Ala)5‐Phe‐resin → Fmoc‐(AIa)6‐Phe‐resin in DMF/CH2Cl2 1:1 from 89.4 to 97.1% (for polyethylene oxide) on polystyrene ( PEO‐PS) resin) or from 77.5 to 93.8% (for poly‐(N,N′‐dimethylacrylamide) on ‘Kieselgur’ (PDMAA‐KG) resin) without and with 0.4M LiCl, respectively), (ii) increase resin swelling (e.g. for Fmoc‐(Ala)5‐Phe‐(polystyrene resin) from 2.42‐ to 5.73‐fold in 1‐methylpyrrolidin‐2‐one (NMP) without and with LiCl, (respectively), and (iii) change coupling rates. Example;; of coupling reactions and swelling behaviour (degree and rate) in different solvents (DMF, DMF/CH2Cl2 1:1, THF, NMP, N,N‐dimethylpropyleneurea ( DMPU) with and without salts) using different resins (polystyrene (PS); PEO–PS, and PDMAA‐KG) and an improved analysis of alanine oligomers up to Ala12‐Phe by HPLC and FAB‐MS are reported.
[5‐Leucin]enkephalin‐Related Glycoconjugates: Structurally Novel Agents Effective against HIV‐1
Authors: Horvat Štefica , Varga Lidija , Horvat Jaroslav , Pfützner Andreas , Suhartono Haryadi , Rübsamen‐Waigmann Helga 
Published: December 2004

AbstractA series of [Leu5]enkephalin‐related glycoconjugates with an ester‐, ether‐, or amide‐type linkage were synthesized and evaluated for antiviral activity against HIV‐1 in a cell‐culture system using peripheral blood lymphocytes. All tested glycoconjugates exhibited a certain antiviral activity which was significantly higher than the activity of the parent peptide compound itself. These results indicate that synthetic glycoconjugates of opioid peptides are good candidates for the development of anti‐HIV agents.
Photo‐induced molecular transformations. Part 123. One‐step synthesis of 1H‐benz[f]indole‐4,9‐diones by a new regioselective photoaddition of 2‐amino‐1,4‐naphthoquinone with various alkenes and its application to one‐step synthesis of kinamycin skeleton
Authors: Kobayashi Kazuhiro , Takeuchi Hiroyasu , Seko Shinzo , Suginome Hiroshi 
Published: December 2004

Abstract2,3‐Dihydro‐1H‐benz[f]indole‐4,9‐diones are formed in one‐step in 45–82% yields by an unprecedented [2+3]‐type regioselective photoaddition of 2‐amino‐1,4‐naphthoquinone with various electron‐rich alkenes and the [2+3] adducts derived from ammonaphthoquinone with vinyl ethers and vinyl acetate to give 1H‐benz[f]indole‐4,9‐diones including a benzindole‐dione with a kinamycin skeleton in 33–72% yields. A probable pathway leading to the formation of the dihydroindole‐dione involving air oxidation of an intermediary hydroquinone is proposed.
Biphenyltetrols and Dibenzofuranones from Oxidative Coupling of Resorcinols with 4‐Alkylpyrocatechols: New Ciues to the Mechanism of Insect Cuticle Sclerotization
Authors: Miessner Merle , Crescenzi Orlando , Napolitano Alessandra , Prota Giuseppe , Andersen Svend Olav , Peter Martin G. 
Published: December 2004

AbstractOxidation of 4‐alkylpyrocatechols 2 by means of an insect diphenoloxidase (laccase) or K3 [Fe(CN)6] yields, in the presence of resorcinols 1 (R2  H), complex mixtures of products from which biphenyltetrols 3 (R3  H) and dibenzofuranones 5 and 6 were isolated. It is suggested that similar homo‐coupling products are formed from pyrocatechols 2b and 2c in insects during cuticle sclerotization.
Synthèse énantiospécifique du (—)‐(1S,3R,5R)‐1,8‐diméthyl‐3‐éthyl‐2,9‐dioxabicyclo[3.3.1]non‐7‐ène
Authors: Kallimopoulos Thomas , Deschenaux Pierre‐François , Jacot‐Guillarmod André 
Published: December 2004

Enantiospecific Synthesis of (—)‐(1S,3R,5R)‐1,8‐Dimethyl‐3‐ethyl‐2,9‐dioxabicyclo[3.3.1]non‐7‐eneThe isomer (—)‐(1S,3R,5R)‐1,8‐dimethyl‐3‐ethyl‐2,9‐dioxabicyclo[3.3.1]non‐7‐ene ((1S,3R,5R)‐8) was synthesized from (—)‐(3R)‐methyl 3‐hydroxypentanoate with an enantiomeric excess ≥ 96%.
3:1 Molecular Complex of Hydroquinone and C60
Authors: Ermer Otto 
Published: December 2004

AbstractThe preparation of a 3:1 complex of hydroquinone (HQ) and C60, (HQ)3C60, is reported and its X‐ray crystal structure described. The HQ host builds up a single H‐bonded super‐polonium network with super‐cubes as building blocks, which accommodate the large C60 guest molecules. The enclathration of C60 is rather tight (high density of the complex) owing, in part, to favorable charge‐transfer host‐guest interactions (π‐donor‐acceptor complex). Nonetheless, the C60 molecules arc orientationally disordered, and no individual bond lengths could be measured. In contrast, the HQ host network is essentially ordered and well‐defined with normal intramolecular geometry. No appreciable (powder) conductivity could be observed for (HQ)3C60, yet ESR spectra of single crystals showed interesting narrow signals.
3‐Deazaguanine N7‐ and N9‐(2′‐Deoxy‐β‐D‐ribofuranosides): Building Blocks for Solid‐Phase Synthesis and Incorporation into Oligodeoxyribonucleotides
Authors: Seela Frank , Lampe Sigrid 
Published: December 2004

AbstractOligonucleotides continuing 3‐deaza‐2′‐deoxyguanosine (I) or its N7‐regioisomer 2 were prepared by solid‐phase synthesis using P111 chemistry. Protection of 1 or 2 with N,N V‐dimethylformamide diethyl acetal followed by 4,4′‐dimethoxytritylation afforded imidazo[4,5‐c]pyridines 10b and 11b, respectively. The latter were converted into the 3′‐phosphonates 10c or lie, respectively; the cyanoethyl N,N‐diisopropylphosphoramidite 10d was also prepared. The oligonucleotide building blocks were employed in automated solid‐phase synthesis. 1 he self‐complementary oligomers 13, 15, and 17 were prepared and characterized by enzymatic hydrolysis with snake‐venom phosphodiesterase followed by alkaline phosphatase. There CD spectra exhibited the general structure of a B‐DNA.
New Dolabellane Derivatives from the Brown Alga Dictyota pardalis
Authors: Wright Anthony D. , König Gabriele M. , Sticher Otto , Lubini Paolo , Hofmann Patrick , Dobler Max 
Published: December 2004

AbstractReinvestigation of the brown alga Dictyota pardalis f. pseudohamata CRIBB led to the crystallization of 1 and to the isolation of the two new dolabellane derivatives 2 and 3. X‐Ray analysis of 1 and 2, together with detailed 1D‐and 2D‐NMR studies on 2 and 3, allowed their structures to be elucidated as (1R*,3S*,7S*,11R*,4Z)‐dolabella‐4,8(17), 12(18)‐triene‐3,7‐diol (1), (1R*,3S*,4S*,7S*,8S*,11R*,14R*,12E)‐3,4:7,8‐diepoxydolabe11‐12‐ene‐14, 18‐diol (2), and (1R*,3S*,4S*,7S*,8S*,11R*,14R*)‐3,4:7,8‐diepoxy‐l,4,8,12,12‐pentamethylbicyclo[9. 3. 0]tetra‐decan‐14‐ol(3).
Steric Effects on Reaction Rates. Part XII. Force‐Field Calculations for the Solvolysis of Cyclobutyl and Tricyclyl Derivatives
Authors: Müller Paul , Milin Didier 
Published: December 2004

AbstractForce‐field parameters have been developed for the molecular‐mechanics calculation of tertiary carbenium ions with tricyclane structure, for tertiary cyclobutyl and cubyl cations. The cyclobutyl parameters are also applicable to tertiary 7‐norbornyl cations. Satisfactory plots are obtained for correlation of the rates of solvolysis with the differences in steric energies between carbenium ions and the corresponding bromides.
Helicity Induction in Helicate Self‐Organisation from Chiral Tris(bipyridine) Ligand Strands
Authors: Zarges Wolfgang , Hall Jonathan , Lehn Jean‐Marie , Bolm Carsten 
Published: December 2004

AbstractThe chiral tris, and pentakis(bipyridine) ligand strands 3a and 4 were synthesised, each in optically pure form with (S,S)‐configuration. Ligand 3a yielded substituted double‐helical metal complexes, derived from the parent trihelicate structure 2, with CuI and AgI ions. The spectral data, in particular the 1H‐NMR spectra and the large positive Cotton effect, indicate that helicate formation occurs with very high induction of helicity. Together with consideration of the steric effects in the two possible helical diastereoisomers (P)‐1 and (M)‐1 that may be formed, the data favour the preferential generation of the right‐handed double helicate (P)‐1 from the tris(bipyridine) strand 3a of(S,S)‐configuration.
Stereoselective Hydrolysis of Substituted Cyclopropanedicarboxylates with Pig Liver Esterase
Authors: Walser Paula , Renold Peter , N'Goka Victor , Hosseinzadeh Fatemeh , Tamm Christoph 
Published: December 2004

AbstractThe hydrolysis of the meso‐cyclopropane‐1,2‐dicarboxylates 1a‐3a, 4, 5a, 6a, and 9, containing various substituents at C(3), and of the rac‐3‐phenylcyclopropane‐1,2‐dicarboxylates7a, 8a, and 10 with pig liver esterase (PLE) is described. The stereoselectivtty and absolute configurations of the products were determined. An interpretation of results was attempted on the basis of a recent active‐site model for PLE.
Energy Transfer within Oligonucleotides from a Lumazine (= Pteridine‐2,4(1H,3H)‐dione) Chromophore to Bathophenanthroline‐ruthenium(II) Complexes
Authors: Bannwarth Willi , Pfleiderer Wolfgang , Müller Francis 
Published: December 2004

AbstractThe chemical insertion of 1‐(2′‐deoxy‐β‐D‐ribofuranosyl)‐6,7‐dimethyllumazine (1) and of a bathophenan‐throline‐ruthenium(II) complex into synthetic oligodeoxynucleotides is described. This combination represents a new energy‐transfer system with the lumazine chromophore as donor and the Ru complex as acceptor within the nucleotide. The system can be measured by time‐resolved fluorometry or by lifetime measurements of the lumazine fluorescence and bears the potential of a spectroscopic ruler.
Synthesis of N,N‐Disubstituted Lactone Hydrazones via (Sulfonylimino)‐ethers
Authors: Fritschi Stephan , Vasella Andrea 
Published: December 2004

AbstractThe dihydropyran 3 reacts with sulfonyl azides to give the known (sulfonylimino)‐ethers ( = lactone sul‐fonylimines) 4 and 18. Reaction of 4 with NH2NH2 · H2O leads to the aminoiriazole‐dibulanol 5, characterized as its tetraacetate 8, and not, as previously claimed, to 6 or 7. Similarly, the dihydrofuran‐derived (tosylimino)‐ether 10 yields 11 The structure of 5 was established by X‐ray analysis, and a mechanism for its formation is proposed. Reaction of 4 with NH2NMe2 afforded the lactone hydrazone 16 and the hydrazidine 17. Catalysis by imidazole suppressed the formation of 17similarly, the [(trifluoromethyl)sulfonyl]imine 18 yielded 16, and, by reaction with NH2N(Me)Ph or 4‐amino‐4H‐1,2,4‐triazole, the lactone hydrazone 19 and the adduct 20, respectively. The 1,4‐lactone hydrazone 21 was obtained from 10 or from 22. The structure of 20 was established by X‐ray analysis. Treatment of 16 with BuLi followed by BnBr yielded the α‐alkylated lactone hydrazone 23.
Radical Cations and Radical Anions of Three Bridgehead Azopolycycloalkanes: A Fluid‐Solution ESR Study
Authors: Gescheidt Georg , Lamprecht Axel , Rüchardt Christoph , Schmittel Michael 
Published: December 2004

AbstractThe radical mono‐ions of three azoalkanes in which the azo group is connected to the polycyclic alkane moieties at the bridgehead C‐atoms, i. e. 1,1′‐azonorbornane (1), 1,1′‐azotwistane (2), and 1,1′‐azobi‐cyclo[3.2.1]octane (3), were studied in fluid solution by ESR spectroscopy. According to the ESR parameters and MO models, the radical cations of 1–3 should be considered as σ radicals, whereas the corresponding radical anions are π radicals. INDO calculations point to a remarkable dependence of the l4N‐coupling constants on the geometry at the N‐atoms in the radical cations of aliphatic azo compounds.
A Highly Convergent Total Synthesis of (+)‐Myxovirescine M2. Preliminary Communication
Authors: Seebach Dieter , Maestro Miguel A. , Sefkow Michael , Neidlein Axel , Sternleld Francine , Adam Geo , Sommerfeld Thimo 
Published: December 2004

AbstractThe antibiotic myxovirescine M2was synthesized from seven building blocks (1–7,Scheme 1), with the following chiral starting materials being employed: (S)‐malic acid, (+)‐D‐ribonolactone, (S)‐2‐(hydroxymethyl)butanoate, and (2R,4S)‐5‐hydroxy‐2,4‐dimethylpenLanoate. Three new nucleophilic reagents,8–10, for C‐C bond formation have been used. The key steps of the synthesis are: aSuzukicoupling between an alkyl borane and a vinyl bromide (4+12e→13), aJuliaolefinalion (14+17→18), and aYamaguchimacrolactonizalion to form the 28‐membered lactone (18→19), This extremely convergenl synthetic approach will allow the preparation of a number of the 31 known myxovirescine molecules.
Chiral Tetraamines Based on (S)‐2‐(Aminomethyl)pyrrolidine: Template synthesis and properties of copper(II) complexes
Authors: Bernhardt Paul V. , Comba Peter , Hambley Trevor W. , Martin Lisandra L. , Várnagy Katalin , Zipper Luc 
Published: December 2004

AbstractThe template reaction of {bis[(S)‐2‐(aminomethyl)pyrrolidine]}copper(II) with formaldehyde, nitroethane, and base in MeOH yields optically pure {1,7‐bis[(S)‐pyrrolidin‐2‐yl]‐4‐methyl‐4‐nitro‐2,6‐diazaheptane}‐ copper(II) ([Cu((S,S)‐mnppm)]2+) in high yield. The same reaction with rac‐2‐(aminomethyl)pyrrolidine is also described. Preparative details and spectroscopic and electrochemical properties of the CuII complexes and of the free ligands are reported and compared with structural, spectroscopic and electrochemical data of the CuII complex of the unsubstituted parent ligand 1,7‐bis[(S)‐pyrrolidin‐2‐yl]‐2,6‐diazaheptane (ppm). The crystal structure of [Cu(ppm)]Cl ClO4 has been determined by X‐ray diffraction methods.
X‐Ray Crystal Structure of 25‐O‐Deacetyl‐27, 28‐didehydro‐27‐demthoxy‐11‐deoxo‐11, 29‐epoxy‐28,29‐dihydro‐21,23‐O‐isopropylidenerifamycin S
Authors: Bartolucci Cecillia , Cellai Luciano , Cerrini Silvio , Di Filippo Patrizia , Lamba Doriano 
Published: December 2004

AbstractIn search of new types of semisynthetic derivatives of the natural antibiotic rifamycin S (1), we synthesized 25‐O‐deacetyl‐27,28‐didehydro‐27‐demethoxy‐11‐deoxo‐11,29‐epoxy‐28, 29‐dihydro‐21,23‐O‐isopropyli‐denerifamycin S (3). Its X‐ray crystal structure shows a new type of ansa‐chain with an 11,29‐epoxy moiety, the loss of the MeO group on C(27), and the shift of the CC bond from C(28),C(29) to C(27),C(28). These modifications result in a conformational rearrangement of the whole ansa‐chain, nonetheless the overall spatial shape of the molecule is still close to that of most rifamycins. As found in other 11‐deoxo‐11‐hydroxyrifamycin‐S derivatives, the chromophore rings of 3 give rise to π‐π association in the crystal.
Diastereoselective Spirocyclization of Imines of 2‐Substituted 1H‐Indole‐3‐ethylamines ( = Trypatamines): Variation of the electrophile and the substituent at C(2) and its influence on the steric outcome. 6th Communication on indoles, indolenines, and indolines
Authors: Freund Ralf , Martinović Suzanna , Bernauer Karl 
Published: December 2004

AbstractTryptimines of type 7 form with various acyl halogenides EX preferentially tricycles of type 8 (cf: Scheme 2). The homochiral imines 9 and 17 are transformed into (2′R,3S)‐configurated products. The synthetic and mechanistic importance of these results is discussed.
Fluctuating Double‐Bond Localization and Charge Migration in π Systems
Authors: Heilbronner Edgar , Shaik Sason 
Published: December 2004

AbstractIn π systems with localized double bonds, the switch from one localization pattern to another symmetry‐equivalent one, and the corresponding changes in electron distribution are often considered to proceed via a delocalized transition state of higher symmetry. We present a different mechanism, according to which the double‐bond localization and the concomitant charge distributions can fluctuate without change in energy and without passing through a delocalized, higher‐symmetry transition state. This result is obtained within a simple, independent‐electron (HMO‐type) treatment.
Unusual and Novel C11H16 Hydrocarbons from the Southern Australian Brown Alga Dictyopteris acrostichoides (Phaeophyceae)
Authors: Wirth Dieter , Fischer‐Lui Iris , Boland Wilhelm , Icheln Detlef , Runge Thorsten , König Wilfried A. , Phillips Julie , Clayton Margaret 
Published: December 2004

AbstractUnusual and novel C11H16 olefins with (E)‐ or (E,E)‐configuration instead of the previously known (Z)‐ or (E,Z)‐configuration at the double bond(s) within the longer side chain are the main products of the Australian phaeophyte Dictyopteris acrostichoides. This configuration anomaly refers to all four series of alicyclic C11H16 hydrocarbons, namely the disubstituted cyclopentenes and cyclopropanes, as well as the monosubstituted cycloheptadienes and cyclopentenes. Chiral compounds within the above series have the same absolute configuration. The two (cyclopent‐3‐enyl)hexa‐1, 3‐dienes 11 and 13 are found for the first time. The absolute configuration and optical purity of the hydrocarbons are determined by gas chromatography on modified cyclodextrins as chiral stationary phases. The synthesis of chiral references via lipase‐catalyzed resolutions is described.
Homolytic Substitution Reaction at a Silicon Atom
Authors: Kulicke Klaus. , Chatgilialoglu Chryss Stomos , Kopping Birgit , Iese Bernd 
Published: December 2004

AbstractTris(trimethylsilyl)silane (2) is an efficient hydrosilylating agent of 1,6‐dienes 1 operating via a free‐radical chain mechanism. The intermediate alkyl radical 3 attacks the second olefinic bond of the diene 1 and forms cyclopentylalkyl radical 4. Using a low concentration of the hydrogen donor 2, a radical substitution reaction at the Si‐center of cis‐4 occurs and yields the bicyclic silane 6. The rate of this homolytic substitution at the Si‐atom is 2.4 · 105 s‐1 (80°).
Synthesis of N‐Acetylallosamine‐Derived Disaccharides
Authors: Maloisel Jean‐Luc , Vasella Andrea 
Published: December 2004

AbstractThe protected disaccharide 44, a precursor for the synthesis of allosamidin, was prepared from the glycosyl acceptor 8 and the donors 26–28, best yields being obtained with the trichloroacetimidate 28 (Scheme 6). Glycosidation of 8 or of 32 by the triacetylated, less reactive donors 38–40 gave the disaccharides 46 and 45, respectively, in lower yields (Scheme 7). Regioselective glycosidation of the diol 35 by the donors 38–40 gave 42, the axial, intramolecularly H‐bonded OHC(3) group reacting exclusively (Scheme 5). The glycosyl acceptor 8 was prepared from 9 by reductive opening of the dioxolane ring (Scheme 3). The donors 26–28 were prepared from the same precursor 9 via the hemiacetal 25. To obtain 9, the known 10 was de‐N‐acetylated (→ 18), treated with phthalic anhydride (→ 19), and benzylated, leading to 9 and 23 (Schemes 2 and 3). Saponification of 23, followed by acetylation also gave 9. Depending upon the conditions, acetylation of 19 yielded a mixture of 20 and 21 or exclusively 20. Deacetylation of 20 led to the hydroxyphthalamide 22. De‐N‐acetylation of the 3‐O‐benzylated β‐D‐glycosides 11 and 15, which were both obtained from 10, was very sluggish and accompanied by partial reduction of the O‐allyl to an O‐propyl group (Scheme 2). The β‐D‐glycoside 30 behaved very similarly to 11 and 15. Reductive ring opening of 31, derived from 29, yielded the 3‐O‐acetylated acceptor 32, while the analogous reaction of the β‐D‐anomer 20 was accompanied by a rapid 3‐O→4‐O acyl migration (→34; Scheme 4). Reductive ring opening of 21 gave the diol 35. The triacetylated donors 38–40 were obtained from 20 by debenzylidenation, acetylation (→36), and deallylation (→37), followed by either acetylation (→38), treatment with Me3SiSEt (→39), or Cl3CCN (→ 40).
Synthesis of Allosamidin
Authors: Maloisel Jean‐Luc , Vasella Andrea , Trost Barry M. , Van Vranken David L. 
Published: December 2004

AbstractThe previously prepared disaccharide 2 was deprotected (→3) and transformed into the trichloroacetimidate 4. In the presence of Me3SiOTf, 4 reacted regioselectively with the racemic allosamizoline benzyl ether 5, to yield (61%) the pseudotrisaccharides 7–10 (44:40:9:7) and the elimination product 6 (Scheme 1). Selective dephthaloylation (MeNH2, MeOH) of 7 and 8, followed by acetylation, gave 12 (73%) and 13 (74%), respectively (Scheme 2); harsher conditions (NH2NH2.H2O, EtOH, reflux), followed by acetylation, transformed 7 into 11. Deacetylation of 11–13 yielded 14–16, respectively. Allosamidin (1) was obtained in high yield by hydrogenation of 15 under acidic conditions (Scheme 3). Similarly, 16 and 14 were transformed into 17 and 18, respectively. Preliminary data on the inhibition of endochitinases by 1 and 17 are reported.
Tetrahydrolipstatin: Degradation products produced by human carboxyl‐ester lipase
Authors: Stalder Henri , Oesterhelt Gottfried , Borgström Bengt 
Published: December 2004

AbstractThe fate of tetrahydrolipstatin (1) incubated with human carboxyl‐ester lipase (HCEL) was investigated. The primary metabolite was identified as δ‐(N‐formyl‐L‐leucyloxy)‐β‐hydroxy acid 2a with conserved configuration. It is formed by attack of the active‐site serine of HCEL at the carbonyl C‐atom of the β‐lactone ring of 1 followed by hydrolysis of the intermediate serine ester. Further products isolated were identified and a complete degradation scheme is proposed.