bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pyridinium N‐Phenolate Betaine Dyes and Their Application to the Characterization of the Polarity of Solvents, XXII. Syntheses and UV/Vis Spectroscopic Properties of Solvatochromic, Halochromic, and Chiro‐Solvatochromic Pyridinium N‐Phenolate Betaine Dyes with Four Stereogenic Centers
Authors: Reichardt Christian , Blum Andreas , Harms Klaus , Schäfer Gerhard 
Published: July 2007

AbstractSyntheses (Schemes 1–3), negative solvatochromism (Table 1), cation‐induced negative halochromism (Table 2), and chiro‐solvatochromism (Tables 3 and 4) of the new crown ether‐substituted chiral pyridinium N‐phenolate betaine dyes 18a, b and 28a, b, each posessing four stereogenic centers, are described. The absolute configuration at the four stereogenic centers of the chiral betaine dyes has been confirmed by X‐ray crystal structure analysis of the intermediate phenol 14a (Figure 1). Solutions of the chiral betaine dyes 18a, b and 28a, b, prepared by addition of monochiral amines and amino alcohols to solutions of the salts 17a, b and 27a, b in ethanol, exhibit in some cases small but significant chirosolvatochromic band shifts of up to Δλ = 10–12 nm (Tables 3 and 4), caused by chiral recognition of the monochiral guest molecules.
Galacturonic Acid Derivatives, VIII. Synthesis of N‐(D‐Galacturonoyl) Amino Acids and Dipeptides
Authors: Vogel Christian , Jeschke Udo , Kramer Sven , Ott Andrej‐Jakob 
Published: July 2007

AbstractD‐Galacturonic acid derivatives, amide‐linked to amino acids or dipeptides, have been synthesized. These glycoconjugates exhibit stability when the uronic acid residue is protected with isopropylidene and acetyl groups or is in its pyranoside form. The formation of the amide or peptide linkages was best achieved by the EDCI/HOBt coupling method; an alternative method employing the 1,2;3,4‐di‐O‐isopropylidene‐α‐D‐galactopyranuronosyl chloride 2 furnished only moderate yields of the conjugates. The use of NMR spectroscopy to detect racemization of the amino acid moiety is also discussed herein.
Structures of Peptaibol Antibiotics Hypomurocin A and B from the Ascomycetous Fungus Hypocrea muroiana hino et katsumoto
Authors: Becker Dieter , Kiess Michael , Brückner Hans 
Published: July 2007

AbstractFrom a submerse culture of the fungus Hypocrea muroiana Hino et Katsumoto (Ascomycetes: Hypocreales) two major groups of peptides, designated hypomurocin (HM) A and B, belonging to the peptaibol family, could be characterized. Both groups showed antibiotic activity (Bacillus subtilis) and caused hemolysis of rat erythrocytes, HM A being less active than HM B. Peptides were isolated from the culture broth by chromatography on XAD‐2 adsorber resin, octyl silica, and Sephadex LH 20. HM A and B were separated by preparative TLC, and individual peptides from each microheterogeneous group were isolated by preparative HPLC. Amino acid analysis and sequence determination by fast atom bombardment and electrospray tandem mass spectrometry revealed the composition and structures of six 11‐mer peptides of the HM A group and of six 18‐mer peptides of the HM B group. Positions of isomeric amino acids Leu/Ile and Val/Iva (present in some of the peptides) were determined by methanolytic cleavage of the pure peptides, followed by trifluoroacetylation of the dipeptide methyl esters released and assignment of their structures by gas chromatography‐selected ion monitoring mass spectrometry. As examples, two sequences of HM A and HM B are presented (exchange positions in parentheses). – HM A‐1(2): Ac‐Aib1(D‐Iva1)‐Gln‐Val‐Val‐Aib‐Pro‐Leu‐Leu‐Aib‐Pro‐Leuol11; HMB‐1(2): Ac‐Aib1‐Ser‐Ala‐Leu‐Aib‐Gln‐Aib‐Val‐Aib‐Gly‐Aib‐Pro‐Leu‐Aib‐Aib‐Gln‐Valol18 (Leuol18), (Ac = acetyl, Aib = α‐aminoisobutyric acid, Iva = D‐isovaline, Leuol = L‐leucinol, Valol = L‐valinol).
Diastereo‐ and Enantioselective Synthesis of 4,5,6‐Trisubstituted and 6‐Monosubstituted Piperidin‐2‐ones
Authors: Enders Dieter , Bartzen Dominika 
Published: July 2007

AbstractA convenient, versatile and highly diastereo‐ and enantioselective synthesis of 4,5,6‐trisubstituted piperidin‐2‐ones 1 in satisfactory overall yields is described. The procedure involves the efficient and highly anti‐diastereo‐ and enantioselective Michael addition of aldehydes to enoates via their lithiated SAMP hydrazones, followed by nucleophilic 1,2‐addition of organometallic reagents to the CN double bond of the corresponding aldehyde SAMP hydrazone‐lithium ester enolate and subsequent lactamisation. In addition, 6‐monosubstituted piperidin‐2‐ones 8 are prepared with enantiomeric excesses of ee = 79–92% via a similar three‐step sequence starting from ethyl 5‐oxovalerate (9).
[2+2] Photocycloadditions of Homobenzvalene
Authors: Christl Manfred , Braun Max 
Published: July 2007

AbstractThe irradiation of methyl phenylglyoxylate, benzil, benzophenone, and 1,4‐benzoquinone in the presence of homobenzvalene (3) gave products of the Paternò‐Büchi reaction, i.e. the oxetane derivatives 4–8, 13 and 14, which contain a tricyclo[4.1.0.02,7]heptane subunit. A regioselectivity was observed in favour of the compounds with the 8‐oxatetracyclo‐[5.2.0.02,4.03,5]nonane skeleton (4, 5, 7, 13). In the case of benzophenone, the cycloaddition was competing with the isomerisation of 3 to cycloheptatriene. No cycloaddition but only isomerisation proceeded with acetophenone and acetone. The irradiation of 1,4‐naphthoquinone and cyclopent‐2‐en‐1‐one in the presence of 3 afforded the cyclobutane derivatives 15 and 17, respectively.
Cycloadditions, 27. The Thermal Rearrangement of the Bicyclo[2.2.2]‐ to Bicyclo[3.2.1]octadiene Moiety in Tricyclic Lactams
Authors: Himbert Gerhard , Diehl Klaus 
Published: July 2007

AbstractThe tricyclic lactams 4a–h, possessing a bicyclo[2.2.2]octadiene moiety, obtained by intramolecular Diels‐Alder reaction of the vinylidene malondiamides 1a–h, generally isomerize in boiling xylene to give the new lactams 7a–h, now bearing a bicyclo[3.2.1]octadiene part. The difference in the rates of the isomerizations 4 → 7 and the results with the nitro ‐ and methoxy‐substituted derivatives 4i–l are in accordance with the proposed intermediate zwitterion 6, which is formed by the migration of one vinyl group from position 1 to position 5 of the lactam moiety.
β‐Peptides: Oligo‐β‐homoalanines – the Amide Analogues of Poly(3‐hydroxybutanoate)
Authors: Matthews Jennifer L. , Overhand Mark , Kühnle Florian N. M. , Ciceri Paola E. , Seebach Dieter 
Published: July 2007

AbstractThe linear oligo‐β‐peptides derived from β‐homoalanine (Hβ‐HAlaOH) have been prepared by Arndt‐Eistert homologation of Boc‐alanine and subsequent peptide coupling procedures. Cyclisation via pentafluorophenyl esters resulted in the formation of the cyclic β‐peptides in remarkably high yields. The X‐ray crystal structure analysis of Boc–(β‐HAla)2–OBn is presented. The cyclic derivatives were found to be highly insoluble (m.p. >300°C with decomposition) and the effect of lithium salts on their solubility, particularly with respect to obtaining NMR data, is discussed. The CD spectra of the cyclo‐β‐tetrapeptides are presented and these give an indication that “nanotube‐like” structures may be present.
Structural Aspects of Cyclopropyl Homoconjugation: Experimental Studies and Ab Initio Calculations
Authors: Haumann Thomas , Benet‐Buchholz Jordi , Klärner Frank‐Gerrit , Boese Roland 
Published: July 2007

AbstractLow‐temperature crystal structural studies of a series of saturated and unsaturated bicyclo[2.2.1]heptadiene, heptene and heptane compounds with 7‐spirocyclopropyl substitution reveal significant differences in the bond lengths of the three‐membered rings and in the CC single bonds of the bicyclic fragment. A complex interplay of strain and different types of conjugation influence the molecular structure of the bicycloheptadiene derivative1, where the difference in the length of the three‐membered ring bonds is 0.040 Å and all CC single bonds in the bicyclic fragment are lengthened significantly. Ab initio calculations at the HF/6‐31G(d) (to a minor extent) and MP2/6‐31G(d) levels are in good agreement with the experimental data. Calculated charge distributions and dipole moments further support the relevance ofcyclopropyl homoconjugationin the investigated prototype of Walsh and through‐space π‐orbital interaction. Static difference electron density maps have been derived from the experimental data by multipole refinements which showed exocyclic shifts of electron density in the planes of the three‐membered rings and significant bond ellipticities at the CC single bonds in the unsaturated bicyclic units.
4,5‐Diazafluorenylidene: Preparation, Reactivity, Multiplicity, and Selectivity Studies
Authors: Abdel‐Wahab Abdel‐Magd A. , Ismail Mohamed T. , Mohamed Omima S. , Dürr Heinz , Ma Yinmin 
Published: July 2007

AbstractThe chemistry of 4,5‐diazafluorenylidene (3), generated from the diazo compound 3a by photolysis, has been studied with regard to reactivity, multiplicity and selectivity. Reaction of 3 in 2,3‐dimethylbutene gave exclusively ketazine 24. The [1 + 2] cycloaddition with styrenes 5–11 afforded cyclopropanes 16–23 in 25–54% yields and 24 as a side product. In these reactions no diazirine intermediate was involved. Irradiation of 3a in methanol afforded the ether 26 (25% yield). The stereoselectivity of 3 was studied by its addition to (E)‐ and (Z)‐β‐methylstyrene. A mixture of the (E)‐ and (Z)‐cyclopropanes 22 and 23, respectively, was detected. Thus for 3, triplet multiplicity was concluded. The results of competition experiments with singlet/triplet scavengers (methanol/dimethylbutadiene) demonstrated that an equilibrium between singlet and triplet manifold of 3 exists at room temperature. Selectivity studies with carbene 3 were carried out by evaluating the competition experiments of the cycloaddition of 3 with differently substituted styrenes. A plot of the krel values from the competition studies versus Hammett σ constants gave ρ = −0.65 indicating that carbene 3 reacts as an electrophile.
Interaction Between Benzene and Naphthalenophane: In the Gas Phase and the Crystalline Lattice
Authors: Nakamura Yosuke , Suzuki Hideaki , Hayashida Yoshitou , Kudo Takako , Nishimura Jun 
Published: July 2007

AbstractThe interaction between naphthalenophane 1 and another aromatic compound in the gas phase was investigated by molecular orbital calculations, mainly focusing on the arrangement of both aromatic compounds and the effect of the substituents in the benzene ring. The X‐ray crystallographic analysis of some clathrates of 1 with an aromatic solvent was also carried out in order to clarify the relationship between the gas and condensed phases. The most stable arrangement calculated for a complex of 1 and benzene or substituted benzene in the gas phase was found to be the arrangement in which the edges of the two naphthalene rings of 1 are directed to the face of the benzene ring. Such an arrangement was also observed in the clathrate crystals, according to the X‐ray crystallographic analysis. This result suggests that the stable arrangement in the gas phase is probably maintained in solution, leading to the same arrangement in the crystals. The order of stabilization of the clathrates with some substituted benzenes is in agreement with that of the electron‐donating ability of the functional group present in the benzene. A slight difference in the stabilization was observed between the complex with toluene and that with chlorobenzene, and such a difference is considered to affect the inclusion behavior of 1.
Functionalized Derivatives of Benzocrown Ethers, II. Supramolecular Complexes of L‐Amino Acids as Efficient Activators of the Zinc Enzyme Carbonic Anhydrase
Authors: Barboiu Mihai , Supuran Claudiu T. , Scozzafava Andrea , Briganti Fabrizio , Luca Constantin , Popescu Georgeta , Cot Louis , Hovnanian Nadine 
Published: July 2007

AbstractThe preparation of a series of supramolecular complexes of the ammonium salt of 2,3,11,12‐bis[4‐(10‐aminodecylcarbonyl)]benzo‐18‐crown‐6 with different natural and non‐natural amino acids is reported. In all these ditopic supramolecular complexes, with the exception of the histidine derivative, the ammonium moiety of the amino acid is anchored by means of hydrogen bonds within the macrocyclic cavity of the host, whilst the carboxylate moiety interacts with the ammonium group of the derivatized crown ether. The new complexes act as very efficient activators of the zinc enzyme carbonic anhydrase (isozymes I and II).
Pyrolytic Generation and Rearrangement of N‐Substituted 1,2‐Didehydrocarbazoles
Authors: Brown Roger F. C. , Choi Neil , Coulston Karen J. , Eastwood Frank W. , Ercole Frances , Horvath Julianna M. , Mattinson Mark , Mulder Roger J. , Ooi Hua Chee 
Published: July 2007

AbstractThe flash vacuum pyrolysis (900–940°C) of a series of N‐R‐substituted carbazole‐1,2‐dicarboxylic anhydrides (R = methyl, phenyl, o‐tolyl, benzyl, and ethyl) leads to 1,2‐didehydrocarbazoles which undergo ring expansion, cyclisation, and other reactions but which appear not to undergo ring contraction to exocyclic carbenes. Thus the N‐methyl compound 4 gives phenanthridine in 27% yield, the N‐phenyl compound 5 undergoes C‐2′C‐1 cyclisation to indolo[3,2,1‐jk]carbazole 27, and the N‐o‐tolyl compound 6 gives both C‐6′C‐1 cyclisation and 2′‐CH3C‐1 cyclisation. The N‐benzyl compound 7 mainly suffers loss of the benzyl group, but a minor product, benzo[a]carbazole 33, is probably formed by an intramolecular cycloaddition. The N‐ethyl compound 8 forms mainly carbazole and phenanthridine and in addition the minor C‐2′C‐1 cyclisation products pyrrolo[3,2,1‐jk]carbazole 44 and its 4,5‐dihydro derivative 45. The formation of phenanthridine from the N‐methyl anhydride 4 has been investigated by labelling of 4 with 13C at C‐9a.
A Generalized Solvent Acidity Scale: The Solvatochromism of o‐tert‐Butylstilbazolium Betaine Dye and Its Homomorph o,o′‐Di‐tert‐butylstilbazolium Betaine Dye
Authors: Catalán Javier , Díaz Cristina 
Published: July 2007

AbstractA total of 121 organic solvents were studied and classified by means of the solvatochromic comparison method of Kamlet and Taft, to give a solvent acidity scale for hydrogen‐bond donor solvents based on the parameter SA. This parameter can readily be evaluated from the visible spectrum of a suitable basic probe (o‐tert‐butylstilbazolium betaine dye, TBSB) and its non‐basic homomorph (o,o′‐di‐tert‐butylstilbazolium betaine dye, DTBSB). The proposed scale has many advantages when compared to the more widely used acidity scales such as that based on Gutmann's acceptor number (AN) and the Taft‐Kamlet α scale. Whilst data for the proposed scale are derived from electronic transitions only, they do provide an accurate description for solvent acidity effects in spectroscopy and other chemical areas, including thermodynamics and kinetics.
Synthesis of 21‐(3‐Methylbutyl)cholest‐5‐ene‐3β,3′,25‐triol and 21‐(2‐Methylpropoxy)cholest‐5‐ene‐2′,3β,25‐triol, the First “Double Side Chain” Cholesterol Analogues
Authors: Kurek‐Tyrlik Alicja , Makaeva Fliur Z. , Wicha Jerzy , Calverley Martin J. 
Published: July 2007

AbstractThe 21‐(3‐hydroxy‐3‐methylbutyl)‐ and 21‐(2‐hydroxy‐2‐methylpropoxy)cholestane derivatives 3 and 5, formally double chain hybrid (20R)‐ and (20S)‐cholesterol analogues, were synthesized. The C‐22 to C‐27 section of the 25‐hydroxycholestane side chain was established by stereoselective alkylation with 5‐bromo‐2‐methyl‐2‐(triethylsilyl)oxypentane of the pregnanoic ester 8, derived from 3β‐acetoxyandrost‐5‐en‐17‐one (7). Reduction of the ester 9 to the 21‐alcohol 10 permitted elaboration of a second hydroxylated side chain, either via the tosylate 11 by alkynation/hydrogenation (yielding intermediate 13) or by alkylation of 10 with bromoacetate (yielding 14) followed by reaction with methyl magnesium bromide.
Synthesis of Optically Active 2‐siloxycyclopropanecarboxylates by Asymmetric Catalysis, V. Baeyer–Villiger Oxidations of γ‐Oxo Esters – Determination of the Absolute Configurations of Methyl 2‐Siloxycyclopropanecarboxylates – Interpretation of the Enantioselective Cyclopropanations of Silyl Enol Ethers
Authors: Reißig Hans‐Ulrich , Schumacher Ralf , Ferse Dirk 
Published: July 2007

AbstractRacemic and enantiomerically enriched methyl 2‐siloxycyclopropanecarboxylates 1 have been ring‐opened to furnish γ‐oxo esters 2. Depending on the electronic properties of substituents, these could be transformed into either succinate derivatives 3 or 3‐oxybutanoates 4 by Baeyer‐Villiger oxidation. By comparison with known reference compounds the absolute configurations of 3a and 4d, and hence those of their cyclopropane precursors, could be determined. Further literature data on the optical rotations of related cyclopropanes have been collected and compared. A mechanistic interpretation of the asymmetric cyclopropanation of silyl enol ethers based on Pfaltz's model is suggested.
Highly Stereoselective Synthesis of the 1‐O‐Acylglycosyl Ester of Diclofenac via Glycosyl Phosphorothioates, ‐Selenoates and ‐Dithioates as Glycosyl Donors
Authors: Borowiecka Joanna 
Published: July 2007

AbstractStereoselective glycosylation of o‐(2,6‐dichloroanilino)phenylacetic acid (Diclofenac, 1), as a free carboxylic acid with glycosylthio (2a–c), ‐dithio (3a–e) and ‐selenophosphates (4a–c) as glycosyl donors is reported. The reactions were carried out in aprotic solvents, in the presence of silver carbonate as a leaving group activator. 1‐O‐Acyl sugars 7a–e, new derivatives of Diclofenac, were obtained in high yields as stable, crystalline compounds.
Efficient Enantioselective Synthesis of Chiral Precursors for the Preparation of Vitamin E
Authors: Tietze Lutz F. , Görlitzer Jochen 
Published: July 2007

AbstractEnantioselective bishydroxylation of the protected hydroxymethyl enynes 7a–d and 8a, b, which are easily obtained from commercially available 5 and 6, gave the triol derivatives 9a–d and 11a, b in good yields and moderate to high enantiomeric excess. Palladium‐catalyzed coupling of 9a–d and 11a, b with the iodoarene 13 led to the desired precursors for the vitamin E synthesis ent‐3a–d and 15a, b.
Aromatic Sulfonation, 131. Formation of Sulfonic Acids and Sulfonic Anhydrides in the Sulfur Trioxide Sulfonation of Some Dialkylbenzenes and 1,ω‐Diarylalkanes
Authors: Cerfontain Hans , Koeberg‐Telder Ankie , van Lindert Helen C. A. , Bakker Bert H. 
Published: July 2007

AbstractAn exploratory study has been made on the SO3 sulfonation of a number of alkylarenes in [D2]dichloromethane as an aprotic solvent, mostly in the presence of [D8]1,4‐dioxane as a reactivity moderator, in order to obtain information on sulfonic acid and sulfonic anhydride formation. 1,2‐Dimethylbenzene (1) with 1.0 mol‐equiv. of SO3 yields predominantly the 4‐sulfonic acid (1‐4‐S), whereas with 4.0 mol‐equiv. of SO3, 18 mol‐% of the corresponding (intermolecular) sulfonic anhydride (1‐4‐SO2)2O is additionally formed. 1,4‐Dimethylbenzene (2) with 0.8 mol‐equiv. of SO3 yields predominantly 2‐2‐S, whereas with 4.0 mol‐equiv. of SO3 the sulfonic anhydride (2‐2‐SO2)2O and its 6‐S and 6,6′‐S2 derivatives are formed, the eventual main product being (6‐S‐2‐2‐SO2)2O. Reaction of 1‐ethyl‐4‐methylbenzene (3) with 2.0 mol‐equiv. of SO3‐[D8]dioxane at −78 → −40 °C leads to the predominant formation of the 2‐ and 3‐S derivatives in a molar ratio of 26:74, with small amounts of the three corresponding intermolecular anhydrides. Upon performing the sulfonation of 3 at 0 → 22 °C, the relative amounts of the anhydrides are larger, and in addition the 3,5‐S2 derivatives of the intermolecular anhydrides are formed. The absence of the isomeric 2,6‐S2 derivative is ascribed to the buttressing effect of the 2‐sulfo on the 1‐ethyl group, hampering the sulfonation at C(6). Reaction of diphenylmethane (4) with 4.2 mol‐equiv. of SO3 at −20 → 25 °C yields initially 4‐4′‐S and subsequently 4‐4′,4″‐S2. Sulfonation of 1,2‐diphenylethane (5) with 4.0 mol‐equiv. of SO3 at −78 → 22 °C for 4.5 h leads mainly to the cyclic dimeric disulfonic anhydride [5‐4′,4″(‐SO2)2O]2, which upon hydrolysis affords 9% of 5‐2′,4″‐ and 91% of 5‐4′,4″‐S2. However, sulfonation of 5 at 0 → 22 °C for ca. 0.8 h was found to lead to the formation of the intermolecular sulfonic anhydride (4′‐S‐5‐4″‐SO2)2O. On sulfonation of 1,2‐di‐p‐tolylethane (6) with 1.0 mol‐equiv. of SO3, only ca. 20% of the substrate was sulfonated to give, after hydrolysis, 3% of the 2′‐ and 12% of the 3′‐sulfonate, whereas with 4.0 mol‐equiv. of SO3 the initial monosulfonic acids are almost completely converted to yield the 2′,3″,5″‐S3, 3′,3″,5″‐S3, and 3′,3″,5′,5″‐S4.
A Short Synthesis of (±)‐Oxetin
Authors: Bach Thorsten , Schröder Jürgen 
Published: July 2007

AbstractThe antibiotic β‐amino acid oxetin (rac‐1) has been prepared by the stereoselective Paternò‐Büchi reaction of enecarbamate 2 and n‐butyl glyoxylate (5). The overall yield of the four‐step synthesis is 14%. The order of the deprotection steps proved to be important in minimizing possible side reactions.
Dihydrocolchicine 8,12‐Endoperoxide: A Novel Starting Material for Convenient Syntheses of the Allocolchicinoids N‐Acetylcolchinol O‐Methyl Ether and Androbiphenyline
Authors: Brecht René , Haenel Frank , Seitz Gunther 
Published: July 2007

AbstractOptically pure dihydrocolchicine‐8,12‐endoperoxide 2 is used as the starting material for the synthesis of some bioactive allocolchicinoids. Depending on the reaction conditions and reagents employed, different modifications of the C ring of colchicine (1) are achieved. Triphenylphosphane deoxygenation of 2 leads to the well known N‐acetylcolchinol O‐methyl ether (NCME, 6, 40% yield from 1). Treatment of the endoperoxide 2 with CH3OH/CH2Cl2/silica gel provides the plant alkaloid androbiphenyline (11) in a yield of 60% from 1. Triethylamine‐catalysed transformation of 2 yields (−)‐colchicine‐8,12‐dione (12) (17% yield), together with a mixture of interconverting tetracyclic hemiketals 8a and 8b. For the formation of the allo colchicinoids 6 and 11 plausible reaction pathways are suggested. In contrast to what is found in the literature, the assignment of the absolute configuration of natural (−)‐colchicine (1), and the allo‐congeners 6 and 11, should be (M,7S) or (aR,7S) instead of (aS,7S).
Efficient In‐Situ Redox Catalytic NAD(P)+ Regeneration in Enzymatic Synthesis Using Transition‐Metal Complexes of 1,10‐Phenanthroline‐5,6‐dione and Its N‐Monomethylated Derivative as Catalysts
Authors: Hilt Gerhard , Lewall Burhanshah , Montero Guillermo , Utley James H. P. , Steckhan Eberhard 
Published: July 2007

AbstractIn comparative studies, we have been able to demonstrate that redox catalysts based on transition‐metal complexes using 1,10‐phenanthroline‐5,6‐dione as a ligand or based on N‐methylated 1,10‐phenathroline‐5,6‐dione acting via hydride ion abstraction are superior to alternative methods for the redox catalytic aerobic or indirect electrochemical in situ NAD(P)+ regeneration in enzymatic syntheses using alcohol dehydrogenases as production enzymes. Under preparative conditions in the gram scale we were able to obtain turnover frequencies of up to 130 turnovers per hour with respect to the redox catalyst. These are far larger than those of the presently most popular regeneration system.
Lactones, 2. Synthesis of Enantiomeric Pairs of Lactones with the Pinane or the Fenchane system
Authors: Paruch Edyta , Ciunik Zbigniew , Wawrzeńczyk Czeslaw 
Published: July 2007

AbstractStarting from (+)‐ and (−)‐myrtenols, and via iodolactonization, the enantiomerically pure tricyclic lactones, with pinane systems, were obtained. In the course of an acidic lactonization of the γ,δ‐epoxy esters 6a and 6b, the rearrangement of the pinane system to that of the fenchane was observed. The absolute configurations of the newly formed chiral centres of the lactones 4b and 11b were established by X‐Ray diffraction analyses.