bluuebunny/crossref_metadata_2025 huggingface dataset:
Non‐chelate‐controlled addition of 1‐Bromo‐1‐lithio‐1‐alkenes to O‐protected lactaldehydes and 3‐alkoxybutyraldehydes
Authors: Braun Manfred , Mahler Hellmut
Published: July 2007

Non‐chelate control is found to be the favored stereochemical outcome in the addition of the 1‐bromo‐1‐lithio‐1‐alkenes 2b and (S)‐5b to O‐protected lactaldehydes (S)‐1. Thus diastereoselectivities of 84 to 96% d.e. are reached in the formation of alcohols 3 and 6, which are converted into the O‐protected 2,3‐dihydroxyaldehyde 31 or O‐protected 1,2,3‐triols 24 and 27. In an analogous way, a non‐chelate‐controlled addition of (R)‐5b to (R)‐3‐(benzyloxy)butyraldehyde (14a) leads to the predominant formation of the diastereomer 15a (92% d.e. after enrichment by chromatography) which yields the alcohol 42a upon debromination, O‐protection, and ozonolysis. Thus, the carbenoids 2b and 5b enable the introduction of the synthons −CH2OH and −CHO into enantiomerically pure aldehydes (S)‐1 and (R)‐14 in a highly stereoselective manner. Relatively low diastereoselectivities are reached in the „mismatched”︁ combination of (R)‐5b with (S)‐1 as well as (S)‐5b with (R)‐14. The dilithium compound 20b, generated at −78°C, reacts in a retro‐1,4‐Brook rearrangement at −20°C to give vinylsilane 44b after protonation.
Bausteine von Oligosacchariden, CIX. Synthese von modifizierten Oligosacchariden der N‐Glycoproteine zur Untersuchung der Substratspezifität der N‐Acetylglucosaminyltransferase I
Authors: Paulsen Hans , Springer Matthias , Reck Folkert , Meinjohanns Ernst , Brockhausen Inka , Schachter Harry
Published: July 2007

Building Units of Oligosaccharides, CIX. — Synthesis of Modified Oligosaccharides of N‐Glycoproteins for Substrate Specificity Studies of N‐Acetylglucosaminyltransferase I

A series of modified derivatives of the trisaccharide octyl α‐D‐Man(1→3)‐[α‐D‐Man(1→6)]‐β‐D‐Man were synthesized for substrate specificity studies of N‐acetylglucosaminyltransferase I (GlcNAc‐T I). The hydroxyl groups at C‐3, C‐4 and C‐6 of the α(1→3)‐linked Mannose were replaced by hydrogen and methoxy groups. At the α(1→6)‐linked mannose the hydroxyl group at C‐2 was deoxygenated and the hydroxyl groups at C‐3, C‐4 and C‐6 were replaced by methoxy groups. The syntheses of the ten trisaccharides were carried out by the interchangeable combination of modified building blocks. The trichloroacetimidate method was favourable for all glycosylation steps.
Terpenes and terpene derivatives, XXXIV. Synthesis of rac‐porosadienone
Authors: Weyerstahl Peter , Schwope Ina
Published: July 2007

(±)‐Porosadienone (9) is easily synthesized by starting from (±)‐2,6‐dimethylcyclohexanone via indenone 1 and dienone 4. All compounds (rac‐4‐6 and rac‐9) with the α,β,γ,δ‐dienone system are very prone to air oxidation forming the corresponding mono epoxides rac‐7, rac‐8, rac‐10, and rac‐11.
Eine unerwartete Reaktion zwischen Oxalylchlorid und atropisomeren Diaminen
Authors: Lindauer Dirk , Atzrodt Jens , Beckert Rainer , Görls Helmar
Published: July 2007

An Unexpected Reaction between Oxalyl Chloride and Atropisomeric Diamines

Chiral diamines like (S)‐1,1′‐binaphthalene‐2,2′‐diamine (3a) were acylated by oxalyl chloride to yield mainly a macrocyclic lactame 5, whereas the eight‐membered oxamide 4 was formed only in small quantity.
Progress towards a generalized solvent polarity scale: The solvatochromism of 2‐(dimethylamino)‐7‐nitrofluorene and its homomorph 2‐fluoro‐7‐nitrofluorene
Authors: Catalán Javier , López Vicenta , Pérez Pilar , Martin‐Villamil Rosa , Rodríguez José‐Gonzalo
Published: July 2007

More than 100 solvents and the gas phase were used to develop a solvent dipolarity‐polarizability scale that combines the medium dipolarity and polarizability into a single parameter (SPP) calculated from the UV‐visible spectra of 2‐(dimethyl‐amino)‐7‐nitrofluorene (DMANF) and its homomorph 2‐fluoro‐7‐nitrofuorene (FNF). The proposed scale compares favourably for nonprotic solvents with existing solvent polarity scales including Kosower's Z, Dimroth and Reichardt's ET(30), Brooker's χR, Dong and Winnick's Py; Kamlet, Abboud, and Taft's π*, and Drago's S′ scale. When data are derived from electronic transitions, they provide an accurate description for the solvent effect in UV‐Vis, IR, NMR, and fluorescence spectroscopy as well as in other chemical areas including thermodynamics and kinetics.
η6‐(1‐oxobenzocyclobutene)tricarbonylchromium(0): Preparation, reduction, and ring‐opening/cycloaddition chemistry of the 1‐hydroxybenzocyclobutene complex
Authors: Brands Michael , Wey Hans G. , Krömer Rainer , Krüger Carl , Butenschön Holger
Published: July 2007

The syntheses of the tricarbonylchromium complexes 2 and 3 of 1‐oxobenzocyclobutene and 1‐hydroxybenzocyclobutene are described. Alcoholate 6 of 3 undergoes a ring opening to the corresponding ortho‐quinodimethane intermediate between −30 and −20°C, which is trapped by dienophiles with high diastereoselectivity. While with most dienophiles products with a 1,2‐cis configuration (7, 8, 10) are formed, vinyl sulfones react in an exo‐selective cycloaddition with formation of 1,2‐trans‐configurated cycloadducts (12, 13). The configuration of the cycloadduct with phenyl vinyl sulfone is confirmed by an X‐ray crystal structure analysis. As one of the important aspects of the chemistry of benzocyclobutene complexes is the chirality of compounds like 2 and 3, the enantiomeric resolution has been achieved via the semioxamazones of ketone 2.
Pseudosugars, 35. Synthesis of glycosylceramide analogs composed of imino‐linked unsaturated 5a‐carbaglycosyl residues: Potent and specific gluco‐ and galactocerebrosidase inhibitors
Authors: Tsunoda Hidetoshi , Inokuchi Jin‐Ichi , Yamagishi Kiwamu , Ogawa Seiichiro
Published: July 2007

5a‐Carba‐β‐glucosyl‐ E‐3 and galactosylceramide analogs E‐4 were synthesized by coupling of the protected derivatives 5 of β‐valienamine and 15 of 4‐epi‐β‐valienamine with the aziridines E‐6 and Z‐6, as the sphingosine precursors, respectively, and subsequent deprotection and N‐acylation. Both the new analogs and their corresponding Z‐isomers Z‐3 and Z‐4 were shown to be very potent and specific gluco‐ and galactocerebrosidase inhibitors, and, interestingly, the Z‐isomers possess inhibitory activity comparable to that of the corresponding E‐isomers.
Azo bridges from azines, XIV. Rigid polycycles with NN and CC functionalities
Authors: Hünig Siegfried , Kraft Petra , Klarner Frank‐Gerrit , Artschwanger‐Perl Uwe , Peters Karl , Von Schnering Hans‐Georg
Published: July 2007

Bifunctional 9, 3, 17, and trifunctional 20 dienophiles have been subjected to Diels‐Alder reactions with 4H‐pyrazoles 8 or 14 with inverse electron demand to form monoadducts 13, 15, 18, and 21 and bisadducts 16, 19, and 26. Acid‐catalyzed reactions at 20°C occur according to 14 + 3 → 15 + 16 and 14 + 17 → 18 + 19. By contrast, the solution of barrelene (20) and 8 has to be subjected to 10 kbar and 130°C to give monoadduct 21 and bisadduct 26, In daylight 21 undergoes [2 + 2] cycloaddition to 27. The norbornene derivative 10 reacts with cyclopentadiene to form 13 which is obtained in higher yield by reaction of 10 with hexachlorocyclopenta‐diene and subsequent reductive dehalogenation of adduct 12. X‐ray analyses of 11 and 13 reveal only small differences in the structural parameters.
2,7,9‐trimethylenetricyclo[4.3.0.03,8]nonane and 2,9‐dimethylenetricyclo[4.3.0.03,8]non‐4‐ene. Synthesis and properties
Authors: Gleiter Rolf , Herb Thilo , Borzyk Oliver , Hyla‐Kryspin Isabella
Published: July 2007

The synthesis of 2,7,9‐trimethylenetricyclo[4.3.0.03,8]nonane (8), 7,9‐dimethylenetricyclo[4.3.0.03,8]nonan‐2‐one (15), and 2,9‐dimethylenetricyclo[4.3.0.03,8]non‐4‐ene (9) has been achieved. The first key step of the synthesis is a Diels‐Alder reaction. In the reaction sequence affording 8 and 15 the starting materials are 1,3‐cyclohexadiene (10) and acetylallene (11) and in the synthesis of 9 the diene 16 and methyl vinylketone (17). Further key steps are an intramolecular Paterno‐Büchi and an oxetane ring‐opening reaction. Compound 8 as well as 15 rearrange to the corresponding triquinane derivatives according to a Cope rearrangement. The PE spectra of 8, 9, and 15 reveal a considerable through‐space and through‐bond interaction of the double bonds.
Enantioselective synthesis of bis(γ‐butyrolactones). Their oxidative degradation to tetraols as a key step in stereoselective syntheses of 1,3,5,7,9‐pentaol synthons for polyhydroxylated natural products
Authors: Menges Markus , Brückner Reinhard
Published: July 2007

The syntheses of two enantiopure skipped‐chain pentaol building blocks 51 and 56 are described. They are based on a strategy which derives 1,3,7,9‐tetraols from bis (γ‐butyrolactones). Two equivalents of γ‐lactone 17, readily available from L‐glutamic acid, and one equivalent of the diiodoisobutene 22 furnished bis(γ‐butyrolactone) trans,trans‐21 stereoselectively in a single step. The same lactone, combined in a 2:1 ratio with the dibromoisobutene derivative 18, led in four steps and with good stereocontrol to the isomeric bis(γ‐lactone) cis,trans‐21. On the basis of the 1H‐ and 13C‐NMR spectral data of these and other lactones it was possible to distinguish 1,3‐cis‐ and 1,3‐trans‐disubstituted γ‐lactones. Each of the bislactones was subject to a Criegee rearrangement of derived bis(peroxosulfonates) to give the diastereomerically pure 1,3,7,9‐tetraols 26 and 31. The configuration of these tetraols was proven by the 13C‐NMR shifts of the corresponding bis(acetonides) 27 and 32. Ozonolytic cleavage of the CC bond of 27, reduction of the obtained ketone 28 to alcohol 29, acetonide rearrangement under thermodynamic control (→ 30), and fuctionalization of the liberated hydroxy group delivered the end group‐differentiated 1,3,5,7,9‐pentaol building block 51. It represents a segment of the polyol parts of the antibiotics roxaticin (52) and mycoticin (53). The oxidative cleavage of the CC bond of bis(acetonide) 32 and chelation‐controlled reduction of the resulting ketone 33 with Zn(BH4)2 furnished after acetonide migration and functionalization of the unprotected hydroxy group the all‐syn‐configured 1,3,5,7,9‐pentaol building block 56. The latter compound should provide an entry into total syntheses of the naturally occurring poly(methyl ethers) 57 and 58.
Glycosyl imidates, 70. Synthesis of a coumarin C‐glucoside
Authors: Mahling Jürgen‐Andreas , Schmidt Richard R.
Published: July 2007

3,5‐Dimethoxyphenol (2) was glycosylated with O‐(2,3,4,6‐tetra‐O‐benzyl‐α‐D‐glucopyranosyl) trichloroacetimidate (1) and trimethylsilyl triflate (TMSOTf) as the promoter to yield the aryl C‐glycoside 3 via an O‐glycoside intermediate and subsequent Fries rearrangement. After formylation, the coumarin C‐glycoside 7 was synthesized either by Perkin reaction with acetic anhydride or by Wittig reaction followed by cyclization at 150°C. Deprotonation yielded the coumarin 8‐C‐glycoside 8, a dimethyl ether of an isomer of naturally occurring coumarin 6‐C‐glycosides.
Reactions of cyclic oxalyl compounds, 37. Substituent effects on the site of nucleophilic attack at 1H‐pyrrole‐2,3‐diones
Authors: Kappe C. Oliver , Terpetschnig Ewald , Penn Gerhard , Kollenz Gert , Peters Karl , Peters Eva‐Maria , von Schnering Hans Georg
Published: July 2007

Reactions of 1H‐pyrrole‐2,3‐diones 2a‐i with N‐ and O‐nucleophiles proceed by initial attack at C‐2 or/and C‐5. Consequently, earlier results suggesting structures of type A (attack at C‐3) have to be revised (5, 13, 17, 18b). In general, electron‐withdrawing substituents at C‐4 favor attack at C‐5 with formation of 2‐pyrrolones 5, 6, 10, 13, 17, and 20. Alternatively, attack at C‐2 leads to α‐oxobutenoic acid derivatives 3, 7, 11, 12, 15, and 18. IR and 13C‐NMR spectroscopic techniques were employed to differentiate between the possible isomeric addition products formed. The structure of methyl α‐oxobutenoate 15 was established by an X‐ray crystallo‐graphic analysis.
Neue Synthese von 4‐Azaphenothiazin
Authors: Kutscher Bernhard , Dieter Hans Reinhold , Trömer Hans‐Günther , Bartz Beate , Engel Jürgen , Kleemann Axel
Published: July 2007

New Synthesis of 4‐Azaphenothiazine

Herrn Dr. W. A. Schuler zum 80. Geburtstag gewidmet.

The reaction of 2‐chloropyridine with 2‐aminothiophenol gives N‐(2‐mercaptophenyl)‐2‐pyridinamine (2) which is cyclised to give 4‐azaphenothiazine (3), a useful intermediate for pharmaceuticals. An improved one‐pot synthesis is reported and a reaction mechanism proposed.
Stereoselective Synthesis of (E)‐Tagetone
Authors: Kunz Joachim , Breitmaier Eberhard
Published: July 2007

(E)‐Tagetone (8) was prepared in four steps by successive alkylation of 1,3‐dithiane (1) by 1‐iodo‐2‐methylpropane (2) and by 3‐ethoxy‐2‐methylacrolein (3), followed by treatment of the intermediate 4 with sulfuric acid. Wittig alkylenation of the resulting aldehyde 5 and removal of the protecting group affords the title compound in good yield.
The synthesis of rac‐peniolactol and some related compounds
Authors: Rama Nasim H. , Saeed Aamer , Bird Clive W.
Published: July 2007

The structure (±)‐3,6,8‐trihydroxy‐3‐pentadecyl‐3,4‐dihydroisocoumarin 1 assigned by earlier workers to peniolactol, a metabolite of Peniophora sanguinea, has been confirmed by total synthesis of this compound and some of its derivatives.
Cyclization reactions of tricarbonylmethane thiosemicarbazones: Formation of 1,3,4‐thiadiazole derivatives with concomitant CC bond cleavage
Authors: Somogyi László
Published: July 2007

Under acylating conditions 3‐acetyl‐4‐hydroxy‐2H‐pyran‐2‐one thiosemicarbazones (1a, b and 2a, b) are transformed into 2‐(acylamino)‐5‐methyl‐1,3,4‐thiadiazoles 3b, c, e, f and 2H‐pyran‐2‐ones 1c and 2c via C–C bond cleavage. Similarly, the reaction of 1b with RCO2H/EtOH (R = Me, Et) affords 2‐anilino‐5‐methyl‐1,3,4‐thiadiazole (3d) and triacetic acid lactone 1c. Upon treatment with Ac2O/Et3N the dehydroacetic acid derivative 1b is transformed into the thiadiazoline 4, while the benzo derivative 2b is converted into thiadiazole 3e and 4‐acetoxycoumarin (2c).
A Short Synthesis of a Thromboxane B2 Key Intermediate from (R)‐2,3‐Isopropylideneglyceraldehyde. γ‐Lactones as Templates for Chemoselective cis‐Annulation of Pyranosides
Authors: Mulzer Johann , Graske Klaus‐Dieter , Shanyoor Mazin
Published: July 2007

A six‐step synthesis of the bicyclic lactone pyranoside 1, which has served as a key intermediate in numerous syntheses of thromboxane B2, from (R)‐2,3‐isopropylideneglyceraldehyde is described. In contrast to the previous syntheses of 1 the lactone part is prepared first and acts as a template in the annulation of the hemiketal unit. Further aspects of interest are the Felkin‐Anh‐controlled addition of vinyl cuprates to the acrylic ester 16 and the considerable rate difference in the formation of the γ‐lactones 13, 14, 19, and 21 from the corresponding hydroxy acids.
Photochemistry of di‐Schiff bases and related compounds
Authors: Tauer Erich , Grellmann Karl‐Heinz , Heinrich Angelika
Published: July 2007

The photochemical properties of the di‐Schiff base 2 have been investigated. The first reaction step of 2 in 2‐propanol or in cyclohexane is an intramolecular photoreductive coupling affording the diazocine meso‐4. Subsequent photoreactions of meso‐4 in 2‐propanol are studied. In concentrated solutions of phenanthridine in cyclohexane a photodimerization takes place during which two CH bonds are broken and two NH bonds are formed. The photodimer reconverts with high quantum yield quantitatively to the monomer.
Synthesis of sphingosines, 11. Convenient synthesis of phytosphingosine and sphinganine fromD‐galactal andD‐arabitol
Authors: Wild Robert , Schmidt Richard R.
Published: July 2007

3,4,6‐Tri‐O‐benzyl‐D‐galactal (3) was directly converted into 3,4,6‐tri‐O‐benzyl‐2‐deoxy‐D‐galactose (5). Wittig reaction of5with alkyltriphenylphosphonium salts in the presence ofn‐butyllithium as the base afforded olefins6a, bwhich could be readily transformed into phytosphingosines1a, bvia different routes: (i) at first azido group introduction and then double bond and protective group removal, and azido group generation via hydrogenation; (ii) 2‐O‐mesylation, then double bond and benzyl group removal via hydrogenation, and finally nitrogen introduction; (iii) selective double bond hydrogenation, then nitrogen introduction, and finally benzyl group removal and amino group generation via hydrogenation. Wittig reaction of5with alkyltriphenylphosphonium salt in the presence of potassiumtert‐butoxide as the base afforded diene7awhich proved to be a convenient precursor for sphinganine syntheses; thus, 2‐O‐mesylation, then double bond and benzyl group removal via hydrogenation and 1,3‐O‐acetylation, and finally nitrogen introduction and de‐O‐acetylation afforded23a.Based on the convenient transformation of D‐arabitol into the 1,3‐O‐benzylidene derivative25a further phytosphingosine synthesis is outlined.
Simple and condensed β‐lactams, XIX. Synthesis Of some new 7‐acylamino‐2‐iso‐oxacephem‐4‐carboxylic acids
Authors: Tombor Zoltán , Greff Zoltán , Nyitrai József , Kajtár‐Peredy Mária
Published: July 2007

General methods have been developed for the synthesis of 7‐amino‐2‐iso‐oxacephem‐4‐carboxylic acid esters 21a,b; 35b. Clayfen [Fe(III) nitrate supported by montmorillonite] was used for the preparation of benzyl 2,3‐dioxobutyrate (3). The latter readily reacted with N(1)‐unsubstituted β‐lactams (9a, 28) to give products formed by addition reaction on the middle carbonyl‐C atom. These intermediates furnished the corresponding acetoacetic esters 10, 29 which gave by ring closure the O‐mono‐ and the O,N‐diprotected‐2‐iso‐oxacephems (11, 30). Intermolecular carbene insertion was used for the synthesis of tert‐butyl 2‐(2‐oxoazetidin‐1‐yl)acetoacetates 19a,b whose ring closure led to the tert‐butyl 2‐iso‐oxa‐cephem‐4‐carboxylates 20a,b. The O‐protecting tert‐butyl group could be removed without decomposition of the 2‐isooxacephem moiety to give 2‐iso‐oxacephem‐4‐carboxylic acids 2a,b which exhibit antibacterial activity against Grampositive microorganisms.
Substituent effects on the CC bond strength, 18. Stabilization of alkyl radicals by 4‐pyridyl, 1‐naphthyl or 2‐naphthyl substituents in α‐position
Authors: Herberg Clemens , Peyman Anuschirwan , Nölke Margot , Beckhaus Hans‐Dieter , Rüchardt Christoph
Published: July 2007

The formation of the α‐substituted radicals 7–9 with the 4‐pyridyl (7), 1‐naphthyl (8), and the 2‐naphthyl (9) substituent by thermolysis of their dimers 1–3 in solution was investigated. The activation parameters of the homolysis of the central CC bond were obtained from kinetic measurements of the thermal cleavage of 1–3 in the presence of radical scavengers. These data were compared with those obtained from the thermolysis of alkanes which cleave into α‐alkyl branched radicals, and which lose the same amount of strain during the dissociation. The „strain‐free”︁ radical stabilization enthalpies of the α‐substituted radicals [RSE = 7.9 ± 1.8 (7), 12.0 ± 1.4 (8), and 8.7 ± 1.9 kcal/mol (9)] were obtained in this way.
Syntheses and CD studies of 5α‐cholesteno[3,2‐d]‐, ‐[2,3‐d]‐ and ‐[3,4‐d]pyrimidines
Authors: Hasan Mashooda , Rashid Naghmana , Khan Khalid Mohammed , Snatzke Günther , Duddeck Helmut , Voelter Wolfgang
Published: July 2007

Syntheses of 5α‐cholesteno[3,2‐d]‐ (5a), [2,3‐d]‐ (12a), and [3,4‐d]pyrimidines (15a) have been achieved by using hydroxymethylene derivatives of relevant cholestanones prepared from cholesterol (1). Their CD spectra exhibit at least three Cotton effects between 300 to 200 nm, a first CD band around 290, a second one around 260 and a third one around 220 nm. A quadrant rule is developed and applied to the determination of the sign of the first CD band, while a helicity rule is applicable to the third CD band. The first band is positive in the [3,2‐d] series, whereas it is negative in the [2,3‐d] and the [3,4‐d] series. The third band is negative in all three series.
Zur Energiedelle von Diradikalen, VII. Konjugativ stabilisierte Trimethylenmethan‐Derivate. Geometrieabhängigkeit der Singulett‐Triplett‐Aufspaltung
Authors: Roth Wolfgang R. , Winzer Markus , Korell Michael , Wildt Holger
Published: July 2007

Energy Well of Diradicals, VII. – Conjugative‐Stabilized Trimethylenemethane Derivatives. Geometry Dependence of the Singlet‐Triplet Splitting

For the three 2,1′‐bis‐allyl diradicals 3–5 the singlet‐triplet splitting has been determined by the oxygen‐trapping technique. In agreement with theory the value for the planar diradical is large (>14 kcal · mol−1) whereas for the orthogonal geometry the energy gap is small (6.3 kcal · mol−1). In all cases a triplet groundstate is observed. From the rotational barrier of the exo methylene groups in 6 it is shown that the interconversion of the planar and orthogonal singlet states have activation barriers (6–9 kcal mol−1) which are responsible for their kinetic stability. In contrast to 6, where the formation of the orthogonal diradical proceeds by way of the planar diradical 3, the formation of the analogous orthogonal diradical 29 from homofulvene 17 is a concerted process. This difference is an important observation with respect to the fundamental understanding of concerted and non‐concerted reactions.
Synthesis of pyruvated saccharide fragments related to the aggregation factor of the marine sponge Microciona prolifera
Authors: Ziegler Thomas
Published: July 2007

Treatment of phenyl 2,3,6,2′,3′‐penta‐O‐benzoyl‐1‐thio‐β‐D‐lactoside (7) with BF3 in methyl pyruvate afforded the corresponding phenyl 4′,6′‐O‐[(R)‐1‐(methoxycarbonyl)ethylidene]‐1‐thio‐β‐D‐lactoside (9) in 91% yield. The latter was converted via bromide 10 into the corresponding lactal 11 the azidonitration of which afforded an unseparable mixture of the „gluco”︁‐ and „manno”︁‐configurated azido nitrates 12 (97%). As an alternative, benzyl O‐(β‐D‐galactopyrnosyl)‐(1→4)‐2‐azido‐2‐deoxy‐α‐D‐glucopyranoside (15) was prepared in two steps and 91% yield from the corresponding fully acetylated 2‐azido‐2‐deoxylactosyl bromide 13 and was further modified in four steps to give the benzoylated benzyl 4′,6′‐O‐benzylidene‐2‐deoxy‐2‐[(2,2,2‐trichloroethoxycarbonyl)amino]‐α‐D‐lactoside 18 in 78% overall yield. The benzylidene acetal of the latter was cleaved to give the diol 19 the pyruvation of which as for compound 9 afforded the corresponding pyruvated lactosamine derivative 20 (81%). Hydrogenolysis of 20 followed by treatment with trichloroacetonitrile gave the corresponding pyruvated disaccharide trichloroacetimidate 22 (77%). Coupling of the latter with Z‐protected 5‐amino‐1‐pentanol followed by deblocking of the intermediates furnished 5‐aminopentyl 2‐acetamido‐4′,6′‐O‐[(R)‐1‐carboxyethylidene]‐2‐deoxy‐β‐D‐lactoside (2). Similarly, condensation of 22 with 5‐[(benzyloxycarbonyl)amino]‐pentyl 2,4‐di‐O‐benzyl‐β‐L‐fucopyranoside (25) followed by deblocking of the intermediate trisaccharide afforded 5‐aminopentyl O‐{4,6‐O‐[(R)‐1‐carboxyethylidene]‐β‐D‐galactopyranosyl}‐(1→4)‐2‐acetamido‐2‐deoxy‐β‐D‐glucopyranoside‐(1→3)‐β‐L‐fucopyranoside (3). Saccharides 2 and 3, represent fragments of the Microciona prolifera aggregation factor.
Medium‐sized cyclophanes, 37. [n.2]metacyclophanediquinones: Synthesis, conformational studies and reduction to tetrahydroxy[n.2]metacyclophanes
Authors: Yamato Takehiko , Matsumoto Jun‐Ichi , Sato Mitsuhiro , Noda Kozo , Moriguchi Tetsuji , Tashiro Masashi
Published: July 2007

The title compounds, [n.2]metacyclophanediquinones 6a‐f, were prepared by oxidation of the corresponding di‐tert‐butyldihydroxy[n.2]metacyclophanes 5a‐f with Tl(OCOCF3)3 in CF3COOH. When [n.2]quinonophanes 6a‐e were reduced with Zn powder in acetic acid, the corresponding tetrahydroxy derivatives 8a‐e were obtained, which were converted to the tetraacetates 9a‐e. The solution conformations of diquinones 6a‐f and tetrahydroxy[n.2]MCPs 8a‐e are sensitive to the chain length of the bridges. The ring inversion barriers determined by variable‐temperature 1H‐NMR spectroscopy decrease with increasing length of the bridges. In addition, a solvent effect on the ratio of anti to syn conformers was found to occur in tetrahydroxy[6.2]metacyclophane 8d and dihydroxy[6.2]metacyclophanes 5d, 10d, and 12d. The conformationally rigid tetraacetoxy[n.2]metacyclophanes 9 exhibit fixed „anti”︁ and „syn”︁ conformations. The anti and syn ratio is strongly governed by the number of methylene bridges. Thus, a anti‐to‐syn ratio of the tetraacetoxy[5.2]‐ (9c) and ‐[6.2]metacyclophane (9d) differing from that of the tetraols 8c and 8d was obtained. This difference is due to the ring inversion of 8c and 8d. The assignment of anti and syn conformations was confirmed by 1H‐NMR analyses. The dynamics of the ring inversion is also discussed.
Liquid crystals derived from carbohydrates: Synthesis and properties of oxadecaline compounds
Authors: Vill Volkmar , Tunger Hanns‐Walter
Published: July 2007

Reaction of glucal 1 with alkoxybenzene leads after hydrogenation and deacetylation to β‐C glycosides 4, which can be used as chiral compounds in the synthesis of chiral calamitic liquid crystals. The combination with aliphatic aldehydes leads to liquid crystals 5 showing a monotropic SA phase, with aromatic p‐alkoxy‐substituted aldehydes to compounds 6 with enantiotropic cholesteric and SA phases. Reaction with p‐alkoxy‐substituted phenylboronic acids gives liquid crystals 7 forming SA and ferroelectric SC* phases. They all exhibit a high twisting power and blue phases in contact preparation.
Stereo‐ and regioselective intramolecular heck reaction of α‐amino acid derivatives for the synthesis of enantiopure 3,4‐dihydroisoquinolinones
Authors: Tietze Lutz F. , Burkhardt Olaf
Published: July 2007

Acylation of the alkenes 1a–d and 3, easily prepared from the corresponding α‐amino acids, with 2‐iodobenzoyl chloride gives 2a–d and 4 which cyclize to the enantiopure dihydroisoquinolinones 5a–d and 9, resp., in an intramolecular Heck reaction using 5 mol‐ % of Pd(OAc)2 in the presence of PPh3, TPAB, and KOAc with excellent diastereoselectivity.
Diastereo‐ and enantioselective synthesis of the 18‐membered lichen macrolide (+)‐aspicilin
Authors: Enders Dieter , Prokopenko Oleg F.
Published: July 2007

The asymmetric synthesis of the lichen macrolide (+)‐aspicilin (1) was realised in 19 steps and with high stereoselectivity (de ≥ 91 %, ee ≥ 96%). Three of the four stereogenic centres were generated by employing the SAMP/RAMP hydrazone method. Key steps of the synthesis are the α,α′‐double alkylation of RAMP hydrazone (R)‐10 of 2,2‐dimethyl‐1,3‐dioxan‐5‐one B and the enantioselective synthesis of the bromo alcohol (S)‐9 (subunit A) by a combination of SAMP hydrazone α‐alkylation with subsequent Baeyer‐Villiger oxidation.
On the preparation of β‐amino acids from α‐amino acids using the Arndt‐Eistert reaction: Scope, limitations and stereoselectivity. Application to carbohydrate peptidation. Stereoselective α‐alkylations of some β‐amino acids
Authors: Podlech Joachim , Seebach Dieter
Published: July 2007

The Arndt‐Eistert homologation of α‐amino acids was studied to determine the stereoselectivity in this reaction by chromatographic up‐to‐date analytical methods. While carba‐mate‐protected phenylglycine was transformed to the corresponding β‐amino acid methyl ester with a stereoselectivity of only 9:1, all other tested amino acid derivatives (Ala, Phe, Ser, Orn, tert‐Leu and perhydro‐azepine‐2‐carboxylic acid, suitably protected) were homologated with full retention of configuration (products 9–17). The intermediate diazo ketones 1–8 were purified and characterized by their NMR spectra. When nucleophiles derived from partially protected sugars were present during decomposition of the diazo ketones (derived from amino acids or dipeptides), a strong dependence of the yield (products 21–24) on the degree of steric hindrance of the nucleophilic OH group was observed. Two of the β‐amino acids obtained from the homologation reaction were transformed to α‐substituted (25–27, 31, 32) and α,α‐disubstituted β‐amino acid derivatives (28, 29) with excellent selectivities (in most cases, a single diastereoisomer was obtained).
Synthesis of phthalocyanines with one sulfonic acid, carboxylic acid, or amino group
Authors: Kliesch Holger , Weitemeyer Andrea , Müller Silke , Wöhrle Dieter
Published: July 2007

Monofunctional phthalocyanines7a,b, one bearing a sulfo and the other one a carboxyl group, were synthesized by lithium alkoxyde‐catalyzed statistical tetramerization of 4‐(4‐tert‐butylphenoxy)‐1,2‐benzenedicarbonitrile (3c) with 1,2‐dicyanobenzenes3a,bcarrying a carboxyl or sulfo group. Tribenzonaphthoporphyrazines9a,bwith one carboxyl or amino group were prepared under similar reaction conditions by tetramerization of 3,6‐dihexyloxy‐1,2‐benzenedicar‐bonitrile with 6‐amino‐ or 6‐carboxy‐2,3‐naphthalenedicar‐bonitrile6b,6a. The zinc(II)‐containing macrocycles7a, b, 9a, bobtained in yields of 11–20% were purified by column chromatography and characterized by UV/Vis, mass, and1H‐NMR spectroscopy.
Bimolecular formation of radicals by hydrogen transfer, 9. Uncatalyzed transfer hydrogenation of α‐methylstyrene by 9,10‐dihydroacridine and N‐methyl‐9,10‐dihydroacridine
Authors: Friebolin Heike , Rüchardt Christoph
Published: July 2007

Hydrogen is transferred from acridane (1c) and N‐methylacridane (1d) to α‐methyl‐styrene (2) in a bimolecular uncatalyzed reaction at 260–300°C. On the basis of the activation parameters (for 1c: ΔH≠ = 29.0 kcal/mol, ΔS≠ = −23.5 e.u. in triglyme) the kinetic isotope effect (kH/kD = 2.0, in triglyme at 300°C) as well as the small solvent effects and from the observation of an EPR signal of N‐methylhydroacridyl radicals a three‐step radical mechanism is prosposed which is initiated by a retrodisproportionation between 1 and 2.
Enantioselective reformatsky reaction of methyl bromodifluoroacetate
Authors: Braun Manfred , Vonderhagen Anja , Waldmüller Delia
Published: July 2007

The Reformatsky reagent 2 generated from methyl bromodifluoroacetate is added to benzaldehyde in the presence of carbinols 3a, b, amino alcohols 3c‐g, or amino alkoxide 3h. N‐Methylephedrine 3c provides the highest enantioselectivity in the formation of the adduct S‐4a (84% ee; >96% after recrystallization) whose absolute configuration is determined by an X‐ray structural analysis of the amide 6.
Glycolipids from sponges, I. Glycosyl ceramide composition of the marine sponge Agelas clathrodes
Authors: Costantino Valeria , Fattorusso Ernesto , Mangoni Alfonso
Published: July 2007

The marine sponge Agelas clathrodes was analyzed for gly‐cosphingolipids, and four cerebrosides (1a‐4a) were isolated, each as a mixture of homologs. The structure of the new glycosphingolipid 1a was elucidated by extensive NMR studies of its peracetate and by chemical analysis. The presence of unusual α‐glycosphingolipids in sponges of the genus Agelas was confirmed.
Glycolipids from sponges, II. Glycosyl ceramide composition of the marine sponge Agelas longissima
Authors: Cafieri Francesco , Fattorusso Ernesto , Mangoni Alfonso , Taglialatela‐Scafati Orazio
Published: July 2007

A specimen of the marine sponge Agelas longissima was analyzed for glycosphingolipids. Three cerebrosides 1a‐3a were isolated, each as a mixture of homologs. The structure of the new glycosphingolipid 1a was elucidated by extensive NMR studies of its peracetate derivative and chemical analysis. Compound 2a, previously isolated from another specimen of A. longissima, exhibits in the new specimen a remarkably different alkyl chain composition.
Ozonolyses of O‐methyloximes in the presence of acid derivatives: A new access to substituted ozonides
Authors: Griesbaum Karl , Övez Bikem , Huh Tae Sung , Dong Yuxiang
Published: July 2007

Ozonolyses of O‐methyloximes (4) of 5‐, 6‐ and 7‐membered cycloketones in the presence of esters of trifluoroacetic acid (5) or of acyl cyanides (6) afforded ozonides of types 7 and 8, respectively, which are formally derived from vinyl ethers or vinyl cyanides. Similarly, ozonolysis of the O‐methylated oxime of acetone (9) in the presence of esters of trifluoroacetic acid (5) and of the O‐methylated oxime of 2‐naphthaldehyde (11) in the presence of acyl cyanides (6) gave the corresponding ozonides of types 10 and 12, respectively.
Pyridinium N‐phenoxide betaines and their application to the characterization of solvent polarities, XXI Determination of new and corrections of old ET(30) values as empirical measures of solvent polarity for 40 organic solvents
Authors: Reichardt Christian , Schäfer Gerhard
Published: July 2007

By means of the negative solvatochromic betaine dyes 1a and 1b empirical solvent polarity parameters ET(30) for 40 organic solvents of current interest were newly determined or corrected (Table 1).
Functional dyes for molecular switching. Dihydroazulene/vinylheptafulvene photochromism: Effect of π‐arylenes on the switching behavior
Authors: Spreitzer Hubert , Daub Jörg
Published: July 2007

The reversible interconversion of dihydroazulene (DHA) and vinylheptafulvene (VHF) can be utilized to switch a number of physical properties. This communication reports on a fluorescent switch. By a multistep sequence involving an [8 + 2] cycloaddition route 9‐anthracenyl‐1,4‐phenylene was covalently attached to C‐2 of the DHA chromophore affording DHA‐1 which undergoes complete and clean photochemical ring opening to vinylheptafulvene VHF‐1. The latter is thermally reverted to DHA‐1. The kinetics and the energetics of the thermal back reaction are discussed. On/off switching of luminescence was investigated: DHA‐1 displays fluorescence whereas VHF‐1 is nonfluorescent at ambient temperature.
Structure‐odor relationships of sandalwood odorants: Synthesis of (Z)‐7‐oxa‐β‐santalol
Authors: Buchbauer Gerhard , Lebada Philippine , Spreitzer Helmut , Wolschann Peter
Published: July 2007

By means of a convergent synthesis strategy, the title substance (Z)‐7‐oxa‐β‐santalol (4) was prepared starting with the side chain synthon 5‐iodo‐2‐methyl‐2‐pentenylmethoxyethoxymethyl ether (7) and the bicyclic synthon ethyl 3‐methylene‐7‐oxabicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate (5). The new santalol analogue 4 is odorless, although the steric requirements for the sandalwood odor are met. The reasons for this are discussed.
Norpinyl‐norbornyl rearrangements: Destabilized 2‐norpinyl cations
Authors: Fendel Wolfgang , Kautz Cornelia Brigitte , Kirmse Wolfgang , Klar Matthias , Siegfried Rainer , Wonner Aribert
Published: July 2007

In order to explore the effect of electron‐withdrawing substituents on 2‐norpinyl (bicyclo[3.1.1]hept‐2‐yl)→2‐norbornyl (bicyclo[2.2.1]hept‐2‐yl) rearrangements, cyano and penta‐fluoroethyl groups were introduced into the α and β (= bridgehead) positions. The substrates were synthesized from norpinan‐2‐one (8) by addition of HCN or C2F5Li, from 2‐aminonorbornane‐2‐carbonitrile (25) by rearrangement, and from 1‐(pentafluoroethyl)bicyclo[2.1.1]hexan‐2‐one (51) by ring expansion. Arenesulfonates and diazonium ions were used to generate the 2‐norpinyl cations. – Electron acceptors in the α position of 2‐norpinyl substrates promote the norpinyl→norbornyl rearrangement. Internal return of the counterion leads to endo‐2‐norbornyl sulfonates, often without formation of the analogous alcohols, i.e., the destabilized norpinyl cations do not escape from tight ion pairs. Electron acceptors in the β (bridgehead) position favor displacement and elimination processes with retention of the norpinyl structure while the norpinylnorbornyl rearrangement is inhibited, more strongly by β‐C2F5 than by β‐CN. The tendency to separate the positive charge from the electron acceptor explains the divergent effects of α and β substitution. – The kH/kα‐CN and kH/kβ‐CN rate ratios in the 2‐norpinyl and 2‐norbornyl series are virtually the same, and the stereoselectivity of the intervening carbocations is not significantly affected by electron‐withdrawing substituents.
Prearranged glycosides, 2. Intramolecular glycosylation of prearranged saccharides as a novel strategy for the construction of β‐L‐rhamnosidic linkages
Authors: Lau Richard , Schüle Gunter , Schwaneberg Ulrich , Ziegler Thomas
Published: July 2007

Disaccharides containing a β‐L‐rhamnosyl residue were prepared by a novel intramolecular glycosylation strategy. Thus, suitably benzyl‐protected L‐rhamnosyl donors (ethyl and phenyl 1‐thiorhamnoside 7, 18) were prearranged in positions 2 and 3 with benzyl 2‐O‐benzoyl‐4,6‐O‐benzylidene‐α‐D‐glucopyranoside 8 in position 3 by a malonyl, succinyl and phthaloyl bridge, respectively, to give the corresponding connected saccharides 9, 12, 16 and 20. After regioselective opening of the benzylidene ring of the glucoside residue to give compounds 10, 13, 17 and 21, the latter afforded the 3,2′‐ and 3,3′‐bridged disaccharides 22–25 upon intramolecular glycosylation with a thiophilic reagent. The anomeric selectivity of this intramolecular glycosylation is strongly influenced by the nature of the alkanoyl and aroyl bridge, its position at the rhamnosyl residue and the solvent used for the coupling. Best results were obtained in acetonitrile with the succinyl „spacer”︁ attached to position 2 of the phenyl 1‐thiorhamnoside and position 3 of the glucoside that afforded the corresponding β‐(1→4)‐linked disaccharide 22β in 76% yield.
Diterpenoid total synthesis, XXXI. Synthesis and absolute configuration of (−)‐stypoldione, a metabolite of Stypopodium zonale
Authors: Mori Kenji , Koga Yasuo
Published: July 2007

(S)‐3‐Hydroxy‐2,2‐dimethylcyclohexanone (2) was converted to (−)‐stypoldione (1), the ichthyotoxic and cytotoxic metabolite of the brown alga Stypopodium zonale. The present synthesis established the absolute configuration of (−)‐stypoldione as depicted in 1.
Syntheses and CD studies of new cholesteno[4,3‐d]‐ and ‐[7,6‐d]pyrimidines
Authors: Hasan Mashooda , Rashid Naghmana , Khan Khalid Mohammed , Perveen Shahnaz , Snatzke Günter , Duddeck Helmut , Voelter Wolfgang
Published: July 2007

The syntheses of 5α‐ and 5β‐cholest‐3‐eno[4,3‐d]pyrimidines (7) and (7′) could be achieved by using the hydroxymethylene derivative of cholestan‐4‐one (5) prepared from cholesterol (1). Their 2′‐derivatives 7a‐7d and 7′a‐7′c were also synthesized. 5α‐Cholest‐6‐eno[7,6‐d]pyrimidine (13) was prepared by the reaction of 5α‐cholestan‐7‐one (12) with tris‐(formylamino)methane. The CD spectra exhibit at least three Cotton effects between 300 and 210 nm, a first CD band around 290, a second one around 260, and a third one around 220 nm. An earlier developed quadrant rule can be applied to the determination of the sign of the first CD band, while the suggested helicity rule allows prediction of the third CD band.
Tricarbonylmethane acylhydrazones: Reactions under acylating conditions and formation of fused isoxazole derivatives with concomitant NN bond cleavage
Authors: Somogyi László , Sohár Pál
Published: July 2007

Reactivity of 3‐(1‐acylhydrazonoethyl)‐2H‐pyran‐2‐ones 1a–k and 4a–d towards various acetylating agents and nitrous acid, respectively, is studied. Treatment of dehydroacetic acid (DHA) (thio)acylhydrazones 1a, c, f with Ac2O/Et3N afforded the 3‐(1‐triacetylhydrazinoethenyl) derivative 3a. The analogous coumarin derivative 5 was obtained by treatment of acetylhydrazone 4a with AcCl/PhNMe2. With concomitant N–N bond cleavage acylhydrazones 1c–f were converted to the pyrano‐isoxazole 6 by treatment with NaNO2/AcOH whereas coumarin derivative 4d was converted to the imine 4e.
Unusual reactions between chloroketenes and 1,3,5‐tri‐tert‐butylcyclopentadiene
Authors: Dehmlow Eckehard Volker , Bollmann Christof , Neumann Beate , Stammler Hans‐Georg
Published: July 2007

Reaction of title compound 1 with dichloroketene resulted in a complex rearrangement to 2 when the ketene was generated from Cl3CCOCl/Zn. In contrast, treatment of 1 with the ketene produced from dichloroacetyl chloride/triethylamine gave a bicyclo[3.2.0]heptenone (3) along with acylation product 4. Reaction of monochloroketene with 1 afforded the „normal”︁ endo‐chloro compound 6 which thermally rearranged to the formal Diels‐Alder product 7.
Molecular switches: Calculations on the stereodivergent hetero Diels‐Alder reaction of chiral 1‐oxa‐1,3‐butadienes with different lewis acids
Authors: Tietze Lutz F. , Schulz Gerhard
Published: July 2007

The stereodivergent facial differentiation of the intermolecular hetero Diels‐Alder reaction of the 1‐oxa‐1,3‐butadiene 1 with 2 in the presence of trimethylsilyl trifluoromethanesulfonate (TMS‐OTf) or Me2AlCl is explained on the basis of semiempirical calculations (AM1 and PM3). The oxabutadiene 9 was shown to prefer the anti arrangement of the carbonyl groups of the imide moiety in the ground state by 1.8 kcal/mol (Am1) or 2.2 kcal/mol (PM3). In the silylated compound 10 this preference is even more pronounced. In contrast, in the chelate 11 the imide moiety is fixed in a syn conformation. The orientation of the oxazolidinone rings in 10 and 11 is opposite: thus, the absolute configuration of the cycloadducts is determined by a facial differentiation due to an asymmetric induction under chelate control (11) or nonchelate control (10).
A photochemical route to vinylglycine and a vinylglycine dipeptide
Authors: Griesbeck Axel G. , Hirt Joachim
Published: July 2007

Enantiomerically pure vinylglycine (4b) can be prepared from natural („chiral pool”︁) amino acids by photoelimination of γ‐functionalized N‐phthaloyl amino acid esters. Two routes have been developed: (a) a three‐step synthesis of substrate 3b [PhtN‐Met(SO)OMe] from (S)‐methionine and subsequent photolysis, (b) the use of N‐phthaloyl activated methyl 2‐amino‐4‐chloro‐ or ‐4‐bromobutanoates 3d, e which are available from (S)‐methionine (four‐step synthesis) or from (S)‐homoserine (two‐step synthesis). The photoelimination (of HOSMe from 3b and of HX from 3d, e) proceeds quantitatively and leads to N,C‐protected vinylglycine 4a in high yields. This strategy could also be applied to peptide‐bound substrates as was shown for the protected Met‐Gly (5b) which was transformed into the N‐protected vinylglycine‐glycine dipeptide 6 in three steps.
Synthesis of optically active α,β‐disubstituted β‐amino nitriles and β‐amino acids starting from asparagine
Authors: Gmeiner Peter , Hummel Evi , Haubmann Christian
Published: July 2007

Starting from the enantiomerically pure building block 2 which is readily available from D‐asparagine α,β‐disubstituted β‐amino nitriles and β‐amino acids could be synthesized. After deprotonation of the nitrile α‐position the introduction of substituents was performed by alkylation of either 2 or the TBDMS‐protected derivative 3. Starting from the β homoserine equivalent 2 the reaction proceeds via a dianionic intermediate resulting in a preferred formation of the threo‐configured products 6a,b (ratio of isomers: 7:1). Modification of the side chain was demonstrated by displacement reactions with LiBH4 or potassium thioacetate.
Enzymes in organic synthesis. Expedient enantioselective synthesis of (S)‐(−)‐3,4‐dihydroxybutylphosphonate, an isosteric substrate mimic for glycerol phosphate oxidase
Authors: Arth Hans‐Lothar , Sinerius Gudrun , Fessner Wolf‐Dieter
Published: July 2007

The title compound (S)‐(−)‐2 was obtained in enantiomerically pure form and 47% overall yield starting from (S)‐malic acid (S)‐7 by a 5‐step sequence involving reduction to (S)‐1,2,4‐butanetriol (S)‐8, acetalization, and introduction of the phosphonate group by an Arbusow reaction. Compound (S)‐(−)‐2 is a substrate for the L‐glycerol 3‐phosphate oxidase from Pediococcus sp. which quantitatively converts it into 4‐hydroxy‐3‐oxobutylphosphonate 4, an isosteric analog of dihydroxyacetone phosphate. Kinetic constants of the latter reaction were determined.
On the chemistry of α‐formyl‐2‐hydroxyacetophenone
Authors: Széll T. , Sohár P. , Horváth Gy.
Published: July 2007

The title compound 1 undergoes cyclization and self‐condensation in the presence of dil. NaOH yielding chromone (2) and/or 1‐(3‐chromonyl)‐2‐(2‐hydroxybenzoyl)ethene (3). With benzaldehyde in the presence of piperidine in boiling ethanol, 1 reacts both by cyclization, and self‐condensation combined with cyclization to give 2, 3 and bis(3‐chromonyl‐phenyl)methane (5). If less than 0.1 M aq. NaOH is used 1 and benzaldehyde produces 3‐(α‐hydroxybenzoyl)chromone (4) which can also be converted into 5.
Synthesis of 1‐azabicyclo[3.3.1]nonadienes by intramolecular cyclization of 1‐(3‐oxo‐2‐phenylbutyl)tetrahydropyridines
Authors: Sólyom Sándor , Pallagi István , Ábrahám Gizella , Ling István , Szöllõsy Márta , Sziráki István , Jerkovich Gyula
Published: July 2007

Intramolecular cyclization reactions were performed with 1‐(3‐oxo‐2‐phenylbutyl)‐1,2,5,6‐tetrahydropyridine derivatives 6a‐h in sulfuric acid to give 3,6‐diphenyl‐substituted 1‐aza‐bicyclo[3.3.1]nonadienes 9. The intermediate carbinols 7a‐f and 8b, c could be isolated. Carrying out the reaction in methanesulfonic acid stereoselectivity was found in the formation of carbinols with preferential production of derivatives 7. Some of the compounds 9 show remarkable dopamine uptake inhibition.
Studies on ketoses, 11. Pyranoid exo‐ and endo‐glycals from D‐fructose and L‐sorbose: Practical routes for their acquisition and some ensuing reactions
Authors: Lichtenthaler Frieder W. , Hahn Susanne , Flath Franz‐Josef
Published: July 2007

The reductive elimination of the benzoylated β‐D‐fructopyranosyl and α‐L‐sorbopyranosyl bromides 10 and 23 has been examined in order to determine suitable conditions for effecting the elimination from the exo‐ as well as the endo‐positions. Exposure of 10 and 23 to Zn/HOAc or Zn/N‐methylimidazole gave the tribenzoates of exo‐D‐fructal (1) and exo‐L‐sorbal (25), in yields of 79 and 80%, respectively; minor products (ca, 10% each) were the corresponding endo‐D‐fructal (6) and endo‐L‐sorbal esters (26). For the reductive elimination to occur primarily from the endo‐position, enhancement of the leaving group capacity of the respective ring acyloxy group was required, and materialized via the 3‐O‐mesyl analogues of fructosyl bromide 10, which smoothly reacted with Zn/HOAc to give the endo‐D‐fructal esters 20 and 21; their yields, over the five steps from diacetone‐fructose, were in the 50% range. Accordingly, the methodology for generating ketose‐derived glycal esters in exo‐ or endo‐version, is now available. Some ensuing reactions of the exo‐glycals have been exploited, that is, their ozonolysis to the respective pyranoid pentonolactones, and their hydrogenation to 1,5‐anhydro‐6‐deoxy‐hexitols.
Pheromone synthesis, CLXXI. A new synthesis of (2E,4E,6R10R)‐4,6,10,12‐tetramethyl‐2,4‐tridecadien‐7‐one (matsuone), the primary component of the sex pheromone of three Matsucoccus pine bast scales
Authors: Mori Kenji , Furuuchi Takeshi , Matsuyama Keisuke
Published: July 2007

A new synthesis of (2E,4E,6R,10R)‐4,6,10,12‐tetramethyl‐2,4‐tridecadien‐7‐one (1; matsuone) was achieved by starting from (2R,3S)‐4‐(tert‐butyldiphenylsilyloxy)‐2,3‐epoxy‐1‐butanol (21 = E) and methyl (R)‐3‐hydroxy‐2‐methylpropanoate (2 = I). Cleavage of 21 with trimethylaluminium afforded 22 as the major product (56%) and a mixture (14%) of 23 and 24. The abnormal minor product 24 was generated by the migration of a phenyl group from the silicon to a carbon atom.