The present study explores the C-3' site of the 3-deoxy-3-xylofuranosyl ring of nucleoside analogues with an adenine or N6-cyclopentyladenine (CPA) base moiety and evaluates the effect on adenosine receptor affinity. Two series of sugar-modified adenosines, i.e., 3'-amido-3'-deoxyadenosines and 3'-amidated 3'-deoxyxylofuranosyladenines, were synthesized and tested for their affinity at A1 and A2a receptors in rat brain cortex and rat striatum, respectively. The modest affinity found in the "xylo series" prompted us to synthesize the corresponding N6-cyclopentyl derivatives, which proved to be well accommodated by the A1 receptors with potencies in the lower nanomolar range. This represents a new perspective in the purinergic field. The absence of a GTP-induced shift, i.e., the ratio between the affinities measured in the presence and absence of 1 mM GTP indicates an antagonistic behavior of this new class of CPA analogues.

On irradiation of 4-(4-methoxyphenoxy)-3-(N-3-benzozylthymin-1-yl)but-1-ene 1 at 254 nm in THF a single photoadduct 2 is formed as a result of chemo-, regio- and stereo-selective intramolecular ortho photocycloaddition of the thymine double bond to the 1,2-positions of the phenyl ring.

The ease of thermal breaking of the C(sp(3))-O bond of the 2-aryl-2-methyl-2H-1-benzopyrans 1-9 was evaluated by measuring the free energy (Delta G(e)(not equal)) of the racemization reaction of optically active compounds. The variation of Delta G(e)(not equal) of the thermal ring opening in terms of structural modifications is discussed. The synthesis of the studied compounds, the preparative separation of enantiomers by liquid chromatography, the determination of enantiomeric purity, the circular dichroism of enriched enantiomers, and the measurement of rate constants of enantiomerization by monitoring the decrease of the polarimetric angle of rotation at suitable temperatures are described.

4-Methyl-4-(4-methoxyphenyl)-benzo[h]-4H-chromene is synthesised by condensation of 4-methoxyacetophenone and ethyl acetate in strong base, followed by coupling with l-naphthol, reduction to the epimeric lactols and elimination of water.

Biomedical ChromatographyVolume 11, Issue 2 p. 79-80 Extended Abstract Access to Sterically Confined Nucleoside Analogues Via Intramolecular Photocycloadditions of Arene–Alkene Trichromophores Wim Saeyens, Wim Saeyens University of Gent, Faculty of Pharmaceutical Sciences, Harelbekestraat 72, B-9000 Gent, BelgiumSearch for more papers by this authorDenis De Keukeleire, Corresponding Author Denis De Keukeleire University of Gent, Faculty of Pharmaceutical Sciences, Harelbekestraat 72, B-9000 Gent, BelgiumUniversity of Gent, Faculty of Pharmaceutical Sciences, Harelbekestraat 72, B-9000 Gent, BelgiumSearch for more papers by this authorPiet Herdewijn, Piet Herdewijn University of Gent, Faculty of Pharmaceutical Sciences, Harelbekestraat 72, B-9000 Gent, BelgiumSearch for more papers by this authorAndre De Bruyn, Andre De Bruyn University of Gent, Department of Organic Chemistry, Krijgslaan 281 (S-4), B-9000 Gent, BelgiumSearch for more papers by this author Wim Saeyens, Wim Saeyens University of Gent, Faculty of Pharmaceutical Sciences, Harelbekestraat 72, B-9000 Gent, BelgiumSearch for more papers by this authorDenis De Keukeleire, Corresponding Author Denis De Keukeleire University of Gent, Faculty of Pharmaceutical Sciences, Harelbekestraat 72, B-9000 Gent, BelgiumUniversity of Gent, Faculty of Pharmaceutical Sciences, Harelbekestraat 72, B-9000 Gent, BelgiumSearch for more papers by this authorPiet Herdewijn, Piet Herdewijn University of Gent, Faculty of Pharmaceutical Sciences, Harelbekestraat 72, B-9000 Gent, BelgiumSearch for more papers by this authorAndre De Bruyn, Andre De Bruyn University of Gent, Department of Organic Chemistry, Krijgslaan 281 (S-4), B-9000 Gent, BelgiumSearch for more papers by this author First published: 04 December 1998 https://doi.org/10.1002/(SICI)1099-0801(199703)11:2<79::AID-BMC644>3.0.CO;2-AAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume11, Issue2March 1997Pages 79-80 RelatedInformation

Upon a 1,3-dipolar addition reaction with trimethylsilyl acetylene, azides (R,S)-7 were converted to the triazoles (R,S)-8. These diastereoisomers were separated and individually protodesilylated to yield (R)-and (S)-9, fully characterized by NMR. Structural assignments of unsaturated side compounds were deduced from a QUIET-NOESY experiment. Compounds (R)-and (S)-9 represent a new type of homo-C-nucleosides with a “split” 8-azapurine base moiety.

The photochromic behaviour of 3,3-bis[4-(N,N-dimethylamino)phenyl]-3 H-naphtho[2,1-b]pyran (2) and 2,2-bis[4-(N,N-dimethylamino)phenyl]-2 H-1-benzopyran (3) has been studied by flash photolysis and compared to 3,3-diphenyl-3 H-naphtho[2,1-b]pyran (1) in order to delineate effects due to the N,N-dimethylamino groups. © 1997 Elsevier Science Ltd.

We evaluated two internal standards for HPLC determination of creatinine in human serum after ultrafiltration: 2-iminoimidazolidin-4-one for normal-phase HPLC on aluminium oxide, and thymine for C-18 reversed-phase HPLC. Detection of 2-iminoimidazolidin-4-one was done at the same wavelength as that used for creatinine, i.e. 240 nm. For thymine, the wavelength was switched to 280 nm. The suitability of the selected compounds to serve as an internal standard in the described measurement procedures, including ultrafiltration of serum, was evaluated from the precision and accuracy obtained. The method based on normal-phase HPLC with 2-iminoimidazolidin-4-one showed an imprecision expressed as R.S.D. ranging from 0.8 to 3.4% (mean: 2.1%) and an inaccuracy, calculated from the deviations from target values determined by isotope-dilution gas chromatography-mass spectrometry, ranging from -1.3 to +1.8% (mean: +0.4%). For the reversed-phase HPLC procedure with thymine, the imprecision ranged from 0.3 to 1.3% (mean: 1.0%) and the inaccuracy from +0.1 to +3.9% (mean: +1.7%). The occasional observation of interferences with 2-iminoimidazolidin-4-one limited the application of the normal-phase method to a certain extent.

3-Alkyl-4-phencxybut-1-enes (alkyl: methyl, isopropyl, tert-butyl) On excitation at 254 nm in cyclohexane give rise to 4-alkyl-2-oxatetracyclo[5.4.0.0(1.8).0(5,11)]undec-9-enes via intramolecular meta photocycloaddition. Prevailing stereochemical features are the configuration of the alkyl group at C-4 and the conformation of the tetrahydropyran ring contained in the tetracyclic system. These are revealed by detailed H-1-NMR analysis and interpretation of the coupling constants. Whereas the alkyl group at C-4 invariably occurs in the exo configuration, the conformation of the tetrahydropyran ring depends on the bulkiness of the alkyl substituent. Thus, the C-l methyl group occupies an equatorial position in a chair conformation, while a flattened chair conformation accomodates appropriately the C-4 isopropyl group in the pertaining structure. The required equatorial position of the tert-butyl group at C-4. on the other hand, forces the tetrahydropyran ring into a boat conformation, thereby alleviating steric constraints.

H-1 NMR data (400 and 500 MHz) are reported for the intramolecular meta photocycloaddition products from 4-phenoxybut-1-enes and 3-benzyloxyprop-1-enes. The structures of these photoproducts, and in particular the discrimination between the 1,6- and 7,8-bridged isomers, are deduced from COSY 45 and 60 experiments and spin-decoupling techniques.

Upon irradiation of 3-alkyl-4-phenoxybut-1-enes 1a-d at 254 nm in cyclohexane, ortho and meta photocycloadditions occur. The ortho photocycloadducts rearrange readily, while the meta photocycloaddition involves the 2′,6′-positions of the arene as directed by the alkoxy group. In each case only a single meta photocycloadduct with an endo alkyl group is formed resulting in six contiguous stereocentres. A 3-alkyl group does not influence significantly the mode selectivity.

4-Phenoxybut-1-ene undergoes both ortho and meta intramolecular photocycloaddition on 254 nm irradiation: in the latter process the addition is directed by the alkoxy tether to the arene 2,6-positions. Methyl substitution on the ethene and arene units does not affect the regiochemistry of the reaction but the presence of a 2′-methoxy group inhibits the meta process and only the ortho addition occurs.

The mono-oxime of 1,10-phenanthroline-5,6-quinone reacts with 1,3,3-trimethyl-2-methyleneindoline derivatives to give the corresponding spirooxazines, i.e. 1,3-dihydrospiro[2H-indole-2,2'-[2H]-bipyrido[3,2-f][2,3-h][1,4)benzoxazines]. These compounds exhibit particular solvatochromic behaviour, strongly dependent on the substitution pattern. At room temperature and without any light excitation, an equilibrium is established between closed and opened forms. The photochromic characteristics have been determined using flash photolysis coupled to a fast scanning spectrometer allowing the determination of rate constants for thermal bleaching, visible absorption and photocoloration. The coloured opened forms, either photoinduced or arising from the solvation effect, appear to be spectroscopically identical. Structural parameters of the short-lived photomerocyanines have also been obtained.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Irradiation of the aryl-substituted norbornan-2-ones 6 and 7 at 254 nm furnishes the triquinanes 16 and 17(from 6) and 18(from 7)via tandem Norrish Type 1 reaction and intramolecular arene–alkene meta-photocycloaddition of the intermediate unsaturated lactols 12 and 13, respectively.

The norbornan-2-one derivatives 3 and 5 are photoinert on irradiation at 254 nm except in methanol. Photoinduced formation of formic acid leads to the corresponding dimethyl acetals 4 and 6, respectively.

Analysis of 1H and 13C NMR data by 2D NMR techniques was used for the structural identification of triquinanes and bulleranes considered as precursors of complex natural products such as (+)‐cerapicol. The polycyclic molecules are derived from a tandem Norrish Type I photoreaction and intramolecular arene–alkene meta photocycloaddition of aryl‐substituted norbornan‐2‐ones.