Niels Thorup

Conformationally locked aryl C-nucleosides: synthesis of phosphoramidite monomers and incorporation into single-stranded DNA and LNA (locked nucleic acid)

Synthesis of a series of LNA-type β-configured C-aryl nucleosides, i.e., 2′-O,4′-C-methylene-β-D-ribofuranosyl derivatives containing phenyl, 4-fluoro-3-methylphenyl, 1-naphthyl, 1-pyrenyl and 2,4,5-trimethylphenyl groups as aglycons, has been accomplished. The key synthetic step consisted of stereoselective Grignard reactions of the cyclic aldehyde 11 followed by cyclization to give the bicyclic core structure with a locked N-type furanose conformation as confirmed by NOE experiments on the di-O-p-methoxybenzyl derivatives 13a–13e and an X-ray crystallographic study of the phenyl derivative 14a. The phosphoramidite approach was used for automated incorporation of the LNA-type β-configured C-aryl monomers 17a–17e into short DNA and 2′-OMe-RNA/LNA strands. It is shown that universal hybridization can be obtained with a conformationally restricted monomer as demonstrated most convincingly for the pyrene LNA monomer 17d, both in a DNA context and in an RNA-like context. Increased binding affinity of oligonucleotide probes for universal hybridization can be induced by combining the pyrene LNA monomer 17d with affinity-enhancing 2′-OMe-RNA/LNA monomers.

Donor−Acceptor Macrocycles Incorporating Tetrathiafulvalene and Pyromellitic Diimide: Syntheses and Crystal Structures

The Mitsunobu reaction is shown to be a versatile method for the incorporation of pyromellitic diimide (PMDI) acceptors into new macrocyclic structures containing tetrathiafulvalene (TTF) donors. In the case of macrocycle 5, the more efficient bis-pyrroloTTF donor was used instead of TTF. Macrocycle 1 revealed distinct charge-transfer interactions in the trans-configuration, but not in the corresponding cis-form. Depending on the spatial geometry, inter- and intramolecular interactions between the TTF-donor and the PMDI-acceptor take place. X-ray crystal structures of macrocycles 1-cis, 1-trans, 2 and 5 are reported.

The geometry and structural properties of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,­mn]pyrene system in the cationic state. Structures of a planar organic cation with various monovalent and divalent anions

The geometry of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrene system in the cationic state was established by X-ray structural resolution of the salts formed between the cation and various anions. The geometry was found to be planar for the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium and 2,6,10-tri(tert-butyl)-4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium cations with the monovalent anions I(-), BF(4)(-), PF(6)(-), AsF(6)(-), HNO(3).NO(3)(-) and CF(3)SO(3)(-), and the divalent anions S(2)O(6)(2-) and Mo(6)Cl(14)(2-). The salts were found to crystallize in distinct space groups following a characteristic pattern. Mixed cation-anion stacking resulted in space groups with high symmetry: Pbca in three cases and R3;c in one; a temperature study of the latter was made at ten different temperatures. The formation of dimers of anions and cations resulted in lower-symmetry space groups, mainly monoclinic (P2(1)/n, P2(1)/c and C2/c), but also P1;.

New Chiral Bis(dipolar) 6,6′‐Disubstituted Binaphthol Derivatives for Second‐Order Nonlinear Optics

Macro- and microscopic nonlinear optical properties of 6,6′-diacceptor-substituted binaphthol derivatives with C2 symmetry were measured by the Kurtz–Perry powder test (scheme, right) and electric field induced second harmonic generation (EFISHG). These derivatives are axially chiral and possess two equal donor–acceptor systems linked together, to give a V-shaped bis(dipolar) system. The use of this type of chirality (atropisomerism) ensures noncentrosymmetric packing in crystals necessary for second-harmonic generation in bulk.

A conformationally locked tricyclic nucleoside. Synthesis, crystal structure and incorporation into oligonucleotides

A tricyclic nucleoside is synthesised from a bicyclic nucleoside precursor by applying a stereoselective dihydroxylation, a regioselective tosylation and an intramolecular ether formation. This tricyclic nucleoside is constructed as a conformationally locked thymidine analogue and has been analysed by X-ray crystallography. Thus, the furanose ring of this nucleoside adopts a perfect S-type conformation and the torsion angle γ, describing the C4′–C5′ bond is restricted in the +ac range. The tricyclic nucleoside is incorporated into two nonameric oligonucleotide sequences displaying strongly decreased affinity towards complementary DNA and RNA when compared to the corresponding unmodified oligodeoxynucleotide sequences.

Acetylenic dithiafulvene derived donor–π–acceptor dyads: synthesis, electrochemistry and non-linear optical properties

A selection of donor–acceptor chromophores containing the redox-active dithiafulvene unit about acetylenic and aryl scaffolds has been synthesised. The molecules were studied for their optical, redox and structural properties. Moreover, third-order non-linear optical properties were investigated as a function of molecular structure.

Unusual structure-related magnetism in the organic conductor TSF(Ni(dmit)2)3 (tetraselenafulvalenium-tri-(bis-(4,5-dimercapto-1,3-dithiole-2-thione)nickel)-ate)

Abstract TSF(Ni(dmit) 2 ) 3 crystallizes in the triclinic space group PI with unit cell dimensions a = 5.875(1), b = 11.846(1), c = 18.873(1) A , α = 71.35(1) , β = 81.63(1), γ = 78.16(1)°. Thermopower and electrical conductivity measurements show semiconducting behaviour localized in the Ni(dmit) 2 network. At 65 K the unit cell doubles in the a direction and this feature is utilized in explaining an unusual cross-over from a Bonner-Fischer model to a simple singlet-triplet magnetic behaviour in the sheets of weakly interacting TSF cation radicals.

The Crystal Structure of 1,6-Dithiapyrene(DTP)-7,7,8,8-Tetracyano-P-Quinodimethane(TCNQ)

Abstract The crystal structure of the charge-transfer complex between 1,6-dithiapyrene(DTP) and 7, 7,8,8-tetracyano-p-quino-dimethane(TCNQ) is reported. The structure correlates well with the observed physical properties.

A novel thiopyran-4-thione synthesis and crystal structure of a thiopyran-4-thione

The zinc(II) chloride catalysed reaction between ethylene trithiocarbonate (1) and dibenzoylacetylene (3) gave the novel 2,3,5,6-tetrabenzoylthiopyran-4-thione (4a) and its structure was elucidated by X-ray crystallography. Treatment of 2,3,5,6-tetrabenzoylthiopyran-4-chalcogenones (4a,b) with triethyl phosphite afforded the bis-annelated furans 1,3,5,7-tetraphenylthiopyrano[2,3-c∶5,6-c′]difuran-8-chalcogenones (5a,b) in almost quantitative yields. The mechanism for this furan formation is discussed.

A Flexible Cyclophane: Design, Synthesis, and Structure of a Multibridged Tris-tetrathiafulvalene (TTF) Macrocycle

The tris-tetrathiafulvalene (TTF) macrocycles 3 with a large end-cavity were effectively synthesized from the readily available tetrakis(cyanoethylthio)TTF by means of a selective deprotection/realkylation sequence followed by an intramolecular coupling reaction. Crystar structure analyses revealed that the neutral molecules include two (3a) or one chloroform molecule (3b) as solvent of crystallization inside the cavity, whereas the I3- salt of 3b, obtained by electrocrystallization, has a molecular structure which is different from that of the neutral molecule in that the cavity has completely collapsed.