Inger Søtofte

Crystal structures of 2-(N,N-dimethylaminoalkyl)ferroceneboronic acids and their diol derivatives. The quest for a B–N intramolecular bond in the solid state

The crystal structures of (S,S)-2-(N,N-dimethyl-1-aminoethyl)ferroceneboronic acid (2), (S,S)-1-(N,N-dimethyl-1-aminoethyl)-2-(4,4,5,5-tetraphenyl-1,3,2-dioxaborolan-2-yl)ferrocene (3), rac-2-(N,N-dimethylaminomethyl)ferroceneboronic acid (rac-4), (S)-[(1S,2S,3R,5S)-pinane-1,2-diyl] 2-(N,N-dimethylaminomethyl)ferroceneboronate (5) are presented. In connection with our studies of boronic acid-based carbohydrate sensors, we aimed at verifying the existence of an intramolecular B–N bond in these compounds; however, such a bond was not found. This fact, and other structural elements and similarities of the four compounds, are discussed.

Structure of 1,5-Anhydro-D-Fructose: X-ray Analysis of Crystalline Acetylated Dimeric Forms

Abstract Acetylation of 1,5-anhydro-D-fructose under acidic conditions gave two crystalline acetylated dimeric forms, which by X-ray analysis were shown to be diastereomeric spiroketals formed between C-2 and C-2/C-3. The structures of the compounds differed only at the configuration at C-2. Acetylation or benzoylation of 1,5-anhydro-D-fructose in pyridine yielded 3,6-di-O-acetyl-1,5-anhydro-4-deoxy-D-glycero-hex-3-enos-2-ulopyra-nos or crystalline 1,5-anhydro-3,6-di-O-benzoyl-4-deoxy-D-glycero-hex-3-enos-2-ulo-pyranose. 1. Presented at the 9th European Carbohydrate Symposium, Utrecht, Netherlands, July 6-1 1, 1997, Poster A138.

The crystal structure of Cu4Bi4Se9

Abstract The crystal structure of Cu4Bi4Se9, synthesized at 400 °C, was determined from single crystal X-ray diffraction data and refined to the R1 value of 0.05. The compound is orthorhombic, with a = 32.692 Å, b = 4.120 Å, and c = 12.202 Å, space group Pnma. The structure contains three square pyramidal Bi sites, an octahedrally coordinated Bi site as well as two tetrahedrally and two irregularly coordinated Cu sites. The structure is an intergrowth of PbS-like slabs with irregularly configured slabs of Bi pyramids and Cu tetrahedra. It contains covalently bonded Se2 groups. Isotypy with Cu4Bi4S9 is connected with substantial changes in coordination details for two out of five distinct Cu sites. Modular relationships to the structures of the cuprobismutite series of Cu—Bi sulfosalts can be expressed as different ways of recombination of the same large structural fragment in the structures of Cu4Bi4Se9 and of the first cuprobismutite homologue, Cu4Bi5S10.

Design, synthesis and structure of new potential electrochemically active boronic acid-based glucose sensors

In the course of our investigations on new boronic acid based carbohydrate sensors three new boronic acids 3, 7 and 11 containing a ferrocene moiety were synthesised. Their design includes an intramolecular B–N bonding motif in order to facilitate binding at physiological pH. We report the synthesis of the compounds and our investigations on glucose complexation as studied by 13C NMR spectroscopy. The crystal structure of 2,4,6-tris[2-(N-ferrocenylmethyl-N-methylaminomethyl)phenyl]boroxin (13) (boroxin of boronic acid 3) (boroxin = cyclotriboroxane) was obtained and compared with structures obtained of 2,4,6-tris[2-(N,N-dimethylaminomethyl)phenyl]boroxin (14) and 2,2-dimethyl-1,3-diyl[2-(N,N-dimethylaminomethyl)phenyl]boronate (15). The structure of 13 shows the existence of intramolecular B–N bonds in the solid phase.

Short and efficient diastereoselective synthesis of pyrrolidinone-containing dipeptide analogues

The pyrrolidine-2,4-diones have been identified as a convenient starting point for the synthesis of peptide analogues. Herein we describe an optimized two-step reductive amination procedure, which provides a small library of pyrrolidinone-containing dipeptide analogues in high yield and excellent diastereoselectivity.

The crystal structure of Cu1.78Bi4.73Se8, an N = 3 pavonite homologue with a Cu-for-Bi substitution

Summary Cu1.78Bi4.73Se8, synthesized in a dry phase system Cu—Bi—Se at 450 °C, is monoclinic, a = 13.759 Å, b = 4.168 Å, c = 14.683 Å, γ = 115.61°, space group C2/m. It is an N = 3 member of the pavonite homologous series, with the composition limits Cu1.96Bi4.67Se8—Cu1.77Bi4.60S8—Cu1.25Bi4.91Se8. The crystal structure is composed of two types of alternating slabs, with configurations typical for the above series. The first kind of slabs contains paired square pyramidal columns of Bi3, interconnected by octahedral columns with three distinct statistical copper sites (flattened tetrahedral sites in the octahedral interior and a tetrahedral site between adjacent octahedra). They add up to nearly 1.5 Cu. The second kind of slabs contains central octahedra of Bi1, flanked by marginal distorted octahedra of Bi2. These Bi sites are partly replaced by statistically occupied Cu1-3 sites, in flat-tetrahedral and irregular trigonal-planar coordinations. Details of the Cu-for-Bi substitutions are discussed and comparisons with other N = 3 homologues of pavonite are made in the paper.

cis- and trans-2,3,3a,4,5,9b-Hexahydro-1H-benz[e]indoles: synthesis and evaluation of dopamine D2 and D3 receptor binding affinity

Abstract cis- and trans-2,3,3a,4,5,9b-Hexahydro-1H-benz[e]indoles were synthesized as conformationally rigid analogues of 3-phenylpyrrolidine and evaluated for dopamine (DA) D2S and D3 receptor binding affinity. The tricyclic benz[e]indole nucleus was constructed by a previously reported reductive amination-cyclization procedure. Several unexpected side products were isolated and characterized using the general method. The trans-diastereoisomers exhibited greater affinities for the DA D3 receptor than the corresponding cis-isomers. In both the cis- and trans- series the greatest affinity for DA D3 receptors was shown by compounds substituted with N-n-propyl or N-allyl groups. The cis-(±)-N-allyl derivative 21e demonstrated a D2S/D3 selectivity of 290. Resolution of cis-(±)-5 and trans-(±)-21c into individual enantiomers showed that in both series the more active isomer had 3aR absolute configuration. These novel ligands may be useful tools for gaining additional information about the DA D3 receptor.

Unusual ring contraction by substitution of 4-O-activated-pentono-1,5-lactams with cyanide. Stereospecific synthesis of 6-amino-1,4,5,6-tetradeoxy-1,4-imino-hexitols

Abstract Reaction of 4-O-sulfonylated 2,3-O-isopropylidene- d -ribo- or - d -lyxo-1,5-lactams with tetrabutylammonium cyanide gave 4-amino-5-C-cyano-4,5-dideoxy-2,3-O-isopropylidene- l -lyxo-5 or - l -ribo-15-1,4-lactams, respectively. A stereospecific ring contraction with inversion at C-4 had taken place in each case. Reduction of the cyano-lactams with LiAlH4 gave 6-amino-1,4,5,6-tetradeoxy-1,4-imino- l -lyxo-6 or - l -ribo-16-hexitol, respectively. The 6-amino-1,4,5,6-tetradeoxy-1,4-imino- l -ribo-hexitol 16 was found to be a moderate inhibitor of α- l -fucosidase with a Ki of 110 μM.

Organometallic Trinuclear Niobium Cluster Complex in Aqueous Solution: Synthesis and Characterization of Niobium Complexes Containing Nb3(μ-η2:η2(⊥)-NCCH3)(μ2-O)36+ Cluster Core

The synthesis and characterization of an organometallic trinuclear oxo-bridged niobium cluster complex with perpendicularly coordinated mu(3)-eta(2):eta(2)( perpendicular)-acetonitrile ligand in aqueous solution is reported. Reaction of NbCl(5) in acetonitrile with aluminum under argon followed by reaction with aqueous hydrochloric acid affords, after suitable workup, the isolation of the organometallic [Nb(3)(mu-eta(2):eta(2)-NCCH(3))O(3)(H(2)O)(9)](6+) aqua ion by cation-exchange chromatography. The purple niobium aqua ion in 2 M HCl shows a small peak at 365 nm (epsilon approximately 511 M(-1) cm(-1) per Nb) and a broad peak at 565 nm (epsilon approximately 335 M(-1) cm(-1)) in the UV-visible region. It is electron paramagnetic resonance (EPR)-active (g = 1.98), but no hyperfine interaction with the (93)Nb nuclear spin (I = 9/2) was observed. The cyclic voltammogram of [Nb(3)(mu-eta(2):eta(2)-NCCH(3))O(3)(H(2)O)(9)](6+) in 4 M HCl on edge-plane pyrolytic graphite electrode at 50 mV s(-1) in the potential range -1.2 V to +1.1 V (vs SCE) exhibits three anodic peaks at -0.12, +0.53, and +0.85 V and a large cathodic peak at -0.91 V with a slight shoulder at about -0.8 V. The purple aqua ion reacted with potassium thiocyanate to give the green thiocyanate derivative, which was crystallized as ((CH(3))(3)NH)(3)[Nb(3)(mu-eta(2):eta(2)-NCCH(3))O(3)(NCS)(9)].2.5H(2)O (1) and subjected to X-ray structure analysis. Density-functional theory (DFT) calculations fully supported the structure of the cluster.

The crystal structure of Cu2.31TeS0.32 - a condensed cluster compound

The crystal structure of Cu2.31TeS0.32, a sulfur-poor member of the solid solution series Cu61.3Te18.3S20.5 - Cu61.9Te35.7S2.36 prepared at 675°C, was determined and refined from single-crystal diffractometer X-ray data (R = 0.044). The quenched statistical cubic structure (a = 14.836(4)Å, space group F4132) consists at room temperature of two interpenetrating tetrahedral frameworks of icosahedral tellurium cages which enclose icosahedral clusters of half-occupied Cu positions centred by additional, fully occupied central copper sites. In one subset, statistically occupied sulfur tetrahedra occur in the tellurium cages, centred on this central Cu site. The Cu2.31TeS0.32 structure is a stuffed derivative of Cr3Si (structure type A13) and shows affinities to the structures of Cu9.1TeSb3, the Ag8GeTe6 family and some metal clusters, especially [Cu26Se13(PEt2Ph)14] and [Au13Cl2(PMe2Ph)10].