6,7-Dimethoxy-3-methoxycarbonyl-1-(2-methoxyphenyl)-3,4-dihydroisoquinoline 2-oxide

In the title compound, C₂₀H₂₁NO₆, an N-oxide-based organocatalyst, the N-containing six-membered ring adopts a twisted half-chair conformation. No hydrogen bonding or π–π stacking was found within the crystal structure.

(1S,3S)-Methyl 6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylate

In the title compound, C₁₉H₂₁NO₄, an organocatalyst with a tetra­hydro­isoquinoline backbone, the heterocyclic ring assumes a half-boat conformation. The dihedral angle between the aromatic rings is 82.93 (8)°. In the crystal, mol­ecules are linked via N—H⋯O and C—H⋯O hydrogen bonds, forming a layer parallel to (10).

Benzyl 5-hydroxy-4-oxapentacyclo[5.4.1.02,6.03,10.08,11]dodecane-3-carboxylate

The title compound, C₁₉H₁₈O₄, exhibits a long C—C bond [1.575 (2) Å] in the cage structure. In the crystal, pairs of O—H⋯O hydrogen bonds link the mol­ecules into centrosymmetric dimers. C—H⋯O inter­actions also occur.

Enzymatic activation of a peptide functionalised gold nanoparticle system for prodrug delivery

Gold nanoparticles (GNPs) with a monolayer of peptides were synthesized as a potential tumour activated cancer drug delivery system. The prodrug system was achieved by the attachment of two varying lengths of peptides to GNPs: An 18 amino acid peptide sequence encompassing a shorter fluorescent labelled (coumarin) six amino acid peptide sequence. The longer peptide chain included the sequence D-AFK that is selectively cleavable by the over-expression of proteases in the vicinity of cancer cells. The protease-mediated exposure of the coumarin was demonstrated by the incubation of peptide capped GNPs with adenocarcinomic human alveolar basal epithelial A549 cells and madin-darby bovine kidney epithelial cells. Confocal laser scanning microscopy studies revealed enhanced fluorescence emission intensities in the cancer cell line as compared to the intensity exhibited by the healthy cell line. This work suggests that GNPs functionalised with a cytotoxic agent or fluorophore encapsulated by longer peptide strands may find useful applications for development of GNPs with therapeutic or diagnostic studies.

Pentacycloundecane-based inhibitors of wild-type C-South African HIV-protease

In this study, we present the first account of pentacycloundecane (PCU) peptide based HIV-protease inhibitors. The inhibitor exhibiting the highest activity made use of a natural HIV-protease substrate peptide sequence, that is, attached to the cage (PCU-EAIS). This compound showed nanomolar IC(50) activity against the resistance-prone wild type C-South African HIV-protease (C-SA) catalytic site via a norstatine type functional group of the PCU hydroxy lactam. NMR was employed to determine a logical correlation between the inhibitory concentration (IC(50)) results and the 3D structure of the corresponding inhibitors in solution. NMR investigations indicated that the activity is related to the chirality of the PCU moiety and its ability to induce conformations of the coupled peptide side chain. The results from docking experiments coincided with the experimental observed activities. These findings open up useful applications for this family of cage peptide inhibitors, considering the vast number of alternative disease related proteases that exist.

[(1R,3S)-6,7-Dimeth-oxy-1-phenyl-1,2,3,4-tetra-hydro-isoquinolin-3-yl]methanol 2.33-hydrate

The title compound, C(18)H(21)NO(3)·2.33H(2)O, is the fourth reported member in a series of (1R,3S)-6,7-dimeth-oxy-1-phenyl-1,2,3,4-tetra-hydro-isoquinoline derivatives used in catalysis as ligands (or their precursors). The N-heterocycle in the structure adopts a half-chair conformation. The dihedral angle between the benzene rings is 77.29 (13)°. There are three ill-resolved water molecules of crystallization in the structure (one of them rotationally disordered about a threefold axis) involved in short contacts probably due to hydrogen bonding.

tert-Butyl 2-hy-droxy-3-(4-methyl-benzene-sulfonamido)-butano-ate

In the crystal of the title compound, C(15)H(23)NO(5)S, mol-ecules are linked through N-H⋯O and O-H⋯O hydrogen-bond inter-actions, resulting in centrosymmetric dimers in which the N-H⋯O inter-actions generate R(2) (2)(12) rings and the O-H⋯O inter-actions generate R(2) (2)(14) rings. Weak inter-molecular C-H⋯O inter-actions are also observed.

endo-11-(Dibenzyl-amino)-tetra-cyclo-[5.4.0.0.0]undecane-8-one

The structure of the title compound, C(25)H(27)NO, is a mono-ketone penta-cyclo-undecane (PCU) mol-ecule bearing a tertiary amine group. One of the methyl-ene groups in the PCU is disordered over two orientations with site-occupancy factors of 0.621 (7) and 0.379 (7).

Optically active diaryl tetrahydroisoquinoline derivatives

In (1R,3S)-6,7-dimethoxy-3-(methoxydiphenylmethyl)-1-phenyl-1,2,3,4-tetrahydroisoquinoline, C(31)H(31)NO(3), (I), and (1R,3S)-2-benzyl-3-[diphenyl(trimethylsiloxy)methyl]-6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline, C(40)H(43)NO(3)Si, (II), the absolute configurations have been confirmed to be R and S at the isoquinoline 1- and 3-positions, respectively, by NMR spectroscopy experiments. Both structures have monoclinic (P2(1)) symmetry and the N-containing six-membered ring assumes a half-chair conformation. The asymmetric unit of (I) contains one molecule, while (II) has two molecules within the asymmetric unit. These structures are of interest with respect to the conformation around the exocyclic C-C bond: (I) displays an ap (antiperiplanar) conformation, while (II) displays an sc-exo (synclinal) conformation around this bond. These conformations are significant for stereocontrol when these compounds are used as catalysts. Various C-H...π and C-H...O bonds link the molecules together in the crystal structure of (I). In the crystal structure of (II), three intermolecular C-H...π hydrogen bonds help to establish the packing.

(3S)-2-Benzyl-3-carboxy-1,2,3,4-tetrahydroisoquinolinium chloride monohydrate

In the title compound, C₁₇H₁₈NO₂⁺·Cl⁻·H₂O, a precursor to novel asymmetric catalysts, the N-containing six-membered ring of the tetra­hydro­quinolinium unit assumes a half-boat conformation. In the crystal, inter­molecular O—H⋯O, O—H⋯Cl, N—H⋯Cl and C—H⋯O hydrogen bonds and C—H⋯π inter­actions link the mol­ecules into a three-dimensional network.

(2R,3S)-Methyl 2-hydroxy-3-(4-methylbenzenesulfonamido)-3-phenylpropanoate

In the title mol­ecule, C₁₇H₁₉NO₅S, the p-tolyl ring is oriented approximately parallel to the phenyl ring [dihedral angle = 17.2 (1)°], resulting in an intra­molecular π–π inter­ation [centroid–centroid distance = 3.184 (10) Å]. In the crystal, mol­ecules are linked through O—H⋯O and C—H⋯O hydrogen bonds, forming hydrogen-bonded sheets lying diagonally across the ac face.

(1R,3S)-Methyl 6,7-dimeth-oxy-1-(4-meth-oxy-phen-yl)-1,2,3,4-tetra-hydro-isoquinoline-3-carboxyl-ate

The title compound, C₂₀H₂₃NO₅, is the third in a series of tetra­hydoisoquinoline (TIQ) compounds that are precursors to novel chiral catalysts. The N-containing six-membered ring assumes a half-boat conformation. No hydrogen bonding is observed in the crystal structure.

tert-Butyl N-[(11-exo-benzyl-oxy-carbonyl-8-oxopenta-cyclo-[5.4.0.0.0.0]undecane-11-endo-yloxy)carbon-yl-methyl]carbamate

The structure of the title compound, C₂₆H₂₉NO₇, at 173 K has an inter­molecular N—H⋯O hydrogen bond. This is one of the few examples where a mono-ketone penta­cyclo­undecane (PCU) mol­ecule exibits hydrogen bonding in the solid state. The dihedral angles of the amide and ester groups are normal and unaffected by the cage structure. A longer than normal C—C bond [1.571 (4) Å] was found within the cage structure.

N,N'-[(8-endo,11-endo-Dihy-droxy-penta-cyclo-[5.4.0.0.0.0]undecane-8,11-di-yl)bis-(methyl-enecarbon-yl)]di-l-phenyl-alanine

The title compound, C₃₃H₃₆N₂O₈, is the first example of a disubstituted peptidic pentacycloundecane (PCU) diol. The structure displays an array of inter- and intra­molecular hydrogen bonding by both amide and alcohol functional groups. This hydrogen-bonding system connects the mol­ecules into a three-dimensional network.

Erratum: Tetra-kis-μ-l-alanine-κO:O'-bis-[tetra-aqua-terbium(III)] hexa-perchlorate. Corrigendum

Corrigendum to Acta Cryst. (2009), E66, m193–m194.

The surname of one of the authors and the affiliation of that author in the paper by Mohamed et al. [Acta Cryst. (2009), E66, m193–m194] are corrected.

(R)-4-Phenyl-2-[(S)-1,2,3,4-tetra-hydro-isoquinolin-3-yl]-4,5-dihydro-1,3-oxazole

The asymmetric unit cell of the title compound, C₁₈H₁₈N₂O, contains four molecules. In the crystal structure, an inter­molecular N—H⋯N hydrogen bond helps to establish the packing.

Microwave assisted SPPS of amylin and its toxicity of the pure product to RIN-5F cells

The 37-amino acid polypeptide islet amyloid polypeptide (IAPP), or amylin, is found as amyloid aggregates in the islets of Langerhans in patients with type II diabetes. Herein, we report an efficient microwave assisted solid phase peptide synthesis of amylin (IAPP). The most efficient synthesis used double and triple couplings and 10 equiv. of amino acids. Double couplings were used for most amino acids, whereas triple couplings were utilized for amino acids in selected regions. The most effective method for formation of the disulfide bond in amylin was found to be iodine oxidation. The highest purity amylin was obtained when the crude peptide was purified with HPLC before formation of the disulfide bond. The cytotoxicity of the synthesized amylin product to RIN-5F cells was determined. The synthesized amylin exhibits an exponential increase of cytotoxicity at concentrations >35 microM. Transmission electron microscope studies of a sample of amylin shows that insoluble amyloid fibrils spontaneously formed when 45 microM solution of synthesized amylin was incubated in a suitable buffer for 6 h.

Synthesis and NMR elucidation of novel pentacycloundecane-based peptides

The synthesis and NMR elucidation of two novel pentacycloundecane (PCU)-based peptides are reported. The PCU cage amino acids were synthesised as racemates and the incorporation of the cage amino acid with (S)-natural amino acids produced diastereomeric peptides. The diastereomeric 'cage' peptides were separated using preparative HPLC and the NMR elucidation of these PCU containing peptides are reported for the first time. The (1)H and (13)C NMR spectra showed series of overlapping signals of the cage skeleton and that of the peptide, making it extremely difficult to resolve the structure using one-dimensional NMR techniques only. The use of two-dimensional NMR techniques proved to be a highly effective tool in overcoming this problem.

Synthesis and NMR assignment of pentacycloundecane precursors of potential pharmaceutical agents

The synthesis and complete NMR elucidation of eight novel pentacycloundecane (PCU) derivatives are reported. These compounds are precursors in the synthesis of PCU-based anti-tuberculosis (TB) agents and potential human immunodeficiency virus (HIV) protease inhibitors. Two-dimensional (2D) NMR techniques were used to assign the NMR spectra for these compounds. Substitution of the cage molecule at (C-8/11) further complicates the assignment, since some of the substituted alkyl chain groups overlap with the cage proton signals. The side chain heteroatoms also introduce a rare through-space deshielding effect to some of the carbon atoms of the cage skeleton. Ring strain in the rigid cage skeleton appears to induce drastic electronic changes in some parts of the cage framework. This observation is more dramatic for the C-4 methylene group of the cage diols and the cage ethers.

{(1R,3S)-2-Benzyl-6,7-dimeth-oxy-1-phenyl-1,2,3,4-tetra-hydro-isoquinolin-3-yl}diphenyl-methanol

In the title compound, C₃₇H₃₅NO₃, a precursor to novel chiral catalysts, the N-containing six-membered ring assumes a half-chair conformation. Inter­molecular C—H⋯O hydrogen bonds link the mol­ecules in the crystal structure.

cis-N-(2-Hydroxycyclohexyl)-p-toluenesulfonamide

There are two symmetry-independent mol­ecules in the asymmetric unit of the title compound, C₁₃H₁₉NO₃S. The cyclo­hexane rings in the two mol­ecules adopt chair configurations. The hydr­oxy and amino groups on the cyclo­hexane ring assume axial and equatorial orientations, respectively, with respect to the plane of the ring. The crystal structure is stabilized by two inter­molecular N—H⋯O and O—H⋯O hydrogen bonds from the two symmetry-independent mol­ecules.

Tetra-kis-μ-l-alanine-κO:O'-bis-[tetra-aqua-terbium(III)] hexa-perchlorate

The asymmetric unit of the title compound, [Tb(2)(C(3)H(7)NO(2))(4)(H(2)O)(8)](ClO(4))(6), contains a dinuclear cation and six perchlorate anions, one of which is disordered. In the cation, the four l-alanine mol-ecules are present in their zwitterionic form and bridge two Tb(3+) ions through their carboxyl-ate O atoms. Each Tb atom is also coordinated by four water mol-ecules in a square-anti-prismatic geometry. In the crystal structure, the cations and anions are held together via inter-molecular O-H⋯O and N-H⋯O hydrogen bonds.

(1R,3S)-Methyl 2-benzyl-6,7-dimeth-oxy-1-phenyl-1,2,3,4-tetra-hydro-isoquinoline-3-carboxyl-ate

In the title compound, C₂₆H₂₇NO₄, a precursor to novel chiral catalysts, the N-containing six-membered ring assumes a half-boat conformation. Various C—H⋯π interactions and intermolecular short contacts (C⋯H = 2.81–2.90 Å) link the mol­ecules together in the crystal structure.

3-(2-Amino-1,3-thia-zol-4-yl)-6-chloro-2H-chromen-2-one

The title compound, C(12)H(7)ClN(2)O(2)S, crystallizes with two mol-ecules in the asymmetric unit. The mol-ecular conformation is roughly planar for both these mol-ecules with maximum deviations of 0.177 (3) and 0.076 (4) Å from their respective mean planes. In the crystal, strong N-H⋯N and weak but highly directional C-H⋯O hydrogen bonds provide the links between the mol-ecules. The structure is further stabilised by aromatic π-π stacking inter-actions with centroid-centroid distances in the range 3.650 (3)-3.960 (3) Å.

3-(2-Amino-1,3-thia-zol-4-yl)-6-bromo-2H-chromen-2-one

The mol­ecule of the title compound, C₁₂H₇BrN₂O₂S, is essentially planar with a maximum deviation of 0.234 (3) Å from the mean plane through all non-H atoms. The dihedral angle between the coumarin ring plane and that of the five-membered thia­zole ring is 12.9 (1)°. In the crystal, strong N—H⋯O, N—H⋯N and weak but highly directional C—H⋯O hydrogen bonds provide the links between the mol­ecules. In addition, C—H⋯π and π–π inter­actions [centroid–centroid distances = 3.950 (3)–4.024 (3) Å] provide additional stability to the inter­layer regions in the lattice.

Microwave-assisted synthesis of a new series of resorcin[4]arene cavitand-capped porphyrin capsules

Capsule-shaped molecular receptors are fundamental to the modeling of biological host-guest interactions such as those characteristic of enzymatic processes. Among the more versatile and effective synthetic receptors are the hemicarcerand-type hosts. Herein we report the synthesis of six novel resorcin[4]arene cavitand-capped porphyrin capsules, in a new series of molecular capsules modeled on the classical hemicarcerands initially reported by Cram and co-workers. In the first reported instance of its utilisation in the preparation of supramolecularly-capped porphyrin host molecules, microwave (MW) irradiation was used (in conjunction with Adler conditions) in order to form the porphyrin cap in situ. Additionally, the yields obtained via these conditions exhibited a significant improvement, relative to the traditional refluxing protocol hitherto reported. Capsules 20-25 are indefinitely stable, and we observed that 22 and 25 possess the smallest rigidified cavities yet reported for resorcin[4]arene cavitand-capped porphyrin host molecules.

2-(4-Chloro-3-nitro-phen-yl)-4-(4-chloro-phen-yl)-1,3-thia-zole

The title compound, C(15)H(8)Cl(2)N(2)O(2)S, crystallizes with two mol-ecules in the asymmetric unit. The dihedral angles between the 4-chloro-3-nitro-phenyl ring and the thia-zole ring are 0.5 (1) and 7.1 (1)° and those between the 4-chloro-phenyl ring and the thia-zole ring are 7.1 (1) and 7.4 (1)° in the two mol-ecules. The crystal structure is stabilized by inter-molecular C-H⋯Cl and C-H⋯O hydrogen bonds.

Ethyl 4-(4-chloro-phen-yl)-6-methyl-2-thioxo-1,2,3,4-tetra-hydro-pyrimidine-5-carboxyl-ate

In the title compound, C₁₄H₁₅ClN₂O₂S, the tetra­hydro­pyrimidine ring adopts a twisted boat conformation with the carbonyl group in an s-trans conformation with respect to the C=C double bond of the six-membered tetra­hydro­pyrimidine ring. The mol­ecular conformation is determined by an intra­molecular C—H⋯π inter­action. The crystal structure is further stabilized by inter­molecular N—H⋯O mol­ecular chains and centrosymmetric N—H⋯S dimers.

Ethyl 4-(4-hydroxy-phen-yl)-6-methyl-2-oxo-1,2,3,4-tetra-hydro-pyrimidine-5-carboxyl-ate monohydrate

In the title compound, C₁₄H₁₆N₂O₄·H₂O, the dihedral angles between the planes of the 4-hydroxy­phenyl and ester groups with the plane of the six-membered tetra­hydro­pyrimidine ring are 87.3 (1) and 75.9 (1)°, respectively. The crystal structure is stabilized by O—H⋯O and N—H⋯O hydrogen bonding between the water mol­ecule and the organic functionalities.

Redetermination of chlorido(2,2′:6′,2′′-terpyridine-κ3 N,N′,N′′)gold(I) dichloride trihydrate at 173 K. Corrigendum

Corrigendum to Acta Cryst. (2008), E64, m1240.

The title of the paper by Friedrich, Maguire, Martincigh, McKay & Pietersen [Acta Cryst. (2008), E64, m1240] is corrected.

7,11,15,28-Tetra-kis[(2-formyl-phen-oxy)methyl]-1,21,23,25-tetra-methyl-resorcin[4]arene cavitand ethyl acetate clathrate at 173 K

The title compound, C₆₈H₅₆O₁₆, was synthesized as a novel synthetic inter­mediate towards deeper and more elaborate resorcin[4]arene cavitands. The structure is the first reported example of a resorcin[4]arene cavitand bearing aromatic aldehyde functional groups at the extra-annular rim of the mol­ecule. The 2-formyl­phen­oxy residues are found to assume two different orientations above the mol­ecular cavity. One half of the resorcin[4]arene cavitand mol­ecule appears in the asymmetric unit; the complete resorcin[4]arene cavitand structure was generated across a mirror plane. In addition, a highly disordered ethyl acetate solvent mol­ecule is present within the mol­ecular cavity.

7,11,15,28-Tetra-bromo-1,21,23,25-tetra-phenethyl-resorcin[4]arene cavitand-acetone-chloro-form (1/1.31/0.69) at 173 K

The crystal structure of the title compound, C₆₄H₅₂Br₄O₈·1.31C₃H₆O·0.69CHCl₃, is described. The structure has been reported previously [Bryant, Blanda, Vincenti & Cram (1991). J. Am. Chem. Soc.113, 2167–2172]; however, the lower data acquisition temperature results in an improved refinement model. In addition, the presence of residual acetone and (disordered) chloro­form within the mol­ecular structure of the title compound represents a new clathrate of the title compound. One half of the resorcin[4]arene cavitand mol­ecule appears in the asymmetric unit; the complete resorcin[4]arene cavitand structure was generated across a mirror plane.

NMR elucidation of a novel (S)-pentacyclo-undecane bis-(4-phenyloxazoline) ligand and related derivatives

The NMR elucidation of a novel ligand (S)-pentacyclo-undecane bis-(4-phenyloxazoline) and related pentacyclo-undecane (PCU) derivatives is reported. Two-dimensional NMR proved to be a powerful technique in overcoming the difficulties associated with the elucidation of these compounds when only one-dimensional NMR data is utilized. A chiral substituent was introduced to both 'arms' of the PCU skeleton to produce derivatives 1-3. These derivatives display C(1) symmetry with all thecage atoms being nonequivalent. Owing to overlapping of peaks in the (1)H spectra, identification of these diastereomeric protons was very difficult. The (13)C spectra gave rise to clear splitting of the nonequivalent carbons. This is unusual compared to similar PCU derivatives with chiral substituents as splitting of all the diastereomeric cage carbons has not yet been reported. Nuclear Overhauser enhancement spectroscopy (NOESY) correlations of derivatives 1-3 confirm the different conformations of the molecule in which the side 'arms' occupy different orientations with respect to cage moiety.

Redetermination of chlorido(2,2':6',2''-terpyridine-κN,N',N'')gold(I) dichloride trihydrate at 173 K

The redetermined structure of the title compound, [AuCl(C(15)H(11)N(3))]Cl(2)·3H(2)O, at 173 (2) K is reported. The structure displays O-H⋯Cl and O-H⋯O hydrogen bonding. The distance of one of the chloride ions from the gold(I) atom [5.047 (1) Å] differs from that determined previously.

(4-Hydroxy-3-nitrobenzyl)methylammonium chloride

The title compound, C₈H₁₁N₂O₃⁺·Cl⁻, was synthesized as an inter­mediate in the development of a new sugar sensor. The structure displays N—H⋯Cl and O—H⋯O hydrogen bonding, as well as weak O—H⋯Cl inter­actions and π–π stacking (3.298 Å). There are two formula units in the asymmetric unit.

8-(Biphenyl-4-yl)-8-hydroxy-penta-cyclo-[5.4.0.0.0.0]undecan-11-one ethyl-ene ketal

The title compound, C₂₅H₂₄O₃, synthesized as a potential chiral catalyst, exhibits a range of C—C bond lengths in the penta­cyclo­undecane cage between 1.5144 (18) and 1.5856 (16) Å. The two benzene rings are not planar with respect to each other, but rather are twisted at a torsion angle of 34.67 (17)°. The mol­ecule has an intra­molecular O—H⋯O inter­action and participates in two C—H⋯O inter­molecular inter­actions to form a one-dimensional chain.

7,11,15,28-Tetra-methyl-1,21,23,25-tetra-kis(2-phenyl-ethyl)resorcin[4]arene ethyl acetate clathrate

The title compound, C₆₈H₆₄O₈·C₄H₈O₂, is a new resorcin­[4]arene cavitand synthetic precursor, obtained by alkyl­ation of a previously reported resorcin[4]arene. The additional alkyl bridges significantly rigidify the structure and enforce a ‘bowl’ shape on the mol­ecular cavity. In the crystal structure, the mol­ecule lies on a crystallographic mirror plane, and a single ethyl acetate mol­ecule (also lying on the mirror plane) is present within the compound cavity, illustrating the host capabilities of the mol­ecule.