Synthesis of Novel 3-Hydroxy-3-pyridylcamphor Derivatives

The synthesis of a series of five novel precursor compounds derived from (R)-(+)-camphor is reported. From these precursors, a further four novel pyridyl alcohol ligands were synthesized. The molecules represent the first reported examples where the pyridyl and hydroxyl moieties are pendant on the C3 position of the camphor skeleton. The regioselective synthesis was investigated and an efficient method was identified. The final ligands were obtained in moderate yield with absolute regio- and stereoselective control. The molecules were screened as catalysts in the alkylation of aldehydes with diethylzinc in order to compare the new arrangement of donor groups with previously reported results obtained with C2 pendant ligands. The results demonstrated a significant improvement for the synthesized C3 pendant ligands over previous C2 examples with moderate yields and up to 85 % ee being obtained.Keywords: Chiral, camphor ligands, pyridyl alcohols, asymmetric alkylation reactionsPDF and Supplementry file attache

The Evaluation of Novel Camphor-derived Ligands as Catalysts in the Asymmetric Henry Reaction

The evaluation of a series of camphor-derived ligands as catalysts in the asymmetric Henry reaction is reported. The synthesis of two novel derivatives is detailed and these molecules are also screened as catalysts in this reaction. The single crystal X-ray structure of one of the novel compounds is reported. The reaction is catalyzed with moderate to excellent yields and moderate enantioselectivity.Keywords: Camphor, asymmetric catalysis, Henry reaction, chiral ligand

Application of (S,S)-Pentacycloundecane bis(4-Phenyloxazoline) as a Novel Chiral Ligand for Catalysis of the Asymmetric Diels-Alder Reaction of Cyclopentadiene with 3-Acryloyl-2-oxazolidinone

The synthesis of the novel C1 symmetric (S,S)-pentacycloundecane bis(4-phenyloxazoline) ligand 5 and its evaluation as a chiral Lewis acid catalyst in the benchmark asymmetric Diels-Alder reaction between 3-acryloyloxazolidin-2-one (6) and cyclopentadiene (7) is reported. From the various metal salts screened the anhydrous magnesium perchlorate complex emerged as the best catalyst. The endo-cycloadduct product 8 was afforded in 81% enantiomeric excess with an endo:exo ratio of 98:2. An extensive screening of various metal ions as complexing agents was performed and is also reported.Keywords: Pentacycloundecane, oxazolines, chiral catalysis, Diels-Alder reactionPDF and Supplementry file attache

Synthesis of (S)-3-Aminoethyl- 1,2,3,4-Tetrahydroisoquinoline (TIQ-Diamine) via the Mitsunobu Protocol

The synthesis of (S)-3-Aminoethyl-1, 2, 3, 4-tetrahydroisoquinoline (TIQ-diamine) was successfully achieved via the Mitsunobu protocol. The method from earlier reports utilizing aminolysis of commercially available TIQ-amino methyl ester, and reduction of the amide, proved to be inadequate for preparation of TIQ-diamines. The modified route requires three additional steps and consequently rendered three novel intermediates, which were furnished under mild conditions.Keywords: Tetrahydroisoquinoline, TIQ-diamine, Mitsunobu Reactio

The Evaluation of Novel Camphor-derived Pyridyl Ligands as Catalysts in the Asymmetric Diels-Alder Reaction of Cyclopentadiene with 3-Acryloyl-2-oxazolidinone

A series of camphor-derived pyridyl ligands were evaluated in the Diels-Alder reaction of 3-acryloyl-2-oxazolidinone 1 with cyclopentadiene 2. High yields with good endo:exo selectivity, but only moderate enantioselectivities (43 % ee), were obtained. The structures of the copper (II) complexes of the ligands were calculated using ONIOM density functional theory and the results suggest that chiral induction to the alkene functional group is indeed lacking. This explains the moderate experimental selectivities obtained.Keywords: Camphor ligands, asymmetric catalysis, Diels-Alder cycloaddition, computational modellingPDF and Supplementry file attache

Synthesis and NMR Elucidation of Novel Octa-Amino Acid Resorcin[4]arenes Derivatives

The synthesis of nine novel protected amino acid cavitands is reported. All have four pendant n-undecyl chains and ‘headgroups’ connected by a two-carbon spacer at eight positions on the aromatic rings. The amino acids employed are glycine, alanine, phenylalanine, leucine, proline, tryptophan, serine, glutamine and lysine. The structures of the compounds were elucidated using one and two-dimensional NMR techniques which verified that all octa-substituted cavitands have symmetrical C2v conformation at room temperature. These compounds have potential synthetic ion channel applications.KEYWORDS Octa-amino acid resorcin[4]arenes, 1H-NMR, COSY, HSQC, C4v symmetry, C2v symmetry.PDF and Supp files attache

Synthesis and NMR Elucidation of Novel Pentacycloundecane-Derived Peptides

Herein we report the synthesis and NMR elucidation of five novel pentacycloundecane (PCU)-derived short peptides as potential HIV protease inhibitors. 1H and 13C spectral analysis show major overlapping of methine resonance of the PCU ‘cage’ thereby making it extremely difficult to assign the NMR signals. Attachment of short peptides to the cage at position C-8/C-11 results in conformational differences of the peptide side chains due to diastereomeric interactions between the cage skeleton and the chiral side chains. The use of two-dimensional NMR techniques proved to be highly effective in the elucidation of such systems.Keywords: 1H NMR, 13C NMR, 2D NMR, PCU diol diaminoacid, HIV protease inhibitors PDF and supplementary file attached

Comparison of Tetrahydroisoquinoline (TIQ) Thiazole and Oxazoline Ligands for Asymmetric Henry Reactions

A series of novel C1 symmetric thiazole ligands with a tetrahydroisoquinoline (TIQ) backbone were synthesized. Their application in the catalytic asymmetric Henry reaction was investigated with comparison to a corresponding TIQ oxazoline ligand. The Cu(II)-oxazoline complex was more reactive and furnished moderate enantioselectivities up to 61:36 (syn:anti) with 75:25 diastereomeric excess, while the Cu(II)-thiazole complexes had lower selectivity. This is the first example where a directcomparison between an N, N-type thiazole and oxazoline ligands has been studied.Keywords: Tetrahydroisoquinoline, thiazole, oxazoline, Henry reaction, enantioselectivit

Terpyridyl Complexes as Antimalarial Agents

Anumber of transition metals and their terpyridyl complexes have been evaluated for antimalarial activity on the strain 3D7. The metals, ligands and complexes were each in turn investigated for their efficacy. All activities were in the sub-micromolar range (0.1–1 μM). Their modes of action were compared with that of chloroquine to discover whether or not they were capable of inhibiting haemozoin formation. The data indicate that efficacy could be a result of several mechanisms and that speciation of the metal complex and the manner in which the agents are added to the parasitic broth have a profound effect on the activity of the agents. We believe that our study offers a template by which other researchers should approach their experiments using transition metal complex agents.KEYWORDS Antimalarial agents, terpyridyl and transition metals

Supplement: "Localization and broadband follow-up of the gravitational-wave transient GW150914" (2016, ApJL, 826, L13)

This Supplement provides supporting material for Abbott et al. (2016a). We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands