Organotellurium derivatives : IV. Synthesis of some diaryltellurium dihalides and pseudohalides

Iodine monohalides (ICl, IBr), cyanogen halides (CNBr, CNI) and thiocyanogen (SCN)₂ add oxidatively to diaryltellurium(II), R₂Te (R = Ph, p-Ch₃OC₆H₄) under mild conditions ( °C). The resulting organotellurium(IV) derivatives react metathetically with silver pseudohalides to yield several new diaryltellurium(IV) pseudohalide derivatives.     

Sign ambiguity in dipole moment derivatives of Br2CO

Signs of the dipole moment derivatives, ?p_x/?S₄ and ?p_x/?S₅ where p_x is the dipole moment vector along an axis perpendicular to the CO bond in the plane of the molecule and S_j are the symmetry coordinates for the B₁ vibrations of Br₂CO have been re-evaluated from the reported ?p/?Q_i values (p being the dipole moment of the molecule and Q_i the normal coordinates) and the L matrix elements. The new set of dipole moment derivatives fits well with similar parameters for Cl₂CO and F₂CO.     

Complexing behaviour ofN-phenylcarbamoylpyrrole-2-thiocarboxamide

Summary The complexes Pd(PTH)₂Cl₂ · 3.5 H₂O, Pd(PTH)₃(PPh₃), Ru(PTH)₂(PPh₃)Cl₂, Ru(PTH)₂(PPh₃)Cl₃, Rh(PTH)₂(PPh₃)Cl and Rh(PT)Cl₂ · 0.5 H₂O, where PTH isN-phenylcarbamoylpyrrole-2-thiocarboxamide, have been prepared and characterised by magnetic and spectral (i.r., u.v. and visible) studies.     

Synthesis of polymer-bound hemoglobin samples

Dextran and hydroxyethyl starch have been chemically modified to give aldehyde-substituted polymers. These modified polymers were synthesised either by periodate oxidation of the starting polymer or by attachment of gluteraldehyde to amino-substituted side chains on the polymer. When such modified starches were allowed to react with hemoglobin soluble polymer-bound hemoglobins were formed. These were shown to be capable of binding oxygen but the observed oxygen-binding curves were shifted to the left relative to unbound hemoglobin. Heart perfusion experiments indicate that these polymer-bound hemoglobins are not suitable for use as blood substitutes     

The structure,absolute configuration and biosynthesis of nortiliacorinine a

The incorporation of (±)-norcoclaurine, (±)-coclaurine, (±)-N-methylcoclaurine and dehydro-N-methylcoclaurine into nortiliacorinine A in Tiliacora racemosa colebr has been studied and specific utilisation of the (±)-coclaurine demonstrated. The evidence supports oxidative dimerization of two coclaurine units to give nortiliacorinine A. Experiments with (±)-N-methylcoclaurine and (±)-[1-³H, N-¹⁴CH₃]N-methylcoclaurine established that only one N-methylcoclaurine unit is specifically utilised to constitute that “half” of the base which had phenolic OH group in the benzylic portion and further demonstrated that the H atom at the asymmetric centre in the 1-benzylisoquinoline precursor is retained in the bioconversion into nortiliacorinine A. Double labelling experiment with (±)-[1-³H, 6,0-¹⁴CH₃]N-methylcoclaurine showed that O-Me function of the precursor is lost in the bioconversion into nortiliacorinine A. Parallel feedings of (+)-(S)- and (-)-(R)-N-methyl-coclaurines and (-)-(S)-, and ( + )-(R)-coclaurines revealed that the stereo-specificity is maintained in the biosynthesis of nortiliacorinine A from 1-benzylisoquinoline precursors and established ‘S,S’-configuration at the two asymmetric centres in nortiliacorinine A.     

4-tbutyl iodoxybenzene : an effective ozone equivalent

The specifically designed reagent, 4-^tButyl iodoxybenzene (1)-soluble in hot, benzene, chlorobenzene and nitrobenzene- cleaves a range of π bonds to carbonyl compounds in 50–75% isolated yields. In every case, the reagent 1 is transformed to 4-^tbutyl iodobenzene (2) in 90–97% yields, which can be recycled.     

Metal---metal bond formation promoted by steric effects: The structural chemistry of μ-dichlorobis(di-t-butyl-p-tolylphosphine)tetracarbonyldiruthenium(I)

The bulky teratiary phosphines P-t-Bu₂Ph and P-t-Bu₂-p-tol, provide binuclear ruthenium(I) complexes. An X-ray analysis of [Ru₂Cl₂(CO)₄(P-t-Bu₂-p-tol)₂] shows the RuCl₂Ru bridge to be non-planar and to have an Ru---Ru distance of 2.632Å.     

Binding of high-mannose-type oligosaccharides and synthetic oligomannose clusters to human antibody 2G12: implications for HIV-1 vaccine design

Human antibody 2G12 broadly neutralizes human immunodeficiency virus type 1 (HIV-1) isolates and shows protective activity against viral challenge in animal models. Previous mutational analysis suggested that 2G12 recognized a novel cluster of high-mannose type oligosaccharides on HIV-1 gp120. To explore the carbohydrate antigen for HIV-1 vaccine design, we have studied the binding of 2G12 to an array of HIV-1 high-mannose type oligosaccharides by competitive ELISAs and found that Man9GlcNAc is 210- and 74-fold more effective than Man5GlcNAc and Man6GlcNAc in binding to 2G12. The results establish that the larger high-mannose oligosaccharide on HIV-1 is the favorable subunit for 2G12 recognition. To mimic the putative epitope of 2G12, we have created scaffold-based multivalent Man9 clusters and found that the galactose-scaffolded bi-, tri-, and tetra-valent Man9 clusters are 7-, 22-, and 73-fold more effective in binding to 2G12 than the monomeric Man9GlcNAc2Asn. The experimental data shed light on further structural optimization of epitope mimics for developing a carbohydrate-based HIV-1 vaccine.     

Pyrrole studies part 41. Reactivity of 3,4-diformyl-2,5-dimethylpyrrole with diaminoalkanes. An unusual formation of 2-azafulvenes

3,4-Diformyl-2,5-dimethylpyrrole (1) reacts with ,ω-diamino-alkanes, NH₂(CH₂)_nNH₂t' to form either the potentially tautomeric 2:2 macrocyclic adduct (7a) (8), when N = 2, or the potentially tautomeric 1:1 bicyclic adduct (18) (19), when N = 4, 5, 6, and 12. ¹H and ¹³C N.m.r. spectral data indicate that the 2-azafulvene structures predominate for both types of cycloadducts. Only polymeric material was obtained when N = 3.     

Heterocyclic inflammation inhibitors

Non steroidal anti-inflammatory drugs are the most widely used medicines for relief of pain. These drugs have some side effects, particularly toxicity in the gastrointestinal tract and kidneys. Various approaches have been used for obtaining safer anti-inflammatory drugs. In this review we have summarized the recent developments in the following areas; (i) mode of action of NSAIDs (ii) Role of COX-1 & COX-2 in inflammation, (iii) Different approaches used to improve gastric tolerance i.e. chemical manipulation, formulation & co-administration, development of non specific (COX-1 & COX-2 inhibitors) and specific (COX-2 inhibitors) inflammation inhibitors, and development of inflammation inhibitors having a mode of action other than COX-1 & COX-2 inhibition. We have also focused on the safety of COX-2 inhibitors and the synthesis of heterocyclic compounds and their role as inflammation inhibitors.