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The regioselectivity of sulfonylation of myo-inositol orthoesters was controlled by the use of different bases to obtain the desired sulfonate. Monosulfonylation of myo-inositol orthoesters in the presence of one equivalent of sodium hydride or triethylamine resulted in the sulfonylation of the 4-hydroxyl group. The use of pyridine as a base for the same reaction resulted in sulfonylation of the 2-hydroxyl group. Disulfonylation of these orthoesters in the presence of excess sodium hydride yielded the 4,6-di-O-sulfonylated orthoesters. However, the use of triethylamine or pyridine instead of sodium hydride yielded the 2,4-di-O-sulfonylated orthoester. Sulfonylated derivatives of myo-inositol orthoesters were stable to conditions of O-alkylation but were cleaved using magnesium/methanol or sodium methoxide in methanol to regenerate the corresponding myo-inositol orthoester derivative. These new methods of protection-deprotection have been used: (i) for the efficient synthesis of enantiomers of 2,4-di-O-benzyl-myo-inositol, which are precursors for the synthesis of D- and L-myo-inositol 1,3,4,5-tetrakisphosphate; (ii) for the preparation of 2-O-benzyl-myo-inositol which is a precursor for the preparation of myo-inositol 1,3,4,5,6-pentakisphosphate.

Supported organometallic catalysts based on covalently immobilized rhodium/2,2′-bipyridine complexes are compared to the parent homogeneous system for the hydrogenation of ketones and carbon-carbon multiple bonds under hydrogen pressure. In alkaline methanol, the supported catalyst is more active for the reduction of C=C and C≡C bonds than for the hydrogenation of keto groups; this is in contrast with the analogous system in a homogeneous medium for which the opposite trend is observed. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Silver(I) oxide–silver halide mediated alcoholyses of racemic 2,4-di-O-benzoyl-myo-inositol 1,3,5-orthoformate, and its 6-O-methyl and 6-O-sulfonylated derivatives, under identical conditions have been compared. While only the 4-O-benzoyl group undergoes solvolysis in the former two, to yield the corresponding 2-O-benzoyl-myo-inositol 1,3,5-orthoformate, both the 4-O- as well as the 2-O-benzoyl groups undergo solvolysis in the latter, to yield racemic 6-O-sulfonyl-myo-inositol 1,3,5-orthoformates. These results show that solvolysis of the 2-O-benzoyl group in sulfonates is a consequence of intramolecular assistance by the sulfonyl group. Catalytic efficiency of the silver halides in bringing about solvolysis of the benzoates decreased in the order AgI > AgBr > AgCl. A reaction mechanism involving silver–inositol derivative chelates has been proposed.

Reaction of 2-O-benzoyl-myo-inositol 1,3,5-orthoformate with alkyl halides in the presence of silver (I) oxide under a variety of conditions have been studied systematically and compared with the corresponding reaction of 2,4-di-O-acyl-myo-inositol 1,3,5-orthoformates. The results indicate that the former is not an intermediate during the alkylation of the latter in DMF. Results obtained on alkylation of the orthoformate esters mentioned above in acetonitrile show that the alkylation of 2-O-benzoyl-myo-inositol 1,3,5-orthoformate which is formed via the transesterification of 2,4-di-O-benzoyl-myo-inositol 1,3,5-orthoformate could be a side reaction. Silver halides, which are generated during alkylation of 2,4-di-O-acyl-myo-inositol 1,3,5-orthoformates, increase their transesterification in DMF.

(±)-2,4-Di-O-benzoyl-myo-inositol 1,3,5-orthoformate, on heating in the presence of a base, undergoes transesterification to give 2,4,6-tri-O-benzoyl-myo-inositol 1,3,5-orthoformate and 2-O-benzoyl...

Convenient high yielding methods for the preparation of 4,6-di-O-benzyl-myo-inositol, myo-inositol 1,3,5-orthoformate and myo-inositol 1,3,5-orthoacetate, without involving chromatography are described. Myo-inositol was converted to racemic 2,4-di-O-benzoyl-myo-inositol 1,3,5-orthoformate by successive treatment with triethyl orthoformate and benzoyl chloride. The dibenzoate obtained on benzylation with benzyl bromide and silver(I) oxide gave 2-O-benzoyl-4,6-di-O-benzyl-myo-inositol 1,3,5-orthoformate. Deprotection of the benzoate and the orthoformate with isobutylamine and aqueous trifluoroacetic acid, respectively gave 4,6-di-O-benzyl-myo-inositol in an overall yield of 67%. Myo-inositol orthoformate and orthoacetate were prepared and isolated as their tribenzoates. The free orthoesters were regenerated by deprotection of the benzoates by aminolysis with isobutylamine.

Metal film over nanosphere (MFON) has been employed as a reproducible and predictable SERS‐active device in biosensing applications. In addition to its economic fabrication process, such substrate can be further processed to a prism‐structure with increased SERS enhancement and wider Plasmon tunability. In this work, we investigate an alternative coating method to deposit a larger area of well‐ordered PS beads with different sizes (o/ = 100nm and 400 nm) onto a glass. The result suggests that the proposed well‐coating technique can be suitably used to form closely‐packed PS beads with diameter less than 100 nm for developing MFON substrates.

A successful detection of inherently weak Raman signal from molecules is possible with giant enhancement of signal by the process of surface-enhanced Raman scattering (SERS). The SERS-induced enhancement is typically achieved when the molecules adsorbed onto the surface of a noble-metal substrate with nanometric roughness. Such SERS-substrate could be economically fabricated by convective assembly of polystyrene beads followed by metal deposition. The characterization of mono-metallic substrate showed that the SERS enhancement factor increases with increasing thickness of Ag or Au, with Ag-substrate giving the greatest SERS enhancement. However, the formation of silver oxide layer could reduce the shelf-life of the Ag-substrate. Alternatively, Au is also used as the coating material owing to its chemical inertness and biocompatibility. Despite the decent enhancement of the Au-substrate, Au-layer was found to be unstable after prolonged incubation in crystal violet solution. The inherent deficiency in adhesiveness of Au to the glass limits its use as a reliable and cost-effective substrate. In an attempt to improve the SERS-substrate, bimetallic substrate was fabricated by depositing the Au-film, as a protective layer, on the Ag-substrate. In this case, the top layer of Au of the bimetallic substrate remained intact after chemical treatment. Furthermore, the bimetallic substrate was shown to give comparable level of enhancement as an Ag-substrate by choosing a proper thickness ratio of the bimetallic layers. The result suggests that the design of bimetallic substrate could be optimized to maximize the SERS enhancement while retaining a decent stability after laser illumination and chemical treatment. Our findings suggest that bimetallic substrates are potentially useful for a reliable SERS-based biosensing.

A photophysical study describing the effects of the polymer polyvinylpyrrolidone (PVP), on the binding interaction between chlorin e6 (Ce6) with bovine serum albumin (BSA) and human plasma proteins such as very low-density lipoprotein (VLDL), high-density lipoprotein (HDL) and low-density lipoprotein (LDL) was performed using a steady-state fluorescence technique. Combined Ce6–PVP was found to have very stable photostability at three different temperatures (4 °C, 21 °C and 37 °C) when dissolved in an aqueous solution containing 5% and 10% fetal calf serum. The partition coefficient of combined Ce6–PVP was relatively more hydrophilic than that of Ce6 alone. There was a marked increase in the emission profile of Ce6–PVP and the correlated bathochromic shift on the addition of proteins. These results also suggest that Ce6–PVP might have slightly greater association energy with VLDL in comparison to Ce6 alone. The co-localization of Ce6 and Ce6–PVP in cells was also assessed using confocal microscopy. The association of Ce6 with PVP resulted in an enhanced cellular uptake of Ce6 within the cytoplasmic compartment of cells. The present study supported the hypothesis that PVP improves the permeability of Ce6 through the biological membranes of cells.

An attempt is made to survey and categorize selective protection and deprotection reactions, so that practicing chemists/biologists may be able to choose a method for the preparation of protected inositol derivatives, depending on their requirement. In addition to being useful for those who work with inositols, it is hoped that this review will help to widen the scope of using cyclitol derivatives for the synthesis of various classes of natural and unnatural compounds with interesting properties. Emphasis is given to the literature published between 1985 and the end of the year 2002, involving selective protection/deprotection of inositol hydroxyl groups.

International audience; A water-soluble version of N,N′-dimethyl-1,2-diphenylethane-1,2-diamine was prepared by introduction of phosphonic acid moieties on the para position of the aromatic rings. Preliminary investigation of the catalytic properties of the iridium complex of this ligand under biphasic conditions showed that this system compared well with the homogeneous counterpart for the asymmetric hydrogenation of ketones but with noticeably higher reaction rates for the biphasic system.

Convenient high yielding methods for the preparation of 4,6-di-O-benzyl-myo-inositol, myo-inositol 1,3,5-orthoformate and myo-inositol 1,3,5-orthoacetate, without involving chromatography are described. Myo-inositol was converted to racemic 2,4-di-O-benzoyl-myo-inositol 1,3,5-orthoformate by successive treatment with triethyl orthoformate and benzoyl chloride. The dibenzoate obtained on benzylation with benzyl bromide and silver(I) oxide gave 2-O-benzoyl-4,6-di-O-benzyl-myo-inositol 1,3,5-orthoformate. Deprotection of the benzoate and the orthoformate with isobutylamine and aqueous trifluoroacetic acid, respectively gave 4,6-di-O-benzyl-myo-inositol in an overall yield of 67%. Myo-inositol orthoformate and orthoacetate were prepared and isolated as their tribenzoates. The free orthoesters were regenerated by deprotection of the benzoates by aminolysis with isobutylamine.

International audience; Supported rhodium. and iridium. 2,2 ' -bipyridine complexes were prepared for the hydrogenation of aromatic ketones under hydrogen pressure. The key feature of the immobilization process is the functionalization of the 2,2 ' -bipyridine unit with two phosphonic acid moieties, thus allowing the covalent grafting of the catalytic complex onto in situ generated titanium oxide particles. A very good catalytic activity is observed with the resulting materials that compares well with the homogeneous parent system and gives evidence that the major part of the catalytic sites are readily accessible. Moreover, the catalyst can be reused, and no significant rhodium. leaching is observed.