Intramolecular acetal formation by primary versus secondary hydroxyl groups

On acid-catalyzed equilibration in aqueous solution, three aldoheptoses, d-glycero-l-manno-, d-glycero-l-allo-, and d-glycero-l-altro-heptose, give 15, 54, and 98%, respectively, of the 1,6-anhydropyranose, a much higher proportion than is formed from the homomorphous aldohexoses. This is another example of the greater tendency of secondary, compared to primary, hydroxyl groups to participate in the formation of cyclic acetals.     

Silica containing primary hydroxyl groups for high-performance affinity chromatography

Primary hydroxyl groups were incorporated into silica by a four-step reaction procedure which includes modification of the silica surface with gamma-glycidoxypropyltrimethoxysilane, leading to an epoxide silica; hydrolysis with acid to yield a diol silica; oxidation of the diol silica with periodate to yield a silica resin with aldehyde functions; and reduction with sodium borohydride to obtain the primary hydroxyl-containing silica. The hydroxyl groups were activated with chloroformates or carbodiimidazole. Proteins were coupled under mild conditions in high yield to these activated silica resins. Columns containing these newly developed silica derivatives were used for the fast and efficient purification of antibodies on antigen-containing silica, as well as for the purification of trypsin on a trypsin inhibitor column (or vice-versa). The effect of pressure on association and dissociation of the affinity complex is discussed.     

Selective replacement of primary hydroxyl groups in carbohydrates: preparation of some carbohydrate derivatives containing halomethyl groups

Selective halogenation of hydroxymethyl groups in sugars and nucleosides has been achieved by use of triphenylphosphine and carbon tetrahalides (chloride, bromide, or iodide) in pyridine. Methyl α-d-glucopyranoside, 1,2,-O-isopropylidene-α-d-glucofuranose, inosine, and uridine give almost quantitative yields of their primary halomethyl analogs. Similarly, 6,6′-dichloro-6,6′-dideoxysucrose is prepared from sucrose. Chlorination and bromination of 5,6-anhydro-1,2-O-isopropylidene-α-d-glucofuranose by these reagents give 6-chloro-6-deoxy-1,2-O-isopropylidene-α-d-glucofuranose and 6-bromo-6-deoxy-1,2-O-iso-propylidene-α-d-glucofuranose, respectively.     

Accelerated biodegradation of poly(vinyl alcohol) by glycosidations of the hydroxyl groups or addition of sugars

Biodegradabilities of N-acetyl-d-glucosamine (GlcNAc)- (1) and chitobiose-substituted (2) poly(vinyl alcohol)s (PVA)s in a soil suspension (pH 6.5) were investigated at 25 degrees C for 40 days. Biochemical oxygen demand of 1 with a degree of substitution of 0.2-0.3 (DP = 430-480) was higher than that of PVA under the degradation condition. Size exclusion chromatography, (1)H NMR, and Fourier-transform infrared measurements of the recovered sample indicated that biodegradation of the PVA main chain was accelerated by partial glycosidation of hydroxyl groups in PVA. Similar acceleration was observed in a PVA/GlcNAc (50:50, w/w) mixture. Microbes which relate with degradation of the glycosidated polymers were grown in a culture medium including the soil suspension and the polymer as the carbon source. Polyacrylamide gel electrophoresis (SDS-PAGE) and IR measurements indicated that a cell-free extract derived from GlcNAc-substituted PVA was different from that in the PVA/GlcNAc mixture. The results suggested that the PVA main chain in GlcNAc-substituted PVA was cleaved by a different microorganism or via a mechanism different from that in the mixture. Chitobiose-substituted PVA 2 showed more enhanced acceleration, indicating that the sugar length influenced the degradability.     

Regiospecific alkaline protease-catalyzed divinyl acyl transesterifications of primary hydroxyl groups of mono- and di-saccharides in pyridine

This paper describes highly selective transesterification reactions, catalyzed by an alkaline protease from Bacillus subtilis in pyridine, of several mono- and di-saccharides with divinyl dicarboxylates ranging from 4 to 10 carbon atoms. A series of polymerizable vinyl fatty acid sugar esters were obtained with good selectivity and high yields. Most products had high proportions of the alpha anomer. The influences of the enzymes, solvents, temperature, and acyl donor chain length on the reaction were studied. Vinyl sugar esters offer a new family of functional water-soluble monomers for preparation of sugar-containing polymers.     

Development of hydrophilic photolabile hydroxyl protecting groups

Hydrophilic photolabile protecting groups (PPGs) for hydroxyl protection have been developed. The new PPGs are derived from 3-(dimethylamino)trityl (DMATr) by replacing the two methyl groups with two hydrophilic butyryl groups. The new PPG reagents can be readily prepared and installed. They are stable in the dark but can be removed cleanly and efficiently in aqueous environments upon irradiation with a UV lamp or sunlight.     

Per-O-(3-hydroxy)propyl-beta-cyclodextrin: a cyclodextrin derivative bearing only primary hydroxyl groups

Natural beta-cyclodextrin (cyclomaltoheptaose) was treated with sodium hydride and allyl bromide to form the per-O-allyl-beta-cyclodextrin. 9-BBN, sodium hydroxide and hydrogen peroxide were then added to form, after adequate treatments, the desired per-O-(3-hydroxy)propyl-beta-cyclodextrin in yields close to 65%. This modified cyclodextrin, which bears only primary hydroxyl groups, can be used as a macro-initiator of the anionic polymerisation of ethylene oxide to form star-shaped polymers. The presence of only primary hydroxyl groups allows us to expect identical initiation kinetics for all the hydroxyl groups of the modified glucopyranosyl units.     

Dansylation of hydroxyl and carboxylic acid functional groups

Fluorescent labeling of primary and secondary amines using dansyl chloride has been widely used in the past. Its application provides an extremely sensitive means to detect amine functional groups to amounts of less than 1 microg of material. This work describes a method for the dansylation of hydroxyl (-OH) and carboxylic acid (-COOH) functional groups. This technique is demonstrated with ethanol, gamma hydroxy butyric acid (GHB), benzoic acid, and p-chloroaniline. Sensitivity of detection for all compounds are microgram or microliter. For the compounds ethanol and GHB which are liquids at room temperature, as little as 1 microl quantity can be detected. Benzoic acid and p-chloroaniline which are solids at room temperature can be detected at levels of 1 microg. Fast thin layer chromatography was accomplished using acetone as the resolving solvent, which resulted in good differentiation of analytes for R(f) measurement. The dansylation reaction performed similarly at pH 11, 10 and 9.6 and uses 2 molar Na(2)CO(3).     

Esterification of polymer-supported hydroxyl groups using the Mitsunobu reaction

Summary Resin-bound hydroxyl groups were esterified by N-protected amino acids using triphenylphosphine and diethyl azodicarboxylate (Mitsunobu reaction) in tetrahydrofuran or dimethylformamide. The typical reaction time was 1 h and the yield for different amino acids varied from 65 to 100%. No racemization was detected in model peptides.     

Chiral derivatizing reagents for drug enantiomers bearing hydroxyl groups

This review extensively summarizes and critically evaluates the recent research on the indirect resolution technique for enantiomeric alcohols. Twenty-one chiral derivatizing reagents divided in seven types, including chiral acids, activated acids, chloroformates, isocyanates, carbonyl nitriles, oxazolidin-2-ones and lactones, are described. The derivatization methods of the various chiral reagents, the liquid chromatography separation systems, the detection systems used for the diastereomeric derivatives of alcohols as well as their limitations and the prospects of the indirect resolution technique for the future are thoroughly discussed. This paper aims to instruct the application of a particular chiral reagent and the technical approach to be used and should be beneficial to the development of an indirect resolution method for enantiomeric alcohols as well as to the biomedical investigation of the differences between the antipodes of chiral alcohols.     

A novel carbonochloridate for activation of supports containing hydroxyl groups

The conditions for the introduction of active carbonate groups into supports containing hydroxyl groups by reaction with 5-norbornene-2.3-dicarboximido carbonochloridate are described. Up to 1.5 mmol carbonate groups/g dry Sepharose 4B could be bound. In the case of glycine the reaction of the activated supports with the amino groups takes place with a 10-fold higher rate than the hydrolysis of the carbonate groups, and high coupling yields can be reached. It is shown that the activated supports are well suitable for the preparation of carriers for affinity chromatography or the immobilization of enzymes.     

Mild detritylation of nucleic acid hydroxyl groups by warming up

It is challenging to effectively deprotect hydroxyl groups of acid-or-base sensitive bio-macromolecules without causing even minor defects and compromising high quality of final products. We report here a mild detritylation strategy in mildly acidic buffers to remove the DMTr protection from the 5'-hydroxyl groups of synthetic nucleic acids. The DMTr-groups can be easily and effectively removed at pH 4.5 or 5.0 with slight warming up (40 °C), offering virtually quantitative deprotection. This warming-up strategy is particularly useful for deprotection of the modified nucleic acids that are sensitive to the conventional acid deprotection. As a first step towards our long-term goal of synthesizing defect-free nucleic acids, our novel and simple strategy further increases the quality of synthetic nucleic acids.     

Participation of the tRNA A76 hydroxyl groups throughout translation

The free 2'-3' cis-diol at the 3'-terminus of tRNA provides a unique juxtaposition of functional groups that play critical roles during protein synthesis. The translation process involves universally conserved chemistry at almost every stage of this multistep procedure, and the 2'- and 3'-OHs are in the immediate vicinity of chemistry at each step. The cis-diol contribution affects steps ranging from tRNA aminoacylation to peptide bond formation. The contributions have been studied in assays related to translation over a period that spans at least three decades. In this review, we follow the 2'- and 3'-OHs through the steps of translation and examine the involvement of these critical functional groups.     

Monitoring of hydroxyl groups in wood during heat treatment using NIR spectroscopy

This paper deals with the evaluation of thermally treated wood by near-infrared (NIR) spectroscopy. In the NIR second derivative spectrum, the absorption band at 6913 cm(-1) appeared with the procession of heat treatment, which conclusively assigned to the phenolic hydroxyl groups due to the lignin in comparison with the spectrum of acetylated spruce wood. As a result of the changes in the ratio of the areal integral calculated from spectral separation in the region of hydroxyl groups (7200-6100 cm(-1)) by the Gauss-Newton method, it was clear that the degradation of hydroxyl group in the cellulose started predominantly from the amorphous region and followed to semicrystalline and crystalline region. There was an obvious correlation between the weight decrement of wood and the decrement of hydroxyl groups in the cellulose by heat treatment.