Diols derivatization

For the classical form of size exclusion chromatography in organic solvents, packings based on highly cross-linked styrene-divinylbenzene are used. For SEC of polar polymers using polar or aqueous solvents, packings based on a polar methacrylate polymer are used. Diol-derivatized silica is used for the separation of proteins and other polar polymers. The different packings will be discussed in sections dedicated to their different application areas. 

Porous affinity membranes based on hydrolyzed poly(GMA-co-EDMA) grafted with glicidyl methacrylates oligomers were also reported [2,60]. Tennikova et al. [2] prepared functionalized macroporous poly(GMA-co-EDMA) membranes by reaction with propane sulfone, diethylamine, or water, leading to the formation of corresponding sulfonic acid, diethylamino or diol-derivatized stationary chromatographic phases. Unfortunately, the poly(GMA-co-EDMA) membranes are mechanically weak and due to their hydrophobic character may cause nonspecific adsorption of proteins. 

Malawer et al. [7] reported in 1984 the SEC of PVP K-15, K-30, K-60, and K-90 using diol-derivatized silica gel column sets and aqueous mobile phase modified with various polar organic solvents. Senak et al. reported in 1987 [8] the determination of the absolute molecular weight and molecular-weight distribution of PVP by SEC-LALLS and SEC with universal calibration. T e column set used consists of TSK-PW 6000, 5000, 3000, and 2000 columns and a mobile phase of water-methanol (50 50, v/v) with O.IM LiNOj. One hundred percent recovery was reported. The results showed good agreement in from SEC-LALLS and... 

Dial monofunctionalization. Formation of stannylene acetals and then treatment with electrophilic reagents achieve the purpose of selective diol derivatization. A primary hydroxyl group is preferentially protected, and in the case of a secondarysecondary diol their respective steric environments have important influence on the regiochemistry, as shown in several carbohydrates. " ... 

Ketalization, however, requires acidic catalysis, with its potential for damage to some substrates. Boronic acids [RB(OH)2] have accordingly been advanced [205] as diol derivatization agents capable of functioning under neutral conditions. The... 

Figan 4 Dependence of the retention of proteins on the ionic strength. Column Protein Pak 300 SW, 7.S nun x 300 mm. Waters Corporation. The stationary phase is a diol-derivatized silica. 

Method 6 (Figure 5) developed by Zhang et al. (32) is based on Fmoc-chemistry synthesis of a C-terminal diol peptide on a diol-derivatized 2-chlorotrityl resin. Oxidation of the free diol peptide gives the peptide aldehyde. A detailed procedure for the preparation of a diol trityl resin and C-terminal peptide aldehyde is given in the following protocols. 

Other polar phases, i.e., silicas with covalently bonded nitrile, nitro, amine, or diol groups, are valuable alternatives to silica. They are less polar (hence the mobile phase can be weaker) and have different selectivities. However, in most cases, they are used in the reversed-phase mode with aqueous mobile phases. Normal-phase applications of some importance are the separation of aromatics on nitro-derivatized phases, and of non-ionic surfactants on diol-derivatized phases. The theoretical plate numbers are usually lower than with non-derivatized sUica. Activity control (see Section 2.2.4 on troubleshooting of NP separations) is not necessary. The stability of the chemical bonding can be limited. 

Another successhil strategy for derivatization of erythromycin employed modification of functional groups involved in intramolecular cyclizations. The C-9 ketone, C-6 hydroxyl group, C-8 proton, and/or C-ll,12-diol of erythromycin were converted into functional groups which participate poorly, if at all, in intramolecular cyclizations. Some derivatives which have been extensively evaluated in preclinical and clinical trials exhibit such desirable properties as better stabiUty under acidic conditions, greater oral bioavadabihty, and higher and more prolonged concentrations of antibiotic in semm and tissues. 

In eonjunetion with the addition of moleeular sieves. Sharpless et al. as also developed an in situ derivatization of produet epoxy aleohols that were previously diffieult to isolate. The derivatization of the produet has been aeeomplished via esterifieation or sulfonylation of the aleohol funetionality. The derivatization is possible only under eatalytie eonditions given the overwhelming presenee of isopropoxide from stoiehiometrie amounts of Ti(0-i-Pr)4 and the presenee of the diol ligand diethyl tartrate. 

Several alternative routes can be used in order to derivatize the carboxy function (Fig. 7-7). Ketones can be transferred by hydrazines and diols to the corresponding hydrazines or acetals. 2,2,2-Trifluoro-l-phenylethylhydrazine [19] is an example of the first group, while 2,3-butanediol or l,4-dimethoxy-2,3-butanediol can be used to form diastereomeric acetals. 

Cyclic diethylsilylene and di-tert.-butylsilylene derivatives have been used to protect diol groups in steroids and prostanoids [539-541]. N,0-bis(diethylhydrogensilyl)trifluoro-methylacetamide simultaneously converts Isolated hydroxyl groups to the diethyllu ogensilyl ether allowing a single step derivatization toVp used for the analysis of corticosteriods. 

The location of the position of double bonds in alkenes or similar compounds is a difficult process when only very small amounts of sample are available [712,713]. Hass spectrometry is often unsuited for this purpose unless the position of the double bond is fixed by derivatization. Oxidation of the double bond to either an ozonide or cis-diol, or formation of a methoxy or epoxide derivative, can be carried out on micrograms to nanograms of sample [713-716]. Single peaks can be trapped in a cooled section of a capillary tube and derivatized within the trap for reinjection. Ozonolysis is simple to carry out and occurs sufficiently rapidly that reaction temperatures of -70 C are common [436,705,707,713-717]. Several micro-ozonolysis. apparatuses are commercially available or can be readily assembled in the laboratory using standard equipment and a Tesla coil (vacuum tester) to generate the ozone. Reaction yields of ozonolysis products are typically 70 to 95t, although structures such as... 

Yeste et al.7 have developed chiral derivatization protocols for determination of enantiopurity of chiral diols by the H and 19F NMR spectroscopy. Three-component method has required the treatment of diol with 2-formylphenylboronic acid and a-methyl-4-fluorobenzylamine [4],... 

The principal side reaction to epoxide coupling is hydrolysis. Particularly at acid pH values, the epoxide ring can hydrolyze to form adjacent hydroxyls. This diol can be oxidized with periodate to create a terminal aldehyde residue with loss of one molecule of formaldehyde (Chapter 1, Section 4.4). The aldehyde then can be used in reductive amination reactions. The reaction of an epoxide group with an ammonium ion generates a terminal primary amine group that also can be used for further derivatization. 

Whereas low and medium polarity analytes are usually well suited for El, highly polar or even ionic compounds, e.g., diols or polyalcohols, amino acids, nucleosides, peptides, sugars, and organic salts should not be subject to El unless properly derivatized prior to EI-MS. [70-75]... 

Das offenbar stark begiinstigte Dikation 173 laBt sich als Haupt-produkt auch aus dem arabino-Derivat 178 in HF in 24 Stunden erhal-ten 42). Die Reaktion verlauft iiber das Ion 179, aus dem in einer cis-Diol-Reaktion jetzt bevorzugt Essigsaure zu 173 und nicht Benzoesaure abge-spalten wird. Die Hydrolyse liefert das erwartete Dibenzoat 176 42). 

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